Reduced Dark Current in Cd0.9Zn0.1Te Detector Arrays by Aluminium Oxide Passivation
Contrary to the prevailing view that processing cadmium zinc telluride (CZT) semiconductors above 150 °C leads to irreversible device degradation, here we show that Al2O3 passivation layer deposited by atomic layer deposition at 250 °C not only preserves CZT detector performance but also substantially improves it. Pixelated metal-semiconductor (MS) and metal-insulator-semiconductor (MIS) CZT detectors were passivated with a thin atomic-layer-deposited Al2O3 film and characterized electrically. The passivated devices exhibited no measurable degradation, even under a high-bias operation of 1000 V. Instead, the dark current decreased by approximately a factor of five, while the interpixel leakage current was reduced by nearly one order of magnitude, from ~41 nA to ~2-3 nA at -200 V. Passivation also produced highly uniform dark-current characteristics across adjacent pixels and completely eliminated current-voltage hysteresis, indicating suppression of defect-assisted charge transport. Furthermore, no significant difference in dark current was observed between the MS and MIS detectors after passivation, suggesting that the Al2O3 layer dominates the surface electrical behavior. These results demonstrate that optimized Al2O3 passivation at 250 °C is fully compatible with high-performance CZT detector processing and provides a practical route toward lower-noise, higher-spectral-resolution X-ray imaging systems.