Base Transit time in Abrupt GaN/InGaN/GaN and AlGaN/GaN/AlGaN HBTs

摘要

Base transit time, #tau#_b, in abrupt npnGaN/InGaN/GaN and AlGaN/GaN/AlGaN doubleheterojunction bipolar transistors (DHBTs) is reported. Basetransit time strongly depends not only on the quasi-neutral basewidth, but also on the low field electron mobility, #mu#_n, inthe neutral base region and the effective electron velocity, S_c,at the edge of base-collector heterojunction. #mu#_n and S_care temperature-dependent parameters. A unity gain cut-offfrequency of 10.6 GHz is obtained in AlGaN/GaN/AlGaNDHBTs and 19.1 GHz in GaN/InGaN/GaN DHBTs for aneutral base width of 0.05um. It is also shown that non-stationary transport is not required to study #tau#_b for neutralbase width in the range of 0.05um for GaN-based HBTs.