Defect and impurity properties of hexagonal boron nitride: A first-principles calculation

In this paper, we have systematically studied the structural and electronic properties of vacancy defects and carbon impurity in hexagonal boron nitride (h-BN) by using both normal GGA calculations and advanced hybrid functional calculations. Our calculations show that the defect configurations and the local bond lengths around defects are sensitive to their charge states. The highest negative defect charge states are largely determined by the nearly-free-electron state at the conduction band minimum of BN. Generally, the in-gap defect levels obtained from hybrid functional calculations are much deeper than those obtained from normal GGA calculations. The formation energies of neutral defects calculated by hybrid functional and GGA are close to each other, but the defect transition energy levels are quite different between GGA and hybrid functional calculations. Finally, we show that the charged defect configurations as well as the transition energy levels exhibit interesting layer effects.