First-Principles Exploration Of Defect Complexes In GaN

GaN has gradually become one of the most promising semiconductors used in light-emitting diodes,high electron mobility transistors,GaN-based lasers and many other aspects,owing to its excellent electronic and optical properties.With relative insensitivity to ionizing radiation,GaN-based devices are now increasingly used for aerospace and military applications,while they also suffer from the radiation damage caused by high-energy particles,such as proton,electron,neutron and?-ray.Meanwhile,high-energy particle irradiations may bring some new defects,such as defect-pairs.We explored all the 21 defect-pairs in GaN and considered 6 different structural configurations of them each.15 defect-pairs are found to be stable during structural relaxation,so they can exist in the GaN lattice once formed during the irradiation of high-energy particles.9 defect-pairs have formation energies lower than 10 eV in the neutral state.Moreover,the vacancy-pair V_N-V_N is found to have a very low formation energy,as low as 0 eV in Ga-rich and p-type GaN.These defect-pairs are therefore likely to appear in radiation-damaged GaN.The properties of defect-pairs,which are fundamental for understanding the radiation damage mechanism and simulating the defect formation and diffusion process under irradiation,enrich the understanding of the defects in the GaN lattice.Furthermore,Mg is the most effective p-type dopant in GaN,so we study defect complexes formed between Mg dopants and intrinsic defects or H dopants in GaN.Some donor-acceptor complexes,where acceptors are compensated by donors,may limit the p-type conductivity.Among all the donor-acceptor compensated complexes,we found that two triple-site complexes Mg_Ga-Mg_Ga-V_N and Mg_Ga-Mg_Ga-H_N have low formation energies,especially in the Ga-rich and n-type GaN,which have never been reported.Mg_Ga-Mg_Ga-V_N also can give rise to a red and broad photoluminescence band at 1.76 eV.These triple-site defect complexes,which is first proposed by us,should be considered in the future study on the defects in GaN and related semiconductors.