Spectrally Selective and Highly Sensitive UV Photodetection with UV-A,C Band Specific Polarity Switching in Silver Plasmonic Nanoparticle Enhanced Gallium Oxide Thin-Film

Traditional photodetectors generally show a unipolar photocurrent response when illuminated with light of wavelength equal or shorter than the optical bandgap. Here, it is reported that a thin film of gallium oxide (GO) decorated with plasmonic nanoparticles, surprisingly, exhibits a change in the polarity of the photocurrent for different UV bands. Silver nanoparticles (Ag NPs) are vacuum-deposited onto beta-Ga2O3 and the AgNP@GO thin films show a record responsivity of 250 A W-1, which significantly outperforms bare GO planar photodetectors. The photoresponsivity reverses sign from +157 mu A W-1 in the UV-C band under unbiased operation to -353 mu A W-1 in the UV-A band. The current reversal is rationalized by considering the charge dynamics stemming from hot electrons generated when the incident light excites a local surface plasmon resonance in the Ag nanoparticles. The Ag nanoparticles improve the external quantum efficiency and detectivity by nearly one order of magnitude with high values of 1.2 x 10(5) and 3.4 x 10(14) Jones, respectively. This plasmon-enhanced solar blind GO detector allows UV regions to be spectrally distinguished, which is useful for the development of sensitive dynamic imaging photodetectors.