Unipolar rectifying silicon nanowires-TCAD study

Due to the large surface to volume ratio in nanowires, small changes in surface condition result in large changes in current-voltage characteristics. As a consequence, the overlap of the end-wire contact with the oxide-covered surface along the length of the nanowire can have a significant effect on the current-voltage characteristics of the wire. We present TCAD studies of this effect. One of the contacts at the end of the wire envelops a part of the surface along the length of the oxide-covered nanowire, resulting in a partial gating of the wire by the voltage applied to the Ohmic contact. This gating causes rectifying behaviour in the unipolar nanowire, creating a conducting surface channel in forward bias and space-charge-limited current in reverse bias. TCAD studies show that the length of contact overlap relative to the length of the nanowire influences the off-current to a large extent, dramatically decreasing the off-current with increasing overlap. TCAD results of the influence of wire diameter, length, and workfunction on the rectifying behaviour of the unipolar nanowire are also presented.