Study On Growth And Ag Doping Of ZnO Nanorods/GaN Heterostructures

The wide band-gap semiconductor ZnO is an excellent ultraviolet light-emitting materials because of it’s higher exciton binding energy. But, it is difficut to prepare high quality p-Zn O, which hampered the development of ZnO based LED. GaN and ZnO are wurtzite structure, and they have the similar lattice constants. So p-GaN is the most suitable candidate to replace p-ZnO and prepare n-ZnO/p-GaN heterojunction. However, the infulence of substrate to morphology and luminescence properties of ZnO has been ignored. In view of the above problems, we investigated the effects of different substrates on the structure and optical performances of the n-Zn O nanorods（NRs） and Ag doping on the optical performances of the n-ZnO NRs/p-GaN heterojunction. The main results are as follows:1. ZnO nanorods were grown on undoped GaN/Al₂O₃ and p-GaN/Al₂O₃ substrate by hydrothermal method. The results show that all ZnO nanorods with well-aligned are hexagonal wurtzite structure. The roughened interface in p-GaN/Al2O3 promote the growth of ZnO nanorods, which leads to the formation of a larger density ZnO-NRs with smaller diameters compared to the nanorods grown on undoped GaN/Al2O3 substrate. The room-temperature photoluminescence spectrum of Zn O nanorods growth on p-GaN/Al₂O₃ revealed a much stronger near-band-edge luminescence at 378.3 nm. The results confirm that ZnO-NRs grown on p-GaN/Al₂O₃ have a high crystal quality and excellent optical properties.2. ZnO nanorods doped with different Ag contents were fabricated on p-GaN films using a facile hydrothermal method. The effects of Ag doping concentration on ZnO nanorods and ZnO NRs/p-GaN heterostructure has been studied. The results show that the（0002） diffraction peak has a shift to the direction of small angle slightly with the increase of Ag doping concentration. It could be ascribed to the increase in lattice constant of ZnO nanorods,which is due to the replacement of Zn²⁺ by Ag⁺. With the increase of Ag doping concentration, the near band edge emission peak of ZnO nanorods shows a redshift, the intensity of near band edge emission peak weakened gradually and the intensity of yellow band emission peak has the opposite trend, it is due to the decrease of crystal quality after Ag doping treatment. We found that ZnO nanorods / p-GaN heterojunction reveals a better transmission efficiency with the increases of Ag doping concentration.3. We have fabricated the Ag doped ZnO NRs/p-GaN heterojunction by adjusting the growth time,and investigated the effect of the growth time on the morphology and optical performance of the n-ZnO NRs/p-GaN heterojunction. There is a slightly reduced in transverse dimension with the increase of growth time. When the growth time increased from 6 h to 9 h, the rod-like ZnO clusters appeared in the Zn O nanorods.With the increase of growth time, the intensity of the near band edge emission peak first increases and then decreases, and the intensity of yellow band emission peak has the opposite trend. In summary, the Ag-doped ZnO nanorods/p-GaN with a growth time of 6 h shows the best morphology and optical properties.