| Gallium oxide(Ga2O3),aluminum nitride(AlN)and diamond as the representative of the wide bandgap semiconductor materials have become the most promising semiconductor materials of the new generation.The high forbidden band width and high breakdown voltage greatly broaden the depth and breadth of applications for electrical and optical devices.Gallium oxide has gained market popularity for high quality and large-scale substrate manufacturing,which has caused an intensive exploration of its performance optimization in both academic and commercial circles.However,the relatively low carrier mobility hinders the efficiency and scope of Ga2O3 devices.Alloying and low-dimensiona-lization of Ga2O3 is expected to give the material better carrier transport performance.Therefore,this paper systematically investigates the carrier transport properties of β-(AlxGa1-x)2O3 alloys and two-dimensional monolayer and bilayer Ga2O3 based on first-principles calculations and Boltzmann transport equation,and the main works include:Based on the β-(AlxGa1-x)2O3(β-AlGO)alloying rules,the alloy structure with concentration X≤0.5 is constructed,and the Density functional theory(DFT)and Density functional perturbation theory(DFPT)are used as the basic theories,combined with firstprinciple calculations,to investigate the effect of aluminum alloy ratio on the energy band structure,anisotropic elastic constants,high frequency and static dielectric constant matrices ofβ-AlGO alloy.The effect of aluminum alloy ratio on the physical parameters such as energy band structure,anisotropic elastic constants,high frequency and static dielectric matrices was investigated.It is found that the band gap of β-AlGO energy band increases when the aluminum concentration increases,causing a significant increase of breakdown voltage.In addition,the anisotropic elastic constants,static dielectric constants and high frequency dielectric constants of β-AlGO alloys basically show an increasing trend,reflecting the significant influence of aluminum alloying on the mechanical and optical properties of gallium oxide.The carrier transport properties of β-AlGO alloy,including electron mobility,acoustic deformation potential scattering,ionized impurity scattering,polar optical phonon scattering,and electron-phonon interactions,were systematically analyzed based on the theory of Boltzmann transport equation.It is found that the electron mobility of acoustic deformation potential scattering(μADP)and ionized impurity scattering(μIMP)is 2-3 orders of magnitude higher than that of polar optical phonon scattering mobility(μPOP),indicating the dominant role of polar optical phonon scattering.In addition,the electron-phonon interactions strength was evaluated based on the Fr?hlich coupling constant,and the results show that the electronphonon interaction strength increases with increasing aluminum concentration,leading to a decrease in μPOP and μtotal for β-AlGO alloys.The increased β-AlGO alloy Baliga figure of merit indicates that the power devices prepared based on β-AlGO alloy have lower power loss and better performance than Ga2O3.The[100]-crystal oriented two-dimensional monolayer and bilayer gallium oxide were constructed based on bulk β-Ga2O3 crystals,and the energy band structure and carrier transport properties were investigated.It is found that the forbidden band width of two-dimensional Ga2O3 decreases with the increase of the number of layers.Further,the Δε(Δε=εs-ε∞)of low-dimensional Ga2O3 was calculated by combining it with the theory of dielectric function,and the values of Δε were 3.77 and 4.60 for monolayer and bilayer Ga2O3,respectively.Such large values indicate that the role of electron-longitudinal optical phonon coupling effect(polar optical phonon scattering)in the carrier mobility needs to be further evaluated.The theoretical predictions establish the dominant role of polar optical phonon scattering in the electron mobility of 2D Ga2O3.In addition,the increase in the number of 2D Ga2O3 layers is accompanied by an increase in the Frohlich coupling constant and electron mobility.This work further improves the low-dimensional Ga2O3 carrier transport properties and scattering mechanism,and provides theoretical guidance for practical applications. |
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