Search

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]

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]

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]

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]

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]

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]

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]

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]

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]

This paper presents a comprehensive overview of nonlinear thermal effects in bipolar transistors under static conditions. The influence of these effects on the thermal resistance is theoretically explained and analytically modeled using the single-semiconductor assumption. A detailed review of experimental techniques to extract the thermal resistance as a function of backside temperature and/or dissipated power from DC measurements is provided; advantages, underlying approximations, and limitations of all methods are clarified, and guidelines for their correct application are given. Accurate FEM thermal simulations of an InGaP/GaAs and a Si/SiGe HBT are performed to verify the accuracy of the single-semiconductor theory. The thermal resistance formulations employed in the most popular compact bipolar transistor models for circuit simulators are investigated, and it is found that they do not properly describe nonlinear thermal effects. Alternative implementations of the more accurate single-semiconductor theory are then proposed for the future versions of the compact models. [ABSTRACT FROM AUTHOR]

Many different methods have been proposed in the literature for the extraction of the thermal resistance of heterojunction bipolar transistors (HBTs). This review presents a detailed evaluation and discussion of several widely used methods. Special emphasis is put on a generalized analysis of the underlying assumptions, suitable operating point range, and necessary measurement effort of each method. The accuracy of each method is determined by applying it to data based on circuit simulations of advanced SiGe and III-V HBT technologies. Experimental data from those technologies are used to highlight practical issues. A guideline for the selection of the most suitable method in practice is also given. [ABSTRACT FROM AUTHOR]

An efficient, broadband SiGe HBT cascode nonuniform distributed power amplifier (NDPA) is presented for low-cost, fully integrated Si-based phased arrays. Optimum load impedances at each SiGe HBT cascode in a four-stage NDPA core are obtained by scaling the characteristic impedance ($Z_{0}$) of the collector transmission lines (TLs) and tapering the SiGe HBT emitter area simultaneously. A novel compact, lumped-element two-section $\lambda $ /4 output impedance transformer (OIT) is proposed to lower the NDPA load impedance ($Z_{L}$) from 50 to 25 $\Omega $ over more than one decade bandwidth (BW). Each $\lambda $ /4 impedance transformer is realized by four cascaded CLC $\pi $ -networks integrated into a single three-turn symmetric inductor in order to achieve compact size, high passive efficiency, and high LC cutoff frequency ($f_{c}$). The systematic design approach of a lumped-element $\lambda $ /4 impedance transformer with an arbitrary $Z_{0}$ is described in detail. The prototype NDPA was fabricated in 0.13- $\mu \text{m}$ SiGe HBT BiCMOS technology. The proposed SiGe HBT cascode NDPA supports both high linearity (HL) and high gain (HG) modes, each suited to a specific application. The NDPA attains a peak power gain of 10.3/12.5 dB, a saturated output power ($P_{\mathrm {out}}$) of 21.3/21.5 dBm, and a power added efficiency (PAE) of 12.2%/12.5%–21.6%/22.0% for HL/HG modes, with a 3-dB BW from 1.5 to 24.0 GHz. The NDPA delivers 13.0-dBm average $P_{\mathrm {out}}$ with a PAE of 10.0% at 6-Gbit/s data rate 64 QAM modulation. [ABSTRACT FROM AUTHOR]

In this paper, the thermal stability of GaAs heterojunction bipolar transistor (HBT) power amplifier (PA) in a sub-6G band has been improved by a multi-source co-simulation method. To reduce the parameter errors caused by the variations of thermal resistances, a co-simulation method for the multiple heat sources of fully-integrated PA is proposed. Specifically, an adjustable bias circuit is applied on the PA for temperature compensation using a zero-to-absolute-temperature (ZTAT) current. To verify the proposed method, a sub-6G PA is realized in the GaAs HBT process. The experimental results show that the variations in power added efficiency and output power is stabilized due to the 3.5% error ZTAT current. The errors between simulation and measurement are reduced from 6% to 1%. According to the thermal factor defined in co-simulation, the working temperature decreases 10 °C, while the area only increases 27%. The above results prove that that thermal stability and the simulation reliability can be co-designed with the minimal area cost. [ABSTRACT FROM AUTHOR]

