First-principles Study Of 3C-SiC Doping System

Silicon carbide(SiC),which is regarded as an emblematic representative of the third-generation semiconductor materials,can be widely used in the field of high temperature,high voltage,and high power electronic device s manufacturing due to the wide bandgap,high carrier saturation rate,high thermal conductivity and excellent mechanical properties compared with traditional silicon materials.In recent years,pure SiC materials are gradually unable to meet the actual needs with the rapid development of semiconductor devices and SiC materials are modified by means of doping in order to broaden its application fields.Based on this situation,the electronic structures,optical properties and magnetic properties of SiC model are calculated and analyzed by changing the type and concentration of dopant through first-principles calculation in this present contribution.The specific contents of this paper are shown as follows:1.The electronic structures and optical properties of IV A elements(Ge,Sn and Pb)doped 3C-SiC are investigated by means of the first-principles calculation.The results reveal that the structure of Ge-doped system is more stable with a lower formation energy of 1.249 eV compared with those of Sn-and Pb-doped 3C-SiC systems of 3.360 and 5.476 eV.Doping of the IV A elements can increase the bandgap of 3C-SiC,and there is an obvious transition from an indirect bandgap semiconductor into a direct bandgap semiconductor.Furthermore,charge difference density analysis proves that the covalent order of bonding between the doping atoms and the C atoms is Ge-C > Sn-C > Pb-C,which is fully verified by population values.Due to the lower static dielectric constant,the service life of 3C-SiC dramatically improved in production practice.Moreover,the lower reflectivity and absorption peaks in the visible region,implying its wide application foreground in photoelectric devices.2.By changing the doping concentration of N,P and As elements(0.03125,0.0625 and 0.125,respectively),we can find that the lattice constant of 3C-SiC system is inversely proportional to the doping concentration of N,while the lattice constant is positively proportional to the doping concentration of P and As elements.Compared with the band structures of different doping systems,it can be seen that N,P,As doping systems exhibit the characteristics of direct band gap semiconductor,and cannot be affected by the change of concentration,which is very beneficial for the application of 3C-SiC in the field of light emitting devices.The Fermi level enters into the conduction band after the doping three elements at different concentrations,which is typical feature of N-type doping.The static dielectric constant of N-,P-and As-doped systems show an increasing trend with the increasing doping concentration.The 3C-SiC system doped with 3.125% N has the smallest static dielectric constant and dielectric loss,which is helpful to prolong the service life of 3C-SiC devices in practice,helping to save resources and reduce energy consumption.However,the 3C-SiC system with P doping concentration of 12.5% exhibits the largest static dielectric constant and dielectric loss,which makes SiC widely utilized in military and aerospace fields as absorbing materials.When the doping concentration of N,P,As reaches 3.125%,the systems have relatively samller absorption coefficient and reflectivity in the low energy region,implying that the low doping concentration of N,P and As elements is beneficial to the application of 3C-SiC materials in the field of anti-reflection coatings of solar cells.3.The magnetic properties of TM elements(Ti,V,Cr,Mn,Fe,Co,Ni,Cu)single doping and TM-Al co-doping in 3C-SiC systems are investigated by simulation.Compared with TM single-doped 3C-SiC,TM-Al co-doped 3C-SiC systems have greater formation energy and binding energy,which is mainly due to the introduction of an additional Al atom.According to the total and partial densities of states,Ti and Fe doped 3C-SiC systems exhibit completely symmetrical characteristics,no spin splitting occurs near the Fermi level,and Ti and Fe doped 3C-SiC systems do not have magnetic properties.The densities of states of the other six TM elements show asymmetric characteristics in the vicinity of the Fermi level,indicating that spin magnetization occurs in these doping systems,that is,these doping systems exhibit magnetic characteristics.In addition,in the Cr,Mn,Co,Ni and Cu doped systems,the upper spin state density passes through the Fermi level and presents the metallic property,while the lower spin state density is 0 near the Fermi level(showing semiconductor characteristics),so these doping systems exhibit the semi-metallic feature as a whole.Similarly,Ti-Al,V-Al and Co-Al co-doped 3C-SiC systems show nonmagnetic properties,while Cr-Al,Mn-Al,Fe-Al,Ni-Al and Cu-Al co-doped 3C-SiC systems exhibit magnetic properties.The introduction of Al atoms into different TM elements single-doped systems has diverse effects on their magnetic properties,for example,the magnetic properties of Ni-Al co-doped system is lower than that of Ni-doped system,the introduction of Al element can stabilize the antiferromagnetic properties of V and Co co-doped systems,result in the nonmagnetic properties of Fe-doped system change to the magnetic properties of Fe-Al co-doped system,and have no effect on the magnetic properties of Cu-doped system.Therefore,researchers should carefully select Al element for co-doping in magnetic properties experiments.