Interface-phonon-limited two-dimensional mobility in AlGaN∕GaN heterostructures

Abstract

The room temperature polar-optical-phonon-limited two-dimensional electron mobility in AlxGa1−xN∕GaN heterostructures is calculated taking into account the interaction of conduction electrons and interface-phonon modes. The polar optical oscillations are described via the uniaxial dielectric continuum model. Electron–polar-optical-phonon scattering rates are evaluated from a general expression that is always valid as long as the interaction Hamiltonian matrix elements depend only on the magnitude of the phonon wave vector. Values for the 300K low-field mobility (μ) of a few hundreds cm2∕Vs are obtained within a simplified relaxation time scheme involving electron-phonon absorption scattering rates. It is found that the way of describing the electronic states in the conduction band strongly affects the calculation of μ. The typical triangular well model gives the poorest results compared with a previously proposed analytical approximation of the conduction band potential profile. We present a discussion on the relevance of an appropriate model for long-wavelength polar optical phonons in the obtention of realistic values of the electron mobility in wurtzite heterostructures.