Showing papers by "Adrian Powell published in 1992"

SiCGe Ternarv Allovs - Extending Si-based Heterostructures

Abstract: We have synthesized Si 1-y C y and Si 1-x-y C y Ge 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.

Scanning tunneling microscopy and spectroscopy of Si/SiGe(001) superlattices

Abstract: Cross‐sectional scanning tunneling microscopy and spectroscopy were used to study a modulation‐doped Si/Si0.76Ge0.24(001) superlattice. Contrast between the Si and Si0.76Ge0.24 layers has been observed in topographic images. Features such as band‐edge discontinuities and band bending arising from doping have been detected in spectroscopic measurements at a series of points across the superlattice structure.