| As a new type board band gap semiconductor material, Gallium Oxide has a forbidden band width as large as4.9eV, breakdown electric field of3.5×10V/cm, ionization energy of5.9eV, and excellent chemical and thermal stability. Unintentional doped gallium oxide often shows high resistance or weak n type electrical conductivity, but after appropriate doped with silicon or tin, it presents good n type conductive properties. Based on the above advantages, gallium oxide materials have important application value in deep ultraviolet transparent conduct, blind detection, gas sensor and electronics manufacturing. Therefore, people pay more and more attention to the control of gallium oxide growth pattern research in recent years, this direction has become a frontier field in the current research of oxide semiconductor material.There are various preparation methods of gallium oxide thin film, including the heat evaporation, spray pyrolysis, magnetron sputtering, chemical vapor deposition, pulsed laser deposition, electron beam evaporation and metal organic compound vapor deposition (MOCVD) and so on. In this paper, by the MOCVD method, triethyl gallium and high purity oxygen as gallium source and oxygen source respectively, epitaxial growth of gallium oxide thin film was accomplished. By two ways of dealing the substrate’s surface state and adjust reaction chamber gas pressure, to realize the control for the gallium oxide thin film growth mode. The main works are as follows:In the first part of the thesis, we use the GaN/Al2O3as epitaxial substrates of gallium oxide material, and GaN substrates are oxidized at different temperature to study in detail on the influence of surface oxidation state of GaN substrates to the epitaxial crystallization properties of gallium oxide thin film. X-ray diffraction test results show that GaN substrate thermal oxidation states are affected by the oxidation temperature significantly:Under the condition of relatively low temperature of550℃～650℃, on the surface of the thermal oxidized GaN substrate has appeared a (601) plane orientation of gallium oxide layer; When the temperature of the thermal oxidation is750℃, the GaN substrate does not form is kind orientation of gallium oxide layer; And when the thermal oxidation temperature is up to850℃, GaN substrate appear obvious gallium oxide thin layer with a single orientation; But after the thermal oxidation temperature continues to rise to950℃, GaN layer’s relatively severe decomposition and oxidation, makes the formation of the gallium oxide layer shows varieties of orientations. At the same time we found that in follow up epitaxial growth of gallium oxide thin film on the thermal oxidized substrates, gallium oxide layer’s orientations are consistent with the substrate surface. This suggests that we can deal with the GaN substrate’s surface thermal oxidation states to control the orientation of epitaxial gallium oxide thin film.The second part of this paper studies the controlling of Ga2O3film’s MOCVD epitaxial growth pressure to the growth mode. By XRD, SEM and other characterization methods, the result was found to be:at a relative low growth pressure400Pa, epitaxial of Ga2O3film follows island growth mode; when growth pressure increase to2000Pa, layer-island growth mode is observed; When growing pressure reach to7000Pa, a dense film of Ga2O3epitaxial layer is prepared and exhibit a layer growth mode; but when growing pressure is too large (20000Pa), the pre-reaction becomes very intense, which leads to the thickness and properties of the epitaxial film decreased significantly. Hence, the law of growth pressure’s control to the Ga2O3film’s growth mode is found. |
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