Hetero-epitaxial films were grown onto GaAs substrates, by means of metalorganic chemical vapor deposition, and were shown to have a higher concentration of Zn in interstitial sites than did equivalent mono-epitaxial InP layers. A Zn interstitial-related donor-acceptor photoluminescence peak was observed in hetero-epitaxial films. It was absent from homo-epitaxial sample spectra. Capacitance-voltage measurements yielded a lower hole concentration in hetero-epitaxial layers, as compared with homo-epitaxial layers. This was attributed to the existence of a higher fraction of Zn in interstitial sites within the hetero-epitaxial layers. In addition, the hole concentration of the hetero-epitaxial layers was found to be lower when near to the heterojunction; as compared with the surface region. This was related to the dislocation density near to the heterojunction, as observed by transmission electron microscopy. It was concluded that the increased Zn interstitial concentration, and reduced hole concentration, were due to interactions between dislocations and Zn solutes.

R.M.Sieg, B.Chatterjee, S.A.Ringel: Applied Physics Letters, 1995, 66[23], 3108-10