DISCRETE STRUCTURE OF THE DX CENTER IN GAAS-ALAS SUPERLATTICES

Short-period GaAs-AlAs superlattices selectively doped with Si donors have been investigated by use of Hall and persistent-photoconductivity techniques. We show that the DX center in GaAs layers has lower energy than the conduction miniband. The difference in thermostimulated capture of electrons in atomic configurations corresponding to all-Ga and all-Al near-neighbor environments of the Si donor is determined. A configuration-coordinate model of various atomic environments is proposed, which predicts that the all-Al environment of the Si atom has a larger lattice relaxation than the all-Ga environment.