Backgating and light sensitivity in ion-implanted GaAs integrated circuits

Ion-implanted GaAs integrated circuits have been characterized under dark and illuminated conditions to determine the sensitivity of ac parameters to light. Auxiliary experiments were performed on discrete IC elements using white and monochromatic illumination and backgating. Discrete MESFET's were characterized under the various conditions to determine corresponding variations in the magnitudes of Sehottky-barrier height and parasitic channel resistances. We have determined that light sensitivity and backgating are strongly interrelated and arise from a depletion layer at the substrate active-layer interface. We will describe the effect of trap filling on channel resistance and the resulting speed-power variations arising from illumination and backgating.