n-ZnO : Ga/p-GaN heterojunction light-emitting diodes with different interfacial layers are fabricated by pulsed laser deposition. All the devices demonstrate nonlinear rectifying behaviour. Due to the formation of Ga2O3 interfacial layers, n-ZnO : Ga/p-GaN exhibits strong ultraviolet emission centred at 382 nm and blue emission centred at 423 nm. Compared with a n-ZnO : Ga/MgO/p-GaN light-emitting diode, the turn-on voltage of n-ZnO : Ga/p-GaN with a Ga2O3 interfacial layer drops down to 7.6 V and the ultraviolet emission intensity is enhanced. Detailed electroluminescence mechanisms influenced by the interfacial layer are discussed using the band diagram of heterojunctions.
Heterojunction light-emitting diodes (LEDs) based on arrays of ZnO nanorods were fabricated on p-GaN films by the hydrothermal method. Without any phosphors, white-light electroluminescence (EL) from ZnO nanorods/p-GaN heterojunction LEDs operated at reverse breakdown bias was observed. The EL spectra are composed of an ultraviolet (UV) emission centered at 382 nm, a blue light located at 431 nm and a broadband yellow–green light at around 547 nm, which originated from band-edge emission in ZnO, the Mg acceptor levels in p-GaN and the deep-level states near the ZnO/GaN interface, respectively. The chromaticity coordinates of EL spectrum are very close to the (0.333, 0.333) of standard white light. The origin of these emissions has been discussed and the tunneling effect in the interface is probably the mechanism to explain EL emission.
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