Scanning photocurrent microscopy analysis of Si nanowire field-effect transistors fabricated by surface etching of the channel.

High-performance field-effect transistors were fabricated by etching the channel regions of surface-doped Si nanowires. On/off ratios of 10(6) and field effect mobilities up to 525 cm(2)/(V x s) represent significant improvements over transistors fabricated from uniformly doped n-Si nanowires. Analysis by scanning photocurrent microscopy (SPCM) confirmed that the devices function similarly to traditional metal-oxide semiconductor field-effect transistors; in accumulation, the device current is controlled by channel conductance modulation, while n(+)-n junctions determine subthreshold characteristics as the channel is depleted. The principles of operation and the drain current saturation mechanisms were investigated by correlating current versus voltage data with integrated photocurrent profiles from SPCM.