Extrinsic and intrinsic defects at molecular-beam-epitaxy regrown GaAs interfaces

To identify the defects responsible for anomalous electronic properties at the molecular-beam-epitaxy regrown interface, the interfaces of Si-doped GaAs epitaxial layers (n = 7 x 10(16) cm(-3)) have been investigated. A significant reduction of the carrier concentration in a large region around the regrown interfaces has been observed by capacitance-voltage measurement. Photoluminescence spectra measured at different etching depths below the sample surface show that the intensity of the emissions associated with carbon accepters and As vacancy-carbon acceptor complexes strongly increases in the interface region. The carbon-related emission line is absent in the photoluminescence spectra of the sample without regrown interface. The carrier concentration profiles obtained by capacitance-voltage measurements fit well that calculated numerically with the assumption that a high concentration of carbon is present at the interface. These results indicate that carbon and As vacancies are main defects responsible for the carrier depletion at the regrown interface. This carrier depletion is believed to be due to the direct compensation of Si donors by carbon accepters. On the other hand, a high concentration of As vacancies at the interface is favorable for the formation of As vacancy-oxygen complexes that may act as deep-level electron traps. (C) 1999 Elsevier Science B.V. All rights reserved.