Substantial band-gap narrowing of α-Si3N4 induced by heavy Al doping

Our first-principles study on the structural and electronic properties of Al-doped α-Si3N4 predict a significant band-gap narrowing, which makes this material a more efficient phosphor. Strong attraction of substitutional and interstitial Al atoms leads to the formation of stable (3+1)(3+1) complexes that behave as isoelectronic traps. The near-mid-gap states of the interstitials reduce nearly half of the band-gap of α-Si3N4. Such a new nitride-based semiconductor could be a promising photocatalyst with high reactivity in solar irradiation or interior lighting in visible spectrum.

► Al-doped α-Si3N4 could be a promising photocatalyst with high reactivity in visible spectrum.
► Strong attraction of substitutional and interstitial Al atoms leads to stable (3+1)(3+1) complexes.
► The stable Al complexes behave as isoelectronic traps.
► The near-mid-gap states of the interstitial Al reduce nearly half of the band-gap of α-Si3N4.