Enhanced CDMA performance from an InGaP/InGaAsN/GaAs N-p-N double heterojunction bipolar transistor

We have demonstrated the DC characteristics and CDMA performance of an NpN InGaP/InGaAsN/GaAs double heterojunction bipolar transistor (DHBT) and compared the results to conventional InGaP/GaAs HBTs. A 100 mV reduction in base-emitter turn-on voltage and 35 mV reduction in offset voltage is established relative to InGaP/GaAs HBTs using a low energy-gap InGaAsN alloy base material and optimized heterointerfaces. InGaP/InGaAsN DHBT structures with high p-type doping levels (/spl sim/3/spl times/10/sup 19/ cm/sup -3/) have demonstrated DC current gains of /spl beta/=70 at 350 /spl Omega///spl square/ base sheet resistance. The DC current gain of InGaP/InGaAsN DHBTs has been improved by 46 % by grading the base layer composition. InGaAsN DHBTs have demonstrated 1.9 GHz CDMA IS-95 performance of 21 dBm output power (0.31 mW//spl mu/m/sup 2/ - 933 mW/mm), with 18.5 dB associated gain and greater than 53 % power-added efficiency at 45 dBc ACPR and 3 V operation. This represents an 83 mW/mm increase in output power and 3.8 percentage points improvement in PAE performance relative to InGaP/GaAs HBTs.