Preparation Of ?-Ga₂O₃ Thin Films And Ga₂O₃/GaN Interface Growth Mechanism

Gallium oxide?Ga₂O₃?,as one of the representative materials of the third generation semiconductor,has wide band gap,high dielectrics constant,high saturation electron drift speed,high breakdown field,excellent thermal stability and strong radiation resistance etc,which have attracted great attentions.There are still many physical and process problems in the new optoelectronic devices and high-power,high-frequency power electronic devices represented by?-Ga₂O₃.This paper is aimed at several key issues in the preparation of high quality thin films in?-Ga₂O₃ based devices,such as pretreatment of substrates,oxidation control of epitaxial wafer surface,and intrinsic properties of deposited Ga₂O₃ thin films by various characterization technology,and the influence of various factors to further improve the performance of the device.The main research contents are as follows:?1?In order to improve the quality of?-Ga₂O₃ films,the Al₂O₃?0001?substrates were cleaned by sonication in organic solution,inorganic solution wet etching and high temperature annealing in an air atmosphere,which can obtained with atomically flat step surfaces.Then?-Ga₂O₃ thin film were grown on the substrates by pulsed laser deposition.Compared with the substrate treated by direct organic cleaning,the crystalline quality of the thin film grown on the flat step surface of the atomic level is significantly higher.The high-resolution transmission electron microscope shows that the out-of-plane epitaxial relationship between the film and the substrate is?-Ga₂O₃?`201?//Al<sub>2</sub>O<sub>3</sub>?0001?.?2?Taking a two-step deposition method?turn off the oxygen gas for the first few molecular layers,and then continue the growth with oxygen partial pressure increasing up to 0.5 Pa?,?-Ga<sub>2</sub>O<sub>3</sub> thin film were grown on GaN/Al<sub>2</sub>O<sub>3</sub>?0001?substrates by pulsed laser deposition technique.The crystallization quality of?-Ga<sub>2</sub>O<sub>3</sub> thin film can be improved effectively by overcoming the oxidation problem of GaN surface,The samples were analyzed by high-resolution transmission electron microscope and selected area electron diffraction.The out-of-plane epitaxial growth relationship of the film is?-Ga<sub>2</sub>O<sub>3</sub>?`201?//GaN?0002?,and the in-plane epitaxial relationship is?-Ga₂O₃[132]//GaN[2`1`10].?3??-Ga₂O₃ thin films were grown on?100??-Ga₂O₃ single crystal substrates using pulsed laser deposition?PLD?,which can avoid interface lattice mismatch and thermal expansion mismatch.From the High resolution transmission electron microscope?HRTEM?characterized,we can know that single crystal film grown along the?-Ga₂O₃?100?direction.In conclusion,we have greatly improved the epitaxial quality of?-Ga₂O₃ thin films by pre-treatment of the surface of the sapphire substrate and the regulation of oxide layer on the GaN epitaxial surface and home-epitaxial method,which could be able to lay a foundation for its application in deep ultraviolet optical and high power semiconductor electric devices.