Optimizing Gaas Nanowire-Based Visible-Light Photodetectors

Sole surface passivation for III-V nanowire photodetectors exhibits limited photoresponse improvement. Consequently, a well-customized contact design is crucial. Here, GaAs nanowire-based metal-semiconductor-metal photodetectors via surface treatment and interfacial contact optimization are reported. The passivation strategy inhibits the surface recombination and, importantly, effectively reduces the Fermi-level pinning effect by the redistribution of surface states. It leads to the Schottky barrier height reduced from similar to 0.63 to similar to 0.36eV at the Ni/GaAs nanowire contact. The design contributes to the prominently enhanced more than tenfold photoresponsivity and the much-shortened response time, in comparison with the pristine ones. When applying the design to the intrinsic GaAs nanowire photodetector, it demonstrates a responsivity of 4.5x10(4) A/W, a specific detectivity of 3.3x10(14) Jones, and response time less than 50ms under 520nm laser illumination. Additionally, good repeatability of dynamic photo-switching characteristics and stability measured with slight degradation after 2months are demonstrated. With the same approach, it is found that the responsivity could be further enhanced by over 50 times up to 6.4x10(5) A/W via fermi level adjustment in a p-doped single GaAs nanowire device. Featuring the nanoscale footprint and compact size, the results establish the GaAs nanowire as a promising and competitive candidate for high-performance and reliable nano-photodetection operating in the visible range.