The conduction band structure and deep levels in Ga1-xAlxAs alloys from a high-pressure experiment

Abstract

High-pressure Hall effect measurements on liquid phase epitaxial crystals of Ga_1-xAl_xAs with compositions in the range 0.23-6, (5.5+or-0.2)*10^-6 and -1.5*10^-6 eV bar^-1 respectively. The implications of such a model on the conduction band structure of GaAs are discussed. The sub-band gap Delta E_{Gamma X} between the Gamma and X minima in GaAs is determined to be (0.485+or-0.007) eV at 300K. A deep impurity level in Ga_1-xAl_xAx has been determined from the pressure experiment to exist in crystals under pressure. For alloys with a high Ga content and before the Gamma -X crossover, the impurity level lies below the L minima at an energy of 205+or-5 meV. For pressures higher than that needed for the Gamma -X crossover, its impurity activation energy below the lowest-energy X minima decreases monotonically with pressure.