Identification and Mitigation Strategies of Etch Pit-Associated Defects in MBE-Grown HgCdTe Thin Films

Hg_1-xCd_xTe (MCT) is recognized as an ideal material for infrared detector applications due to its superior internal quantum efficiency. However, a minor process deviation can deteriorate the crystal quality because of the extremely harsh epitaxial processes of MCT, leading to a dramatic increase of defect type and density. Here, MCT thin films were grown on lattice-matched CdZnTe substrates by regulating deliberately molecular beam epitaxy (MBE) processes. Two types of etch pit defects with triangular (EP-A) and foliate (EP-B) morphologies have been characterized by scanning electron microscope and transmission electron microscopy. The atomic structural information and origin of the two etch pit microdefects were investigated in detail. The processes of EP-A defects correlated to low growth temperature and Hg pressure, contrary to those of EP-B ones. On the basis of MBE process optimization, extremely high-quality MCT thin films with a low defect density of an average etch pit density less than 3 × 10⁴ cm⁻² and full width at half-maximum of only 14.4 arcsec measured by double crystal rocking curve were yielded. The formation mechanisms and mitigation strategies of the defects are detailed, providing a vital guidance for higher-quality MCT infrared detector applications.