Stable p-Type Doping of ZnO Film in Aqueous Solution at Low Temperatures

Abstract

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.

Designing green, self-healing coatings for metal protection

“…Th e naturally passivating oxide on zinc, under near-neutral saline aqueous conditions (solution or drops), develops a bilayer with a thick, porous outer layer of variable composition covering a thinner, compact fi lm of ZnO at the metal interface [20]. Under atmospheric conditions, the porosity of the outer layer, comprised of corrosion products such as gordaite and zinc hydroxyl-carbonate [21], gradually decreases, providing a pH-buff ering eff ect and developing an outer oxide that possesses a negative surface charge in mildly acidic environments [22]. Th e porosity of the inner layer also decreases over time [20].…”

“…For instance, ZnO is an n-type semiconductor, and cathodic reactions (i.e. oxygen reduction) can occur on the oxide pore surfaces rather than penetrating to the metal/oxide interface [22]. Modeling indicates that with zinc overlaid by such a porous oxide, the corrosion current is initially very high (due to the large cathodic area) but rapidly falls as oxygen is consumed within the pores of the oxide.…”

Sputtering Power Induced Physical Property Variation of Nickel Oxide Films by Radio Frequency Magnetron Sputtering

“…Especially, the attractiveness of NiO material lies in the fact that the NiO films has an natural p-type conductivity and low preparation costs compared to the high-quality p-type ZnO and GaN materials, which are difficult to achieve due to the less stability and high resistance [5][6][7][8][9][10] . Recently, Patel et al 11 fabricated NiO/ ZnO heterojunction on plastic substrate for ultraviolet photodetector applications.…”

Electrically pumped ultraviolet random lasing action from p-NiO/n-GaN heterojunction

“…For the past few years, the electrically pumped ultraviolet random laser actions have been realized by using highly disordered ZnO film and various ZnO micro-and nanostructures [4][5][6][7][8]. But it is not propitious to obtain high ultraviolet random laser performance based on ZnO random cavities due to the difficulties in producing highly conductive and stable p-type ZnO material [9][10][11][12]. Recent research has suggested that the ultraviolet random laser action could also be observed in the GaN material [13].…”