| Zinc oxide (ZnO) is a Ⅱ-Ⅳ 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 300cm-1. Due to these features, ZnO has become a promising candidate for applications in LED and LDs as a short-wavelength material. Generally ZnO occurs as a n-type conduction with good electronic properties by doping Al, Ga atoms. However, it is difficult to achieve p-type conduction because of the low solubility of the dopant and high self-compensating process upon doping due to its intrinsic donor defects (Zni or Vo). Yamamoto predicted theoretically that p-type ZnO could be obtained by simultaneous co-doping using reactive donor co-dopants (e.g. Al, Ga and In) and acceptor co-dopants (e.g. N) because the former could enhance the incorporation of N acceptors and give rise to shallower N-acceptor levels in the band gap of p-type co-doped ZnO crystal as well.The state key laboratory of silicon materials of Zhejiang University is one of the earliest groups devoted in the research of ZnO thin films. With the instruction of Dr. Ye, we had been realized p-ZnO thin films by Al-N co-doping method using Magnetron sputtering technique. In this work, we've prepared the p-type ZnO thin films with good electrical properties by the (A1,N,H) co-doping method, and we mainly focused on the good p-type conduct of ZnO thin film by optimizing the prepared method. The followings are results.1. We had studied the effect of Al content on the (A1,N,H) co-doping ZnO thin film. A moderate Al content(0.4%4%) is necessary for the p-type ZnO realization, instead of the higher or lower content both leading to n-type conduction. Considered the co-doping mechanism, we suggested that the existence of H can facilitate the solubility of N by the form of N-H. Annealed the as-grow ZnO thin film can activate the N atom as effective acceptor.2. We have prepared the stable and reproducible p-ZnO thin film based on the (A1,N,H) co-doping by introduce a high temperature homo-buffer layer. With a buffer layer deposited times between 3min and 5min, a good p-type conduct had got, such as resistivity of 16-25Ω cm, hole concentration of 1017-1018cm-3.3. The post annealing treatment to (A1,N,H) co-doping n-type ZnO thin film under the O2 ambient can realize the p-type conversion, while the same one under Ar ambient remain n-type conduct. This indicate that O atom enter into the ZnOthin film and occupy the O vacancy partly.4. Compared with the ZnO homojunction, the double heterojunction with n-ZnO/n-Zn0.8Cd0.2O/p-ZnO exhibits a better rectifying characteristics, and reverse breakdown voltage can reach as high as 15 V, and leakage current 10-6A.ZnO:(Al,N,H) thin film;Direct Current Reactive Magnetron Sputtering;high temperature homo-buffer layer;rapid thermal process;p-ZnO/n-Zn0.8Cd0.2O/n-ZnO heterojunction... |
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