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We report the fabrication and characterization of a depletion-mode n-channel ZnS/sub 0.07/Se/sub 0.93/ metal-semiconductor field effect transistor (MESFET). A ZnSSe FET could be a key element in opto-electronic integration consisting of light emitters, light receivers and MESFET pre-amplifiers. Mesa isolation, recess etching and self-alignment techniques were adopted to optimize the MESFET performance. Source and drain (S/D) ohmic contacts and gate Schottky contact were formed by Cr/In/Cr and Au deposition, respectively. Depletion mode FET's with varying gate width-to-length ratio of W/L=200 μm/20 μm, 200 μm/4 μm and 200 μm/2 μm were fabricated. A 2 μm FET was characterized as follows: the turn-on voltage, V/sub on//spl ap/1.75 V, the pinch-off voltage, V/sub p//spl ap/-13 V, the unit transconductance, g/sub m//spl ap/8.73 mS/mm, and the breakdown voltage with zero gate-source bias, BV/spl ap/28 V.