High-performance low-base-collector capacitance AlGaAs/GaAs heterojunction bipolar transistors fabricated by deep ion implantation

Low-base-collector capacitance (C/sub bc/) AlGaAs/GaAs HBTs with f/sub MAX/>200 GHz and f/sub T/=52 GHz have been fabricated. With co-implants of high energy, high dose He/sup +/ and H/sup +/ ions through the external base layer, part of the heavily doped n/sup +/ sub-collector was compensated leading to a decrease in the extrinsic portion of C/sub bc/. The implants caused only a slight increase of base resistance. Using this approach in combination with a standard low dose, shallow collector compensating implant, C/sub bc/ of double implanted HBT's can be reduced by more than 35%.<
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