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The deviations of cryogenic collector current–voltage characteristics of SiGe heterojunction bipolar transistors (HBTs) from ideal drift-diffusion theory have been a topic of investigation for many years. Recent work indicates that direct tunneling across the base contributes to the non-ideal current in highly scaled devices. However, cryogenic discrepancies have been observed even in older-generation devices for which direct tunneling is negligible, suggesting that another mechanism may also contribute. Although similar non-ideal current–voltage characteristics have been observed in Schottky junctions and were attributed to a spatially inhomogeneous junction potential, this explanation has not been considered for SiGe HBTs. Here, we experimentally investigate this hypothesis by characterizing the collector current ideality factor and built-in potential of a SiGe HBT vs temperature using a cryogenic probe station. The temperature dependence of the ideality factor and the relation between the built-in potential as measured by capacitance–voltage and current–voltage characteristics are in good qualitative agreement with the predictions of a theory of electrical transport across a spatially inhomogeneous junction. These observations suggest that inhomogeneities in the base–emitter junction potential may contribute to the cryogenic non-idealities. This work helps to identify the physical mechanisms limiting the cryogenic microwave noise performance of SiGe HBTs. [ABSTRACT FROM AUTHOR]

The reliability of inverse-mode silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) under dc stress and its potential impact on the performance of basic analog amplifiers are investigated. In order to properly reflect the stress effects in various circuit applications, the degradations under three different configurations (active bias, diode connection, and off state) were experimentally characterized with the stress voltages applied up to 3000 s for each case. Based on the changes in the Gummel response, the degradations in device parameters such as current gain (β), transconductance (gm), and base-to-emitter resistance (rπ) were extracted and compared with the forward-mode counterpart. In addition, with the use of a small-signal equivalent model of a SiGe HBT, simple single-stage analog amplifiers were simulated as representative examples and their circuit-level performance metrics including gain and bandwidth were studied to estimate degradation characteristics with accumulated stress. It was found that transimpedance gain decreases and operation bandwidth increases to different levels due to device degradation, whereas a voltage amplifier exhibited much less changes. [ABSTRACT FROM AUTHOR]

A fully integrated gallium arsenide (GaAs) heterojunction bipolar transistor (HBT) power amplifier (PA) for wireless local area network 802.11ax applications is presented in this paper. The structure consists of two‐stage power cells. To satisfy the high linearity requirements of IEEE 802.11ax, we analyzed the distortion of amplitude‐to‐amplitude and amplitude‐to‐phase. Due to the thermal and voltage sensitivity of GaAs HBT, an adaptive bias circuit is designed to ensure linearity. Moreover, an efficient passive output matching network is designed by analyzing the efficiency of the passive network. The design electromagnetic structure is fabricated in a 2‐μm GaAs HBT process. Under continuous wave testing, the output power reaches 27.2 dBm and the maximum efficiency of 28% at 2.4 GHz. Under the excitation of a 40 MHz 1024‐quadratic amplitude modulation signal, the output power meeting error vector magnitude of −35 dB reaches 16.8–17.2 dBm from 2.4 to 2.5 GHz. [ABSTRACT FROM AUTHOR]

Hot carrier (HC) induced degradation effects on the high-frequency characteristics of SiGe Heterojunction Bipolar Transistors (HBTs) are investigated using the TCAD tool. Simulations are carried out on a 2D structure with specific trap definitions to analyse the high-frequency figures of merit. The DC and low-frequency AC gains show similar degradation due to the generation of nonideal base current. No significant variation is observed in cut-off frequency mainly due to the minimal effect of HCs on transconductance and base emitter capacitance. However, significant degradation in maximum oscillation frequency is observed primarily because of the rise in base resistance. Finally, S parameter simulations are also carried out to investigate the hot carrier effect on RF characteristics and found that the parameters S11 and S21 are affected by HCs. [ABSTRACT FROM AUTHOR]

III–V/III-nitride p–n junctions were realized via crystal heterogeneous integration, and the resulting diodes were characterized to analyze electrical behavior and junction quality. p-type In0.53Ga0.47As, which is a well-established base layer in InP heterojunction bipolar transistor (HBT) technology, was used in combination with a homoepitaxial n-type GaN. The latter offers low dislocation density, coupled with high critical electric field and saturation velocity, which are attractive for use in future HBT collector layers. Transmission electron microscopy confirms an abrupt interface in the fabricated heterogeneous diodes. Electrical characterization of the diodes reveals a near-unity ideality factor (n ∼ 1.07) up to 145 °C, a high rectification ratio of ∼108, and a low interface trap density of 3.7 × 1012 cm−2. [ABSTRACT FROM AUTHOR]

The extraction of small‐signal parameters is of great importance for the modeling of InP heterojunction bipolar transistors (HBTs). This letter proposes an improved small‐signal parameter extraction method that considers both the emitter–collector capacitance effect and the current crowding effect. The corresponding parameter extraction procedure based on closed‐form equations is outlined. Furthermore, the model parameter extraction method is validated using two different‐sized InP HBT devices with multibias S‐parameters. The results demonstrate that the established small‐signal model exhibits greater than 90% accuracy across the frequency range of 1–110 GHz. In particular, in the high‐frequency band (above 50 GHz), the proposed model exhibits an improvement in accuracy of 7.4% after considering the emitter–collector capacitance and current crowding effects. This method can contribute to accurate modeling of the noise and large‐signal performance of InP HBT. [ABSTRACT FROM AUTHOR]

Ultrathin oxides (UOs) and ultrathin nitrides (UNs) play a crucial role in forming lattice-mismatched semiconductor heterostructures that are fabricated by using semiconducting grafting approach. The grafting approach has shown its great potential to realize GaN-based heterojunction bipolar transistors by fulfilling the missing high-performance p-type nitrides with other p-type semiconductors. A handful of UO and UN dielectrics readily available by atomic layer deposition (ALD) satisfy the requirements of double-sided surface passivation and quantum tunneling for semiconductor grafting. Due to the states existing between the UO or UN conduction band and that of the GaN, the ALD deposited UO or UN layer can generate significant effects on the surface band-bending of GaN. Understanding the band parameters of the interface between UO or UN and c-plane Ga-face GaN can guide the selection of interfacial dielectrics for grafted GaN-based devices. In this study, we performed x-ray photoelectron spectroscopy measurements to obtain the band-bending properties on c-plane, Ga-face GaN samples coated by different ALD cycles of ultrathin-HfO2 or ultrathin AlN. The valence band spectra of GaN coated with ultrathin-ALD–Al2O3, ALD–HfO2, or PEALD–AlN/ALD–Al2O3 were further analyzed to calculate the valence and conduction band offsets between the ALD dielectrics and the Ga-face GaN under different thicknesses and post-deposition annealing conditions of the dielectrics. [ABSTRACT FROM AUTHOR]

