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 ∼0.63 to ∼0.36 eV 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 4.5 × 104 A/W, a specific detectivity of 3.3 × 1014 Jones, and response time less than 50 ms under 520 nm laser illumination. Additionally, good repeatability of dynamic photo-switching characteristics and stability measured with slight degradation after 2 months are demonstrated. With the same approach, it is found that the responsivity could be further enhanced by over 50 times up to 6.4 × 105 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.