Zinc oxide (ZnO) is a wide band-gap material with excellent optical properties for optoelectronics applications. However, device fabrication has been hampered by difficulties in obtaining a stable p-type doping. Here, we present the first report on the growth and doping of ZnO film through the incorporation of potassium (K) from group I in aqueous solution at 90 °C to yield a stable p-type doping. The contribution of potassium toward p-type conductivity is confirmed using Hall effect measurements and SIMS. A new growth strategy was introduced to obtain a good film coverage with a lower native defect density without the use of surfactants. Photoluminescence measurements confirmed the reduction of defect-related emissions and enhancement of UV band-edge emissions. Variation of carrier concentrations with temperature points to the presence of unstable hydrogen donors that can be removed by annealing at temperatures above 400 °C for extended durations. The instability of these hydrogen defects is attributed to the low growth temperatures. Finally, a p-ZnO/n-GaN junction is demonstrated to have a rectifying I−V characteristic and two dominant electroluminescence peaks in the UV range of 370−390 nm, as well as a broad yellow-orange peak.
Bright and stable structured green luminescence (GL) is achieved from solution-grown Cu-doped ZnO nanorods. Dependence of photoluminescence on the annealing parameters reveals that GL is correlated with creation of Zn vacancies (VZn) and then formation of Cu dopants at Zn sites (CuZn). High internal quantum efficiency (43%) of the GL can be sustained up to 240 K due to negative thermal quenching. In contrast to the poor stability of defects-related visible emission, the structured GL shows good stability with respect to sample heating. Cu-doped ZnO nanorods with strong and stable GL have potential applications in visible light display and lighting.
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