Peak separation method for sub-lattice strain analysis at atomic resolution: Application to InAs/GaSb superlattice

TL;DR

This paper introduces a novel atomic resolution method for measuring sub-lattice strain in superlattices, revealing detailed strain distributions and interface characteristics crucial for material properties.

Contribution

The study presents a new atomic-scale strain measurement technique using Z-contrast imaging, enabling direct analysis of cation and anion sub-lattice strains in superlattices.

Findings

Identified compressive strain in GaSb layers.

Detected tensile strain at layer interfaces.

Revealed In incorporation and interface intermixing.

Abstract

We report on a direct measurement of cation and anion sub-lattice strain in an InAs/GaSb type-II strained layer superlattice (T2SLs) using atomic resolution Z-contrast imaging and advanced image processing. Atomic column positions in InAs and GaSb are determined by separating the cation and anion peak intensities. Analysis of the InAs/GaSb T2SLs reveals the compressive strain in the nominal GaSb layer and tensile strain at interfaces between constituent layers, which indicate In incorporation into the nominal GaSb layer and the formation of GaAs like interfaces, respectively. The results are compared with the model-dependent X-ray diffraction measurements in terms of interfacial chemical intermixing and strain. Together, these techniques provide a robust measurement of atomic-scale strain which is vital to determine T2SL properties.