Structural stability and electronic properties of the (0001) inversion domain boundary in III-nitrides

A structural investigation of (0 0 0 1) plane inversion domain boundaries (IDBs) in group III-nitrides (GaN, AlN and InN) has been carried out by means of Monte Carlo (MC) simulation of Stillinger-Weber empirical potential. Eight possible IDB configurations were found to be stable during the structural searching process. Their energetics, chemical bonding properties as well as electronic structures were further investigated using first-principle calculations based on density functional theory (DFT). The comparison of relative energetic stability revealed that the H4 configuration is the most stable structure among H (Head-to-Head type) IDBs except in AlN; as for T (Tail-to-Tail type) IDBs, T2 is more energetic favorable within all materials. The electron localization function (ELF) and the Bader population analysis clearly point out 2-dimensional hole gas (2DHG) in H IDBs and 2-dimensional electron gas (2DEG) in T IDBs. And this is ascribed to the polarization discontinuity. A detailed analysis of Projected Density of States (PDOS) shows a metallic character in all IDBs. The hybridization states at the valance band edge crossed the Fermi level in H boundaries which acts as a p dopant. For T type IDBs, the PDOS is largely extended in density with the Fermi level shifted up above the conduction band maximum (CBM) which suggests an electron excess in boundaries.