Growth of p-type ZnO single crystal films by photo-assisted metal-organic chemical vapor deposition

作为II-VI族化合物半导体，氧化锌有望成为高效率紫外光半导体激光器的材料。然而，高质量的p型薄膜的生长是困难的。在本研究中，我们对MOCVD低温生长的氧化锌薄膜进行了如下表征。用原位紫外光吸收法研究了锌金属有机物的分解温度、气相中锌金属有机物与氧源的早期反应以及载气(H_2、N_2)的差异。利用上述结果筛选出了分解温度低、早熟反应活性低的原料。结果表明，在生长温度为400℃左右时，叔丁胺适合作为氮掺杂的源材料。氧化锌薄膜的生长以二甲基锌或二异丙基锌和异丙基拉莫尔或叔丁基拉莫尔为原料，在低于40 0℃的生长温度下，用MOCVD法生长了具有镜面的氧化锌薄膜。以自由激子发射为主的光致发光光谱表明，得到了高纯度的氧化锌薄膜。然而，源材料的n型杂质的掺入通过改变源腐烂而成为一个问题。受此问题的影响，薄膜的电子浓度为10℃；18℃；~10℃；19℃；cm^&lt；-3℃；在这些实验中，没有表现出对底物的光照射效应。氮掺杂氮气掺杂是在低II/VI条件下进行的。低温光致发光光谱、拉曼光谱和霍尔效应的表征表明，得到了氮掺杂10^&lt；18&gt；~10^&lt；19&gt；cm^&lt；-3&gt；然而，由于未掺杂薄膜的电子浓度较高，最佳空穴浓度仅为10^&lt；18&gt；cm^&lt；-3&gt；，MOCVD源材料纯度的提高和光照射的效果有待进一步研究。

II-VI compound semiconductor, ZnO is expected as a material for high efficiency uv semiconductor lasers. However, the growth of high quality p-type thin films is difficult. In this study, we have performed the characterization for the low temperature growth of ZnO films by MOCVD as shown below.1. The decomposition of source materialsThe decomposition temperature, premature reaction between Zn metal organics and oxygen sources in vapor phase and the difference of carrier gas (H_2, N_2) are investigated by in situ uv absorption measurements. The source materials with low decomposition temperature and low premature reactivity were selected using above results. It was found that t-butylamin is suitable for the source materials for nitrogen doping at the growth temperature around 400℃.2. The growth of ZnO thin filmsThe growth of ZnO thin films with specula surface were grown by MOCVD at the growth temperature below 400℃ using dimethylzinc or di-isopropropylzinc and isopropylarchol or t-butylarchol. The photoluminescence spectra dominated by free exciton emission indicate that the high purity ZnO films were obtained. However, incorporation of n-type impurities of source materials became a problem by changing the source rot. By this problem, the electron concentration of the films were 10^<18>〜10^<19>cm^<-3>, and this value have not been improved. The effects of photo-irradiation to the substrate were not shown in these experiments.3. Nitrogen dopingNitrogen doping was carried out at low II/VI conditions. The characterizations by low temperature photoluminescence spectra, Raman spectra and Hall effect show that nitrogen incorporation of 10^<18>〜10^<19>cm^<-3> was obtained. However the best hole concentration was only the order of 10^<18>cm^<-3> because of high electron concentration of undoped films.The improvement of purity of source materials and the effect of photo-irradiation for MOCVD should be investigated.