The effect of interface-roughness and dislocation scattering on low temperature mobility of 2D electron gas in GaN/AlGaN

We present the results of our experimental and theoretical studies concerning the temperature dependence of electron mobility in a two-dimensional electron gas (2DEG) confined at the GaN/AlGaN interface. Experimental mobility of 2912 cm2 (V s)−1 at 4.2 K, remains almost constant up to lattice temperature TL = 150 K, it then decreases rapidly down to 1067 cm2 (V s)−1 at TL = 300 K. In order to compare the experimental results with the theory we use a simple analytical formula for low-field electron mobility based on 2D degenerate statistics for a 2DEG confined in a triangular well. We consider acoustic phonon, polar-optical phonon, dislocation and interface-roughness (IFR) scattering. The polar-optical phonon scattering is the dominant mechanism at high temperatures. At low temperatures, however, both the IFR and dislocation scattering explain, equally well, the observed mobility. In reality, however, a mixture of the two mechanisms together with the deformation potential and piezoelectric scattering will determine the low temperature mobility. The experimental results are discussed in the light of the calculations.

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