| Zinc oxide(ZnO) is a II-VI compound semiconductor with a wide direct band gap of 3.37eV at room temperature. It has an exciton binding energy of 60meV and high exciton emission efficiency of 320cm-1. Due to these features, ZnO has become a promising candidate for applications in LED and LDs as a short-wavelength material. Obviously, the realization of practical applications for optoelectronic devices based on both high-quality p-type and n-type ZnO films. High-quality n-type films can be achieved by doping with Al,Ga,In etc. However, it is very difficult to achieve good and reliable p-type conduction because of its low solubility of dopant and high self-compensating process on doping. Among possible acceptor dopants, nitrogen is the most suitable candidate for producing p-type ZnO films. Furthermore, Both theory and experiment show that co-doping acceptor (N) and donors (Ga, Al, In) can be expected to enhance the solubility of nitrogen in ZnO and fabricate high-quality p-type ZnO films.Based on codoping method is hopeful preparation for p-ZnO films with high carrier concentrations and low resistance, dopant in power target is easily controlled, in this letter, N-In codoped p-type ZnO films on quartz glass substrates using RF magnetron sputtering techonlogy of ZnO:In2O3 powder target combining with the two-step N-implantation are prepared successfully.Through XRD and SEM analysis, all of the films exhibit preferential c-axis orientation, the good crystal structure of one of the best samples corresponding optimal p-type electrical properties. With the increase of annealing time, the re-crystallization cause the surface of films worse and became rough; X-ray photoelectron spectroscopy analysis confirmed the presence of nitrogen and indium in the form of N–Zn bond and N–In bond in the codoped films, and the incorporation of indium causes the change in the chemical state of nitrogen, which promotes the formation of p-type conduction; The effects of thermal annealing on electrical properties of the ZnO films are investigated by Hall measurement system. The experimental results suggest that the film annealed for 45min at 700°C exhibits the optimal p-type electrical properties with hole concentration of 4.04×1018cm-3, hall mobility of 1.35cm2V-1s-1, and low resistivity of about 1.15?cm. In addition, the electronic properties of co-doped films are improved, compared with N-doped films, the hole carrier concentration increases 2 order magnitude and the resistance decreases very obviously; It is also found that codoped ZnO films have high transmission rate, discovered the highest thin film transmittance is up to 90%, whose wavelength is at 387nm, corresponding to energy of 3.2eV which is slightly lower compared with undoped ZnO film of Eg.Finally, the p-ZnO(In,N)/n-ZnO:In p-n homojunction has been fabricated on the basis of realizing optimal p-type electrical properties, with In-Ga alloys as electrodes. The I-V characteristic of the ZnO homojunction showed a good rectifying behavior with a turn-on voltage of 2.2V and a reverse breakdown voltage of 4.9V.
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