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Novel In0.12Al0.88N/AlN/AlxGa $_{1-\mathrm {x}}\text{N}$ /In0.12Al0.88N metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) grown on a SiC substrate with a drain field-plate (DFP) were investigated. A symmetrically-graded AlxGa $_{1-\mathrm {x}}\text{N}$ (x = $0.32~\to ~0.1~\to ~0.32$ ) wide-gap channel with an In0.12Al0.88N back-barrier was devised to enhance the carrier confinement, channel conductivity, and breakdown characteristics. The MOS-gate structure, employing high-k Al2O3 gate dielectric and surface passivation deposited by the non-vacuum ultrasonic spray pyrolysis deposition (USPD) technique, has resulted in enhanced gate modulation and decreased gate leakage current. A control MOS-HFET (sample A) with an equivalent Al0.21Ga0.79N channel and DFP was fabricated in comparison with the present design without/with DFP (samples B1/B2). The present sample B2 (A) has demonstrated a superior maximum drain-source current density ( $I_{DS, max}$ ) of 937.4 (838.8) mA/mm, maximum extrinsic transconductance ( $g_{m, max}$ ) of 89.6 (80.6) mS/mm, on/off-current ratio ( $I_{on}/I_{off})$ of $1.8\times 10^{8}$ ( $1.3\times 10^{8}$ ), two-terminal off-state gate-drain breakdown voltage ( $BV_{GD}$ ) of −530 (−490) V, three-terminal on-state drain-source breakdown voltage ( $BV_{DS}$ ) of 520 (465) V at 300 K, and the corresponding Baliga’s figure-of-merit (BFOM) of 79.5 (39.3) MW/cm2. The present design is promising for high-voltage power-switching circuit applications.

The dual treatment method, based on the combination of ledge and sulfur passivation, to study the temperature-dependent dc characteristics of InGaP/GaAs heterojunction bipolar transistors on the base surface is applied. Better temperature-dependent characteristics, inclusive of higher dc gain, and lower saturation voltage is observed.

Channel doping profile has a significant influence on GaAs camel-gate field effect transistors (CAMFETs). Mathematical derivations successfully predict the performance of CAMFET with one-step, bi-step and tri-step doping channels. The one-step high-doping channel FET exhibits large transconductance but a small drain current. The tri-step doping channel CAMFET shows not only an enhanced drain current but also a high voltage-independent transconductance. The theoretical results are validated by successfully fabricating a tri-step doping channel CAMFET.

Experimental studies of a switching device, with a p-type delta-doped sheet in the center of an InGaAs-GaAs quantum well, suggest that temperature significantly influences device operation and also peak-current voltage, valley-current voltage and peak-current and valley-current densities. Current-voltage measurements suggest an N-shaped negative-differential-resistance process caused by the resonant-tunneling effect through the miniband.

The fabrication and the dc performance of InP/InGaAs p-n-p heterostructure-emitter bipolar transistor (HEBT) are described. The offset voltage of the device is found to be the lowest value among the InP/InGaAs p-n-p HEBTs.

The confinement effect and electrical characteristics of heterostructure-emitter bipolar transistors with an AlGaInP bulk-confinement layer and an AlGaInP/GaAs superlattice-confinement layer are first demonstrated and compared by experimentally results. In the two devices, the relatively large valence band discontinuity at AlGaInP/GaAs heterojunction provides excellent confinement effect for holes to enhance current gain. As to the AlGaInP/GaAs superlattice-confinement device, part of thermionic-emission electrons will be trapped in the GaAs quantum wells of the superlattice. This will result in lower collector current and current gain as compared with the bulk-confinement device. Nevertheless, the superlattice-confinement device exhibits a larger current-gain cutoff frequency, which can be attributed that the tunneling behavior is included in the carrier transportation and transporting time across the emitter region could be substantially reduced. [ABSTRACT FROM AUTHOR]

This article first compares the difference of InGaP/GaAs heterostructure-emitter bipolar transistors (HEBTs) with tunneling- and superlattice-confinement structures at room temperature. In the two devices, the insertion of a thin n-GaAs layer at base-emitter junction helps to eliminate the potential spike and a relatively low collector-emitter offset voltage of about 40 mV is observed. The difference of tunneling mechanism will be investigated. Experimentally, a maximum current gain of 285 (176) and a current gain cutoff frequency of 26.4 (16.3) GHz are achieved for the tunneling (superlattice) device. As comparing the superlattice device, the tunneling device shows higher current gain at small B-E bias, while it has smaller current gain at large B-E bias. [ABSTRACT FROM AUTHOR]

High-performance InP/GaAsSb double heteroj unction bipolar transistor (DHBT) employing GaAsSb/lnGaAs superlattice-base structure is demonstrated and compared with GaAsSb bulk-base structure by two-dimensional simulation analysis. The proposed device exhibits a higher current gain of 257 than the conventional InP/GaAsSb type-II DHBT with a lower current gain of 180, attributed to the tynneling behavior of minority carriers in the GaAsSb/lnGaAs superlattice-base region under large forward base—emitter bias. In addition, a larger unity gain cutoff frequency of 19.1 GHz is botained for the superlattice-base device than that of 17.2 GHz for the bulk-base device. [ABSTRACT FROM AUTHOR]

