Energetics of intrinsic defects and their complexes in ZnO investigated by density functional calculations
| Autor: | Ponniah Ravindran, B. G. Svensson, Eduard Monakhov, R. Vidya, Risto M. Nieminen, Helmer Fjellvåg, Maria Ganchenkova |
|---|---|
| Přispěvatelé: | Perustieteiden korkeakoulu, School of Science, Teknillisen fysiikan laitos, Department of Applied Physics, Aalto-yliopisto, Aalto University |
| Jazyk: | angličtina |
| Rok vydání: | 2011 |
| Předmět: |
oxygen
zinc Physics ta214 ta114 ta221 Charge density Crystal structure Electronic structure Condensed Matter Physics Crystallographic defect Acceptor Molecular electronic transition Electronic Optical and Magnetic Materials Pseudopotential Condensed Matter::Materials Science Crystallography ZnO Atomic physics Electronic band structure defects ta218 |
| Zdroj: | Physical Review B. 83(4):1-12 |
| ISSN: | 1098-0121 |
| Popis: | Formation energies of various intrinsic defects and defect complexes in ZnO have been calculated using a density-functional-theory-based pseudopotential all-electron method. The various defects considered are oxygen vacancy (${\mathrm{V}}_{\mathrm{O}}$), zinc vacancy (${\mathrm{V}}_{\mathrm{Zn}}$), oxygen at an interstitial site (${\mathrm{O}}_{i}$), Zn at an interstitial site (${\mathrm{Zn}}_{i}$), Zn at ${\mathrm{V}}_{\mathrm{O}}$ (${\mathrm{Zn}}_{\mathrm{O}}$), O at ${\mathrm{V}}_{\mathrm{Zn}}$(${\mathrm{O}}_{\mathrm{Zn}}$), and an antisite pair (combination of the preceding two defects). In addition, defect complexes like (${\mathrm{V}}_{\mathrm{O}}+{\mathrm{Zn}}_{i}$) and Zn-vacancy clusters are studied. The Schokkty pair (${\mathrm{V}}_{\mathrm{O}}+{\mathrm{V}}_{\mathrm{Zn}}$) and Frenkel pairs [(${\mathrm{V}}_{\mathrm{O}}+{\mathrm{O}}_{i}$) and (${\mathrm{V}}_{\mathrm{Zn}}+{\mathrm{Zn}}_{i}$)] are considered theoretically for the first time. Upon comparing the formation energies of these defects, we find that ${\mathrm{V}}_{\mathrm{O}}$ would be the dominant intrinsic defect under both Zn-rich and O-rich conditions and it is a deep double donor. Both ${\mathrm{Zn}}_{\mathrm{O}}$ and ${\mathrm{Zn}}_{i}$ are found to be shallow donors. The low formation energy of donor-type intrinsic defects could lead to difficulty in achieving $p$-type conductivity in ZnO. Defect complexes have charge transitions deep inside the band gap. The red, yellow, and green photoluminescence peaks of undoped samples can be assigned to some of the defect complexes considered. It is believed that the red luminescence originates from an electronic transition in ${\mathrm{V}}_{\mathrm{O}}$, but we find that it can originate from the antisite ${\mathrm{Zn}}_{\mathrm{O}}$ defect. Charge density and electron-localization function analyses have been used to understand the effect of these defects on the ZnO lattice. The electronic structure of ZnO with intrinsic defects has been studied using density-of-states and electronic band structure plots. The acceptor levels introduced by ${\mathrm{V}}_{\mathrm{Zn}}$ are relatively localized, making it difficult to achieve $p$-type conductivity with sufficient hole mobility. |
| Databáze: | OpenAIRE |
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