Nitrogen-doped P-type Zno Thin Film Growth And Theoretical Research

Zinc Oxide (ZnO) is an important wide band gap semiconductor materials (Eg=3.37eV), which is known as twenty-first century semiconductor due to its excellent optoelectronic performance. Nominally undoped ZnO typically exhibits n-type conductivity ascribed to native point defects such as oxygen vacancies (V_O) and zinc interstitials (Zn_i). The fabrication of p-type ZnO is difficult due to the self-compensation effect from native defects and low solubility of p-type dopants. The fabrication of p-type ZnO has become the bottleneck of the application of ZnO-based optoelectronic devices. In recent years, ZnO films have attracted a considerable amount of interest in the world.Group-V dopants have been considered as possible dopants for p-type ZnO. Among these acceptors, N has proven to be suitable acceptor for making p-type ZnO, since the ionic radius of N is about of O. N-doped ZnO (ZnO:N) films have been fabricated by various deposition methods such as molecular-beam epitaxy, metalorganic chemical vapor deposition, sputtering, pulse laser deposition, and thermal oxidation of Zn₃N₂, but the methods exist these problems such as complex process, expensive equipment and poisonous solid precursor. Therefore, it is very important to realize p-type ZnO by single source chemical vapor deposition (SSCVD) using a novel solid precursor of Zn₄(OH)₂(O₂CCH₃)₆·2H₂O.In this thesis, based on a comprehensive review of the theories and fabricating techniques of ZnO materials and p-type doping, we conducted a detailed study of ZnO p-type doping. The main content of this thesis is as follows:1. Nitrogen-doped p-type ZnO thin films have been realized by two-step SSCVD. Thin films exhibit a-b preferential orientation and transparency of about 70-80% in the visible-light region.2. The effect of substrate temperatures on the conductivity of ZnO:N by two-step SSCVD. It is shown that ZnO:N films become p-type material at substrate temperatures between 500-600℃. An optimized result with a resistivity of 1.34Ωcm, Hall mobility of 149.01 cm²/Vs, and hole concentration of 3.12×10¹⁶cm^-3 was achieved at 600℃. 3. The one-step SSCVD method can't realize ZnO:N, and ZnO by one-step SSCVD contain excessive Zn atomic. Photoluminescence spectra show the stimulated emission peak due to exciton-exciton scattering.4. p-ZnO/n-Si heterojunction was fabricated by deposition of a N-doped p-type ZnO layer on a n-type Si(100) layer. The I-V characteristics of the p-n heterojunction show a rectifying behavior.5. Electronic structures of ZnO:N_O+V_Zn was calculated by the first-principle. Comparing with the electronic structures of ZnO, ZnO:N, ZnO:N_O+V_Zn, it was revealed that V_Zn broadened the acceptor level produced by doping N, weakened localized of donor level, activated N atom and increased the solubility of N. The results indicate that high quality p-type ZnO thin films can be fabricated by doping N into ZnO:V_Zn.