IMPORTANCE OF COLLECTOR DOPING IN THE DESIGN OF ALINAS GAINAS/INP DOUBLE-HETEROJUNCTION BIPOLAR-TRANSISTORS/

AlInAs/GaInAs/InP double heterojunction bipolar transistors (DHBTs) ha ve been made with an InP collector thickness of 0.75 mum and collector dopings of 1.4, 2.4, and 3 X 10(16) cm-3. It is shown that because of the conduction band potential barrier between the GaInAs base and the InP collector in DHBTs and particular velocity-field characteristics of InP, the dc and rf performance of the DHBT is very sensitive to the collector doping level. With a collector doping of 3 X 10(16) cm-3 de vices conducted a collector current density of 1 X 10(5) A/cm2 without gain compression and had a I(C)-V(CE) saturation voltage of about 2 V Base-collector and collector-emitter breakdown voltages were 22 and 1 4.5 V, respectively, and f(T) and f(max) were in the range of 65-70 GH z.