A Modelling study of Electron transport in GaN/AlGaN superlattices using Monte Carlo simulation

Abstract

Electron transport in GaN/AlxGa1-xN superlattices is investigated using a single particle Monte Carlo approach. To establish the band structure required GaN, AlN and their ternary alloy are investigated using a single electron Monte Carlo approach and a 3-band approximation to the full band structure. The interplay of the inter-valley scattering and electron-longitudinal optical polar phonon scattering in determining electron velocity and velocity overshoot is examined for the binaries and their alloy. We use a Schrodinger wave equation coupled to a Poisson solver to self-consistently calculate the energy band structure of the superlattice using the single band approximation for the materials, determine the Fermi energy and the superlattice miniband energy position and its energy width. We then analyze the miniband band structure and determine the effective masses for the superlattice miniband in the superlattice direction which will determine the electron mobility in that direction. Then the single particle Monte Carlo method is applied to investigate electron transport in the miniband where we find that for low Al concentration in the barrier and short periods electron velocity, very similar to that in bulk GaN can be obtained and observe that velocity overshoot can occur, purely due to electron-LO phonon scattering and non-parabolicity in the single band. This modelling approach provides a fast and convenient method to investigate high-field electron transport in n-doped GaN/Al$_x$Ga$_{1-x}$N superlattices and should be suitable for use in device design.