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 ( Λ) and lateral size ( Δ) 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.