Doping-induced modulation of electrical and optical properties of silicon nitride

This work presents first-principle calculations of electronic structure and optical properties of doped α-Si3N4. It is found that B and P impurities form shallow acceptor and deep donor bands, respectively, in the band gap of α-Si3N4. Analysis of the charge neutrality level indicates that bipolar doping of α-SiNx is possible and that both n- and p-type electrical conductivity can be expected. This result can be helpful to extend the list of device applications of SiNx. Furthermore, it is shown that upon heavy doping with these impurities, the optical properties of the material are modified by doping. Both the refractive index and extinction coefficients are increased over the photon energy range 0-4 eV as a result of the doping.