In GaAs-type materials, the primary mechanism for intra-valley scattering of low-energy electrons is their interaction with acoustic photons. These collisions are of the elastic and isotropic type, with their main effect being the nearly uniform scattering of the velocity vector of the electrons. Since the drift current in heterojunction bipolar transistors is proportional to the electric field, the contribution of the majority drift current cannot be neglected, as even a very small internal field produces a significant current when the number of carriers is very high. At the metallurgical heterojunction (x = 0), the total current is equal to the sum of the two thermionic emission components. The paper analyses the variation of the direct current of the Al0.3Ga0.7As/GaAs heterojunction, used as an emitter-base NP junction in heterojunction bipolar transistors, using the Python program. [ABSTRACT FROM AUTHOR]

In this study, we conduct a comprehensive examination of the influence of hydrogen (H2) carrier gas flux on the uniformity of epitaxial layers, specifically focusing on the InGaP single layer and the full structure of the InGaP/GaAs heterojunction bipolar transistor (HBT). The results show that an elevated flux of H2 carrier gas markedly facilitates the stabilization of layer uniformity. Optimal uniformity in epitaxial wafers is achievable at a suitable carrier gas flux. Furthermore, this study reveals a significant correlation between the uniformity of the InGaP single layer and the overall uniformity of HBT structures, indicating a consequential interdependence. [ABSTRACT FROM AUTHOR]

For single crystal diamond (SCD) to gain practical use in technical applications including solid state electronics, thin (< $1 ~\mu \text{m}$), doped epitaxial SCD layers with very low (<1 nm) surface roughness are required. Conventional SCD chemical mechanical polishing (CMP) processes are insufficient to meet the requirements of such applications because the material removal rate (MRR) is often characterized inappropriately, and the material removal uniformity is seldom considered. In this study, chemical vapor deposition (CVD) growth of two lightly boron doped (p-) epilayers was performed on 3° misoriented (100) high pressure high temperature substrates of 4.5 x $4.5 mm^{2}$ area. A subsequent 8-hour oxidative CMP process utilizing potassium permanganate and a novel self-leveling holder design decreased the average surface roughness from 3.83 nm and 1.57 nm to 0.20 nm and 0.16 nm for the two samples, respectively. MRRs were determined by evaluating five circular wear monitor structures in each sample by atomic force microscopy before and after the CMP process. The average MRRs were found to be 38.6 nm/hr and 37.3 nm/hr for the two samples. The purpose of this study is to demonstrate a CMP process suitable for polishing thin SCD epilayers to meet the needs of solid-state electronics applications. [ABSTRACT FROM AUTHOR]

In this study, the degradation characteristics of radio frequency (RF)-low-noise amplifiers (LNA) due to a total ionizing dose (TID) is investigated. As a device-under-test (DUT), sample LNAs were prepared using silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs) as core elements. The LNA was based on a cascode stage with emitter degeneration for narrowband applications. By using a simplified small-signal model of a SiGe HBT, design equations such as gain, impedance matching, and noise figure (NF) were derived for analyzing TID-induced degradations in the circuit-level performance. To study radiation effects in circuits, the SiGe-RF-LNAs fabricated in a commercial 350 nm SiGe technology were exposed to 10-keV X-rays to a total ionizing dose of up to 3 Mrad(SiO2). The TID-induced performance changes of the LNA were modeled by applying degradation to device parameters. In the modeling process, new parameter values after irradiation were estimated based on information in the literature, without direct measurements of SiGe HBTs used in the LNA chip. As a result, the relative contributions of parameters on the circuit metrics were compared, identifying dominant parameters for degradation modeling. For the TID effects on input matching (S11) and NF, the base resistance (RB) and the base-to-emitter capacitance (Cπ) of the input transistor were mostly responsible, whereas the transconductances (gm) played a key role in the output matching (S22) and gain (S21). To validate the proposed approach, it has been applied to a different LNA in the literature and the modeling results predicted the TID-induced degradations within reasonable ranges. [ABSTRACT FROM AUTHOR]

We demonstrate a highly biomimetic spiking neuron capable of fast and energy-efficient neuronal oscillation dynamics. Our simple neuron circuit is constructed using silicon–germanium heterojunction based bipolar transistors (HBTs) with nanowire structure. The HBT has a hysteresis window with steep switching characteristics and high current margin in the low voltage range, which enables a high spiking frequency (~ 245 kHz) with low energy consumption (≤ 1.37 pJ/spike). Also, gated structure achieves a stable balance in the activity of the neural system by incorporating both excitatory and inhibitory signal. Furthermore, inhibition of multiple strengths can be realized by adjusting the integration time according to the amplitude of the inhibitory signal. In addition, the spiking frequency can be tuned by mutually controlling the hysteresis window in the HBTs. These results ensure the sparse activity and homeostasis of neural networks. [ABSTRACT FROM AUTHOR]

The single-event effects (SEEs) of frequency divider circuits and the radiation tolerance of the hardened circuit are studied in this paper. Based on the experimental results of SEEs in InP HBTs, a transient current model for sensitive transistors is established, taking into account the influence of factors such as laser energy, base-collector junction voltage, and radiation position. Moreover, the SEEs of the (2:1) static frequency divider circuit with the InP DHBT process are simulated under different laser energies by adding the transient current model at sensitive nodes. The effect of the time relationship between the pulsed laser and clock signal are discussed. Changes in differential output voltage and the degradation mechanism of unhardened circuits are analyzed, which are mainly attributed to the cross-coupling effect between the transistors in the differential pair. Furthermore, the inverted output is directly connected to the input, leading to a feedback loop and causing significant logic upsets. Finally, an effective hardened method is proposed to provide redundancy and mitigate the impacts of SEEs on the divider. The simulation results demonstrate a notable improvement in the radiation tolerance of the divider. [ABSTRACT FROM AUTHOR]

