Base transit time in abrupt GaN/InGaN/GaN and AlGan/gAn/AlGaN HBTs

摘要

Base transit time, tau sub b, in abrupt npn GaN/InGaN/GaN and AlGaN/GaN/AlGaN double beterojunction bipolar transistors (DHBTs) is reported. Base transit time strongly depends not only on the quasi-neutral base width, but also on the low field electron mobility, mu sub n, in the neutral base region and the effective electron velocity, S sub c, at the edge of base-collector heterojunction. mu sub n and S sub c are temperature-dependent parameters. A unity gain cut-off frequency of 10.6 GHz is obtained in AlGaN/GaN/AlGaN DHBTs and 19.1 GHz in GaN/InGaN/GaN DHBTs for a neutral aase width of 0.05 um. It is also shown that non-stationary transport isnot tequired to study tau sub for neutral base width in the range of 0.05 um for GaN-based HBTs.