This article presents an orthogonal load-modulated balanced amplifier designed to mitigate the effects of the load mismatch on the power-added efficiency and output power of the amplifier. This is achieved by electronically adjusting the ratio between the two input signals of the power amplifier (PA) (in phase and amplitude) and the reactive termination at the output nominally isolated port. The mode of operation of the PA is described using a theoretical analysis that highlights the role of the different tuning parameters and is confirmed by simulations using a simplified transistor model. The design and characterization under load mismatch of a prototype PA, working in the 1.6–3.2 GHz band are described and the experimental results compared to those of an analogous balanced PA, where it is shown that the orthogonal balanced amplifier is able to increase substantially the mismatch region on which a given target performance is achieved. [ABSTRACT FROM AUTHOR]

The manufacturing technology for heterojunction bipolar transistor (HBT) is different from the one used for bipolar silicon junction transistor (BJT). The base in case of BJT is manufactured by using diffusion and the diffusion laws determine a Gaussian type of profile in the base. HBT devices are manufactured using molecular epitaxy which gives a contact doping profile. In case of HBT, producing an internal field by using uniform doping is no more possible. This is the reason why was used in the gradation of the molar composition. The Analysis using Octave soft was made for the transit time through the base of the drift HBT transistors type GaAs/AlxGa1-xAs. [ABSTRACT FROM AUTHOR]

In this paper, the dynamic response of the optical gain of optical integrated device composed of a heterojunction bipolar transistor (HBT) and a laser diode (LD) has been numerically analyzed. This type of optical integrated device is called transistor laser (TL). First, the rate equation of LD has been solved to obtain its transfer function. Second, the overall transfer function of the whole structure has been analyzed numerically. The effect of HBT cutoff frequency on the amplitude and phase frequency response has been studied. The obtained results show that HBT has a strong influence on the device performance. In particular, higher values of HBT cutoff frequency result in lower amplitudes and higher phase values in the low-frequency range. The device is stable and has a fast response and high optical gain at higher frequencies. Therefore, it can be used as an optical amplifier or optical switch in high-speed optical systems. [ABSTRACT FROM AUTHOR]

Keywords: C-ring; InP-HEMT; switch; terahertz meta-chip EN C-ring InP-HEMT switch terahertz meta-chip 2037 2044 8 05/12/22 20220401 NES 220401 1 Introduction Terahertz has wide applications in the next-generation communication, radar and imaging systems because of its high frequency and wide bandwidth [[1]], [[2]], [[3]], [[4]]. From the view point of traditional radio-frequency circuit, terahertz switch can be realized by using high-performance active materials such as InP, GaAs et al. and impedance matching technology [[12]], [[13]], [[14]], [[15]], [[16]]. For example, Thome F et al. realized a single-pole-double-throw (SPDT) switch operating at 122-330 GHz by four GaAs-HEMT, the average insertion loss and switching ratio was 2.2 and 17.4 dB, respectively [[12]]. [Extracted from the article]

The degradation characteristics of silicon-germanium heterojunction bipolar transistors (SiGe HBTs) under different bias modes (forward, cutoff and saturation) during irradiation were reported after multiple pulsed neutron-gamma irradiation at room temperature. The radiation-sensitive parameters of the test samples, including base current IB, collector current IC and DC current gain $\beta $ , were measured and compared before and after every reactor n- $\gamma $ pulse irradiation. The test results show that IB increased with increasing fluence, and IC slightly increased in the low base-emitter voltage VBE region (approximately from 0.4 V to 0.5 V) and decreased in the high-VBE region (approximately VBE >0.5 V). Moreover, the degradation degree of the test samples was different under different bias conditions. The performance of the test samples under cutoff bias mode displayed the most serious degradation, while those under forward bias mode suffered minimum damage. Meanwhile, the time-dependent annealing characteristics of the DC current gain for SiGe HBTs at various bias conditions were compared and analyzed.

This work describes the development of an amplifier frequency doubler chain (AFDC) operating at around 300 GHz based on SiGe BiCMOS technology. The driver amplifier is based on the differential cascode configuration, which employs coupled-line transformers for compact design. The frequency doubler is based on the class-B topology, which is known for exhibiting a large output power with low DC power consumption. The integrated AFDC, which consists of the frequency doubler and the preceding driver amplifier, exhibited a measured peak output power and DC-to-RF efficiency of -0.9 dBm and 0.97%, respectively, along with a conversion gain of -0.1 dB. It operates from 284 to 328 GHz with a 0-dBm input signal, consuming a total DC power of only 84 mW. The chip size is 720 x 310 µm², excluding RF and DC pads. [ABSTRACT FROM AUTHOR]

