ZnSSeTe PIN photodiode was grown on p-type GaAs (100) substrate by molecular beam epitaxy. Dark current-voltage was measured. It was found that the turn on voltage was 0.7V and the breakdown voltage was 16V. When the applied reverse bias was greater then 3V, the appearance of 1/f noise was observed. The noise equivalent powers (NEP) for the bias of -3V, -4V, and -5Vwere calculated to be 141pW, 347pW, and 620pW, respectively. The corresponding normalized detectivities (D(superscript *)) were 1.4×10^10, 5.7×10^9, and 3.2×10^9 cmHz(superscript 1/2)W^(-1), respectively. Such values of D(superscript *) are reasonably good compared to nitride-based photodiodes and commercial silicon photodiodes.