Low-temperature Si and Si:Ge epitaxy by ultrahigh-vacuum/chemical vapor deposition. Process fundamentals

This paper is an overview of work at the IBM Thomas J. Watson Research Center on the chemical and physical considerations underlying the development of a low-temperature chemical vapor deposition process, designated ultrahigh-vacuum/chemical vapor deposition (UHV/CVD). The origins of the rigorous vacuum and chemical purity requirements of the process are discussed. Operating in the range of 500°C, the process has made it possible to explore the use, in silicon-based devices and atomic-length-scale structures, of a number of metastable materials in the Si:Ge system. Also discussed is associated experimental work on the fabrication of high-speed heterojunction bipolar transistors and high-mobility two-dimensional hole-gas structures.