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A novel photonic-sensitive InAlGaAs/InP negative-differential-resistance heterojunction bipolar transistor (NDR-HBT) is fabricated and demonstrated. Due to the appropriately designed narrow base width and the employment of a δ -doped sheet at the emitter–base (E–B ) heterojunction, the base resistance effect results in the significant NDR phenomenon. In addition, the experimental results show that the device studied is very sensitive to the applied light source. The N-shaped NDR phenomena are clearly observed under illumination. This phenomenon is attributed to the base resistance and barrier lowering effect resulting from holes induced by the applied light source.

An InP/InGaAs superlattice-emitter resonant tunneling bipolar transistor (SE-RTBT) has been fabricated and demonstrated. The influence of the superlattice and emitter thickness on the device characteristics is studied. The insertion of the superlattice and a well-designed emitter improve the characteristics of the SE-RTBT. Common-emitter current gains up to 170 and 54 are obtained for the studied devices with emitter thicknesses of 800 A and 150 A, respectively. Based on the specified structure, the lower offset voltage and saturation voltage ( ≤ 1.5 V) are obtained. Experimentally, the device with a 5-period superlattice and an emitter thickness of 800 A provides higher dc performance and stable temperature-dependent characteristics.

In this paper, we demonstrate multiple-negative-differential-resistance (MNDR) switching behaviors based on the InGaP/GaAs heterostructure-emitter bipolar transistor (HEBT) and InGaAlAs/InP heterojunction bipolar transistor (HBT) structures. The devices act like conventional HBTs under forward operation mode. The proposed HEBTs show lower offset voltage due to the correct design of the emitter thickness. On the other hand, MNDR phenomena resulting from avalanche multiplication, confinement effects and the potential redistribution process are observed under inverted operation mode for both devices. In addition, three-terminal NDR characteristics are investigated under the applied base current I B . Moreover, for the InGaAlAs/InP HBT, anomalous multiple-route and multiple-step current–voltage ( I – V ) characteristics at 77 K are observed due to the insertion of a InGaAs quantum well (QW) between the base and collector layers.

An i-InGaP/n-In x Ga 1 − x As/i- GaAs step-graded doped-channel field-effect transistor (SGDCFET) has been fabricated and studied. Due to the existence of a V-shaped energy band formed by the step-graded structure, a large output current density, a large gate voltage swing with high average transconductance, and a high breakdown voltage can be expected. In this study, first, a theoretical model and a transfer matrix technique are employed to analyze the energy states and wavefunctions in the step-graded quantum wells. Experimentally, for a 1 × 80 μ m 2 gate dimension device, a maximum drain saturation current density of 830 mAmm − 1 , a maximum transconductance of 188 mSmm − 1 , a high gate breakdown voltage of 34 V, and a large gate voltage swing 3.3 V with transconductance larger than 150 mSmm − 1 are achieved. These performances show that the device studied has a good potentiality for high-speed, high-power, and large input signal circuit applications.

A lattice-matched In0.49Ga0.51P/GaAs/In0.49Ga0.51P doubleδ -doped heterojunction bipolar transistor, prepared by low-pressure metal organic chemical vapor deposition (LP-MOCVD), is fabricated successfully and reported. Due to the insertion of δ -doped sheets and setback layers both at base–emitter (B–E) and base–collector (B–C) heterojunctions, the potential spikes are suppressed significantly. In addition, the electron blocking effect is removed and a dramatic improvement of current gain is obtained. A modified Ebers–Moll model is employed to study and analyse the device performances. The experimental results show that the common-emitter current gain over 210 at the collector current of 35 mA and an offset voltageΔVCE smaller than 50 mV are obtained. Also, a lower knee-shaped voltage of 1.4 V at the collector current of 40 mA is observed. These results indicate that the device studied is a good candidate for high-speed and high-power circuit applications.