In this paper, a novel wideband low noise amplifier (LNA) operating in the 9–23 GHz frequency range is presented. The proposed LNA design utilizes a combination technique consisting of pole‐tuning technique, shunt resistive‐capacitor negative feedback, and gate‐capacitive peaking technique to achieve significant bandwidth extension while maintaining acceptable overall performance. For verification, a one‐stage triple‐stacked LNA using the combination technique is designed and implemented in a 0.18‐μm SiGe BiCMOS heterojunction bipolar transistor (HBT) process. The fabricated prototype demonstrates a peak gain of 13.8 dB at 19.5 GHz, minimum noise figure of 3.1 dB at 14 GHz, 3‐dB bandwidth of 14 GHz, and a fractional bandwidth of 87.5%, while consuming a dc power of 39.6 mW. Moreover, the chip occupies a small silicon area of 0.39 mm2 including all testing pads with a core size of only 0.192 mm2. [ABSTRACT FROM AUTHOR]

We fabricated a heterojunction structure composed of n-CdS and p-C10H10N2 films. The CdS film was prepared using the CBD method, while the C10H10N2 film was prepared using the spin coating method. Later, we performed the current-voltage (I-V) measurement of this PN diode which we made using Keithley 2400 sourcemeter. As can be seen from the logI-V diagram, this heterojunction structure exhibits rectifying properties. Using traditional methods, an ideality factor (n) of 1.93 and a barrier height value (Φb) of 0.79 eV were determined. An ideality factor of more than one indicates non-ideal I-V behavior in the CdS/C10H10N2 heterojunction diode formed. The interface layer, interface states and series resistance are some of the causes of this deviation. Moreover, Cheung's functions and a modified Norde function were used to determine the diode parameters, such as ideality factor, barrier height, and series resistance. With the Cheung method, n=4.33, series resistance (RS)=168.65 kΩ and Φb=0.62 eV were found. Additionally, RS=686.08 kΩ and Φb=0.78 eV were found by the Norde method. Consistent barrier height values were found in all methods through comparison, suggesting compatibility. However, it was discovered that the series resistance values yielded by the Norde function exceeded those obtained by the Cheung functions. [ABSTRACT FROM AUTHOR]

Silicon–germanium heterojunction bipolar transistors (HBTs) are of interest as low-noise microwave amplifiers due to their competitive noise performance and low cost relative to III–V devices. The fundamental noise performance limits of HBTs are thus of interest, and several studies report that quasiballistic electron transport across the base is a mechanism leading to cryogenic non-ideal IV characteristics that affect these limits. However, this conclusion has not been rigorously tested against theoretical predictions because prior studies modeled electron transport with empirical approaches or approximate solutions of the Boltzmann equation. Here, we study non-diffusive transport in narrow-base SiGe HBTs using an exact, semi-analytic solution of the Boltzmann equation based on an asymptotic expansion approach. We find that the computed transport characteristics are inconsistent with experiments, implying that quasiballistic electron transport is unlikely to be the origin of cryogenic non-ideal IV characteristics. Our work helps to identify the mechanisms governing the lower limits of the microwave noise figure of cryogenic HBT amplifiers. [ABSTRACT FROM AUTHOR]

The intrinsic performance of "type-II" InP/GaAsSb double heterojunction bipolar transistors (DHBTs) toward and beyond THz is predicted and analyzed based on a multi-scale technology computer aided design modeling platform calibrated against experimental measurements. Two-dimensional hydrodynamic simulations are combined with 1D full-band, atomistic quantum transport calculations to shed light on future DHBT generations whose dimensions are decreased step-by-step, starting from the current device configuration. Simulations predict that a peak transit frequency fT,peak of around 1.6 THz could be reached in aggressively scaled type-II DHBTs with a total thickness of 256 nm and an emitter width WE of 37.5 nm. The corresponding breakdown voltage BVCEO is estimated to be 2.2 V. The investigations are put in perspective with two DHBT performance limiting factors, self-heating, and breakdown characteristics. [ABSTRACT FROM AUTHOR]

Transient γ-radiation and laser-simulated experiments were carried out to investigate the transient dose rate effect (TDRE) in SiGe heterojunction bipolar transistors (HBTs) for the first time. The results indicate that IBM43RF0100 SiGe HBTs experience a significant sensitivity of TDRE. For the laser-simulated experiment, the duration of transient current and charge collection are matched well with that of transient γ-radiation. The amplitude of transient photocurrent induced by the lower energy order of μJ approaches the transient photocurrent induced by transient γ-radiation. It is demonstrated that laser-simulated experiments are a candidate and a convenient method to evaluate the TDRE response of SiGe HBTs, which avoids serious electromagnetic interference in the transient γ-radiation environment. [ABSTRACT FROM AUTHOR]

Taking into consideration the inaccurate temperature predictions in traditional thermal models of power devices, we undertook a study on the temperature rise characteristics of heterojunction bipolar transistors (HBTs) with a two-dimensional cross-sectional structure including a sub-collector region. We developed a current-adjusted polynomial electro-thermal coupling model based on investigating floating heat sources. This model was developed using precise simulation data acquired from SILVACO (Santa Clara, CA, USA). Additionally, we utilized COMSOL software (version 5.6) to simulate the temperature distribution within parallel power cells, examining further impacts resulting from thermal coupling. The research findings indicate that the rise in current induces modifications in the local carrier concentration, thereby prompting variations in the local electric field, including changes in the heat source's peak location and intensity. The device's peak temperature exhibits a non-linear trend regulated by the current, revealing an error margin of less than 1.5% in the proposed current-corrected model. At higher current levels, the drift of the heat source leads to an increase in the heat dissipation path and reduces the coupling strength between parallel devices. Experiments were performed on 64 GaAs (gallium arsenide) HBT-based power cells using a QFI infrared imaging system. Compared to the traditional temperature calculation model, the proposed model increased the accuracy by 6.84%, allowing for more precise predictions of transistor peak temperatures in high-power applications. [ABSTRACT FROM AUTHOR]

