Ultraviolet and visible photoresponse properties of a ZnO/Si heterojunction at zero bias

Abstract

High quality ZnO microwires (MWs) with an electron concentration of 1.06 × 10¹⁷ cm⁻³ and carrier mobility of 1.68 cm² V⁻¹ s⁻¹ were synthesized by a simple chemical vapor deposition (CVD) method. Based on a single n-type ZnO MW and a p-type Si film, an ultraviolet (UV)-visible photodetector (PD) has been constructed from the p–n junction, which showed a high rectification ratio larger than 10³ at ±3 V and an ideal factor of about 2. Under zero bias, the PD exhibited high photosensitivities of ∼2 × 10⁴ and ∼5 × 10³ for UV (325 nm) and visible (514 nm) light, respectively, with a fast response time of about 7.4 ms. Also, detailed characterizations indicated that the short-circuit current (I_sc) and the open-circuit voltage (V_oc) showed square root and logarithmical dependences on the light intensity, respectively. The results support that n-ZnO MW/p-Si film PDs have potential application in the field of UV-visible detection and might be used as elements for powering low-energy micro/nanosystems.