Negative Differential Resistance in Laser-Assisted Field Emission from Si Nanowires

Semiconducting nanowires (NWs) are studied in field-emission (FE) for expanding electron gun performances and functionality in terms of stability, brightness and pulsed emission. Here we report on a pronounced double negative differential resistance (NDR) in the FE IV characteristics measured during photo-assisted field emission experiments on highly crystalline ptype silicon nanowires (NWs). The main feature is a double NDR in the current saturation regime, which can be modulated by both temperature and light intensity. These results contrast with previous FE studies in which only barely discernable single NDR was reported. Several mechanisms for the physical explanation of the NDR are currently under consideration : photo-generated carrier instabilities in the depletion region, which give raise to a pulsed space-charge current build-ups in the nanowire or the presence of a double quantum well formed by confinement near the Si nanowire apex. Because NDRs are signatures of pulsed currents, these results suggest new functionalities for which pulsed electron sources can potentially be achieved at high repetition rates.