Electron scattering in AlGaN/GaN structures

We present data on mobility lifetime τt, quantum lifetime τq, and cyclotron resonance lifetime τCR, of a sequence of high-mobility two-dimensional electron gases in the AlGaN/GaN system, covering a density range of 1 to 4.5×1012 cm−2. We observe a large discrepancy between τq and τCR(τq∼τCR/6), and explain it as the result of density fluctuations of only a few percent. Therefore, only τCR—and not τq—is a reliable measure of the time between electron-scattering events in these specimens. The ratio τt/τCR increases with increasing density in this series of samples, but scattering over this density range remains predominantly in the large-angle scattering regime.