Abstract

The analysis of frequency-dependent characteristics of an ion-implanted buried-gate GaAs MESFET, with front side illumination has made achieving improved performance in I-V characteristics possible. When photo energy falls on the device, flow of charge carriers changes corresponding to the change in wave length and frequency of incident light. It has been observed that the channel conductance and I-V characteristic of buried gate increase. The data suggest that the magnitude of drain-to-source current increases, and as a result there are more uncovered ionic charges in the space charge region toward the drain-side of the gate. This analysis includes surface states and the ion implanted buried-gate process. The access charge density at the drain-side of the depletion induces opposite charges in the gate electrode. Consequently, it gives forward biasing to the Schottky barrier gate which increases with increasing values of Ids. As a result, the modulation of channel conductance and photo-voltage characteristics due to the buried-gate GaAs MESFET become highly effective. The results indicate very good performance of the device compared to other devices like MESFET under back illumination and MESFET with front illumination having surface gate.

Key words: AC model optically illuminated field-effect transistor (OPFET), GaAs OPFET, optically controlled metal–semiconductor–field-effect transistor (MESFET).