Strain mapping in interband cascade lasers

Abstract

A typical interband cascade laser wafer contains more than 2000 multilayers composed of InAs, AlSb, GaSb, and GaInSb. The lattice constants of the three materials except GaSb have a certain degree of mismatch with the GaSb substrate. Therefore, to grow a high-quality epitaxial layer, it is necessary to optimize the growth conditions to achieve strain balance in the entire epitaxial layer. In this work, the strained superlattice structure was characterized via scanning transmission electron microscopy and high-resolution x-ray diffraction. The strain distribution was mapped using geometric phase analysis of high-angle annular dark-field images. We demonstrate that strain compensation has been achieved in both the InAs/AlSb superlattice clad layers and the InAs/InGaSb/InAs W quantum well active region.