Session R40 - Poster Session III.
POSTER session, Wednesday afternoon, March 14
Exhibit Hall, Washington State Convention Center
A theory of polar optical phonon limited transport is developed in degenerate GaN-based heterostructures for which the effective width of the triangular quantum well depends on the electron density. A linearised Boltzmann equation approach is used to produce a series of difference equations for the effective momentum relaxation time. These are solved using a ladder technique and the electron mobility is calculated. Numerical solutions for the variations of the effective momentum relaxation time with electron energy, lattice temperature and electron density and the variations of mobility with lattice temperature and electron density are presented and discussed. We also investigate an approximate solution where the results are analytical and determine the regimes in which it provides a good representation of the theory.
The most salient feature in the variation of the effective momentum relaxation time with energy is the sharp change at multiples of the optical phonon energy due to the onset of emission at the optical phonon energy. If the electron density is increased so that the Fermi energy is greater than the optical phonon energy these discontinuities are smoothed out. Another feature of our solution is the existence of a minimum in the variation of the mobility with electron density, which is due to increased scattering as the Fermi energy passes through the optical phonon energy.