InGaP/InGaAs doped-channel direct-coupled field-effect transistor logic (DCFL) with relatively low supple voltage is demonstrated by two-dimensional analysis. In the integrated enhancement/depletion-mode transistors, subband and two-dimensional electron gas (2DEG) are formed in the InGaAs strain channels, which substantially increase the channel concentration and decrease the drain-to-source saturation voltage. The integrated devices show high turn-on voltage, high transconductance, broad gate voltage swing, and excellent high frequency performance, simultaneously. Furthermore, the integrated devices exhibit large noise margins for DCFL application with low supply voltage of 1.5 V attributed from the relatively small saturation voltages of the studied integrated devices. [ABSTRACT FROM AUTHOR]

In this article, a novel InGaP/GaAs pnp δ-doped heterojunction bipolar transistor is first demonstrated. Though the valence band discontinuity at InGaP/GaAs heterojunction is relatively large, the addition of a δ-doped sheet between two spacer layers at the emitter-base (E-B) junction effectively eliminates the potential spike and increases the confined barrier for electrons, simultaneously. Experimentally, a high current gain of 25 and a relatively low E-B offset voltage of 60 mV are achieved. The offset voltage is much smaller than the conventional InGaP/GaAs pnp HBT. The proposed device could be used for linear amplifiers and low-power complementary integrated circuit applications. [ABSTRACT FROM AUTHOR]

New metal-semiconductor-metal hydrogen sensors are fabricated to take advantages of symmetrically bidirectional detection. Unlike commonly used single catalytic metal layers, a mixture of Pd and Si02 inserted between Pd and GaN was employed as sensing media. There are three sensing regions (i.e., 2-D dipole, transient, and 3-D dipole regions) observed in static response. Room-temperature sensitivity larger than ~ was ob- tained in 1080-ppm H2/N2 ambient. The barrier-height variation is as high as 422 mY. To our best knowledge, these are the highest values ever reported. According to transient response, a short response time of 70 s is obtained at room temperature. Thus, a newly developed concept of forming 3-D dipoles is introduced to possibly explain experimental results. [ABSTRACT FROM AUTHOR]

GaAs/InGaP and AlGaAs/GaAs/InAlGaP npn heterostructural optoelectronic switches (HSOSs) have been fabricated to demonstrate the bulk-barrier and potential-spike height effects on the switching. It is seen that the illumination decreases the switching voltage VS and increases the switching current IS in the GaAs/InGaP HSOS characteristics. But in the AlGaAs/GaAs/InAlGaP HSOS, the VS and IS present contrary trends. These characteristic variation differences in the two HSOSs are mainly due to the photogenerated carriers that affect the bulk-barrier and potential-spike heights. [ABSTRACT FROM AUTHOR]

Temperature-dependent dark and optical characteristics of the InGaP/GaAs heterojunction phototransistors (HPTs) with and without sulfur treatment are studied. As compared to the HPT without (NH4)2S treatment (HPT A), treatment at 50°C for 20 mm leads to a reduced p-i-n dark current (Idark) and a reduced collector dark current (ICdark) for the HPT (HPT D) in the emitter-floated and base-floated configurations, respectively. Moreover, the effective reduction of the surface defects also induces an enhanced p-i-n photocurrent (Igb). The enhanced Igb combined with the promoted dc current gain results in an enhanced optical gain (G) and signal-to-noise ratio (SNR). For HPT A (D) under Pin = 107.6 nW at 298 K, the G is 1.42 (20.3) while the SNR is 42 (94) dB. Experimental results indicate that the treated HPTs, compared to the untreated one, are more sensitive to low-power illumination. [ABSTRACT FROM AUTHOR]

Double heterostructure-emitter bipolar transistors (DHEBTs) with emitter edge-thinning design and DHEBTs without that design have been investigated. In the characteristics modeling, a two-dimensional continuity equation and boundary conditions in the base region are employed to determine the various components of base current in a cylindrical mesa-type DHEBT. The influence of structure parameters and emitter edge-thinning design on the current gain of the DHEBT is studied. The effect of quasi-electric field in the base region is taken into account. Switching mechanisms in the DHEBT are also discussed. In the experimental measurement, a DHEBT with an exposed p+-GaAs base surface exhibits a small offset voltage of 100 mV and a common-emitter current gain of 17. Due to the emitter edge-thinning to suppress the surface recombination current, a DHEBT with an N-AIGaAs passivated surface has a common-emitter current gain of 140 and a negligible offset voltage of 40 mV. With symmetric structures, both devices present bidirectional switching phenomena. Moreover, the emitter edge-thinning design is found having the capability for reducing the holding power in the switching. Possessing both amplifying and switching features, the DHEBTs show good potentials for circuit applications. [ABSTRACT FROM AUTHOR]

New InP/InGaAs δ-doped heterojunction bipolar transistors have been successfully fabricated and demonstrated. The use of a δ-doped sheet between two undoped spacer layers more effectively eliminates the potential spike at the base–emitter junction and lowers the collector–emitter offset voltage. The maximum current gain and offset voltage of 455 (533) and 55 mV (33 mV) are observed, respectively, for the unpassivated (passivated) emitter device at room temperature. The base surface recombination current of the studied devices is also investigated in this paper. The studied devices are therefore promising for practical circuit applications. [ABSTRACT FROM AUTHOR]

Provides information on a study that developed a field-effect transistor using a high-barrier InGaP/GaAs/InGaAs camel-like gate. Discussion on the effect of the applied gate voltage on the barrier height for a homojunction camel-diode; Methodology; Results and discussion.