Weak-beam stereomicrography of defects in GaAs/In x Ga1−x As interfaces

Abstract

Weak-beam stereomicrography was used to image dislocation arrays at the two interfaces in GaAs/In x Ga1−x As/GaAs sandwich structures. For samples with mismatch equal to 1.8%, separate dislocation arrays were found at each interface. The measured dislocation density at the upper interface was only 10% of the density found at the lower interface. This is attributed to reduced mismatch at the upper interface due to strain in the In0.25Ga0.75As layer. Also, the dislocation spacing asymmetry along the [01l] and [01l] directions is exhibited at each interface. In the upper interface, it is attributed to growth on asymmetrically strained In0.25Ga0.75As. Stereo-imaging of samples with higher mismatch (f = 2.9%) showed 3-dimensional details of dislocation half-loop nucleation that leads to a semiorthogonal array with increasing In0.4Ga0.6As layer thickness.