Disentangling the Role of the SnO Layer on the Pyro-Phototronic Effect in ZnO-Based Self-Powered Photodetectors.

Abstract

Self-powered photodetectors (PDs) have been recognized as one of the developing trends of next-generation optoelectronic devices. Herein, it is shown that by introducing a thin layer of SnO film between the Si substrate and the ZnO film, the self-powered photodetector Al/Si/SnO/ZnO/ITO exhibits a stable and uniform violet sensing ability with high photoresponsivity and fast response. The SnO layer introduces a built-in electrostatic field to highly enhance the photocurrent by over 1000%. By analyzing energy diagrams of the p-n junction, the underlying physical mechanism of the self-powered violet PDs is carefully illustrated. A high photo-responsivity (R) of 93mA W-1 accompanied by a detectivity (D*) of 3.1 × 1010 Jones are observed under self-driven conditions, when the device is exposed to 405nm excitation laser wavelength, with a laser power density of 36mW cm-2 and at a chopper frequency of 400Hz. The Si/SnO/ZnO/ITO device shows an enhancement of 3067% in responsivity when compared to the Al/Si/ZnO/ITO. The photodetector holds an ultra-fast response of ≈ 2 µs, which is among the best self-powered photodetectors reported in the literature based on ZnO.