On the mechanism of formation of AsGa+anti-site defects in electron-irradiated n-type GaAs

Abstract
Data have been obtained specifically to test a recent suggestion that mobile arsenic interstitials in electron-irradiated GaAs interact with impurities on the gallium sub-lattice via a 'Watkins' replacement to produce AsGa+. A comparison was made of the production of arsenic anti-site defects (AsGa+) in two Bridgman GaAs crystals, one doped with silicon and the other with sulphur. IR (LVM) absorption and EPR measurements show that the chemical nature of the n-type dopant (SiGa or SAs) is unimportant: AlGa defects play no role and boron and carbon impurities are not relevant to the process. Finally, no effects were observed in changing the incident beam current from 24 to 2.4 mu A cm-2. The authors conclude that the impurity replacement mechanism cannot be correct.