High-Hole-Mobility Silicon Germanium on Insulator Substrates with High Crystalline Quality Obtained by the Germanium Condensation Technique

Abstract

Thin SiGe-on-insulator (SGOI) substrates with Ge content varying between 42 and 93% were produced by the Ge condensation technique and full structural characterization was carried out. In a second step, the electrical properties of these substrates were analyzed by the pseudo metal-oxide semiconductor field-effect transistor technique which allowed determination of the carrier low-field mobilities, as well as the density of fixed charges in the buried oxide (BOX) and the density of interface traps at the BOX-SiGe film interface. Optimization of intermediate anneals in argon during the condensation process made the production of high crystalline quality and high-mobility substrates possible (up to for a 93% SGOI). Opposite trends were observed for holes and electrons: while the hole mobility increases with increasing Ge content, the electron mobility decreases. In addition, the density of interface traps and also the density of oxide charges were found to increase with increasing Ge content. Possible causes for this increase are discussed.