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−xZn_xTe (CZT) substrate, used for the growth of the Hg_1−xCd_xTe (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 × 10⁴ cm⁻² and 6 × 10³ 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.