Au/MgO/ZnO/MgO/Au structures have been designed and constructed in this study. Under a bias voltage, a carrier avalanche multiplication will occur via an impact ionization process in the MgO layer. The generated holes will be drifted into the ZnO layer, and recombine radiatively with the electrons in the ZnO layer. Thus obvious emissions at around 387 nm coming from the near-band-edge emission of ZnO will be observed. The reported results demonstrate the ultraviolet （UV） emission realized via a carrier multiplication process, and so may provide an alternative route to efficient UV emissions by bypassing the challenging p-type doping issue of ZnO.
The p-NiO thin film is prepared by radio frequency magnetron sputtering on the n-GaN/sapphire substrate to form p-NiO/n-GaN heterojunction diodes.The structural,optical and electrical properties of the p-NiO thin film are investigated.The results indicate that the NiO film has good crystal qualities and stable p-type conductivities.The current-voltage measurement of the p-NiO/n-GaN diode exhibits typical rectifying behaviour with a turn-on voltage of about 2.2 V.Under forward bias,a prominent ultraviolet emission centered at 375 nm is observed at room temperature.Furthermore,the mechanism of the light emission is discussed in terms of the band diagrams of the heterojunction in detail.
We reported the growth of N-polar InN films on N-polar GaN/sapphire substrates by pulsed metal-organic vapor phase epitaxy. The crystalline quality, surface morphology, optical and electrical properties of N-polar InN films were investigated in details by varying the breaking time and trimethylindium（TMIn） duration of pulse cycle. It has been found that when the breaking time and the TMIn duration in each cycle remain at 30 and 60 s, respectively, the N-polar InN film obtained exhibits a better crystalline quality and greater optical properties. Meanwhile, the surface morphology and electrical properties of the N-polar InN films also greatly depend on the given growth conditions.
