Simulation Study On HVPE Growth Of Ga₂O₃ Thin Films

The third-generation semiconductor material represented by gallium nitride?GaN?has many characteristics such as wide band gap,high thermal conductivity,large electron saturation drift rate,high breakdown voltage and strong radiation resistance,not only in blue-violet photovoltaic devices.In the fields of full-color display and white light illumination,it has become a leader in high-voltage,high-frequency power electronic devices and microwave devices in recent years,showing many advantages over traditional silicon-based devices.However,due to the lack of homogeneous substrate materials,high defects and dislocation densities caused by heteroepitaxial growth are difficult to avoid.Nanomaterials are increasingly valued for their unique quantum confinement effects,Coulomb blockade effects,and high specific surface area and excellent single crystal properties in nanowires.On the other hand,we need to be more efficient and powerful.Electronic components for power handling capabilities.Nowadays,power semiconductor Ga₂O₃ is beginning to challenge GaN,opening the way for new possibilities that cannot be realized by existing semiconductors.Although,studies have shown that Ga₂O₃ has poor thermal conductivity,its band gap?about 4.8 eV or eV?exceeds the band gap of GaN?about 3.3 eV?.And Ga₂O₃ plays an important role in improving solar,electric vehicles and other renewable energy sources.This thesis focuses on the research of GaN nanostructures and Ga₂O₃ thin films,including the optical properties of PVT grown GaN nanowires and the HVPE growth simulation of Ga₂O₃ films.A series of studies are carried out from temperature,substrate and catalyst using physical vapor transport technology to experimentally prepare GaN nanowires.The samples are characterized by scanning electron microscopy?SEM?,photoluminescence?PL?and Raman spectroscopy?Raman?.It is found that temperature,catalyst type and substrate have a great influence on the morphology of GaN nanowires,and when studying the optical properties of the sample,it is characterized by PL and found that at twice the wavelength of the excitation wavelength,there is also a spectral peak with a weaker intensity,which is determined by the characteristics of the grating spectroscopic.Furthermore,by the Raman spectroscopy of the sample,a large blue shift occurred on the sapphire substrate because the heteroepitaxial effect brought about a large lateral compressive stress.The results show that at 1100°C,the nanowires on the GaN substrate cover the entire substrate surface through different substrate growth experiments,which is more conducive to the nucleation of the nanowires.For the preparation of Ga₂O₃ thin films by HVPE,the computational fluid dynamics?CFD?principle is used.The two-dimensional modeling and simulation are carried out.Firstly,the mass fraction of GaCl and the flow rate of GaCl which affect the ratio of VI/III are analyzed.When the mass fraction of GaCl is 0.2,the relative uniformity of Ga₂O₃ film on the substrate surface is the best,and the flow of GaCl is changed.Ga₂O₃ The growth rate is highest at a flow rate of 50 slm,and the uniformity of the film is also good.Then,in the experiment of changing the flow rate of the separated gas N₂,it is found that the growth rate decreased with the increase of the N₂ flow rate,but the amplitude is small.When the gas flow rate is 38.4 slm,the uniformity of the Ga₂O₃ film is optimal,and the reaction in the cavity is stable.These data analyses provide a theoretical basis for parameter optimization of HVPE growth process,which alleviates the difficulties in practical operation and has far-reaching significance for the research and production of Ga₂O₃ thin films.