Defect Engineering in Epitaxially Grown Cd(Zn)Te Thin Films on Lattice-Mismatch Substrates

II–VI (Hg)(Cd)(Zn)Te semiconductors are significant materials with a wide range of applications in high-end infrared (IR) sensing/imaging, radiation detectors, and solar cells. However, due to the soft and brittle nature of II–VI materials, II–VI substrates normally are of lower crystal quality, smaller wafer size, and higher unit cost compared to other Group IV and III–V substrates, which hinder II–VI epitaxial materials from being widely adopted in applications demanding compact, sensitive, and inexpensive optoelectronic devices. Heteroepitaxial growth of II–VI semiconductors on commercially available III–V or IV alternative substrates is a promising pathway to achieve high-performance and cost-effective optoelectronic devices. Particularly, II–VI HgCdTe infrared imaging arrays based on high-quality II–VI Cd(Zn)Te buffer layers epitaxially grown on alternative substrates could provide a low-cost, high-volume fabrication route for next-generation IR imagers. However, the major challenge in heteroepitaxy comes from lattice and thermal expansion coefficient mismatches between the dissimilar materials, which can result in a high density of defects that are stringent restrictions for fabricating high-performance optoelectronic devices. In this chapter, we review our findings concerning use of strained CdZnTe/CdTe superlattice layers as dislocation filtering layers for heteroepitaxial growth of CdTe buffer layers on alternative substrates such as III–V GaAs substrates. The structural and optical properties of the CdTe buffer layers were investigated by using various methods including etch pit density (EPD) measurements, high-resolution x-ray diffraction, cathodoluminescence, and photoluminescence spectroscopy. The correlation between the structural/growth parameters and the dislocation filtering efficiency was explored and discussed. The results reviewed in this chapter provide an alternative framework for defect engineering of heteroepitaxial II–VI semiconductors for applications in next-generation optoelectronic devices.