This brief presents a wideband, low insertion loss, high attenuation range digital step attenuator (DSA) implemented using SiGe HBTs. In a switched-type topology, the off-state capacitances ($\text{C}_{OFF}$) in both reference and attenuation states cause different poles and zeros, which trigger amplitude and phase errors and limit the operating bandwidth. To achieve wide bandwidth, methods to relocate poles and zeros to the highest possible frequencies in both states are investigated. In the reference state, minimizing the size of the shunt switching transistors extends the bandwidth. In the attenuation state, switching in a capacitor at the base of an anti-parallel (AP) SiGe HBT pair series switch reduces the effective $\text{C}_{OFF}$ , enhancing the bandwidth. The proposed techniques facilitate the realization of a 16-dB attenuator cell to support wide bandwidth and offer lower insertion loss than conventional cascaded 8-dB cell designs. Fabricated in 130-nm SiGe BiCMOS technology, the proposed DSA with an attenuation range of 31.5 dB in 0.5 dB steps operates from DC to 67 GHz and achieves an insertion loss lower than 7.8 dB. The RMS amplitude error is less than 0.4 dB above 1 GHz, while the RMS phase variation is less than 13.1°. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive analysis of the terahertz (THz) rectification process with modern high-speed silicon–germanium (SiGe) heterojunction bipolar transistor (HBT) devices to enable low-power and close-to-optimum detector sensitivity in a near-THz fractional bandwidth. The influence of all major device internal parasitics on the detector responsivity and noise equivalent power (NEP) is analyzed in detail as a function of the device bias point and the operating frequency. By analogy to the cold MOSFET operation, the fundamentals of the detector operating in weak and deep saturation are studied and compared with the forward-active region, indicating its potentially superior NEP performance with a suitable readout path. The antenna’s broadband radio frequency (RF) power coupling aspects are further elaborated and related to the device bias conditions to maximize the internal base–emitter driving voltage. A set of single- and dual-polarized antenna-coupled detectors with close-to-optimum detector operation in a near-THz fractional bandwidth and a state-of-the-art optical performance was implemented in a 0.13- $\mu \text{m}$ SiGe HBT technology with $f_{t}/f_{\text {max}}$ of 350/550 GHz and extensively characterized across 200–1000 GHz to support the underlying analysis. For the forward-active operation, the following maximum optical current responsivity and minimum optical NEP values have been demonstrated: 5 A/W, 1.9 pW/ $\sqrt {\text {Hz}}$ at 300 GHz and 0.65 A/W, 19 pW/ $\sqrt {\text {Hz}}$ at 900 GHz. The corresponding NEP values for deep saturation (with unbiased collector) are 5.1 pW/ $\sqrt {\text {Hz}}$ and 45 pW/ $\sqrt {\text {Hz}}$ but they are largely limited by the noise floor of the consecutive external amplifier. [ABSTRACT FROM AUTHOR]

The article presents a monostatic $D$ -band frequency-modulated continuous-wave (FMCW) radar based on a fully integrated monostatic single-channel silicon-germanium (SiGe) transceiver (TRX) chip. The chip is fabricated in Infineon’s bipolar-complementary metal–oxide–semiconductor (BiCMOS) production technology B11HFC which offers heterojunction bipolar transistors (HBTs) with an $f_{\mathrm {T}}/f_{\mathrm {max}}$ of 250 GHz/370 GHz. The monolithic microwave integrated circuits (MMICs) output signal is coupled by a fully differential substrate integrated waveguide (SIW) based coupling network. The output power at the WR-6.5 antenna flange is more than −10 dBm over a bandwidth of 37.5 GHz. For a sweep within a single-loop phase-locked loop (PLL) circuit from 174.5 to 121.5 GHz, a spatial resolution of almost 3 mm with a metallic plate as the target is achieved. The radar provides a small form factor of $2 \times 4 \times 5$ cm3 and low power consumption of 2.2 W at 5 V. Finally, the capabilities of the sensor for non-destructive testing (NDT) are demonstrated using a millimeter scanner. With radar imaging, it was possible to measure the orientation of the fiber layers up to a depth of 7.03 mm. [ABSTRACT FROM AUTHOR]

