Evidence for existence of deep acceptor levels in SiGe-on-insulator substrate fabricated using Ge condensation technique

Abstract

By back-gate metal-oxide-semiconductor field-effect transistor method, we examined acceptor concentration (NA) in nondoped SiGe-on-insulator (SGOI) substrates fabricated using Ge condensation. We found NA’s were much higher than the hole concentration (p) measured by Hall effect for low-Ge% SGOI, while NA’s were almost the same as p for high-Ge% SGOI. Such different behaviors between NA and p as a function of Ge% are closely related to the existence of deep acceptor levels (ETA) in SGOI and ETA energy shift toward valence band with increasing in Ge%, which was confirmed from the temperature dependence of p.