Concentration-dependent self-diffusion coefficients in amorphous Si1−xGex solid solutions: An interdiffusion study

Abstract

Self-diffusion coefficients of Si and Ge in amorphous Si1−xGex (a-Si1−xGex) solid solutions were determined quantitatively in the temperature range of 440 °C – 460 °C by the investigation of interdiffusion in amorphous Si/Si0.52Ge0.48 multilayers using Auger electron spectroscopy sputter-depth profiling. The determined concentration dependent self-diffusion coefficients of Si and Ge in a-Si1−xGex with 0 ≤ x ≤ 0.48 at. % Ge are about ten orders of magnitude larger than in the corresponding crystalline phases, due to the inherent, excess free volume in the amorphous phase. The self-diffusion coefficient of Si (or Ge) in a-Si1−xGex increases in association with a decreasing activation enthalpy with increasing Ge concentration. This concentration dependence has been related to an overall decrease of the average bond strength with increasing Ge concentration.