Annealing experiments on supercritical Si1-xGex layers grown by RPCVD

This paper presents a study of the relaxation mechanisms for SiGe epitaxy p erformed by reduced pressure chemical vapor deposition (RPCVD) in a commerc ially available single wafer epitaxial reactor. The samples were grown at 5 00 degrees C and an overall pressure of 40 Torr, with SiH2Cl2 and GeH4 as p recursor gasses. In contrast to the situation for molecular beam epitaxy (M BE), we found that under RPCVD conditions the relaxation by 3D-growth was s trongly suppressed. Relaxation then occurred by the development of misfit d islocations even in the case of high Ge-concentrations (>40%). This behavio r is attributed to the high hydrogen coverage of the substrate surface duri ng the RPCVD, which reduces the surface migration of the adsorbed species. Furthermore, the relaxation mechanism has been studied in annealing experim ents where wave and island formation was observed. The annealing experiment s clearly confirm that surface migration plays a significant role for 3D-gr owth. Using the annealing procedure layers of high island density and stron g photoluminescence have been produced. (C) 2000 Elsevier Science S.A. All rights reserved.