Photoelectrical Properties Investigated on Individual Si Nanowires and Their Size Dependence

Abstract

Periodically ordered arrays of vertically aligned Si nanowires (Si NWs) are successfully fabricated with controllable diameters and lengths. Their photoconductive properties are investigated by photoconductive atomic force microscopy (PCAFM) on individual nanowires. The results show that the photocurrent of Si NWs increases significantly with the laser intensity, indicating that Si NWs have good photoconductance and photoresponse capability. This photoenhanced conductance can be attributed to the photoinduced Schottky barrier change, confirmed by I–V curve analyses. On the other hand, electrostatic force microscopy (EFM) results indicate that a large number of photogenerated charges are trapped in Si NWs under laser irradiation, leading to the lowering of barrier height. Moreover, the size dependence of photoconductive properties is studied on Si NWs with different diameters and lengths. It is found that the increasing magnitude of photocurrent with laser intensity is greatly relevant to the nanowires’ diameter and length. Si NWs with smaller diameters and shorter lengths display better photoconductive properties, which agrees well with the size-dependent barrier height variation induced by photogenerated charges. With optimized diameter and length, great photoelectrical properties are achieved on Si NWs. Overall, in this study the photoelectrical properties of individual Si NWs are systematically investigated by PCAFM and EFM, providing important information for the optimization of nanostructures for practical applications.

Opto Field-Effect Transistors for Detecting Quercetin–Cu2+ Complex

“…The dark current I dark is indicated in the plot to show that the I DS under illumination, I illumination , is lower than I dark in the wavelength range of interest. Many factors affect the polarity of the photocurrent, such as the photon wavelength, intensity, type of channel doping and concentration, and feasible device design [ 20 , 21 ]. However, the magnitude of the photocurrent, rather than the polarity, is relevant for the application of photodetectors.…”