High-speed InGaP/GaAs HBT's using a simple collector undercut technique to reduce base-collector capacitance

High-speed InGaP/GaAs HBT's were fabricated using a simple collector undercut (CU) technique to physically remove the collector material underneath the extrinsic base region by selective etching for seducing base-collector capacitance (C-BC) The best HBT's achieved a f(T) of 80 GHz and a f(max) (MSG/MAG) of 171 GHz. To our knowledge, this is the highest f(max) (MSG/MAG) ever reported for the InGaP/GaAs HBT's. Compared to the HBT's without CU's, the CU HBT's shored a factor of 1.38 times improvement in the highest achievable f(max) (MSG/MAG) due to the significant reduction of the C-BC.