An improved model of ion-implanted GaAs OPFET

A seminumerical model of an ion-implanted GaAs optical-field-effect-transistor (OPFET) is presented. The objective of the present work is to overcome the limitations of the existing model without changing the basic approach. Analytical expressions obtained using the one-dimensional Poisson's equation have been solved numerically to obtain the I-V characteristics of the device in dark and illuminated conditions. It is seen that the saturation drain current of the device changes significantly in the illuminated condition. The existing model of the device has been improved by considering the effects of the photovoltage generated across the metal-semiconductor junction and optical modulation of depletion edge depths in the illuminated condition. Unlike in the previous model, it has been concluded that for a high gate bias resistance the optical radiation controls the saturation drain current by changing the channel conductance rather than its conductivity.<
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