Formation mechanism and elimination of needle defects on CdZnTe epitaxial films prepared by close-spaced sublimation

Needle defects, one of the common surface defects in II-VI/III-VI semiconductor epitaxial films, negatively impact surface morphology and photoelectric properties of films limiting their application in solar cells, detectors, substrates, etc. Hence, the formation mechanism of needle defects in CdZnTe/GaAs system was investigated. It was found that needle defects have medium and low temperature adaptability. High resolution transmission electron microscope (HRTEM) characterization reveals needle defects are generated by the intersection of twins and film surface. The locations of stacking faults (SFs) were shown by HRTEM figures of two mutually perpendicular 〈1 1 0〉 planes. The results demonstrate that SFs are correlated to lattice mismatch, domain deflection, substrate steps and interface bonding. Under stress accumulation, SFs react with slip dislocations to form twins. In the process of a 3D to a quasi-2D growth, the pinning effect of twins on the lateral growth of islands leads to needle defects left on surface. This work illustrates the formation mechanism of needle defects and suggests the possibility of their elimination from kinetic perspectives, providing a new idea for interfacial stress control and semiconductor films quality improvement.