LAUSR

Abstract Differences of electron structures and optical properties between Mg-interstitial doped and Mg-substitution doped Al 0.25 Ga 0.75 N were investigated by First-principles calculations based on density functional theory and the pseudopotential method. The results of these calculations demonstrate that it is more stable for a substitution Mg atom to replace a Ga atom than a interstitial Mg atom located at the center of Al 0.25 Ga 0.75 N crystal. Mg substitution doping increases the band gap of Al 0.25 Ga 0.75 N and makes crystal exhibit p-type properties. While an interstitial Mg impurity narrows the band gap of Al 0.25 Ga 0.75 N and makes crystal become n-type semiconductor. Analysis of E-Mulliken charge distribution indicates that a substitution Mg atom acts as an acceptor impurity, and an interstitial Mg atom acts as a donor impurity. There is surface state for Al 0.25 Ga 0.75 N with a Mg atom interstitial doping, which means that crystal possesses metal properties. The comparison results show that Al 0.25 Ga 0.75 N with Mg atoms substitution doping has higher absorption coefficient, lower reflectivity and energy loss function than with Mg atoms interstitial doping. This work provides a profound guiding for the ways of Mg doping at Al 0.25 Ga 0.75 N.