Electron Scattering in AlGaN/GaN Structures

Abstract

We present data on mobility lifetime, ${\tau }_t$, quantum lifetime, ${\tau }_q$, and cyclotron resonance lifetime, ${\tau }_{CR}$, of a sequence of high-mobility two-dimensional electron gases in the AlGaN/GaN system, covering a density range of $\sim 1-4.5\times 10^{12}$cm${}^{-2}$. We observe a large discrepancy between ${\tau }_q$ and ${\tau }_{CR}$ (${\tau }_q\sim {\tau }_{CR}$/6) and explain it as the result of density fluctuations of only a few percent. Therefore, only ${\tau }_{CR}$ --and not ${\tau }_q$ -- is a reliable measure of the time between electron scattering events in these specimens. The ratio ${\tau }_t/{\tau }_{CR}$ increases with increasing density in this series of samples, but scattering over this density range remains predominantly in the large-angle scattering regime.