Electron scattering in AlGaN/GaN structures

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 1 to 4.5x10(12) cm(-2). We observe a large discrepancy between tau(q) and tau(CR)(tau(q)similar totau(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. (C) 2004 American Institute of Physics.