Effect of local alloy disorder on the emission kinetics of deep donors (DX centers) in AlxGa1-xAs

In this paper we summarize our recent studies of the effects of local alloy disorder on the properties ofDX levels. A single emission rate is observed in GaAs where all Si-donors have identical local environments. In contrast, three discrete emission rates are observed in dilute AlGaAs alloys, suggesting that the group IV donor moves towards the interstitial site, thereby “selecting” three of the twelve surrounding group III atoms. We present evidence for an ordering of theDX levels consistent with Morgan’s model of a deepening potential well for theDX level as Al atoms are subsequently substituted for Ga atoms near the relaxed donor. These conclusions are consistent with earlier calculations of Chadi and Chang.