Scattering behaviours to the two-dimensional electron gasinduced by the Al composition fluctuation in AlxGa1-xNbarrier in AlxGa1-xN/GaN heterostructures

This paper reports that cathodoluminescence (CL) measurements have been done to study the alloy fluctuation of the Al$_{0.3}$Ga$_{0.7}$N layer in Al$_{0.3}$Ga$_{0.7}$N/GaN heterostructures. The CL images and linescanning results demonstrate the existence of compositional fluctuation of Al in the Al$_{0.3}$Ga$_{0.7}$N barrier. A model using a $\delta $-shape perturbation Hamilton function has been proposed to simulate the scattering probability of the two dimensional electron gases (2DEG) induced by Al composition fluctuation. Two factors, including conduction band fluctuation and polarization electric field variation, induced by the Al composition fluctuation have been taken into account. The scattering relaxation time induced by both factors has been estimated to be 0.31~ns and 0.0078~ns, respectively, indicating that the variation of the piezoelectric field is dominant in the scattering of the 2DEG induced by Al fluctuation.