Effects of doping on photoelectrical properties of one-dimensional α-Si₃N₄ nanomaterials: A first-principles study

The structural stability, electronic and optical properties of Al-, Y-, O-doped and Al-O-codoped one-dimensional (1D) α-Si₃N₄ nanomaterials are investigated by first-principles methods. All dopants prefer to locate at the surface of 1D α-Si₃N₄ nanomaterials except Al. The doping difficulties decrease in the order of Al_Si, Y_Si, O_N and Al_Si-O_N. The conduction types and band gap values of 1D α-Si₃N₄ nanomaterials are tunable by doping due to the hybridizations of impurity states with the band edges. The increases of hole and electron effective masses caused by doping are different. The doping greatly affects the optical properties of 1D α-Si₃N₄ nanomaterials mainly at and below the absorption edges. The optical parameters in the parallel direction to the axis are larger than those in the perpendicular direction. Especially if the nanomaterial was doped with Al, its optical parameters are changed most obviously, followed by those of Y-doped nanomaterial, while the differences of the O-doped and Al-O-codoped nanomaterials are not obvious.