Electronic Structure and Impurity Level Location of Rare-Earth (Ce, Pr, Nd, Dy) Doped GaN: GGA Approximation

Electronic structure and impurity level location of rare-earth (RE) doped GaN have been investigated. Based on density functional theory GGA Approximation, the electronic structure of GaN and GaN:RE are calculated in hexagonal structure. The lattice parameter, bond length of Ga-N and the tetrahedral angle of N-Ga-N show the 3% change from experimental results. When we substitute Ga to RE in the GaN structure, the bond length changes 12% longer with the equilibrium bond length of RE-N varies between 2.1382Å - 2.2428Å . The ionic radii of RE larger than Ga, it will affect to tetrahedral angle which vary from 112.68° - 113.60°. In the electronic properties calculation, the pristine GaN has direct band gap 2.58 eV. The impurity energy level of Ce, Pr, and Nd are detected in the band gap while Ce level lies near conduction band minimum and the impurity level is contributed by 4f electron states. By this, the 4f energy can explain the luminescence process from rare-earth atoms to host materials. The band structure of GaN:RE is expected to allow optical transition in IR-UV emission range. GaN:RE has high potential to be applied to lower energy of light emitting diodes and energy-saving devices.