II-VI ultraviolet detectors: issues of detectivity and antireflection coatings

A detectivity study is presented on an MBE- grown ZnS/sub 0.58/Se/sub 0.42/ UV photodiode system. The noise spectral density, impulse response time, bandwidth, responsivity, dark current at reverse bias up to 12 V and zero bias resistance were determined. A detectivity as high as 7.1/spl times/10/sup 14/ cmHz/sup 1/2/W/sup -1/ has been achieved. A set of devices with single-layer/double-layer anti-reflecting coatings (ARCs) of different thicknesses and compositions were fabricated. The results are in general in good agreement with the prediction from the theories.