Ultraviolet light emitting diodes based on hydrothermal grown crystalline n-ZnO on p-GaN film

The growth of single crystalline ZnO film on p-GaN using the hydrothermal method is proposed and its application on n-ZnO/p-GaN heterojunction light emitting diodes (HJ-LED) is demonstrated. The effect of thermal annealing in the nitrogen ambient on the optical and electrical properties of hydrothermally grown ZnO film (HTG-ZnO film) onto a p-GaN substrate is investigated. The current-voltage (I-V) curves in darkness show that the prepared n-HTG-ZnO film/p-GaN HJ with thermal annealing has good rectifying characteristics and a 150% improvement in leakage current at -4 V has been achieved for the n-ZnO/p-GaN with thermal annealing. Strong ultraviolet lights emission from the annealed n-ZnO/p-GaN HJ-LED at around 375 nm without defect-related emissions in the visible region are observed from electroluminescence (EL) spectra.