CdZnTe Crystal Quality Study by Cathodoluminescence Measurements

Improving material quality is an essential step to maintain high electro-optical performance at higher operating temperature (HOT) of cooled II-VI infrared (IR) detectors. Indeed, the electrical activity of crystal defects affects their image quality and stability. A first investigation is to correlate the point defect populations with the crystal quality of the Cd 1− x Zn x Te (CZT) substrate, used for the growth of the Hg 1− x Cd x Te (MCT) active layer. For this purpose, spectrally resolved cathodoluminescence (CL) measurements were performed for wafers with low and high crystal quality, with a respective dislocation density of 1.8 × 10 4 cm −2 and 6 × 10 3 cm −2 . At 295 K, both wafers showed band-to-band transition, and CL spectra were modeled with the generalized Planck law. However, at 10 K, CL spectra showed that the visibility of phonon replicas of the donor–acceptor pair ( DAP ) transition at 1.57 eV is dependent on the crystalline order. In addition, the luminescence of the A-center defect ( V_Cd - D ) was observed at 1.43 eV only in the low-quality CZT substrate.