Electron mobility in InGaN channel heterostructure field effect transistor structures with different barriers

Abstract

InGaN possesses higher electron mobility and velocity than GaN, and therefore is expected to lead to relatively better performances for heterostructure field effect transistors (HFETs). However, the reported mobilities for AlGaN∕InGaN HFETs are lower than GaN channel HFETs. To address this issue, we studied the effect of different barriers on the Hall mobility for InGaN channel HFETs grown by metal organic chemical vapor deposition. Unlike the conventional AlGaN barrier, the AlInN barrier can be grown at the same temperature as the InGaN channel layer, alleviating some of the technological roadblocks. Specifically, this avoids possible degradation of the thin InGaN channel during AlGaN growth at high temperatures; and paves the way for better interfaces. An undoped In0.18Al0.82N∕AlN∕In0.04Ga0.96N HFET structure exhibited a μH=820cm2∕Vs, with a ns=2.12×1013cm−2 at room temperature. Moreover, with an In-doped AlGaN barrier, namely, Al0.24In0.01Ga0.75N, grown at 900°C, the μH increased to 1230cm2∕Vs with a ns of 1.09×1013cm−2 for a similar InGaN channel. Furthermore, when the barrier was replaced by Al0.25Ga0.75N grown at 1030°C, μH dropped to 870cm2∕Vs with ns of 1.26×1013cm−2 at room temperature. Our results suggest that to fully realize the potential of the InGaN channel HFETs, AlInN or AlInGaN should be used as the barrier instead of the conventional AlGaN barrier.