Analysis of edge threading dislocations b→=12〈110〉 in three dimensional Ge crystals grown on (001)-Si substrates

Abstract

Threading dislocations (TDs) in germanium (Ge) crystals epitaxially grown on a patterned (001)-silicon (Si) substrate are investigated using transmission electron microscopy (TEM) techniques. Analysis of dislocations performed on the Ge crystals reveals 60° and edge TDs with Burgers vector b→=12〈110〉. High-angle annular dark-field scanning TEM (HAADF-STEM) is used to observe the core of the edge TDs at atomic scale. Pairs of TDs with b→=12〈110〉 are present in the material running parallel at small distances between them (0.5–1.5 nm). The observation of such parallel dislocation pairs in Ge has not been documented before. The interaction between the edge dislocation pairs is obtained experimentally from the high-resolution HAADF-STEM images by applying geometrical phase analysis. The experimental strain maps are compared to analytical calculations based on the anisotropic elastic theory demonstrating a good match between them.