β-Ga2O3 nanowires for an ultraviolet light selective frequency photodetector

The behaviour of beta-Ga2O3 nanowires as photoconductive material in deep ultraviolet photodetectors to operate in the energy range 3.0-6.2 eV has been investigated. The nanowires were grown by a catalyst-free thermal evaporation method on gallium oxide substrates. Photocurrent measurements have been carried out on both undoped and Sn-doped Ga2O3 nanowires to evidence the influence of the dopant on the photodetector performances. The responsivity spectrum of single nanowires show maxima in the energy range 4.8-5.4 eV and a strong dependence on the pulse frequency of the excitation light has been observed for undoped nanowires. Our results show that the responsivity of beta-Ga2O3 nanowires can be controlled by tuning the chopper frequency of the excitation light and/ or by doping of the nanowires. Non-linear behaviour in characteristic current-voltage curves has been observed for Ga2O3 : Sn nanowires. The mechanism leading to this behaviour has been discussed and related to space-charged-limited current effects. In addition, the responsivity achieved by doped nanowires at lower bias is higher than for undoped ones.