Low VbeGaInAsN base heterojunction bipolar transistors

We report here on the electrical and structural characteristics of InGaP/Ga InAsN DHBTs with up to a 50 mV reduction in turn-on voltage relative to sta ndard InGaP/GaAs HBTs. High p-type doping levels (similar to 3 x 10(19) cm( -3)) and dc current gain (beta (max) up to 100) are achieved in GaInAsN bas e layer structures ranging in base sheet resistance between 250 and 750 Ome ga/square. The separate effects of a base-emitter conduction band spike and base layer energy-gap on turn-on voltage are ascertained by comparing the collector current characteristics of several different GaAs-based bipolar t ransistors. Photoluminescence measurements are made on the InGaP/GaInAsN DH BTs to confirm the base layer energy gap, and double crystal x-ray diffract ion spectrums are used to assess strain levels in the GaInAsN base layer.