Fabrication of room-temperature nuclear-radiation CdZnTe pixel array detectors

The material selection, testing and fabrication technology development of high-performance pixelated CdZnTe (CZT) radiation detectors are reported. The size of the wafer is 10 mm×10 mm×2 mm. The specifications of the anode are 4×4 pixels with a 0.6 mm distance between adjacent pixels. The crystals were evaluated by using infrared microscopy and by being fabricated into planar detectors. The selected crystal has a high resistivity (10¹⁰ Ω·cm), high electron transport product (μτ_e≈1. 07±0.02×10^-3cm²/V) as well as uniform density and size distribution of inclusions. Pixelated detectors were fabricated employing photolithography, lift-off and electrode deposition. The wet-method Passivation and oxidation with low energy atomic oxygen were developed on bared CdZnTe surface. The leakage current of each pixel is between 0.79 nA and 1.2 nA at the bais of 100 V. The γ-ray spectroscopy responses of CZT detectors at different pixels were tested at room temperature using an ²⁴¹ Am radioactive source with the energy of 59.5 keV. The behaviors of different pixels under radiation were discussed through the Shockley-Ramo theorem.