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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.

The performance of an InGaP/GaAs superlattice-emitter bipolar transistor with InGaAs/GaAs superlattice-base structure is demonstrated by experimental results. The injecting electrons from superlattice emitter are easy to transport into the superlattice-base region for promoting the collector current by tunneling behavior. Furthermore, the average energy gap of base regime is substantially reduced by the use of InGaAs/GaAs superlattice structure for the requirement of low turn-on voltage. Experimentally, the transistor exhibits a maximum common-emitter current gain of 295 and a relatively low collector-emitter offset voltage of only 16 mV. In particular, the ideality factor of collector current near to unity is obtained. [ABSTRACT FROM AUTHOR]

New hydrogen-sensing amplifiers are fabricated by integrating a GaAs Schottky-type hydrogen sensor and an InGaP-GaAs heterojunction bipolar transistor. Sensing collector currents (ICN and ICH) reflecting to N2 and hydrogen-containing gases are employed as output signals in common-emitter characteristics. Gummel-plot sensing characteristics with testing gases as inputs show a high sensing-collector-current gain (ICH/ ICN) of > 3000. When operating in standby mode for in situ long-term detection, power consumption is smaller than 0.4 μW. Further- more, the room-temperature response time is 85 s for the integrated hydrogen-sensing amplifier fabricated with a bipolar-type structure. [ABSTRACT FROM AUTHOR]

In order to achieve high optical sensitivity and low holding power, a wide-gap carrier confinement layer was introduced into the collector region of an n-p-n-heterostructure optoelectronic switch. A similar device without the confinement layer was also fabricated to demonstrate the performance improvement. Both devices were found to have bistable electrical states: a high- impedance OFF state connected to a low-impedance ON state by a region of negative differential resistance. The functional characteristics were based on avalanche multiplication. [ABSTRACT FROM AUTHOR]

Presents a novel InGaP/InGaAs/GaAs double delta-doped pseudomorphic high-electron mobility transistor (pHEMT) with n[sup +]-GaAs/p[sup +]-InGaP/n-InGaP camel-like gate structure grown by metal oxide chemical vapor deposition. Turn-on voltage of gate; Unit current cut-off frequency; Maximum oscillation frequency.

Al0.25Ga0.75N/GaN enhancement-mode (E-mode) metal–oxide–semiconductor high-electron-mobility transistors (MOS-HEMTs) obtained by the ozone water oxidization method are investigated in this work. Decreased gate leakage and reduced channel depletion are obtained by forming the Al2O3 dielectric layer of the MOS gate structure by a cost-effective oxidization method. Pulse current–voltage (I–V), low-frequency noise, and Hooge coefficient measurements are compared to verify the interface quality improved by the oxide passivation effect. In comparison, a conventional Schottky-gate HEMT device is also fabricated on the same epitaxial sample. Enhanced device gain, current drive density, breakdown, on/off current ratio, and high-temperature stability up to 450 K are also investigated in this work. [ABSTRACT FROM AUTHOR]