1. Role of self-trapping in luminescence andp-type conductivity of wide-band-gap oxides
- Author
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Anderson Janotti, C. G. Van de Walle, Joel B. Varley, Cesare Franchini, Varley JB, Janotti A, Franchini C, and Van de Walle CG
- Subjects
010302 applied physics ,Materials science ,Condensed matter physics ,Wide-bandgap semiconductor ,02 engineering and technology ,Conductivity ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Polaron ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Hybrid functional ,Delocalized electron ,Condensed Matter::Materials Science ,Impurity ,physics, polaron, semiconductor ,Lattice (order) ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,0210 nano-technology ,Luminescence - Abstract
We investigate the behavior of holes in the valence band of a range of wide-band-gap oxides including ZnO, MgO, In${}_{2}$O${}_{3}$, Ga${}_{2}$O${}_{3}$, Al${}_{2}$O${}_{3}$, SnO${}_{2}$, SiO${}_{2}$, and TiO${}_{2}$. Based on hybrid functional calculations, we find that, due to the orbital composition of the valence band, holes tend to form localized small polarons with characteristic lattice distortions, even in the absence of defects or impurities. These self-trapped holes (STHs) are energetically more favorable than delocalized, free holes in the valence band in all materials but ZnO and SiO${}_{2}$. Based on calculated optical absorption and emission energies we show that STHs provide an explanation for the luminescence peaks that have been observed in many of these oxides. We demonstrate that polaron formation prohibits $p$-type conductivity in this class of materials.
- Published
- 2012
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