Study On Crystal Growth And Properties Of Doped β-Ga₂O₃ Single Crystal By EFG Method

As the basic material of large scale integration,solar cell and other high-tech fields,semiconductor materials are the necessary cornerstone of modern intelligent and scientific industry.Semiconductor materials have special electrical properties and a wide range of applications.It has an important position and application value in modern science and industry.At present,the third generation semiconductor materials with wider gap gradually become the focus of crystal research,β-Ga₂O₃,GaN,SiC and other semiconductors are developing rapidly.β-Ga₂O₃ is an ultra-wide bandgap semiconductor,with the bandgap up to 4.9 eV and the breakdown field up to 8 MV/cm.Benefiting from the high breakdown field and great electron conduction,the BFOM values are four times larger than that of GaN and six times larger than that of SiC in theory[1,2].The outstanding intrinsic properties bring β-Ga₂O₃ has great prospects in high voltage,high power,low loss devices[3,4],and deep ultraviolet optoelectronic devices[5,6].The growth and electrical doping of bulk single crystal have advantages than that of the other ultra-wide bandgap semiconductors such as AlN and diamond.β-Ga₂O₃ is currently in a period of rapid development,single crystal size is constantly expanding,quality has been greatly improved,processing technology,epitaxial process and effect,device structure and performance have entered a period of rapid development,β-Ga₂O₃ has good prospects for development and scientific research value.β-Ga₂O₃ has been studied for a relatively short time in China,and developed countries like the United States have already imposed restrictions on its export,establishing technical barriers.Currently,the growth conditions and processes for β-Ga₂O₃ in China are still in the stage of exploration and optimization,and comprehensive and in-depth research is needed.The highquality single crystals and substrates of β-Ga₂O₃,as the forefront of the industry chain,directly affect the performance of devices and epitaxy,and are also the basis for further research on βGa₂O₃.This paper aims to produce high-quality β-Ga₂O₃,and carries out a series of studies including growth condition and process optimization,doping uniformity control,performance characterization,and exploration of transition metal ion doping.Ⅰ.Growth and electrical properties regulation of Sn⁴⁺doped β-Ga₂O₃ single crystalSn-doped β-Ga₂O₃ single crystals were grown using the EFG method by optimized the growth process.The existence of cross-section inhomogeneous distribution of dopants was found by polariscope,and the degree of inhomogeneous distribution was quantified by capacitance-voltage（C-V）test.By studying the theory of impurity segregation and solid-liquid interface,a reasonable theoretical model of impurity distribution was proposed.Under the guidance of the model,a better solid-liquid interface is obtained,and high homogeneous Sn⁴⁺doped β-Ga₂O₃ single crystal is grown.The results of polariscope and C-V test demonstrate the effectiveness of regulation.Ⅱ.Growth and growth condition optimization of heavy Sn⁴⁺doped β-Ga₂O₃ single crystalsBy doping with Sn⁴⁺,the electron concentration of β-Ga₂O₃ has been increased,meeting the demand for conductive single-crystal substrates in vertical structure devices and expanding the application direction of β-Ga₂O₃.High conductivity is conducive to reducing the on-off resistance and improving the effect of ohmic contact,thus improving the performance of the device.,so our research team improve the doping concentration of Sn⁴⁺.For β-Ga₂O₃,after heavy Sn⁴⁺doped,there will be a problem of increased light absorption in the near infrared band,resulting in interface inversion,which impeded the normal growth.Therefore,the existing growth conditions and process were optimized,and the heavy Sn doped β-Ga₂O₃ single crystal with high electron concentration was obtained.HRXRD was used to prove its high quality.The effect of heavy Sn doping on β-Ga₂O₃ single crystal was studied by Raman spectra and XPS.Ⅲ.Crystal growth and wideband near-infrared luminescence characteristics of transition metal ions Ni²⁺doped β-Ga₂O₃By doping with transition metal ion Ni²⁺,the wide-band near-infrared luminescence characteristics of β-Ga₂O₃ have been discovered,expanding the application direction of βGa₂O₃ in the field of wide-band near-infrared luminescence.When located in the octahedral lattice of oxides and halides,Ni²⁺ ions have multiple excited states participating in the transition process,accompanied by upconversion luminescence.Currently,a large number of materials have shown obvious luminescence bands due to Ni²⁺ ion doping,such as Ni²⁺:SLN,Ni²⁺:MgGa2O4,Ni²⁺:ZnSiO₃,and others.There is currently little research on Ni²⁺ion doping inβ-Ga₂O₃,so our research team combined the characteristics of Ni ions and β-Ga₂O₃,selected a suitable doping concentration,designed a reasonable temperature field structure and mold crucible ratio,and obtained highly homogeneous Ni-doped β-Ga₂O₃ single crystals.The crystal structure and quality were verified by powder XRD and Laue diffraction,and its optical properties were studied by UV-Vis transmission spectroscopy,infrared transmission spectroscopy,and cathodoluminescence spectroscopy,and its wide-band near-infrared luminescence characteristics were discovered.