RF PAs need to be reliable enough to protect them from damage under load mismatch conditions. This paper investigated the characteristics of GaAs heterojunction bipolar transistors (HBTs) under load mismatch conditions using a novel reverse wave injection technique to realize large VSWR ruggedness measurement with the circle centered at 50 Ohm and optimal impedance separately to analyze the device in real applications. With a real-time waveform measurement system, the RF voltage and current waveform information can be acquired, which provide a more-accurate view of what is occurring at the current generator plane of the HBT device. Thereby, the potential failure mechanisms and load impedance can be identified to design the most-suitable PA circuits in communication systems. [ABSTRACT FROM AUTHOR]

In this paper, an aging small-signal model for degradation prediction of microwave heterojunction bipolar transistor (HBT) S-parameters based on prior knowledge neural networks (PKNNs) is explored. A dual-extreme learning machine (D-ELM) structure with an adaptive genetic algorithm (AGA) optimization process is used to simulate the fresh S-parameters of InP HBT devices and the degradation of S-parameters after accelerated aging, respectively. In addition to the reliability parametric inputs of the original aging problem, the S-parameter degradation trend obtained from the aging small-signal equivalent circuit is used as additional information to inject into the D-ELM structure. Good agreement was achieved between measured and predicted results of the degradation of S-parameters within a frequency range of 0.1 to 40 GHz. [ABSTRACT FROM AUTHOR]

With the development and popularization of the Beidou-3 navigation satellite system (BDS-3), to ensure its unique short message function, it is necessary to integrate a radio frequency (RF) transmitting circuit with high performance in the BDS-3 terminal. As the key device in an RF transmitting circuit, the RF power amplifier (PA) largely determines the comprehensive performance of the circuit with its transmission power, efficiency, linearity, and integration. Therefore, in this paper, an L-band highly integrated PA chip compatible with 3 W and 5 W output power is designed in InGaP/GaAs heterojunction bipolar transistor (HBT) technology combined with temperature-insensitive adaptive bias technology, class-F harmonic suppression technology, analog pre-distortion technology, temperature-insensitive adaptive power detection technology, and land grid array (LGA) packaging technology. Additionally, three auxiliary platforms are proposed, dedicated to the simulation and optimization of the same type of PA designs. The simulation results show that at the supply voltage of 5 V and 3.5 V, the linear gain of the PA chip reaches 39.4 dB and 38.7 dB, respectively; the output power at 1 dB compression point (P1dB) reaches 37.5 dBm and 35.1 dBm, respectively; the saturated output power (Psat) reaches 38.2 dBm and 36.2 dBm, respectively; the power added efficiency (PAE) reaches 51.7% and 48.2%, respectively; and the higher harmonic suppression ratios are less than −62 dBc and −65 dBc, respectively. The size of the PA chip is only 6 × 4 × 1 mm3. The results also show that the PA chip has high gain, high efficiency, and high linearity under both output power conditions, which has obvious advantages over similar PA chip designs and can meet the short message function of the BDS-3 terminal in various application scenarios. [ABSTRACT FROM AUTHOR]

In this paper, we present a large-signal and switching analysis for the Heterojunction Bipolar Transistor Laser (HBTL) to reveal its optical and electrical behavior under high current injection conditions. Utilizing appropriate models for carrier transport, nonlinear optical gain, and optical confinement factor, we have simulated the large-signal response of the HBTL in relatively low and high modulation frequencies. Our results predict that for multiple quantum well (MQW) structures at low frequencies, there should not be a difference in either the carrier density or the photon density. However, the carrier concentration can be differently distributed between subsequent wells in the case of a high speed yet large-signal input. This leads to increased linewidth instead as it depends on ΔNqw. We show the effect of different structural parameters on the switching behavior by performing a switching analysis of the single quantum well and MQW structures using computationally efficient numerical methods. A set of coupled rate equations are solved to investigate the large-signal and switching behavior of MQW-HBTL. Finally, to have a comprehensive judgment about this optoelectronic device, we introduce a relative performance factor taking into account all the optoelectronic characteristics such as the output power, ac current gain, modulation bandwidth, and base threshold current, as well as turn-on time in order to design a suitable TL for optoelectronic integrated circuits. [ABSTRACT FROM AUTHOR]

This paper presents the simulation of the novel prototype of a heterojunction perovskite solar cell (PSC) based on CSGeI2Br/CSGeI3. The device consists of two absorber layers (CSGeI2Br, CSGeI3), an electron transport layer (ETL) chosen as TiO2 and a hole transport layer (HTL) given as poly(3-hexylthiophene) (P3HT). Within the simulation, the effects of thickness, doping and defect density in each absorber layer and different back contact metal electrodes on electrical parameters (efficiency, short circuit current, open circuit voltage, and fill factor) are evaluated. In addition, the contribution of the HTL (doping density and thickness), temperature, shunt and series resistance were also checked on the same electrical parameters. The simulations are conducted in standard test conditions with the irradiation normalized as 0.1 W/cm2 using the SCAPS-1D platform. The maximum efficiency obtained within the simulation of this device was about 31.86%. For this device, the thickness of the CSGeI3 layer should be around 900   nm , while that of the CsGeI2Br should be around 100   nm to facilitate optimal absorption of the incident photons. The doping density in the absorber layer is such that in CsGeI3 should be around 10 18   cm − 3 and around 10 16   cm − 3 in the CsGeI2Brlayer. The defects densities in both layers of the perovskite materials should be around 10 14   cm − 3 . Concerning the HTL, the thickness and the doping density of the P3HT should be around 50   nm and   10 18   cm − 3 , respectively. In terms of the back contact electrode, the work function of the metal should be at least equal to 5 eV, corresponding to gold (Au) metal. The series resistance due to the connection of the cell to the external load should be very small, while the shunt resistance due to the leakage current in the solar cell should be high. Furthermore, the operating temperature of the new PSC should be maintained at an ambient level of around 25 °C in order to deliver high efficiency. [ABSTRACT FROM AUTHOR]

In this study, the operation of npn-type GaN-based heterojunction bipolar transistors with different net acceptor concentrations in p-base regions was simulated. It was confirmed that there is a critical net acceptor concentration (NA-ND) depending on the thickness of the base region and that if the NA-ND is lower than the critical value, the collector current may anomalously increase, regardless of base current injection. This phenomenon is caused by the punch-through process via the depletion layer extending from the collector–base junction. The effect of the valence band energy offset at the emitter-base heterojunction (ΔEV) on the current gain (β) was also investigated, and the results showed that β peaks when ΔEV is 0.22–0.30 eV. This is determined by the balance between the hot-electron injection and thermal diffusion processes in the electron transport from the emitter to the base. [ABSTRACT FROM AUTHOR]

