GE COMPOSITION SATURATION BEHAVIOR DURING LOW-TEMPERATURE SI1-XGEX GROWTH BY DISILANE AND SOLID GE MOLECULAR-BEAM EPITAXY

Ge composition dependence on the Ge cell temperature has been studied during the growth of Si1-xGex by disilane and solid Ge molecular beam epitaxy at a substrate temperature of 500 degrees C. It is found that the composition x increases and then saturates when the Ge cell temper ature increases, which is different from the composition-dependent beh avior in growth at high temperature as well as in growth by molecular beam epitaxy using disilane and germane. The enhanced hydrogen desorpt ion from a Ge site alone cannot account for this abnormal composition- variation behavior. We attribute this behavior to the increase of rate constant of H desorption on a Si site when the Ge cell temperature in creases.