High mobility SiGe/Si transistor structures on sapphire substrates using ion implantation

Abstract

We report the fabrication of high mobility n-type SiGe/Si transistor structures on sapphire substrates by ion implanting phosphorus ions into strained 10-nm-thick silicon channels. The strained Si channels were sandwiched between Si0.7Ge0.3 layers, which, in turn, were deposited on Si0.7Ge0.3 virtual substrates and graded SiGe buffer layers. After the molecular beam epitaxy film growth process was completed, donors were introduced and activated using ion implantation and postannealing processes. Microstructural characterization of the buffer layer, virtual substrate, and electron conduction structure using high resolution x-ray diffraction, cross-sectional transmission electron microscopy, atomic force microscopy, and secondary ion mass spectroscopy are reported. Room temperature electron mobilities up to 900 cm2/V s at a carrier density of 1.3×1012 cm−2 were measured. Electron concentration appears to be the key factor that determines mobility, with the highest mobility observed for electron densities in the 1–2×1012 cm−2 range.