A trilevel resist system was employed to fabricate self-aligned, submicron emitter finger In0.52 Al0.48As/ In0.42 Ga 0.58 As0.77Sb0.23/In0.53Ga 0.47As double heterojunction bipolar transistors (DHBTs). Selective wet-etchants were used to define the emitter fingers and to form an InGaAs guard-ring around the emitter fingers. Due to the low energy bandgap of the InGaAsSb base layer and type II base-collector junction, a low turn-on voltage of 0.38 V at 1 A/ cm2 and a high dc current gain of 123.8 for a DHBT with a 0.65×8.65 μ m2 emitter area were obtained. A unity gain cutoff frequency (fT) of 260 GHz and a maximum oscillation frequency (fmax) of 485 GHz at JC =302 kA/ cm2 were achieved.
|Journal||Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics|
|State||Published - May 2011|