Morphological evolution of SiGe films covered with and without native oxide during vacuum thermal annealing

Abstract

The morphological evolution of SiGe films was investigated during vacuum thermal annealing. We found that Ge islands preferentially form in the process of decomposition of native oxide covering the SiGe layer, while pits form as an effective means of relaxing strain in the SiGe layer passivated with hydrogen during vacuum thermal annealing. The formation of small size Ge islands weakly depends on the strain relaxation of the SiGe layer. The size of Ge islands increases with Ge content in the initial SiGe layer and the maximum density of Ge islands is obtained for the SiGe layer with a lower Ge content of 0.06 among the investigated samples. A mechanism to form Ge islands on SiGe films rather than strain driven is proposed in terms of surface potential energy profile induced by the process of decomposition of native oxide.