BELOW THRESHOLD CONDUCTION IN A-SI-H THIN-FILM TRANSISTORS WITH AND WITHOUT A SILICON-NITRIDE PASSIVATING LAYER

We report temperature measurements of inverted staggered amorphous sil icon thin film transistor subthreshold conductance for devices with an d without a top silicon nitride passivating layer. Subthreshold conduc tance activation energies clearly show the different conductance paths in the active layer of these devices. Transistors with no top nitride layer conduct in the bulk amorphous silicon, whereas the devices with a top nitride layer conduct at the interface between the amorphous si licon and the top nitride (a ''back'' channel). Gate bias stressing an d light soaking experiments uphold the existence of the back channel. We also present two-dimensional simulations that support our interpret ation of the experimental data. (C) 1996 American Institute of Physics .