This paper presents an analytical model of an infrared thermal imaging device. This device is composed of a Quantum Well Infrared Photodetector (QWIP), a Heterojunction Bipolar transistor (HBT) and a Light Emitting Diode (LED). It is called as QWIP-HBT-LED Optoelectronic Integrated Device. The device is modeled based on its equivalent circuit by considering a nonlinear gain HBT, early effect. Analytical expressions describing the current time response, rise time, and output derivative as a measure of device speed have been derived. The numerical results show that the transient performance of this device version is enhanced by the injected current from QWIP to the base of HBT, also the output current is increased with the increase of the gain and early coefficient of HBT, on the other hand, it degrades when the base recombination factor of HBT or the load resistance is increased. Also, the rise time increases when the current gain or the early coefficient is increased. This type of models can be exploited as a pixel in thermal image processing applications. [ABSTRACT FROM AUTHOR]

A hydrogen sensing transistor fabricated by a heterojunction bipolar transistor (HBT) with an extended base (EB) formed by a metal–semiconductor–metal (MSM) hydrogen sensor is reported. The power consumption in stand‐by mode is smaller than 2 µW. Common‐emitter characteristics show that the sensing base (collector) current gains at 25°C in 0.01%, 0.1%, and 1% H2/N2 are as high as 75 (512), 134, (977), and 233 (2.89 × 103), respectively. Low‐power consumption and high‐sensitive gains are indicative that our HBT together with planar‐type MSM sensor is very promising for applications to hydrogen sensing transistors using one voltage source. [ABSTRACT FROM AUTHOR]

In this article, we demonstrate the Ti/TiN/Al (15/50/50 nm) ohmic contact on InGaP/GaAs heterojunction bipolar transistors (HBTs) epitaxially grown on 200-mm Si substrate. We study the rapid thermal annealing (RTA) effect of the metal stack on both n-type InGaAs and p-type GaAs. The dc characteristics of the HBT devices fabricated using the Ti/TiN/Al metal contacts have been analyzed. Contact resistances ${(}{R}_{c}{)} < 0.1~\Omega \cdot $ mm for n-InGaAs and $0.8~\Omega \cdot $ mm for p-GaAs can be achieved. A dc current gain of 45 with a collector–base breakdown voltage (BVcbo) of 15.65 V is achieved. The ideality factor of the emitter–base current (${n}_{b}$) and base–collector current (${n}_{c}$) is 1.03 and 1.44, respectively, after RTA at 450 °C. The dc characteristics remain stable upon prolonged annealing at 450 °C for 45 min. This high thermal budget non-gold ohmic contact is suitable for Si-CMOS integration and enables the potential for hybrid III-V CMOS technology for 5G and mm-wave applications. [ABSTRACT FROM AUTHOR]

The measurement of the figures of merit (FOMs) of an advanced and miniaturized transistor becomes a challenge when its ${f}_{\text {MAX}}$ goes above many hundreds of GHz. In fact, the quantities to be measured become smaller and smaller and thus the influence of the measurement environment becomes less and less negligible. Indeed, when measuring the same test structures using two different renowned commercial probes having a different topology, a “signature” of each probe can been observed, in particular, when plotting $\sqrt {U} \times \text {freq}$ (${U}$ is the Mason gain) as a function of frequency, which is usually carried out for ${f}_{\text {MAX}}$ estimation. For millimeter wave (mmW) technologies, ${f}_{\text {MAX}}$ is the key FOM for benchmarking technologies, thus it becomes urgent to clarify this measurement. In this work, we give a proof that measurement becomes probe dependent. We constructed an accurate electromagnetic (EM) model of each probe using X-ray tomography and thus simulated the measurement environment at close proximity of the wafer using EM and SPICE simulation. Hence, each signature of the probe is clearly reproduced by the simulation, highlighting that the unexpected result is not due to an inaccuracy done by the user such as probe positioning or to a limitation of the vector network analyzer (VNA) but is the result of the unwanted coupling between the probe and the substrate or between probes and the inability of the short open load thru (SOLT) and on-wafer thru reflect line (TRL) calibration algorithms to completely remove these couplings. [ABSTRACT FROM AUTHOR]

This paper analyzes the single event transient (SET) response of low noise amplifier (LNA) designed using SiGe heterojunction bipolar transistors (HBT). To verify the radiation tolerance of the proposed LNA, a total of four cascode configurations were designed. Comprehensive mixed-mode simulations were performed to evaluate the SET susceptibility of considered LNA cascode configurations, and we have analyzed how the strike parameters affect their output response. In this fact the strike position, linear energy transfer (LET), and track radius, were varied, and the resulting transients were compared for the different LNA configurations. Through this study, the potential capability of the inverse mode SiGe heterojunction bipolar transistor (HBT) in LNA radiation tolerance was confirmed for various strike operating conditions. It has been demonstrated that the single event sensitivity was reduced for LNA employing inverse mode SiGe HBT for strike device. The strike influence on the different LNA configurations response depends on strike LET, where a reduced SET variation is observed for high LET. [ABSTRACT FROM AUTHOR]

