Electronic, magnetic, optical and transport properties of wurtzite-GaN doped with rare earth (RE= Pm, Sm, and Eu): First principles approach

Abstract

A density functional theory (DFT) and semiclassical Boltzmann transport equations (BTE) has been used to explore the electronic, magnetic, optical and transport properties of Ga1−xRExN (RE=Pm, Sm, and Eu). We have studied the impact of doping of rare-earth (RE) elements on GaN wurtzite structure. In all the doped systems, the stability is ferromagnetic state with minimum ground state energy. Our theoretical calculations revealed that all the doped compounds exhibit half-metallic ferromagnet (HMF) behavior with 100% spin polarization at the Fermi level witin GGA, mBJ and Spin-orbit coupling (SOC). However, within GGA+U, Ga1−xRExN exhibits dilute magnetic semiconducting behaviour with exact integer value of total magnetic moment. A large gap was established with the concentrations of 6.25%, 12.5%. The shift of fermi energy towards the bottom of the conduction band, make these systems an n-type. The mechanism of ferromagnetism in this system has been proposed according to this positioning. The majority-spin density of states (DOS) mainly comprises of Eu-4f states appears in the energy gap. Yet, in the case of the Pm, and Sm-doped GaN, some part of the impurity states of 4f lies below Fermi energy (Ef). The optical absorption for RE-doped GaN is significantly enhanced, in the ultraviolet region. We have noticed the improvement of electrical conductivity as compared to the pristine one for both the concentrations. These features, make RE-doped GaN a transparent material for optoelectronic tools.