Study of Macrodefects in MBE-Grown HgCdTe Epitaxial Layers Using Focused Ion Beam Milling

摘要

This paper presents a study on the initiation and evolution of macrodefects in molecular beam epitaxy-grown two-color HgCdTe epitaxial layers on CdZnTe substrates. A combination of focused ion beam milling and high-resolution scanning electron microscopy was used to look at the defect cross-sections, and energy-dispersive x-ray spectroscopy was used to study the cross-sectional composition. This study shows that the classic microvoids tend to initiate at interfaces, such as the substrate/epitaxial layer interface and n-p junctions, because of nonoptimum growth conditions. Another class of microvoids was traced to Te precipitates existing in CdZnTe substrates. Large circular defects, occasionally seen on HgCdTe epitaxial layers, were traced to a tiny volatile particle on the substrate, which is believed to be organic in nature. Another large, irregularly shaped Te-rich defect is seen initiating abruptly during growth and is attributed to occasional outburst of Te clusters from effusion cells.