Scattering parameters from an analysis of the hall electron mobility in Ga1−xAlxAs alloys

Hall mobilities in high purity epitaxial layers of n-type Ga_1?xA_xAs alloys with room-temperature electron concentrations in the range (5–10) × 10¹⁵ cm^?3 have been measured at 300 K for alloy compositions in the range 0? x ? 0.78. Models for the variation of various material parameters with composition are developed. The acoustic deformation potentials for the Π and X conduction band minima, the intervalley coupling constants for electron scattering among the X-X and L-X minima and the longitudinal optical phonon temperature for these scatterings and the polar optical scattering in the X minima have been determined from a theoretical fit to the experimental data. The electron mobilities in the Π, L and X minima are found to decrease with the composition in the range 0≦ x ? 0.45, show a minimum at x ? 0.50 and then increase again with composition. These mobility variations are reflected in the minimum in the Hall mobility at x ? 0.5 due to intense non-equivalent electron scattering involving the L and x minima. The minimum in the electron mobilities in the Π and X minima have been identified to occur mainly due to the space charge and intervalley scattering among the L and X minima, respectively. The number of equivalent x minima in Ga_1?x Al_x As alloys are estimated to be three and are, thus, situated at the zone edge.