Mobility of two-dimensional electrons in an AlGaN/GaN modulation-doped heterostructure

Abstract

The results of experimental and theoretical studies concerning the temperature dependence of electron mobility in a two-dimensional electron gas (2DEG) confined near the interface of an AlGaN/GaN heterostructure are presented. In order to compare the experimental results with the theory a simple analytical formula is used for the low-field electron mobility, which uses the 2D degenerate statistics for a 2DEG confined in a triangular well. All standard scattering mechanisms, including scattering by acoustic and optical phonons, remote and background impurities and interface roughness (IFR), have been included in the calculations. From the calculated dependence of mobility on temperature, it is clear that IFR and ionised impurity scattering dominate the low-temperature mobility of 2D electrons in AlGaN/GaN structures with a high electron density ns > 1012 cm−2. At intermediate temperatures, acoustic deformation potential and piezoelectric scattering are the dominant mechanisms. The polar optical phonon scattering is found to be the important mechanism of scattering at high temperatures. The experimental results are discussed in the light of the calculated mobility. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)