  Photoresponse of Au nanoparticle functionalized semiconducting GaN (Au-GaN)
nanowires is reported for an optical switching using 532 excitation. Wide band
gap GaN nanowires are grown by catalyst assisted chemical vapour deposition
technique and functionalized with Au in the chemical route. Au-GaN nanowires
show surface plasmon resonance (SPR) mode of Au nanoclusters around 550 nm
along with characteristic band for GaN around 365 nm. An optical switching is
observed for Au-GaN nanowires with a sub-band gap excitation of 532 nm
suggesting possible role of surface plasmon polariton assisted transport of
electron in the system. Role of band conduction is ruled out in the absence of
optical switching using 325 nm excitation which is higher in energy that the
reported band gap of GaN about 3.4 eV (365 nm) at room temperature. A finite
amount of interband contribution of Au plays an important role along with the
inter-particle separation. The switching device is also successfully tested for
a single GaN nanowire functionalized with Au nanoclusters. A resistivity value
of 0.05 Ohm-cm is measured for surface plasmon polariton assisted electrical
transport of carrier in the single GaN nanowire.
