Theoretical Study of Optical Properties of Native Point Defects in α-Al2O3

Using first-principles calculations based on density functional theory with generalized gradient approximation (GGA) parameterized by Perdew-Burke-Ernzerhof (PBE) for the exchange-correlation functional, we studied the native point defects in α-Al2O3. We found that oxygen vacancy (VO), Al vacancy (VAl), and Al interstitial (Ali) are the dominant defects in α-Al2O3 under both Al- and O-rich growth conditions. Because the optical properties of α-Al2O3 are important for many device applications, the optical excitation levels due to these native point defects were studied. Our results revealed that the absorption and emission bands at ∼3.0 and 6.0 eV should be associated with VO (F-center) in good agreement with previous works. Moreover, the observed emission peak at ∼3.8 eV is very close to the calculated emission energy of Ali. The absorption and emission due to other native point defects were also reported.