Reduction in Turn-on Voltage in GaInNAs and InGaAs-Based Double-Heterojunction Bipolar Transistors

A new quaternary material of GaInNAs has been proposed as base material for GaAs-based double-heterojunction bipolar transistors (DHBTs). The used InGaAs as base material results in the lower band gap energy of the base layer in heterojunction bipolar transistors (HBTs) followed by a smaller turn-on voltage. However, the compressive strain induced by the InGaAs grown on GaAs diminishes the influence of indium-addition induced band gap energy reduction, and thus abate turn-on voltage reduction. By incorporating suitable amounts of indium (In) and nitrogen (N) into GaAs, a smaller band gap material of GaInNAs lattice-matched to GaAs substrate can be obtained. In this study, N-p-n InGaP/Ga0.985In0.015N0.005As0.995/GaAs DHBTs have been demonstrated. A turn-on voltage reduction of 215 mV compared to that of the conventional HBT with a GaAs base layer was obtained. The device has a peak current gain of 85 and shows good high-frequency characteristics of fT and fMAX, which are both higher than 40 GHz