An accurate and efficient algorithm is presented, which allows deriving the structure function of a discretized 3-D heat conduction problem. In this approach, the partial thermal conductances and capacitances in the structure function are computed in terms of weighted spatial averages of thermal resistivity and volumetric heat capacity. As a result, the exact influence of all materials and geometric details on each part of the structure function is determined. The approach is validated on a state-of-the-art SiGe heterojunction bipolar transistor (HBT) for high-frequency applications. [ABSTRACT FROM AUTHOR]

The emitter contact in bipolar transistors with polysilicon emitters has been characterized based on an improved open-collector (OC) method, which allows extraction of the nonlinear I-V characteristics of the resistance presented by the poly-/monocrystalline emitter interface. The nonlinear characteristics of the interfacial polysilicon-emitter resistance at low currents are modeled using an approximate rectangular-barrier tunnel junction model to extract an upperbound estimate for the thickness of the oxide layer at the poly-/monocrystalline contact. Having verified that the extracted data based on the improved OC method are consistent with the first-principles rectangular tunnel junction model, a data-driven model accounting for the bias-dependence of the emitter series resistance is presented, which employs a voltage-controlled resistor (VCR) to enable the efficient simulation of the effect of the interfacial nonlinearity as well as the substrate bias. SPICE simulations indicate that the VCR-based model for the emitter resistance accurately predicts the measured I-V characteristics obtained using the improved OC method. The utility of a subcircuit-based model explaining the experimentally observable effect of the substrate bias on the behavior of the emitter resistance is also evaluated for circuit simulation. [ABSTRACT FROM AUTHOR]

The quadrant photoreceivers (QPRs) in the Laser Interferometer Space Antenna (LISA) mission must feature an input-referred current noise below 2 pAHz $^\frac{-1}{2}$ at 25 MHz to avoid degradation of the signal-to-noise ratio. We present a QPR with a dc-coupled transimpedance amplifier (TIA) based on heterojunction bipolar transistors (HBTs). The QPR features an input-referred current noise density below 1.5 pAHz $^\frac{-1}{2}$ at 25 MHz, a 37 MHz bandwidth, and a 56.2 mW power consumption. Additionally, the dc-coupled, HBT-based TIA allows the QPR to fulfill the size and interface requirements of the LISA mission. [ABSTRACT FROM AUTHOR]

This invited paper reviews the progress of silicon–germanium (SiGe) bipolar-complementary metal–oxide–semiconductor (BiCMOS) technology-based integrated circuits (ICs) during the last two decades. Focus is set on various transceiver (TRX) realizations in the millimeter-wave range from 60 GHz and at terahertz (THz) frequencies above 300 GHz. This article discusses the development of SiGe technologies and ICs with the latter focusing on the commercially most important applications of radar and beyond 5G wireless communications. A variety of examples ranging from 77-GHz automotive radar to THz sensing as well as the beginnings of 60-GHz wireless communication up to THz chipsets for 100-Gb/s data transmission are recapitulated. This article closes with an outlook on emerging fields of research for future advancement of SiGe TRX performance. [ABSTRACT FROM AUTHOR]

The rapid recombination of photogenerated electron‐hole pairs is one of the main reasons for limiting the photocatalytic efficiency of semiconductor photocatalysts. This paper investigates and analyzes two methods to improve the separation and lifetimes of electron‐hole pairs: semiconductor heterojunction and metal electron sink. As a specific example, an Au‐TiO2‐ZnO composite film with a sandwich structure is prepared. The energy level gradient formed at the TiO2/ZnO heterojunction separates the electron‐hole pairs effectively, and the AuNPs promote the photo‐induced charge transfer. Moreover, a synergistic effect of TiO2/ZnO heterojunction and AuNPs, which can further improve the photocatalytic performance, has been found by the photoelectric performance measurement. The experimental results demonstrate that the UV photocurrent density of the Au‐TiO2‐ZnO composite film is almost 22 times that of the pure TiO2 film. And a similar result has been observed in the UV light degradation of methylene blue. Such Au‐TiO2‐ZnO composite film combining semiconductor heterojunctions and metal electron sink has a potential prospect in the photo‐degradation of organic pollutants. [ABSTRACT FROM AUTHOR]