Study On The Regulation And Mechanism Of GaN Single Crystal Growth Habits

As a representative of the third-generation semiconductor materials,GaN has a wide band gap,thermal stability,and good physical and chemical properties,making it an ideal material for the semiconductor industry.GaN-based devices have a wide range of applications in production and daily life,and related scientific research is also continuing,but most of the devices are based on heteroepitaxial.Heterogeneous epitaxy will cause a series of problems such as lattice mismatch and thermal expansion coefficient mismatch between the substrate and the device structure,which in turn affects the improvement of device performance.The use of homoepitaxial technology to prepare GaN-based devices on GaN single crystal substrates is a fundamental solution to achieve high-performance devices.The Na-flux method is an important method for preparing GaN single crystal substrates.However,due to the difficulty of spontaneous nucleation and the complexity of the process,further research on it is needed.This thesis first studied the influence of different environments on the solubility of GaN in the melt system.The results of the study found that increasing the reaction temperature,increasing the reaction pressure,and increasing the Na component in the melt will increase the amount of dissolved N in the melt.Also,the environmental pressure that does not come from N₂ will still cause the N increase in solubility in the melt.In addition,this thesis found that the use of GaN substrates will cause poly-crystalline growth to start prematurely,discussed the mechanism of Na-flux method growth of GaN,and determined the subsequent experimental process of GaN growth.This thesis discussed the influence of the Al N-buffer layer on the growth habit of GaN in the Na-flux method.In this thesis,the Al N-buffer layer was used to successfully grow a GaN single crystal thin film by the Na-flux method,,and a high-quality sample was prepared on a c-plane sapphire substrate.The FWHM of the X-ray rocking curve(002)plane achieved77.2 arcsec.The research results show that the introduction of the Al N-buffer layer can promote the nucleation and growth of GaN on the sapphire substrate in the Na-flux method.Also,the thesis compared the effect of the Al N-buffer layer on the sapphire substrate with different crystal planes and found similar results.At the end of the thesis,the prospects for the future of GaN single crystal growth by Na-flux method are put forward.