Theoretical study of the anisotropic electron scattering by steps in vicinal AlGaN/GaN heterostructures

• The anisotropic 2DEG mobility in vicinal AlGaN/GaN heterostructures was studied.
• The mobility anisotropy was caused by the parallel steps at the heterointerface.
• The step limited electron mobility was found to be about 103 cm2/Vs.

It was found by many experiments that the electron mobilities in vicinal AlGaN/GaN heterostructures are highly anisotropic which was believed to be caused by the steps at the vicinal heterointerfaces. However, there is no theoretical explanation for such experimental results because it is difficult to find an universal expression for the electron relaxation time in all directions. In this work, we started from solving the standard linearized Boltzmann equation and separated the electron relaxation time into x- and y-components (perpendicular and parallel to the steps, respectively). In this way, the y-component of the relaxation time was found to be infinite while the x-component part depended on the form of the scattering potential. Subsequently we were able to find an analytic expression for the anisotropic mobility, and the calculated results were found to be consistent with the experimental values.