Preparation Of Ga₂O₃Seed Layer And Its Influence The Epitaxial Growth Of Ga₂O₃Films

With the rapid development of optoelectronic semiconductor technology, more and more people get in favor of the broadband gap semiconductor, materials. Gallium oxide (Ga2O3) is a kind of broadband gap semiconductor material of Ⅲ-Ⅵ groups. The β-Ga2O3is the most stable type in these five isomers. The direct band gap of Ga2O3is wide (4.2eV～4.9eV), and it has good chemical stability and thermal stability, so it has broad application prospects, such as the deep ultraviolet transparent conductive film, ultraviolet detectors, thin film electroluminescent devices, gas sensor, and field effect transistor.In this paper, Ga2O3seed layer was fabricated on sapphire substrates (Al2O3) by RF magnetron sputtering technology, and the sapphire substrate with the seed layer was annealed treatment. Then Ga2O3films were fabricated on sapphire substrates with seed layer and without seed layer by MOCVD technology.1. Ga2O3films were fabricated on sapphire substrates by low-pressure MOCVD technology. The crystal and optical quality of Ga2O3thin films was investigated by X-ray diffraction and optical transmittance spectra. The Ga2O3film is amorphous that grown directly on the sapphire substrate and the transmittance and the optical band gap width of the Ga2O3films are very small. The experiment shows that, the crystal quality and the optical properties of the Ga2O3films are not ideal when the Ga2O3films were fabricated directly on sapphire substrates by using low-pressure MOCVD technology.2. In order to solve the above problem, Ga2O3seed layer was fabricated on the sapphire substrate by RF magnetron sputtering, then the β-Ga2O3films were fabricated on sapphire substrates with the seed layer by low-pressure MOCVD technology. The experiment shows that, Relative to the Ga2O3films fabricated directly on sapphire substrates, the crystal quality and the optical properties of the Ga2O3films fabricated on sapphire substrates with Ga2O3seed layer have improved, but not evidently.3. The Ga2O3seed layer was annealed at a high temperature, then the β-Ga2O3films were fabricated on sapphire substrates with the annealed seed layer by low-pressure MOCVD technology. The XRD shows that, the Ga2O3films have the obvious preferred orientation which deposited on the sapphire substrate with seed layer; the crystal quality was improved remarkably. Meanwhile, the transmittance was improved observably in the visible regions because of the Ga2O3seed layer. Furthermore, the direct band gap energy of the Ga2O3films was enlarged markedly, and the optical quality was enhanced significantly. The experiment shows that, the annealed seed layer can enhance the crystal and optical quality of Ga2O3films apparently.4. We investigated the influence of the oxygen partial pressure in the process of MOCVD in-situ annealing on the crystal quality and the optical properties of the Ga2O3film. The experiment shows that, the crystal quality and the optical properties of the Ga2O3films enhanced evidently when the oxygen pressure is high enough and the low oxygen pressure in the process of cooling can deteriorate the quality of Ga2O3films obviously.