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Temperature-dependent DC performances of InP/InGaAlAs heterojunction bipolar transistors (HBTs) using the InGaAlAs quaternary alloy as the base and collector layers are studied and reported. When compared with conventional InP/InGaAs HBTs, the device studied exhibits a higher common-emitter breakdown voltage and a lower output conductance even at high temperature. In addition, with decreasing temperature from 25 toward -196/spl deg/C, an irregular temperature behavior of current gain has been investigated.

A new AlInAs/GaInAs superlattice negative-differential-resistance switch (SNDRT) is fabricated successfully and demonstrated. A 5-period AlInAs/GaInAs superlattice is used to serve the resonant tunneling route and the confinement barrier for minority carriers. Experimentally, an interesting three-terminal-controlled N-shaped multiple negative-differential-resistance (MNDR) phenomenon and transistor action are obtained for the studied SNDRT device in the saturation and forward active mode at room temperature, respectively. It is believed that the N-shaped MNDR results mainly from resonant tunneling within the 5-period AlInAs/GaInAs superlattice.

A new GaInP/GaAs high-barrier gate and tri-step doped channel heterostructure field-effect transistor (HFET) has been successfully fabricated and demonstrated. A very thin and heavily doped /spl delta/(p/sup +/)-GaInP layer is introduced to increase the high gate turn-on and breakdown voltage and reduce the gate leakage current. A low-medium-high tri-step doped channel structure is used to improve the output current drivability and average transconductance. In addition, a metal-semiconductor field-effect transistor (MESFET) with the same tri-step doped channel structure has also been fabricated for comparison. The studied devices show the good performances of high breakdown voltage, high output drain saturation current and flat and wide transconductance operation regimes. The measured cut-off frequency (f/sub T/) is higher than 15 GHz. From experimental results, the studied devices show good potential in high-power and large input signal circuit applications.

An InGaP/GaAs resonant tunnelling bipolar transistor (RTBT) with superlattice (SL) in the emitters is fabricated and studied. The modulated widths of SL barriers are utilized in the specific SL structure. Based on the calculations, the ground state and first excited state minibands are estimated from the transmission probability. The electron transport of RT through SL structure is significantly determined by the electric field behaviors across SL barriers. Experimentally, the excellent transistor characteristics including the small saturation voltage, small offset voltage, high breakdown voltages are obtained due to the insertion of δ-doping sheet at the base-collector heterointerface. Furthermore, at higher current regimes, the quaternary negative difference resistance (NDR) phenomena are observed in agreement with the theoretical prediction at 300K.