EFFECTS OF THE REAR INTERFACE STATES AND FIXED CHARGES ON THE ELECTRICAL CHARACTERISTICS OF THIN-FILM TRANSISTORS WITH THIN AMORPHOUS-SILICON LAYERS

The electrical characteristics of the thin film transistors (TFT's) wi th hydrogenated amorphous silicon (a-Si:H) films thinner than 0.1 mu m have been carefully studied to show that the interface states and fix ed charges at the rear interface will play the comparable effects to t hose at the front interface on the field effect conductance. It is dea rly demonstrated that as the thickness of the active layer is smaller than the theoretically expected width of the space charge region, the potential at the rear interface will be affected by the gate voltage. This is very different from the conventional case with a thicker activ e layer. Since the TFT's at present have smaller typical thicknesses o f the semiconductor films than the expected width of the space charge region, the effects of the interface states and the fixed charges at b oth the rear and front interfaces, as well as the bulk states of the t hin a-Si:H films, must be taken into account concurrently.