We present a series of TCAD analysis of gallium nitride (GaN) heterojunction bipolar transistors (HBTs) that investigates the impact of various key parameters on the gain characteristics, output characteristics, and breakdown characteristics. It has been observed that the DC gain of the AlGaN/GaN HBTs exhibits a non-linear relationship with the increase in the Al fraction. Specifically, the DC gain initially rises, then declines after reaching its peak value at approximately 7%. By optimizing the concentration of the base and the concentration and thickness of the collector epitaxial layer, it is possible to achieve devices with breakdown voltages of 1270 V (with a collector thickness of 6 μm and a carrier concentration of 2 × 1016 cm−3), specific on-resistance of 0.88 mΩ·cm2, and a current gain of 73. In addition, an investigation on breakdown characteristics is conducted for HBTs with two types of substrates, namely QV-HBTs and FV-HBTs, at different inclinations of the ramp. We propose that critical angles are 79° and 69° to prevent the surface breakdown of the device, which helps to achieve an avalanche in GaN HBTs. We anticipate that the aforementioned findings will offer valuable insights for designing GaN-based power HBTs with elevated breakdown thresholds, heightened current densities, and increased power capabilities. [ABSTRACT FROM AUTHOR]

The optical properties of GaAsN system alloys have not been clarified, particularly for the localized level around the bottom of the conduction band induced by nitrogen atoms. Herein, the recombination mechanism is systematically investigated for heavily Be-doped p-type GaAsN using both continuous-wave (CW) and time-resolved (TR) photoluminescence (PL) characteristics, which is expected to be applied to devices such as a p+-n+ tunnel diode inserted into a multijunction solar cell composed of GaAs system alloys and as the base layer of a heterojunction bipolar transistor. The S-shape characteristic weakened with increasing hole concentration (p) in the CW-PL spectra of Be-doped GaAsN. Both short and long lifetimes were evaluated using TR-PL decay curves. Specifically, the long lifetime was distributed between 0.7 and 1 ns independent of temperature and p. This long lifetime corresponds to radiative recombination lifetime from a localized level, supporting that a localized level is formed in Be-doped GaAsN despite high p on the order of 1019 cm−3. Electrons are tightly bound at a localized level, equivalent to this long lifetime, whereas the electron lifetime decreases with increasing p, resulting in the S-shape characteristic vanishing in the temperature dependence of the CW-PL spectra for ultraheavily Be-doped GaAsN with p of 5 × 1019 cm−3. Moreover, this S-shape characteristic vanished in the temperature dependence of TR-PL spectra for moderately Be-doped GaAsN with p of 8 × 1018 cm−3, indicating that the density of states is limited for a localized level. [ABSTRACT FROM AUTHOR]

This paper presents a critical and detailed overview of experimental techniques for the extraction of the thermal resistance of bipolar transistors from simple DC current/voltage measurements. More specifically, this study focuses on techniques based on a thermometer, i.e., the relation between the base-emitter voltage and the junction temperature. The theory behind the techniques is described with a unified and comprehensible nomenclature. Advantages, underlying approximations, and limitations of the methods are illustrated. The accuracy is assessed by emulating the DC measurements with PSPICE electrothermal simulations of a transistor model, applying the techniques to the simulated currents/voltages, and comparing the extracted thermal resistance data with the values obtained from the target formulation embedded in the transistor model. An InGaP/GaAs HBT and an Si/SiGe HBT for high-frequency applications are considered as case-studies. [ABSTRACT FROM AUTHOR]

In this work, the design of a wideband low-noise amplifier (LNA) using a resistive feedback network is proposed for potential multi-band sensing, communication, and radar applications. For achieving wide operational bandwidth and flat in-band characteristics simultaneously, the proposed LNA employs a variety of circuit design techniques, including a voltage–current (shunt–shunt) negative feedback configuration, inductive emitter degeneration, a main branch with an added cascode stage, and the shunt-peaking technique. The use of a feedback network and emitter degeneration provides broadened transfer characteristics for multi-octave coverage and a real impedance for input matching, respectively. In addition, the cascode stage pushes the band-limiting low-frequency pole, due to the Miller capacitance, to a higher frequency. Lastly, the shunt-peaking approach is optimized for the compensation of a gain reduction at higher frequency bands. The wideband LNA proposed in this study is fabricated using a commercial 0.13 μm silicon-germanium (SiGe) BiCMOS process, employing SiGe heterojunction bipolar transistors (HBTs) as the circuit's core active elements in the main branch. The measurement results show an operational bandwidth of 2.0–29.2 GHz, a noise figure of 4.16 dB (below 26.5 GHz, which was the measurement limit), and a total power consumption of 23.1 mW under a supply voltage of 3.3 V. Regarding the nonlinearity associated with large-signal behavior, the proposed LNA exhibits an input 1-dB compression (IP1dB) point of −5.42 dBm at 12 GHz. These performance numbers confirm the strong viability of the proposed approach in comparison with other state-of-the-art designs. [ABSTRACT FROM AUTHOR]

An analytical modeling method for heterojunction bipolar transistor (HBT) is proposed in this paper. The new neuro-space mapping (Neuro-SM) model applied to DC, small signals and large signals simultaneously consists of two mapping networks, which provide the additional degrees of freedom. Sensitivity analysis expressions are derived to accelerate the training process. When the nonlinearity of device is high, or the response of the model is complex, the weights in the proposed model are automatically adjusted to address the accuracy limitations. The proposed modeling method is verified by measured HBT examples in DC, small signals and large signals Harmonic Balance (HB) simulation. The modeling experiments of the measured HBT demonstrate that the errors of the proposed Neuro-SM model are less than 2% by matching combined DC, small-signal S-parameters and large-signal HB data, which are less than the errors of the traditional Neuro-SM model and the coarse model. The proposed analytic Neuro-SM model fits the response of the fine model well. [ABSTRACT FROM AUTHOR]

