Heavily Sn-Doped GaAs Buffer Layers for AlGaAs/GaAs HBTs

Abstract
The Sn atom profile in MBE grown GaAs with a buried, heavily doped layer was characterized using SIMS analysis. Sn carryforward was prevented by decreasing either the growth temperature or doping concentration. Bulk resistivity of 0.0006 Ω·cm with a free carrier concentration of 1×1019 cm-3 and specific contact resistance of 1.6×10-7 Ω·cm2 were obtained with samples grown at 600°C. To confirm the feasibility of the heavily Sn-doped buffer layer, an AlGaAs/GaAs heterojunction bipolar transistor was fabricated. A current gain of 120 and base-collector junction breakdown voltage of 16 V were obtained.