Spatial distribution of microdefects around dislocations in Si-doped GaAs

The microscale electrical and optical inhomogeneity around dislocations are presented on Si-doped liquid-encapsulated vertical boat grown GaAs. Atmosphere of the dislocations were evaluated by combination use of photoetching, high spatial resolution photoluminescence (PL) mapping and carrier density mapping. A broad PL emission band with a peak at 0.95eV commonly appears in Si-doped GaAs wafers, and the microscopic intensity pattern of the band agree with the photoetching features. The intensity increases in the core region of the dislocations and decreases in the surrounding area. The band-edge emission shows a complementary intensity pattern. The carrier density mapping on a wafer indicates that the carrier concentration is higher in the dislocated area, correlating with the PL intensity pattern. These results indicate that the microdefects responsible for the 0.95eV band are acceptors and act as killer centers for the band-edge emission. After solidification they are gettered by dislocations, and then denuded zone will be formed at the surrounding area. Therefore optical and electrical inhomogeneity will occur around dislocations.