Ge / SiGe Multi Quantum Well Fabrication by Using Reduced Pressure Chemical Vapor Deposition

Abstract

In this paper we have deposited structures comprising a stack of 10 periods made of 15 nmthick Ge multi quantum well (MQW) enclosed in 15 nm-thick Si0.2Ge0.8 barrier have been deposited on SiGe virtual substrates (VS) featuring different Ge contents in the 85% 100% Ge range to investigate the influence of heteroepitaxial strain on the Si0.2Ge0.8 and Ge growth. With increasing Ge concentration of the VS, growth rate of the Si0.2Ge0.8 in the MQW increases. Si incorporation into the Si0.2Ge0.8 layer becomes also slightly higher. However, almost no influence of the growth rate is observed for Ge growth in the MQW. We argue that the increased tensile strain promotes the Si reaction at the surface. In the case of the Si0.2Ge0.8 growth on Ge, we observe a smeared interface due to the Ge segregation during the growth. Furthermore, we observe that this interface width increases with increasing Ge concentration of VS. We attribute this observation to the increased segregation of Ge driven by the increased strain energy accumulated in the in the Si0.2Ge0.8 layers. We also observed that the MQW layer “filters-out” threading dislocations formed in the VS.