Electron Scattering in AlGaN/GaN Structures

TL;DR

This study measures various electron lifetimes in high-mobility AlGaN/GaN 2DEG systems, revealing that cyclotron resonance lifetime is a more reliable scattering indicator than quantum lifetime due to density fluctuations.

Contribution

It demonstrates that cyclotron resonance lifetime accurately reflects electron scattering times, unlike quantum lifetime, in AlGaN/GaN 2DEG structures, highlighting the impact of density fluctuations.

Findings

$ au_q$ is significantly smaller than $ au_{CR}$ due to density fluctuations.

$ au_{CR}$ provides a reliable measure of scattering time.

Scattering remains predominantly large-angle across the studied density range.

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 $\sim1-4.5\times10^{12}$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.