Growth And Properties Study Of ZnO And AlN Thin Films Deposited By MOCVD

ZnO is a II-VI compound wide band gap semiconductor. At room temperature, ZnO has a band gap of 3.3eV and the exciton binding energy of 60meV, which makes the application in the field of optoelectronic devices of ZnO is very optimistic in the future. ZnO performs some better properties than GaN, such as: a higher band gap and exciton binding energy, which are helpful to improve the luminous intensity of the device, component of high abundance of elements and low cost, these factors make ZnO has become a powerful competitor of GaN in the optoelectronic application fields. ZnO photoelectric materials have become a new hotspot of researches. In the future development, ZnO-based optoelectronic devices is likely to replace or partial replace GaN devices. But the research of ZnO-based optoelectronic meets the bottleneck, in the growth of ZnO crystal the control of impurities and defects has not been able to achieve a breakthrough. Therefore, Researchers need to conduct in-depth study of ZnO crystal growth, as well as effects of impurities and defects on material properties.Considering these points of view above, in this article we take a series of studies on the growth and properties of ZnO film. The contents of this dissertation are listed as follows:Using water vapor as oxygen source, diethylzinc as zinc source, We studied the effects of growth conditions on the ZnO film epitaxial growth. We found that a higher DEZn flow is conducive to enhance the UV light intensity of ZnO films, but that will leads the growth of thin-film takes a double-preferred orientation mode. In this context, to maintain a high Zn/O molecular ratio, optimizing the other growth conditions, we prepared ZnO films with a single c-axis preferred orientation and can generate strong UV luminescence successfully. On this basis, the properties of ZnO films were researched. We analyzed the effect of Zn/O molecular ratio, substrate temperature and annealing conditions on ZnO film properties. The conclusions are drawn: UV light of ZnO is mainly comes from the coupling between free exciton and Zni donor, increasing of the concentration of both the above will be conducive to enhance the UV light. The carrier gas N2 was cracked by RF and generated plasma N source, we grown a-axis preferred orientation AlN films. By varying the carrier gas flow, growth temperature, the cracking RF power we obtained a number of series of samples. Results of analysis of these samples showed that the changes in various growth conditions have different effects on AlN film properties. Based on above works we grown ZnO/AlN/Si structure samples, and investigated their characters. This paper is divided into six chapters:The first chapter introduces ZnO, AlN materials, fundamenta properties, application prospects and researches, makes an overview of preparation and characterization methods of thin-film.Chapter II investigates the crystallization properties of ZnO films grown under different gas-intake modes.Chapter III, By optimizing the growth conditions, ZnO films with a strong UV light intensity and a single c-axis preferred orientation are prepared.Chapter IV, by varying the zinc-oxygen molecular ratio, growth temperature and annealing temperature, further studies of the intrinsic defects in ZnO films and ZnO luminescent properties, especially the origin of ultraviolet light-emitting are proposed,. The result shows that: the UV emission of ZnO can be attributed to the coupling between Zni and FX.Chapter V, AlN films with a-axis preferred orientation are prepared by MOCVD, using RF-assisted. The results show that: a higher substrate temperature is conducive to the growth of AlN thin film; increasing of carrier gas flow rate and RF cracking power within a certain range can improve the films quality, but a too high carrier gas flow rate or cracking power makes the film growth adversely affected. The growth and characteristics of ZnO/AlN/Si hetero-structure are investigated. Chapter VI, summary and outlook.