Ultrahigh photocurrent gain in m-axial GaN nanowires

An ultrahigh photocurrent gain has been found in the ultraviolet-absorbed GaN nanowires with m-directional long axis grown by chemical vapor deposition. The quantitative results have shown the gain values at 5.0x10(4)-1.9x10(5) of the GaN nanowires with diameters from 40 to 135 nm are near three orders of magnitude higher than the values of 5.2x10(1)-1.6x10(2) estimated from the thin film counterparts. The intensity-dependent gain study has shown that the gain value is very sensitive to the excitation intensity following an inverse power law and no gain saturation observed in this investigated intensity range from 0.75 to 250 W/m(2). This behavior has strongly suggested a surface-dominant rather than trap-dominant high gain mechanism in this one-dimensional nanostructure. The strong carrier localization effect induced by the surface electric field in the GaN nanowires is also discussed. (c) 2007 American Institute of Physics.