Highly Responsive ZnO/AlN/Si Heterostructure-Based Infrared- and Visible-Blind Ultraviolet Photodetectors With High Rejection Ratio

We report on the hybrid ZnO/AlN/Si heterostructure-based ultraviolet (UV) photodetectors with infrared- and visible-blind characteristics. The heterostructure was formed by depositing ZnO thin films on Si (111) substrate by introducing an AlN as an intermediate layer. The ZnO film has been grown epitaxially on the underlying substrate with the improved crystallinity and excellent optical properties. The vertical transport properties of the ZnO/AlN/Si heterojunction under dark and light illumination demonstrate the intrinsic infrared- and visible-blind characteristics with excellent ultraviolet responsivity. The heterostructure exhibits a high UV responsivity of 14.5 A/W with UV-to-Infrared rejection ratio of nearly 4 orders of magnitude. The vertical electrical transport properties across the heterostructure are dominated by the holes in the reverse bias condition, whereas the transport of electrons in the forward bias is hindered at the ZnO/AlN interface due to an existence of huge conduction band offset between ZnO and AlN layers. The AlN intermediate layer acts as an electron blocking layer which allows the hole to transport across the heterostructure in the reverse bias condition.