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

Low-base-collector capacitance (C_bc) AlGaAs/GaAs HBTs with f_MAX>200 GHz and f_T=52 GHz have been fabricated. With co-implants of high energy, high dose He⁺ and H⁺ ions through the external base layer, part of the heavily doped n⁺ sub-collector was compensated leading to a decrease in the extrinsic portion of C_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_bc of double implanted HBT's can be reduced by more than 35%