Formation mechanisms and suppression method of needle-like defects in HgCdTe epitaxial films

Hg_1−xCd_xTe (MCT) is a critical material for infrared detectors. The foundation of developing ultra-high-performance detectors lies in the suppression of defects in MCT films. In this study, MCT thin films were grown on CdZnTe substrates using molecular beam epitaxy. The formation mechanism and mitigation strategies of needle-like defects—macroscopic surface defects—were systematically investigated. By controlling the growth temperature, it was found that the occurrence of these needle-like defects is associated with a temperature rise on the surface during the later stages of growth. This phenomenon is attributed to stress propagation induced by the formation of internal voids within the material. High-resolution transmission electron microscopy combined with geometric phase analysis was employed to elucidate the atomic structure and strain distribution of the needle-like defects. Through the optimization of the growth process, the formation of such defects on the MCT surface was effectively suppressed. As a result, the full width at half maximum of the x-ray double-crystal rocking curve was reduced to only 41.8 arc sec, indicating a significant improvement in crystalline quality. This work provides essential theoretical insights and practical guidance for defect control and further process optimization in high-performance MCT infrared detectors.