Gamma radiation effects on ZnS/CdTe-passivated HgCdTe detectors with different ZnS thickness

At present, HgCdTe arrays has been commonly used in photodetectors for infrared detection in space system, where they are exposed to the space radiation environment. For high radiation-tolerance and the optimum performance of the detector, surface-passivation technology that provides long-term stability is required. Double layer of ZnS/CdTe passivant is most recommendable, because ZnS/CdTe-passivated HgCdTe detectors could show great insulating and radiation-tolerant properties. However, the thickness ratio of ZnS and CdTe layers has not been optimized. In this study, the gamma radiation effects on ZnS/CdTe-passivated mid-wavelength HgCdTe arrays with different ZnS-layer thicknesses were investigated, by analyzing the current-voltage curves before and after gamma irradiation at a very low rate. To our surprise, increase of ZnS thickness from 300 nm to 700 nm dramatically improved the radiation tolerance, although ZnS is considered to be vulnerable to gamma irradiation. We hypothesized that gamma radiation could be strongly absorbed by ZnS with sufficient thickness and the transmitted intensity is harmless to the HgCdTe arrays. Therefore, increase of ZnS thickness could protect the HgCdTe arrays from gamma radiation damage. Here, we presented an efficient and easy processing method to increase radiation-tolerant properties of the high performance HgCdTe photodetectors.