XAS study of Sn-related DX centers in (Al, Ga)As

We have used fluorescence-detection X-ray absorption spectroscopy to measure the Sn atomic-scale environment in single-crystal Sn doped Al0.23Ga0.77As in two states for direct comparison: in the dark at 80 K, where Sn atoms are in DX states; after photoexcitation at 20 K, where they are in shallow donor states. The observed differences in Sn near neighbors are not consistent with the widely accepted model for DX centers put forth by Chadi and Chang (PRL 1988). © 1995.