PRESSURE AND COMPOSITION EFFECTS ON THE GAP PROPERTIES OF ALXGA1-XAS

Effects of pressure and composition on the gap properties of AlxGa1-xA s randomly disordered alloys are investigated theoretically and experi mentally. The analogy between pressure and alloying effects is explore d. Special attention is given to the direct-to-indirect gap transition region, where the gap sensitivity to both pressure and composition va riations is shown to be strongly enhanced. A 30% decrease in luminesce nce 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 s everal tens of kbar. Calculations are performed within the small cryst al 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.