Structural properties and defect formation mechanisms in MBE-grown HgCdTe on InSb (211)B substrates

This work investigates the structural properties of HgCdTe thin films grown on InSb (211)B substrates using molecular beam epitaxy (MBE). The Cd composition of thin films is accurately determined using non-destructive approaches based on x-ray diffraction (XRD) and reflectance infrared spectroscopy. The as-grown HgCdTe thin films exhibit characteristic surface defects with a size of 7-10 µm and density of ~10⁵ cm^-2, resulting in an additional spread in XRD full width at half maximum. Cross-sectional transmission electron microscopy results indicate that these defects are caused by surface In droplet formation during the oxide removal process of InSb substrate, which subsequently results in the formation of In₄Te₃ inclusions and extended defects in MBE-grown HgCdTe. Our findings provide additional confirmation that suppressing thermally induced damage of the InSb substrate is necessary for fabricating high-performance infrared detectors using HgCdTe grown on InSb substrates.