Homoepitaxial Growth Of β-Ga₂O₃ Films And Fabcration Of Schottky Barrier Diodes

β-phase gallium oxide(β-Ga2O3)has many excellent material properties such as ultra-wide bandgap,high breakdown field strength,and high Baliga figure of merit.It has attracted much attention in the field of high-power devices as the application of βGa2O3-based devices can significantly reduce power loss and improve energy conversion efficiency.In addition,β-Ga2O3 single crystal can be grown by melting method,which makes its high-quality,large-size,low-cost homoepitaxy possible.This paper focuses on the homoepitaxy,device processing,and electrical performance of βGa2O3.The main research contents are as follows:1.Homoepitaxial growth of(001)β-Ga2O3 films by metal-organic chemical vapor deposition(MOCVD)was studied,and high-quality film was obtained as the formation of grooves was suppressed through indium(In)assisted epitaxy.Due to the anisotropic growth and decomposition in the growth of β-Ga2O3 films,large surface roughness of 24.7 nm could appear,accompanied with[010]-oriented striped and grooves.Introducing In as a surfactant can effectively inhibit the decomposition of Ga2O3 and promote the epitaxial lateral overgrowth of the film.Through optimized pulsed Inassisted epitaxy,the roughness of the film decreased to 2.2 nm,without any deterioration in the crystal quality.Eventually,the problem of the groove morphology in the film growth was solved,and high-quality(001)β-Ga2O3 films grown by MOCVD was realized for the first time.2.The homoepitaxial growth of(100)β-Ga2O3 films and Si doping were studied.Due to the low surface energy of the(100)plane,island growth mode was dominant in the film growth.By optimizing the growth conditions,the diffusion of the adatoms was enhanced and the formation of islands was suppressed,bringing a decreasing roughness from 4.5 nm to 2.3 nm.An appropriate amount of Si doping in the epitaxy further optimized the morphology of the film and decreased the roughness to 1.3 nm,with a decreased full width at half-maximum of XRD rocking curve of 26 arc sec.Based on this phenomenon,it is proposed that Si doping introduces nucleation sites,promoting the coalescence of the film and enhancing the epitaxial lateral overgrowth.In the growth process,the random nucleation of Si enhances the lateral diffusion of Ga adatoms,making the adatoms grow laterally around the Si nucleation sites,which compets with the longitudinal growth of 2D islands.As a result,the epitaxial lateral overgrowth and step flow growth mode get enhanced.By controlling the flow rate of SiH4 during the growth,a doping within the range of concentration of 5.41 × 1015～1.74 × 1020 cm-3 and an activation efficiency of 61.5%were realized.Excellent Ohmic contact characteristics such as a specific contact resistivity of 1.29 × 10-4 Ω·cm2 has also been obtained.3.Inductively coupled plasma(ICP)etching,wet etching,Ga etching and ion implantation processes of β-Ga2O3 have been developed and optimized.Through ICP etching,high-efficiency,low roughness,and high-steep mesa structure was realized.The surface morphology of the film was improved and the dry etching damage was reduced by hot H3PO4 solution etching.Ga etching process was adopted to further repair the surface damage and reduce the interface state density.Based on Si-ion implantation and N-ion implantation,good Ohmic contact and electrical isolation have been achieved,respectively.4.Based on the optimized composite etching process,trench Schottky barrier diode(SBD)with low damage was fabricated,achieving a high current density of 1228 A cm-2,a high rectification ratio of 1010,and a low interface state density of 2.9 ×1011 cm-2 eV-1.β-Ga2O3 SBD with guard rings and shallow trenches was prepared by N-ion implantation and trench etching,achieving a high rectification ratio greater than 1010 and a breakdown voltage of 1344 V.The ideality factor of the fabcrated SBD was 1.06,and the Schottky barrier height was 1.18 eV.In addition,the SBD showed good robustness under high reverse voltage,and better dynamic characteristics than the SBD with only guard rings,which confirms the optimization of the electric field distribution and the improvement of the dynamic characteristics of the structure with both guard rings and shallo w trenches.It further verifies the effectiveness of the composite etching process for repairing damage and reducing interface state density.