Superior phototransistors based on a single ZnO nanoparticle with high mobility and ultrafast response time

Conventional film-structured polycrystalline semiconductor devices suffer from grain boundary scattering, which is responsible for low mobility and can even mask intrinsic transport properties. In this work, we show that devices containing only a ZnO single particle can exhibit mobility values one order higher than that of single-crystal nanowires. The ZnO nanoparticle was embedded inside a nanopore structure, surrounded by a gate electrode and connected to top and bottom electrodes. Due to the absence of inter-grain scattering and long traveling distance, we obtained relatively high mobility values of around 600 cm² V^-1 s^-1 at room temperature (300 K) and about 1100 cm² V^-1 s^-1 at low temperature (∼180 K). The devices also presented external quantum efficiency of 5.6 × 10⁷, responsivity of 1.39 × 10⁶ AW^-1, detectivity of 8.69 × 10¹² Jones, and a record-high photoresponse rise time of 90 μs. This single nanoparticle-based device could be an excellent candidate of phototransistors with high performances.