Novel InP/InGaAs D-HBTs with selective multisteps MOCVD regrowth techniques for high-speed application

First successful fabrication of HBTs which can reduce the extrinsic base-collector capacitance C/sub ex/ by selective multisteps MOCVD regrowth techniques is demonstrated. We have achieved cutoff frequency f/sub t/ of the regrown-HBTs with a large 6/spl times/18 /spl mu/m/sup 2/ emitter area of 59.6 GHz, which is superior to that of conventional HBTs of 40.2 GHz. The differences of total delay time of the regrown-HBT and conventional HBT was in good agreement with the collector charging time difference estimated from the device geometry, which indicates improvement of the high speed performance was achieved by the reduction of the C/sub ex/.