Novel fabrication of self-aligned GaAs/AlGaAs and GaAs/InGaP microwave power heterojunction bipolar transistors

Self-aligned processing of high efficiency power heterojunction bipolar transistors (HBTs) using implant isolation, selective wet and dry etching for mesa formation, plasma-enhanced chemical vapor deposited SiN x for sidewall spacers and through-wafer via connections is reported. GaAs/AlGaAs and GaAs/InGaP HBTs were grown by Metal Organic Molecular Beam Epitaxy utilizing carbon for high, well-confined base doping and tin for n-type doping to reduce emitter contact resistance. GaAs/AlGaAs HBTs with twelve 2 x 15 μm 2 double-emitter finger devices produced power-added efficiencies of 63%, power gain of 10 dB and output power of 1.7 W at 4 GHz. The results of power measurements at 4-12 GHz for GaAs/InGaP HBTs with common emitter and common base configuration are also reported.