First-principles study of the diffusion of hydrogen in ZnO
M G Wardle1, J P Goss, P R Briddon
1School of Natural Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, United Kingdom.
Physical Review Letters
|June 29, 2006
Summary
Hydrogen is mobile in zinc oxide, suggesting it must be trapped at defects to form stable donors. This finding is crucial for understanding n-type conductivity in wide-gap semiconductors.
Area of Science:
- Materials Science
- Solid State Physics
- Computational Chemistry
Background:
- Zinc oxide (ZnO) is a wide-gap semiconductor.
- Undoped ZnO typically displays n-type conductivity.
- The origin of native n-type conductivity in ZnO is debated, with hydrogen (H) as a leading candidate.
Purpose of the Study:
- To investigate the migration behavior of hydrogen in zinc oxide.
- To determine the energetic barriers for hydrogen movement.
- To elucidate the role of hydrogen in native n-type conductivity of ZnO.
Main Methods:
- Ab initio calculations were employed to simulate hydrogen migration.
- The migration barrier for isolated hydrogen in ZnO was computed.
Main Results:
- The calculated migration barrier for hydrogen in ZnO is less than approximately 0.5 eV.
- This low barrier indicates that isolated hydrogen is highly mobile at low temperatures.
- Thermally stable hydrogen-related donors are unlikely to be isolated and must be associated with other defects.
Conclusions:
- Isolated hydrogen is mobile in zinc oxide at relevant temperatures.
- The formation of stable, shallow donors in ZnO requires hydrogen to be trapped at other defects.
- This mechanism is likely applicable to other oxide semiconductors where hydrogen acts as a shallow donor.
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