We report on a charge control analysis that relates the characteristic time constants of a three-port laser made of a quantum-well (QW) heterojunction bipolar transistor (HBT) to the electronic gain of the device. For this purpose, we take into account the linear variation of the base transport factor α with the HBT base current. Our approach enables us to obtain QW capture time, base recombination lifetime, and base transit time in terms of the experimental values of base current and of the transistor laser (TL) design parameters such as base width, QW width, and QW location. Whereas the base recombination lifetime is calculated to be a fraction of a nanosecond, the QW capture time is found to be of the order of a picosecond or less. The time constants obtained from our model are used to successfully reproduce the TL experimental optical frequency response. [ABSTRACT FROM AUTHOR]

We investigate the current gain of quantum-well heterojunction bipolar transistors (QW-HBTs) under different operation temperatures. It is experimentally shown that the introduction of a QW into the base region of HBTs results in an increasing current gain with the temperature, which is a behavior opposite to that of typical HBTs. An enhancement of current gain around 226% is observed as the temperature of QW-HBT is raised from 35 to 95 °C. This unusual trend is mainly attributed to the shorter escape time of electrons in the QW at the higher temperature. A modified charge-control model based on thermionic emissions of electrons in the QW region is constructed to model this temperature-dependent phenomenon, and the result agrees well with our experimental observations. [ABSTRACT FROM AUTHOR]

We present an analytic band-to-trap tunneling model based on the open boundary scattering approach. The new model has three major advantages: (i) It includes not only the well-known electric field effect, but more importantly, the effect of heterojunction band offset. This feature allows us to simulate both electric field and band offset enhanced carrier recombination near a heterojunction in heterostructures. (ii) Its analytic form enables straightforward implementation into a parallel Technology Computer Aided Design device and circuit simulators. (iii) The developed method can be used for any potentials which can be approximated to a good degree such that the Schrödinger equation with open boundary conditions results in piecewise analytic wave functions. Simulation results of an InGaP/GaAs heterojunction bipolar transistor (HBT) reveal that the proposed model predicts significantly increased base currents, because the tunneling of holes in the base to traps in the emitter is greatly enhanced by the emitter-base band offset. This finding, which is not captured by existing band-to-trap tunneling models, is consistent with the experimental observation for an InGaP/GaAs HBT after neutron irradiation. [ABSTRACT FROM AUTHOR]

In this paper, the effects of different factors, including the heavy ions striking location, incident angle, linear energy transfer (LET) value, projected range, ambient temperature and bias state, on the single event transient introduced by heavy ions irradiation in the SiGe heterojunction bipolar transistor (HBT) were investigated by the TCAD simulation. The results show that the current transient peak value, collected charge and carrier type of each terminal are changed by the striking location, incident angle and bias state. The current transient peak value and collected charge increase with the LET value, while they decrease with the ambient temperature. When heavy ions vertically irradiate the collector and substrate, the current transient peak value and collected charge increase with the projected range; therefore, the species of heavy ions should be considered in studying the single event effects of the SiGe HBT induced by heavy ions irradiation. The microphysical mechanism of these factors influencing the single event effects of the SiGe HBT is discussed in this work. [ABSTRACT FROM AUTHOR]

Basing our findings on our previous pulsed laser testing results, we have experimentally demonstrated that there is an inflection point of a single event transient (SET) in the silicon-germanium heterojunction bipolar transistors (SiGe HBTs) with a decreasing temperature from +20 °C to −180 °C. Additionally, the changes in the parasitic resistivity of the carrier collection pathway due to incomplete ionization could play a key role. In this paper, we found that the incident-heavy ion's parameters could also have an important impact on the SET inflection point by introducing the ion track structures generated by Geant4 simulation to the TCAD transient simulation. Heavy ion with a low linear energy transfer (LET) will not trigger the ion shunt effect of SiGe HBT and the inflection point will not occur until −200 °C. For high LET ions' incidence, the high-density electron-hole pairs (EHPs) could significantly affect the parasitic resistivity on the pathway and lead to an earlier inflection point. The present results and methods could provide a new reference for the effective evaluation of single-event effects in bipolar transistors and circuits at cryogenic temperatures and provide new evidence of the SiGe technology's potential for applications in extreme cryogenic environments. [ABSTRACT FROM AUTHOR]

This letter presents the architecture and characterization of a Doherty power amplifier (DPA) with a simplified out‐of‐phase power splitter (SOPPS) for fifth‐generation (5G) small‐cell applications. The proposed SOPPS consists of two passive components, which is conducive to chip miniaturization. Additionally, a stable DPA architecture is employed to avoid oscillation caused by out‐of‐phase ports imbalance. A DPA based on gallium arsenide (GaAs) heterojunction bipolar transistor (HBT) technology is fabricated, achieving high gain of 32 dB over 2.5 to 2.7 GHz. Using a continuous‐wave signal, the DPA exhibits a saturation output power of 36 dBm, with a peak power‐added efficiency (PAE) of 42.3% and 37% at saturation and 6‐dB power‐back‐off, respectively, across the operating band. [ABSTRACT FROM AUTHOR]

Heterojunction bipolar transistors (HBTs) with GaAs0.825P0.175 bases and collectors and In0.40Ga0.60P emitters were integrated monolithically onto Si substrates. The HBT structures were grown epitaxially on Si via metalorganic chemical vapor deposition, using SiGe compositionally graded buffers to accommodate the lattice mismatch while maintaining threading dislocation density at an acceptable level (∼3 × 106 cm−2). GaAs0.825P0.175 is used as an active material instead of GaAs because of its higher bandgap (increased breakdown voltage) and closer lattice constant to Si. Misfit dislocation density in the active device layers, measured by electron-beam-induced current, was reduced by making iterative changes to the epitaxial structure. This optimized process culminated in a GaAs0.825P0.175/In0.40Ga0.60P HBT grown on Si with a DC current gain of 156. By considering the various GaAsP/InGaP HBTs grown on Si substrates alongside several control devices grown on GaAs substrates, a wide range of threading dislocation densities and misfit dislocation densities in the active layers could be correlated with HBT current gain. The effect of threading dislocations on current gain was moderated by the reduction in minority carrier lifetime in the base region, in agreement with existing models for GaAs light-emitting diodes and photovoltaic cells. Current gain was shown to be extremely sensitive to misfit dislocations in the active layers of the HBT—much more sensitive than to threading dislocations. We develop a model for this relationship where increased base current is mediated by Fermi level pinning near misfit dislocations. [ABSTRACT FROM AUTHOR]

