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In this work, the off-state breakdown characteristics of two different types InGaP-based high-barrier gate heterostructure field-effect transistors are studied and demonstrated. These devices have different high-barrier gate structures, e.g. the i-InGaP layer for device A and n + - GaAs/p + -InGaP/n-GaAs camel-like structure for device B. The wide-gap InGaP layer is used to improve the breakdown characteristics. Experimentally, the studied devices show high off-state breakdown characteristics even at high temperature operation regime. This indicates that the studied devices are suitable for high-power and high-temperature applications. In addition, the off-state breakdown mechanisms are different for device A and B. For device A, off-state breakdown characteristics is only gate dominated at the temperature regime from 30 to 180 ∘ C. For device B, off-state breakdown characteristics are gate and channel dominated at 30 ∘ C and only gate dominated within 150 to 210 ∘ C.

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.