Study On Electrical And Optical Properties Of Ge-doped SiC Materials

As the third generation of semiconductor materials,SiC material has wide bandgap,low dielectric constant,high thermal conductivity,high critical breakdown electric field and high carrier saturation concentration and other properties.In semiconductor lighting,power electronics,aerospace,nuclear energy detection and development,automotive engine,microwave communication,artificial satellite and other field,SiC is one of the most promising materials.For semiconductor materials,doping will affect the material properties.The study found that the Ge element could reduce the contact resistance and improve mobility of SiC devices.Meanwhile,Ge doping will affect the crystal structure,change the lattice parameters and band structure of SiC.Therefore,properties of SiC device can be improved and high performance SiC devices can be prepared by doping the Ge element.At present,domestic research on Ge-doped SiC is only a theoretically simple analysis.Based on this,this paper proposes a targeted study on electrical and optical properties of Ge-doped SiC materials by adjusting the doping amount and doping position of the Ge element.This paper tests the material of Ge-doped SiC crystal which provided by ShanDong University.Including Raman test and RBS test of the sample material.To confirm crystalline and uniformity of the crystalline we test Raman.Further confirm the Further confirm that the crystallization is good or bad we test RBS.Moreover,we test DLTS to confirm crystal defects and deep level impurities of the sample.The results of the test prove that although the Ge-doped is not completely equally,the sample crystal quality is good.Next,we calculate the electrical and optical properties of Ge-doped 4H-SiC material based on first-principles method.Using density functional theory and material science simulation software Material studio 8.0,the energy band structure and density of states of the 4H-SiC eigenstates are calculated.Then we compare the formation energy of Ge atoms in place of C atoms or Si atoms in SiC.Next,Three Ge-doped 4H-SiC models are selected:the Si_0.984375Ge_0.015625C obtained by replacing one Si atom with one Ge atom in a super lattice of 64 atoms?2×2×2?,the SiGe_0.015625C_0.984375 obtained by replacing one C atom with one Ge atom in a super lattice of 64 atoms?2×2×2?and the SiGe_0.0078125C_0.9921875.9921875 obtained by replacing one C atom with one Ge atom in a super lattice of 128 atoms?4×2×2?.The results of energy band structure,electronic density,dielectric constant,absorption spectrum and reflection spectrum of three doped samples were calculated and analyzed.Finally,the performance of the intrinsic 4H-SiC sample material is compared with this three,so we get the specific effects of different doping positions and doping concentrations of Ge elements on the electrical and optical properties of 4H-SiC materials.For electrical properties,there is almost no change in the energy band structure after Ge_Si-doping.After Ge_C-doping,the trap levels are increased near Fermi level.For optical properties,there is almost no change in absorption spectrum and reflection spectrum after Ge_Si-doping.After Ge_C-doping,the absorption spectrum and the reflection spectrum curve are shift to the low energy end obviously and the absorption spectrum extreme value decreased.In conclusion,the resistivity of the sample has dropped and the conductivity of the sample has increased by Ge-doped.Furthermore,the absorption spectrum and the reflection spectrum of the Ge-doped 4H-SiC are red-shifted.This has guiding significance and practical value for SiC semiconductor devices with better performance in the future.