X-ray characterization of multilayered SiGe nanodots depending on the Si spacer growth temperature

SiGe nanodots (NDs) are attractive materials because of their potential for optoelectronic device applications and their high compatibility with Si-based semiconductor technologies. To develop SiGe NDs as effective optoelectronic devices, it is crucial to characterize the SiGe composition and strain to understand their band structure. In this paper, we present the characterization of SiGe NDs/Si spacer multilayered structures with different Si spacer growth temperatures using lab-based X-ray diffraction (XRD) and reciprocal space mapping (RSM). The RSM determined the spatial arrangement and Ge content of the SiGe NDs. The results showed a decrease in Ge content in the SiGe NDs as the Si spacer growth temperature increased. In-plane XRD measurements revealed the coexistence of tensile- and compressively strained regions within the SiGe NDs and Si spacers, with the proportion of strained regions increasing at higher Si spacer growth temperatures. The calculated bandgap energy of the type-II heterointerface between the Si spacer and SiGe NDs, based on the SiGe composition and strain states determined by XRD and RSM, aligns well with the previously reported blue shift in photoluminescence as the Si spacer growth temperature increased.