In this work, the numerical simulation of a SiGe heterojunction bipolar transistor (HBT) for DC and AC performance operating at cryogenic temperature with a hydrodynamic carrier transport model is analyzed. A new modified temperature-dependent Si1−xGex energy bandgap model was used. Using a simplified 2D TCAD design structure, the device characteristics on 55 nm SiGe HBT technology and the mobility model are calibrated with experimental data. Base current reversal due to induced impact-ionization at the collector-base junction is analyzed, where the estimated collector-emitter breakdown voltage with the base open (BVCEO) is 1.48 V at 300 K. This reveals good voltage handling ability. At cryogenic temperatures, dopant incomplete ionization in the lightly doped collector region shows a 28% decrease in ionized dopant concentration at 50 K; this affects the base-collector depletion capacitance. The emitter electron barrier tunneling leakage on collector current is studied using a non-local e-barrier tunneling model at different temperatures that shows an improvement in peak DC gain at lower temperatures. Using the small-signal ac analysis, the cut-off frequency and the maximum oscillation frequency are extracted for high-frequency application, and the base widening effect is discussed. A comparison of this work with measured data on 90 nm SiGe HBT is also discussed in brief, which shows improvements in the simulated structure. [ABSTRACT FROM AUTHOR]

Quantum key distribution (QKD) has rapidly developed recently. The repetition frequency of the QKD system increases from tens or hundreds of MHz to GHz. A laser diode (LD) operating in gain-switched mode is widely used as a weak coherent light source in a QKD system. We present an LD driver circuit fabricated in 0.18 μm SiGe heterojunction bipolar transistor bipolar complementary metal oxide semiconductor technology. The circuit can operate at frequencies up to 2.5 GHz, satisfying the requirements of high-speed laser drives in practical QKD systems. The output current of the driver circuit can reach 100 mA when driving an LD whose input equivalent resistance is ∼21 Ω. The extinction ratio of the 1550-nm distributed feedback LD light source driven by our driver circuit reaches 23 dB at the operating frequency of 2.5 GHz, meeting the requirements of QKD systems. This circuit will be used in miniaturized QKD systems. [ABSTRACT FROM AUTHOR]

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A planar-type metal-semiconductor-metal (MSM) hydrogen sensor forming on the collector layer was employed as an extended base (EB) of the InGaP-GaAs heterojunction bipolar transistors (HBTs). Then, hydrogen sensing transistors integrated were proposed and studied. After introducing sensing properties of the EB-hydrogen sensor, various sensing current gains defined were addressed for our hydrogen sensing transistor. Instead of the base current, N 2 and/or hydrogen-containing gases were used as a parameter while measuring common-emitter characteristics of the hydrogen sensing transistor at various temperatures. Experimental results show that maximum sensing base current gains in 1% H 2 /N 2 is 330 at 25 °C while it is enhanced to 1800 at 50 °C, then to 2300 at 80 °C, and finally to 2800 at 110 °C. In contrast, a peak sensing collector current gain is as high as 1.2 × 105 (4.3 × 104) in 1% (0.01%) at 110 °C. In addition, response times obtained from the sensing diode (base) and collector currents in 0.01% H 2 /N 2 are 485 (490) and 745 s at 25 °C. Together with important features including one power supply and low-power consumption, the proposed hydrogen sensing transistor is very promising for applications in detecting hydrogen. • Bipolar-type hydrogen sensing transistors with an extended base are reported. • A sensing current gain over 105 is achieved for the hydrogen sensing transistor. • A standby power consumption <2 μW is achieved by the hydrogen sensing transistor. [ABSTRACT FROM AUTHOR]

This letter presents a $D$ -band low-noise amplifier (LNA) in 250-nm InP HBT technology for the next-generation wireless applications. The LNA has a measured peak gain of 13 dB, a 3-dB bandwidth greater than 20 GHz (120–140 GHz), and a measured noise figure (NF) of less than 6 dB in the band. A reduction in the 3-dB bandwidth from simulation was observed during the measurements which was attributed to the substrate waves using full chip electromagnetic (EM) simulation. EM simulations show that a partial or complete removal of the back side metallization of the InP substrate, holes in metal-1 ground plane, or a strategic placement of through-substrate vias suppress these substrate waves. To the authors’ knowledge, this is the first 120–140-GHz LNA in the InP 250-nm HBT technology. [ABSTRACT FROM AUTHOR]

In this paper, a design methodology for a fully integrated impedance-transforming multi-winding 90° coupler is proposed. The oper- ation of the proposed coupler was verified using measurement results. These couplers were fabricated using the WIN semiconductor InGaP/GaAs heterojunction bipolar transistor (HBT) process. To provide an impedance transformation, the proposed couplers were de- signed with 3, 4 and 5 turn coils for 50-, 75-, and 100-Ω impedance transformations, respectively. The center frequencies of each coupler were 5.5, 3.33, and 2.47 GHz. Two copper metal layers were combined together with a via to attain a high Q factor, and its improve- ment was analyzed. The measurement results show that the insertion losses of the proposed couplers are less than 0.37 dB and phase imbalances are less than 2.74°. [ABSTRACT FROM AUTHOR]

Oxide-based electronics have found applications ranging from medical implantable devices to low-cost solar panels and large area displays; however, fabricated circuits and devices have been limited to passive elements and at most PN junctions for sensor and photovoltaic applications. Fabricating active elements, i.e., transistors, with the same materials and techniques would usher in considerable advancement in capabilities and usage. Here the successful fabrication of a metal oxide double heterojunction bipolar transistor (DHBT) using p-CuO/n-Si/p-CuO hetero-structure is reported as the first step toward all oxide transistors in the future. CuO was deposited by sputtering on both sides of a 15 μm thick n-type Si layer and connections were made to three layers separately. IV characteristics of the PNP transistor were then obtained which exhibited a current amplification factor of about 30. A relatively large leakage current at the base–collector junction was present and was consequently remedied by annealing. The leakage was dependent on the deposition conditions of CuO over Si. Oxide semiconductors are either p or n-type making fabrication devoid of doping steps and ion implantation, which greatly simplifies the manufacturing process. [ABSTRACT FROM AUTHOR]

