Strain-induced material intermixing in multiple-stacked Ge/Si quantum dots grown by chemical vapor deposition

Photoluminescence investigations on stacked Ge/Si quantum dots with different thicknesses of Si spacer layer are presented. According to the emission energy shift in the Ge dots, we found that thinner spacer will lead to remarkable Ge-Si intermixing. Such intermixing can be attributed to the strain-induced material intermixing, which tends to shallow the dot potential, soften the dot/spacer interface sharpness, and hence degrade their room-temperature emission properties.