Compliant effect of low-temperature Si buffer for SiGe growth

Relaxed SiGe attracted much interest due to the applications for strained S i/SiGe high electron mobility transistor, metal-oxide-semiconductor field-e ffect transistor, heterojunction bipolar transistor, and other devices. Hig h-quality relaxed SiGe templates, especially those with a low threading dis location density and smooth surface, are critical for device performance. I n this work, SiGe films on low-temperature Si buffer layers were grown by s olid-source molecular-beam epitaxy and characterized by atomic force micros cope, double-axis x-ray diffraction, and photoluminescence spectroscopy. It was demonstrated that, with the proper growth temperature and Si buffer th ickness, the low-temperature Si buffer became tensily strained and reduced the lattice mismatch between the SiGe and the Si buffer layer. This perform ance is similar to that of the compliant substrate: a thin substrate that s hares the mismatch strain in heteroepitaxy. Due to the smaller mismatch, mi sfit dislocation and threading dislocation densities were lower. (C) 2001 A merican Institute of Physics.