Intrinsic Defects And Properties Control Of Single Crystal Silicon Carbide

As an important wide-bandgap semiconductor material,Si C crystal has excellent semiconductor properties and has important applications in the fields of power electronics,optoelectronics,high-power microwaves,etc.Many application scenarios suggest higher electrical performance of Si C crystals.However,there are complex intrinsic defects in Si C crystals,and there are still many problems in the regulation of intrinsic defects on its electrical properties.In addition,the unique electronic structure and properties of the intrinsic defects of Si C crystals have shown great prospects in the fields of diluted magnetic semiconductors and qubit materials.Based on the above background,the author has carried out research on the regulation of electrical properties and magnetic properties with the Si C crystal and its intrinsic defects as the object.The growth principle and growth system of Si C crystal prepared by the physical vapor transport（PVT）method is discussed firstly in this thesis,then,the author grows 6H-Si C crystal ingots from silicon carbide powder,which is cut,polished,and cleaned to produce 2 inches of semi-insulating Si C Wafers provide corresponding materials for subsequent experiments.Based on the performance differences or failure phenomena of Si C devices in practical applications,the thermodynamic environment of the Si C device preparation process is simulated,and the results show that the electrical properties of semi-insulation can remain stable below 1650°C,and the semi-insulation generation mechanism at the edge of the wafer reaches 1650°C.Failure,through GDMS,EPR and other tests,it is found that the semi-insulating properties of Si C crystals are produced by the combined effects of deep-level impurities and intrinsic-level defects,and the intrinsic defects are silicon vacancy(V_Si)that dominate.Based on the experimental results,it is proposed and verified that the disappearance of V_Siin a high-temperature environment will make the remaining deep-level impurities after high-temperature volatilization insufficient to maintain the electrical characteristics of the wafer.The results show that hh-V_C-V_Si is similar to kk-V_C-V_Si,and hk-V_C-V_Si is similar to kh-V_C-V_Si.The former two types of divacancy have low formation energy and are easy to form,but the resulting local magnetism The moment is also low,about 1μ_B,while hk-V_C-V_Si and kh-V_C-V_Si have high defect formation energies,but they can produce nearly twice the local magnetic moment,and all defects can spontaneously form spin polarization.The main source of the magnetic properties of Si C crystals is the hybridization of the 2p orbitals of C atoms adjacent to the defect.