Composition Dependence of Hardness and Moduli in GeSi/Si-Heterostructures Measured by Nanoindentation

Abstract

AbstractGexSi1-x layers (0 ≤ × ≤ 1), with thicknesses ranging from 0.1 to 1.2 µm, were grown on Si(100) and Si(lll) by chemical vapor deposition (APCVD, LP/RTCVD) and liquid phase epitaxy (LPE), respectively. A NanoTest 500 machine served for nanoindentation measurements to evaluate the hardness and elastic moduli. The GeSi layers show strong alloy hardening with an increase varying proportional to x(l-x) as reported for III-V and H-VI-semiconductors. Maximum hardness is close to x = 0.45 at one and a half of the silicon hardness. For binary alloys such as Ge-Si, which show complete solid solubility, the elastic moduli are generally assumed to vary linearly with composition. In contrast to that we found for the indentation modulus E/(l-v2) a positive deviation of 30 % from linear interpolation (Vegard’s law), proportional to x(l-x). The increase in the elastic constants is explained by the structural properties of the Ge-Si alloy.