Thin-film photocathodes have been proposed for high-throughput multi-electron-beam lithography applications. In these approaches, arrays of independently modulated sources are achieved by varying the incident light energy reaching each photocathode. For many applications, however, the optical complexity of such a scheme limits the attractiveness of the photocathode approach. To resolve most of these complex concerns, a novel gated photocathode structure had been proposed, which allows each electron beam to be modulated independently and extinguished completely by applying several volts of negative voltage to the gate relative to that to the cathode. In this article we present a study of the detailed I-V characteristics of the thin-film gated photocathode structure. A typical I-V characteristic from any one of ten gated photocathodes fabricated with different geometrical configurations shows three clearly defined regions. In region I, currents are zero when the gate voltage is less than the negative extinction gate voltage. In region II, the cathode and the anode current increase with the gate voltage. The gate current is constant and its magnitude is much smaller than that of the anode current. In region III, all of the currents increase with the gate voltage but more slowly than in region H. The effects of the gate diameter, the insulator layer thickness, and the accelerating field on these parameters have also been examined. A theoretical model has been developed to explain the results. The calculated I-V curves are in good agreement with the experimental curves.