Preparation and characterization of large-sized CdZnTe epitaxial single crystal

CdZnTe (CZT) epitaxial single crystal with a diameter of 2 inches and a thickness exceeding 1 mm was prepared by the closed spaced sublimation. In order to test the uniformity of the large-sized CZT epitaxial single crystal, the composition, crystalline quality, X-ray response performance and carrier transport property of the central and edge parts of the CZT crystal were characterized. The morphology images show that different areas have flat surfaces with dislocation densities between 3.5 × 10⁴ cm⁻² and 4.5 × 10⁴ cm⁻², respectively. The crystal quality shows a trend of better in the central region than in the edge. The bandgap is between 1.56 eV and 1.57 eV, and the resistivity is between 5 × 10⁹ Ω cm and 6 × 10⁹ Ω cm. The sensitivities of the detectors prepared with the edge and central areas to X-ray is 276.22 μCGy⁻¹ cm⁻² and 283.43 μCGy⁻¹ cm⁻², respectively. The carrier lifetime products of the edge and central parts were tested to be 3.932 × 10⁻⁴ cm ² V⁻¹ and 4.511 × 10⁻⁴ cm² V⁻¹, by fitting the Hecht equation. The lower (μτ)_e values of the edge part may be higher dislocation density, which has a great impact on the transport process of charge carriers, as demonstrated by the photoluminescence (PL) results. The fabricated detectors have a stable response to ²⁴¹Am@59.5 KeV gamma-ray, which shows great potential for future applications in the field of photon counting imaging.