LOW-TEMPERATURE GROWTH-PROPERTIES OF SI1-XGEX BY DISILANE AND SOLID-GE MOLECULAR-BEAM EPITAXY

Low temperature (similar to 500 degrees C) growth properties of Si1-xG ex by disilane and solid-Ge molecular beam epitaxy have been studied w ith an emphasis on surface morphology and growth kinetics. It is found that low-temperature growth(<500 degrees C) is in layer-by-layer mode and atomically-smooth surfaces have been obtained in as-grown samples with large Ge composition (>0.5). Ge composition dependence on substr ate temperature, Ge cell temperature and disilane flow rate have been investigated. It is found that in low-temperature growth (less than or equal to 500 degrees C) and under large disilane flux, Ge composition increases with the increase of Ge flux and further increase of Ge flu x leads to the saturation of Ge composition. Similar compositional dep endence has been found at different growth temperatures. The saturated composition increases with the decrease of substrate temperature. The results can be explained if H desorption is assumed to occur from bot h Si and Ge monohydrides without diffusional exchange and the presence of Ge enhances H desorption on a Si site. (C) 1998 Elsevier Science B .V. All rights reserved.