Research on electronic structure and optical properties of Mg doped Ga0.75Al0.25N

Abstract

In order to study the influence of Mg doping on the electronic structure and optical properties of wurtzite Ga0.75Al0.25N and the hydrogen passivation of Mg-doped Ga0.75Al0.25N, models of Ga0.6875Mg0.0625Al0.25N, Ga0.75Mg0.0625Al0.1875N and Ga0.6875(MgH)0.0625Al0.25N are built. Based on first principle calculation, the atomic structures, band structure, Mulliken population, and optical properties of the Mg doped and Mg–H co-doped crystals are obtained. Results show the formation energy of Mg–H complex is smaller than that of only Mg doping in the material. The Fermi levels of the two Mg doped crystals enter into the valence bands and Mg doping makes the crystals turn into p-type degeneracy semiconductors. Meanwhile, the Fermi level goes back to the gap between conduction band and valence band in the Mg–H codoped model. The Mulliken charge of Mg atom decreases after adding the H atom, showing that hydrogen results in the passivation and weaker ionicity of the Mg impurity. After Mg doping, the first dielectric peak shifts to lower energy since the Al:3p and Ga:4p state in the conduction band move to the range of lower energy. The metal reflective region of the semiconductor also shift to lower energy range after My doping. Mg doping enhances the absorption coefficient at the range of 1.05–3.47eV while weakens it at the range of the 10.00–20.00eV.