Effects Of Group Ⅲ Doping On Electrical And Optical Properties Of Silicon Carbide Nanotubes

Silicon carbide nanotubes(SiCNTs),as one of the most valuable silicon carbide nanomaterials for research,not only have the excellent characteristics of silicon carbide(Si C)crystals,but also show some unique properties of nanotubes,such as high in-and out-surface activity,easy-manipulated electronic structure and good thermal stability,being widely used in the technical field of high frequency,big breakdown strength,high temperature,large thermal conductivity and strong radiation resistance.Doping is an effective method to promote the performance of semiconductor materials.SiCNTs behave better electrical,optical and magnetical properties with group III atoms doped,suggesting a much broader application in fields of microelectronics and optoelectronic devices.Therefore,it is of great importance to investigate the influence of doping on the electrical and optical properties of SiCNTs with group III element.This paper mainly includes the following contents:Firstly,the CASTEP module in Materials Studio(MS)software based on first principles was used to calculate the structure and electrical properties of SiCNTs after group III elements(B,Al,Ga,In)replaced Si atoms and C atoms,respectively.Based on the optimized(6,6)SiCNTs model,the doped SiCNTs with replace Si and C atoms by group III elements was established,and the model is optimized and calculated to obtain its lattice structure and energy band structure.Then,the calculation model of the electron transport and recombination mechanism of SiCNTs was established based on semiconductor physics and solid-state physics,analyzed the influence of different substitutions of group III elements on the electron transport properties of SiCNTs through the calculated data of electrical conductivity,carrier concentration and electrical conductivity.By analyzing and comparing the recombination center concentration,electron(hole)recombination rate,non-equilibrium minority carriers and other data,the influence of different substitutions of group III elements on the recombination properties of SiCNTs is obtained.The results showed that the conductivity of SiCNTs with Si site substitution is about 10 times compared with that of C site replacement,the lifetime of the non-equilibrium minority carrier for C site doped SiCNTs is longer than that of Si site replacement.That is,Si site atom substitution is preference for the transport properties in SiCNTs,while the C site atom doping is more beneficial for the composite properties.Secondly,the influence of the substitution of Si atoms and C atoms by group III elements on the optical properties of SiCNTs was analyzed and studied.The optical properties of SiCNTs before and after doping were calculated,including absorption coefficient and photoconductivity,dielectric constant and refractive index,reflection and transmission.The interaction between photons and electrons in the crystal is used to study the optical properties of SiCNTs.The research results showed that the intrinsic peaks of absorption and photoconductivity of C-substituted SiCNTs are low and broad,while the peaks of Si-substituted SiCNTs are high and narrow.Moreover,a transmission windows were presented at the farinfrared and near-ultraviolet wavelengths for C-substituted SiCNTs comparing with Si site substitution.Finally,Based on the research of single-walled SiCNTs(SWSiCNTs),we explored the electrical and optical properties for DWSiCNTs at different substituted Si positions on the inner and outer walls.By analyzing the lattice parameter,chemical bond and charge transfer characteristics of DWSiCNTs at different doped Si positions,the inter-wall coupling mechanism was obtained.Through the comparative analysis of the conductivity,carrier concentration and mobility of the inner and outer walls of the III-doped DWSiCNTs and the corresponding SWSiCNTs,the influence of the inter-wall coupling on the transport properties was obtained.And we discussed the results of optical properties,such as light absorption,photoconductivity,and refractive index,of the doped SWSiCNTs and DWSiCNTs,and discovered the influence of the inter-wall coupling on the optical properties for DWSiCNTs.The results showed that there is a coupling between the inner and the outer wall,which is stronger for inner one.The coupling effect introduces a larger conductivity for DWSiCNTs compared with SWSiCNTs,which promotes an excellent electrical conductivity for doped DWSiCNTs with inner wall.