High-Purity Ultraviolet Electroluminescence from n-ZnO Nanowires/p+-Si Heterostructure LEDs with i-MgO Film as Carrier Control Layer

Abstract

Pure ultraviolet (UV) light emitting diodes (LEDs) using n-ZnO nanowires as an active layer were fabricated with an insulating MgO dielectric layer as a carrier control layer, where all depositions were continuously performed by metalorganic chemical vapor deposition. The current-voltage curve of the LEDs showed obvious rectifying characteristics, with a threshold voltage of about 7 V in the sample with 4 nm i-MgO. Under the forward bias of the samples with proper MgO thickness, a sharp UV electroluminescence, located at around 380 nm, was emitted from the active ZnO nanowires, while weak visible emission of around 450–700 nm were observed. The pure UV emission from the ZnO nanowires in the n-ZnO/i-MgO/p+-Si heterostructures was attributed to the electron accumulation in the ZnO by asymmetric band offset and preemptive hole tunneling from Si to ZnO by i-MgO.