| With the development of science and technology, transparent conductive oxide films have attracted more and more attentions for their widely used in light-emitting diodes, laser, flat panel displays and thin film solar cells. In recent years, people are extremely interested in the wide band gap semiconductor materials, because those materials could give out light of short wavelength, maintain high transparency in the ultraviolet region, which can be used to make photoelectric devices and detectors in blue and ultraviolet region. Now materials of emitting blue light have been found and preparation, including GaN, ZnSe and so on. High efficiency of the blue lasers and LEDs based on these materials have been made out.Ga2O3is one kind of the wide bandgap semiconductor materials with direct gap. Its forbidden bandwidth is about4.9eV, larger than the band gap of GaN (Eg-3.4eV). Ga2O3becomes a very promising ultraviolet and blue photoelectric material, because the characteristics of good chemical and thermal stability, easy to preparation and batch manufacturing.β-Ga2O3is the most stable structure in a variety of Ga2O3phases, and it is also the material which has got the most applications and researches in Ga2O3phases at present.β-Ga2O3has been widely used in many fields, but β-Ga2O3films prepared by traditional methods usually have been limited in applications for their poor structures and properties. It is very important to further and systemic study the preparation of β-Ga2O3thin films, only in this way the material could be used in photoelectric devices and other applications.The major research works and results are as follows:1. Ga2O3thin films have been deposited on different sapphire substrates at different substrate temperatures by metal-organic chemical vapor deposition. High purity Ga(CH3)3, O2and ultra high purity N2were used as the metallorganic (MO) source, oxidant and carrier gas, respectively. A-plane sapphire α-Al2O3(1120), c-plane sapphire α-Al2O3(0001), m-plane sapphire α-Al2O3(1010) and r-plane sapphire α-Al2O3(0112) were chosen as substrates. The growth temperatures range from550℃to700℃. XRD results show that β-Ga2O3film deposited on α-Al2O3(0001) substrate at650℃has the best crystal quality and α-Ga2O3film deposited on α-Al2O3(1010) substrate at700℃has the best crystal quality.2. Annealed the samples deposited at650℃on four substrates at900℃for1h, grain size changed larger on a-plane and m-plane sapphire substrates, while the crystallization deteriorated after annealing on c-plane and r-plane sapphire substrates. It is not feasible to improve the crystal quality of β-Ga2O3film deposited on α-Al2O3(0001) substrate through annealing in atmosphere.3. β-Ga2O3film deposited on α-Al2O3(0001) substrate at20Torr and650℃has the best crystal quality. The thickness of the film is about120nm. X-ray diffraction and high-resolution transmission electron microscopy measurements have been used to research the structure of the sample.The epitaxial relationship between the film and the substrate is β-Ga2O3(201)||Al2O3(0001) with β-Ga2O3<010>||Al2O3<1100> and β-Ga2O3<102>||Al2O3<1120>.4. The surface morphology of the samples preparation on α-Al2O3(0001) substrate at different tempurtures have been observed by SEM. The film grown at650℃exhibits a larger grain size with a clear and regular edge. This result consists with the XRD observation. The average transmittance of the obtained films in the visible wavelength range was over92%and the band gap was about4.73～4.96eV. |
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