Pressure and composition effects on the gap properties of AlxGa1−xAs

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Abstract
Effects of pressure and composition on the gap properties of AlxGa1−xAs randomly disordered alloys are investigated theoretically and experimentally. The analogy between pressure and alloying effects is explored. Special attention is given to the direct‐to‐indirect gap transition region, where the gap sensitivity to both pressure and composition variations is shown to be strongly enhanced. A 30% decrease in luminescence intensity is produced on a x=0.46 sample under applied pressure of 0.7 kbar, while a similar effect in GaAs would require pressures of several tens of kbar. Calculations are performed within the small crystal approach using 64‐, 216‐, and 1000‐atoms basic cluster sizes, with periodic boundary conditions. Convergence of the calculated properties with the cluster size is discussed.