Simulation And Optimization Of HVPE Growth α-Ga₂O₃ With Dual-reaction Source Gases

The current R&D and industrial layout of power devices are undergoing a rapid migration from traditional silicon-based devices to third-generation semiconductor devices.In this process,the new wide band gap semiconductor material gallium oxide（Ga₂O₃）has attracted increasing attention.As one of the metastable phases,α-Ga₂O₃has the advantages of ultra wide band gap（5.3e V）,ultra-high Barriga’s figure of merit（6726）,high breakdown voltage（10MV/cm）and high transparency to deep ultraviolet light,which surpasses the band gap（4.9e V）,Barriga’s figure of merit（3444）and breakdown voltage（8MV/cm）of stable phaseβ-Ga₂O₃.Compared with Ga N andβ-Ga₂O₃,it exhibits greater advantages in manufacturing deep ultraviolet light emitters,detectors and high-power devices.Sapphire（Al₂O₃）is often used as the substrate for HVPE-heteroepitaxial growth of Ga N and other material films in many researchs,however,the lattice mismatch between film and substrate always caused the problems of high dislocation density or difficulty to peel off.The structure ofα-Al₂O₃andα-Ga₂O₃is similar,and the mismatch along the a-and c-crystal directions is small.Therefore,theα-Ga₂O₃film formed on theα-Al₂O₃substrate is expected to surpassβ-Ga₂O₃in terms of growth rate and film quality,so that,α-Ga₂O₃ has become a hot spot for current reasearchs.HVPE method has the advantages of fast growth rate,high single crystal quality,low cost and the ability to grow large-scale material films,which is unmatched by MBE and Mist-CVD.Due to the limitation of high temperature phase transition,the growth and optimization ofα-Ga₂O₃involves many parameters debugging in the experiment,which needs a long process of exploration,and the dependence among parameters is difficult to understand and summarize.Therefore,in this paper,we used computational fluid dynamics（CFD）method to reaearch the reaction process in the HVPE growth chamber.The simulation of the growth process by adjusting parameters such as reaction airflow and growth temperature can not only support the experimental data with the simulated parameters,but also provide theoretical guidance for the experimental optimization process,it also greatly saved manpower,material resources and costs.The activation energy of chemical reaction is an important parameter for numerical simulation of HVPE growth ofα-Ga₂O₃thin films.According to the existing literature data,the activation energy of Ga Cl₃decomposes into Ga Cl and Cl₂andα-Ga₂O₃transforms intoβ-Ga₂O₃at high temperature were obtained by data fitting.However,the activation energy of the reaction between Ga Cl₃and O₂has not been studied yet,so we calculated it by the quantitative calculation simulation software to be about 5.1×10⁷J/KmolIn this paper,a two-dimensional 2-inch vertical cavity model is established.Firstly,we get the result that average growth rate and the relative uniformity ofα-Ga₂O₃and intoβ-Ga₂O₃is 90μm/h and 71μm/h,and the relative uniformity is 10.7%and 7.3%respectively when the growth temperature is 550℃and the Ga Cl/Ga Cl₃composition ratio is 1:1,meanwhile the growth rate of theα-Ga₂O₃film on the substrate accounts for 57%.Afterwards,we adjusted the key parameters such as the flow rate of the O₂reaction gas and the N₂separation gas to study the average growth rate,relative uniformity and distribution uniformity of the Ga₂O₃film on the substrate.Through simulation optimization,we established that when the O₂flow rate is adjusted to 0.06m/s,when the N₂flow rate is 2.8m/s,the film growth rate is the highest,and the relative uniformity is the best,meanwhile,the average growth rate of theα-Ga₂O₃andβ-Ga₂O₃films on the substrate is 180.6μm/h and 118.7μm/h,respectively,the relative uniformity values are 10.35%and 8.37%respectively,andα-Ga2O3 film growth rate proportion has reached 60%.These data will provide theoretical basis and parameter comparison for the growth of large-scale Ga₂O₃films by HVPE,and have far-reaching significance for the research and production of Ga₂O₃ films.