Optimum Ge profile for the high cut-off frequency and the DC current gain of an SiGe HBT for MMIC

This paper reports the effects of the Ge profiles shape on the cut off frequency and the DC current gain of SiGe heterojunction bipolar transistors (HBT's). Device simulations using ATLAS/BLAZE for a SiGe HBT with a trapezoidal or a triangular Ge profile are carried out to optimize the device performance. A HBT with a 15 % triangular Ge profile shows a higher cut-off frequency and DC current gain than that with a 19 % trapezoidal Ge profile. It was observed that, the cut-off frequency and DC current gain as 84 GHz and 600 respectively for the case of 15 % triangular Ge profile instead of 42 GHz and 200 which was observed for 19 % trapezoidal Ge profile.