Growth and Characterization of UHV/CVD Si/SiGe Strained-Layer Superlattices on Bulk Crystal SiGe Substrates

Abstract

AbstractHigh-quality short-period Si/SiGe strained-layer superlattices have been grown on bulk single-crystal SiGe substrates using a commercial low-temperature ultrahigh vacuum chemical vapor deposition (UHV/CVD) reactor. These superlattices were characterized by high-resolution x-ray diffraction (HRXRD), Auger electron spectroscopy (AES), atomic force microscopy (AFM), cross-sectional transmission electron microscopy (XTEM) and photoluminescence (PL). HRXRD, AES, and XTEM results confirm that the materials deposited are high crystal-quality superlattice layers with abrupt interfaces and excellent thickness and composition uniformity across superlattices of 5 periods. AFM images show similar surface RMS roughness of much less than 1 nm for both the top layer surface and the starting substrate surface, indicating very smooth surfaces. PL measurements further confirm material quality and composition, and show sharp, well-resolved near band-edge BE and FE PL and strong broad sub-gap PL perhaps related to direct-gap superlattice transitions. The materials grown here are very promising for applications of both high-speed electronic devices and high-efficiency optoelectronic devices.