A high-frequency GaInP/GaAs heterojunction bipolar transistor with reduced base-collector capacitance using a selective buried sub-collector

A C-doped GaInP/GaAs HBT using a selective buried sub-collector has been fabricated by two growth steps. The device was fabricated with minimum overlap of the extrinsic base and the sub-collector region to reduce base-collector capacitance. The experiment shows that the base collector capacitance is reduced to about half of that of an HBT without selective buried sub-collector while the base resistance remains unchanged. A current gain of 35, f/sub T/ of 50 GHz and f/sub max/ of 140 GHz are obtained with this technology.