First-principles Study On The Optoelectronic Properties Of Rare Earth Elements (La, Nd, Er, Lu) Doped Mg₂Si

The first principles calculation method based on density functional theory was used to study systematically the effects of La,Nd,Er or Lu doping on the electronic structure and optical properties of Mg₂Si semiconductor materials at four doping concentrations of 1.85 at%,3.7 at%,5.56 at%and 7.4 at%,which is helpful to research and develop new optoelectronic and electronic devices based on rare earth doped Mg₂Si.The Mg₅₄Si₂₇supercell model was constructed by Materials Studio software.Then four doping systems were selected and the Mg atoms were replaced by different numbers of La,Nd,Er or Lu atoms,so sixteen doping models were obtained.The electronic structures and optical properties of these models were calculated by VASP software.The electronic structures and optical properties of intrinsic Mg₂Si were calculated,and the results show that intrinsic Mg₂Si is an indirect-gap semiconductor with the band gap of 0.2391 eV.Its conduction band is mainly provided by Mg-2p,Mg-3s and Si-3p States,and its valence band is mainly provided by Mg-2p,Mg-3s and Si-3p states.The static dielectric constant?₁(0)is 22.71,the maximum absorption coefficient is 19.96×10⁵cm^-1and the refractive index n₀is 4.77,respectively.The electronic structures and optical properties of La-,Nd-,Er-or Lu-doped Mg₂Si with four doping concentrations of 1.85 at%,3.7 at%,5.56 at%and 7.4 at%were calculated and analyzed,and the results show that the conduction type of La-,Nd-or Lu-doped Mg₂Si is n-type,and the conduction type of Er-doped Mg₂Si is p-type.To a certain extent,La,Nd,Er or Lu doping can improve the conductivity of the Mg₂Si materials.In the visible region,the absorption coefficient and reflectivity of La-,Nd-,Er-or Lu-doped Mg₂Si decrease,indicating that the transmittance of the material is improved,which has a certain significance for the preparation of high transmittance materials in the experiment.Intrinsic Mg₂Si hardly absorbs mid-infrared and far ultraviolet photons,but La-,Nd-,Er-or Lu-doped Mg₂Si can still absorb the mid-infrared and far ultraviolet photons.In other words,the doping of La,Nd,Er or Lu atoms enhances the absorption properties of Mg₂Si to infrared and far ultraviolet light,which provides a theoretical basis for the preparation of rare earth doped Mg₂Si optoelectronic devices.When the doping concentration is 1.85 at%or 3.7 at%,the absorption intensity of Nd-doped Mg₂Si to mid-infrared photons is the highest.When the doping concentration is 5.56 at%or 7.4 at%,the absorption intensity of Lu-doped Mg₂Si to mid-infrared photons is the highest.Under the four doping concentrations,the absorption intensity of Nd-doped Mg₂Si to near-infrared photons is the highest.Under the four doping concentrations,the absorption intensity of La-doped Mg₂Si to far ultraviolet photons is the highest.