First-principles study on energetics of intrinsic point defects in LaAlO3

Using density-functional theory (DFT) calculations, the formation energies, electron affinities and electronic levels of various intrinsic defects in bulk LaAlO3 are investigated. Results give the atomic structures of charged interstitials, vacancies, Frenkel pairs, antisite defects, and Schottky defects, respectively. It is found that the formation energies of O vacancy are the lowest in the reducing conditions. In contrast, the La vacancy V-La is more favorable in formation energy as the O chemical potential increasing. Moreover, by considering the defect levels of LaAlO3 with respect to the silicon conduction bands, the effects of the electron and hole trapping in real devices are also simulated. Our results show that the paired charged V-O, which lies in the middle of the silicon band gap, should be the key problematic defect. The deep defect level of V-O can induce a large-tunneling-leakage current and cause instability in the device performance. These predictions provide rich defect structures in LaAlO3 and useful information for the microelectronic designs.