Carrier capture as a mechanism for defect migration at semiconductor surfaces
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Scanning-tunneling-microscopy (STM)-induced vacancy migration on GaAs(110) is shown to result from the trapping of minority carriers in dangling-bond defect states. The energy released when an electron falls into an As vacancy level on p-type GaAs, or when a hole falls into a Ga vacancy level on n-type GaAs, is sufficient to account for the observed migration events. Other hypotheses are inconsistent with our experimental signatures and theoretical calculations. The general notion that carrier capture can promote atomic motion may also apply to other systems with localized levels, and the ramifications for atomic manipulation with the STM are briefly considered.
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