Anisotropy of strain relaxation in (100) and (110) Si/SiGe heterostructures

Abstract

Plastic strain relaxation of SiGe layers of different crystal orientations is analytically analyzed and compared with experimental results. First, strain relaxation induced by ion implantation and annealing, considering dislocation loop punching and loop interactions with interfaces/surfaces is discussed. A flexible curved dislocation model is used to determine the relation of critical layer thickness with strain/stress. Specific critical conditions to be fulfilled, at both the start and end of the relaxation, are discussed by introducing a quality parameter for efficient strain relaxation, defined as the ratio of real to ideal critical thickness versus strain/stress. The anisotropy of the resolved shear stress is discussed for (001) and (011) crystal orientations in comparison with the experimentally observed anisotropy of strain relaxation for Si/SiGe heterostructures.