The effect of electrons and phonons scattering from interface roughness and well-width fluctuations on low-field mobility of 2DEG in GaN/AlGaN

Abstract

The influence of interface roughness on the mobility of two-dimensional electrons in GaN/AlGaN HEMT structures are theoretically investigated in light of the measured mobility. Experimental mobility of 2912 cm(2)/V s at 4.2 K, remains almost constant up to lattice temperature T-L = 150 K. It then decreases rapidly down to 1067 cm(2)/V s at T-L = 300 K. In order to compare the experimental results with the theory we use a simple analytical formula for low-field electron mobility that uses the two-dimensional degenerate statistics for a 2DEG confined in a triangular well. Interface-roughness scattering dominates the low-temperature mobility of two-dimensional electrons in GaN/AlGaN structures with a high electron density n(s) > 10(12) cm(-2). From comparison between theory and experiment, the correlation length (Lambda) and lateral size (Delta) of roughness for GaN/AlGaN 2DEG are estimated. The effect of phonons scattering from interface roughness and well-width fluctuations on low-field mobility of 2DEG in GaN/AlGaN is also investigated.