Purpose: High-speed Indium Phosphide (InP) HBTs have been widely used to design high-speed analog, digital and mixed-signal integrated circuits. The purpose of this study is to propose a new parameter extraction procedure for determining an improved T-topology small-signal equivalent circuit of InP heterojunction bipolar transistors (HBTs). Design/methodology/approach: The alternating current crowding effect is considered through adding the intrinsic base capacitance in the small-signal equivalent circuit. All of the circuit parameters are extracted directly without using any approximation. Findings: The extraction technique is more easily understood and clearer than other extraction methods, as the equations are derived from the S-parameters by peeling peripheral elements from small-signal models to get reduced ones and extracting each equivalent-circuit parameter using each equation. Originality/value: To validate the presented parameter extraction technology, an n-p-n emitter-up InP HBT was analyzed adopting the method. Excellent agreement between measured and modeled S-parameters is obtained up to 40 GHz. [ABSTRACT FROM AUTHOR]

In this article, the design and the development of ultra-wideband UWB branch-line couplers BLCs with a novel method to control the coupling imbalance is proposed. The proposed UWB BLC is suitable for the 5G low-noise amplifier (LNA) design. UWB 4-branch BLC is designed using design curves developed using even and odd mode analyses to cover the 5G (3.3-5 GHz) frequency bands. The vertical branches of the UWB BLC are replaced by modified ones, and their effect on the coupling imbalance is investigated. The proposed BLC occupies an area of 33.9×15.7 mm2. Both conventional and modified BLC are fabricated, and their measured Sparameters are compared with analytical and simulated models. Based on the balanced amplifier topology, a 5G UWB low-noise amplifier is designed. The proposed BLCs and the MGF3022AM InGaP-HBT (Heterojunction Bipolar Transistor) are used to produce acceptable UWB performance. The balanced amplifier return loss, noise figure, and gain are investigated as BLCs coupling imbalance varies. The ultra-wideband LNA exhibits an acceptable small-signal gain, noise figure, input return loss, and output return loss across the 5G different frequency bands. [ABSTRACT FROM AUTHOR]

A high data rate RF-DAC and a power detector (PD) are designed and fabricated in a 250 nm indium phosphide (InP) double heterojunction bipolar transistor (DHBT) technology. A communication link using the Tx-Rx over polymer microwave fiber (PMF) is measured. The link consists of a pulse amplitude modulation (PAM) modulator and a PD as a demodulator, as well as a one-meter-long dielectric waveguide. The working frequency range of the complete link is verified to be 110–150 GHz. The peak output power of the PAM modulator is 5 dBm, and it has a −3 dB bandwidth of 43 GHz. The PD consists of a parallel connected common emitter configured transistor and a common base configured transistor to suppress the odd-order harmonics at the PD's output, as well as a stacked transistor to amplify the output signal. Tx and Rx chips, including pads, occupy a total area of only 0.83 mm2. The PMF link can support a PAM-4 signal with 22 Gbps data transmission, and a PAM-2 signal with 30 Gbps data transmission, with a bit error rate (BER) of <10−12, with demodulation performed in real time. Furthermore, the energy efficiency for the link (Tx + Rx) is 4.1 pJ/bit, using digital data input and receiving PAM-2 output (5.6 pJ/bit for PAM-4). [ABSTRACT FROM AUTHOR]

A very detailed investigation of high-speed silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs) showed an underestimation of the measured peak cutoff frequency by simulations with a hydrodynamic (HD) model. It was speculated that this might be due to a breakdown of the HD approximation or unknown additional mechanical stress. We repeated those simulations with the more fundamental Boltzmann transport equation (BTE) based on the same device model (doping profiles, 2-D geometry, parasitics, and so on) and obtained almost similar results showing that this failure was not due to a breakdown of the HD approximation. Since additional uniaxial stress along the direction of the lateral base has been shown to increase the cutoff frequency, we investigated this effect. We found by 2-D device simulations that the increase in the peak cutoff frequency is rather small, and at high stress levels, it even decreases, if the uniaxial stress is applied homogenously. This is due to the reduction of the conductivity of the highly doped collector layer by the stress. If the stress is limited to the intrinsic transistor, the increase in the cutoff frequency is monotonic with growing stress. On the other hand, the collector current for a given base–emitter voltage also increases with stress leading to an overestimation of the collector current compared with the measurements. If this increase is corrected by a slight decrease in the germanium profile, the gain in the peak cutoff frequency is lost. Thus, the underestimation of the peak cutoff frequency cannot be explained by an additional homogeneous uniaxial stress in the intrinsic transistor. [ABSTRACT FROM AUTHOR]

The effect of InGaAsP and InGaAs cap layers in InP n-p-n heterojunction bipolar transistor (HBT) is presented. The common figures of merit (FOM) in each case are compared to assess their potentials for operation at high frequency. The Gummel-Poon plot of experimental reported result has been used to validate the data obtained from simulation using ATLAS module of Silvaco software tool. After models validation in TCAD tool, the DC and RF characteristics of the HBTs with different cap layers are examined and then a comparative analysis is carried out based on the characteristics such as I–V behaviour, frequency response, minimum noise figure and maximum cut-off frequency. With the change in InGaAs cap to InGaAsP cap, the DC current gain increases from 255 to 300, VCE,offset is reduced from 131 to 76 mV, Early Voltage (VA) increases from −42 to −190 V, cut-off frequency ft is increased from 24.34 MHz to 8.04 GHz, and the maximum oscillation of frequency(fmax) is improves from 13.79 to 37.11 GHz [ABSTRACT FROM AUTHOR]

It is well known that synthetic heterojunction photocatalysts can promote photocatalytic activity. Herein, we successfully combine UiO-66 with g -C3N4 as ultrathin layer coating via a convenient synthesis method, the photocatalytic performance through the degradation of RhB is then shown efficient. The heterojunction and high surface area give the photocatalysts an ability to promote visible light absorption and strengthen the separation and migration of photogenerated electrons, which ultimately leads to the improvement of photocatalytic degradation. The heterostructure nanocatalyst helps the degradation rate of RhB reach 98.98% in 140 min under visible light irradiation. In addition, the hole (h + ) plays a major role in the reaction. This work offers an efficient method for the application in the field of environmental degradation. [ABSTRACT FROM AUTHOR]