SiCGe ternary alloys — extending Si-based heterostructures

Abstract

We have synthesized Si 1−yC y and Si 1−x−yC yGe x alloys using Molecular Beam Epitaxy. When combined with the Si-Ge system, the new ternary system offers greater versatility and freedom in strain and bandgap engineering. Unlike the Si-Ge system, the Si-C system has a high misfit (52%) and low solubility (< 10 -6), with a propensity to compound formation, therefore, the structures are kinetically stabilized by low temperature growth. In this paper, we first describe bandgap engineering applied to this system. We then consider the growth methodology and critical thickness. Strain compensation and strain engineering using the ternary system is then described. Finally we show that thermal degradation of these films does not occur till > 800°C first by interdiffusion and subsequently at higher temperatures by silicon carbide precipitation.