CdSe Nanowire Fielf-Effect Transitor

We report the fabrication and characterization of single and network of CdSe nanowire (NW) field-effect transistors (FETs). The NWs are grown by the Solution-Liquid-Solid (SLS) technique and are on an average 10 nms in diameter and few microns in length.

Back gating is employed to fabricate FETs. Electrical contacts are defined to network of NWs by photolithography while E-beam lithography (EBL) and Focussed Ion Beam (FIB) methods are employedto contact single NWs that act as channels of the FETs. Fabrication of NW FETs, with problems encountered and possible solutions to the problems are discussed in detail.

Individual CdSe NWs are found to be very resistive with current levels in a few pAs for few volts of applied bias. Pronounced photoconductivity is observed in the presence of visible lightwith current levels increasing from a few pAs to 100s of pAs for single NWs and a few nAs to few $mu$As for network of NWs.

Field effect characterization indicates n-type unintentional doping of CdSe NWs. In dark, turn-on to turn-off current ratios between 10 and $~$10$^{3}$ for single NWs and between 10$^{3}$ and 10$^{6}$ for network of NWs FETs have been realized.

Under optical illumination, current increment from over 10 to 10$^{3}$ as gate bias is changed from +40V to -30V is observed for single NW FETs while current increment from over 10 to 10$^{6}$ isobserved for network of NWs FETs as gate bias varies from +10V to -10V. Loss of gate control under optical illumination is observedfor both single and network of NWs.

Our NW FETs show high photoconductivity which makes them suitable for NW based optical sensing.