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A density functional theory study on the passivation mechanisms of hydrogenated Si/Al2O3 interfaces

: Colonna, F.; Kühnhold-Pospischil, S.; Elsässer, C.


Journal of applied physics 127 (2020), Nr.3, Art. 035301, 11 S.
ISSN: 0021-8979
ISSN: 1089-7550
Deutsche Forschungsgemeinschaft DFG
Fraunhofer IWM ()
Fraunhofer ISE ()
alumina; aluminum oxide; amorphous silicon; heat treatment; hydrogen; oxide films; passivation; silicon solar cells; Photovoltaik; Silicium-Photovoltaik; Oberflächen: Konditionierung; Passivierung; Lichteinfang; simulation; interface

Amorphous aluminum oxide (Al2O3) films are known to provide a high-quality passivation on silicon (Si) surfaces which can result in an enhanced efficiency of Si-based solar cells. After deposition of Al2O3 on Si, a certain temperature treatment is needed to activate the highest surface passivation quality. When the applied temperature is exceeded by a certain level, the passivation quality degrades. This behavior is well known in the production of Si-based solar cells. In order to further elucidate the microscopic origin of passivation mechanisms and its interplay with thermal treatments, we investigate four different atomistic Si/Al2O3 interface models by means of density functional theory simulations. As interfacial hydrogen (H) is deemed to play a key role in Si/Al2O3 surface passivation mechanisms and its amount changes during thermal treatments, two of these models contain hydrogen in different amounts; the other two do not contain any hydrogen. The simulations show that both chemical passivation and field-effect passivation depend on the relative amount of hydrogen via partially competing mechanisms. The obtained results provide novel insights into the passivation mechanisms of Si/Al2O3 interfaces. The results are qualitatively compared to the thermally induced activation and degradation of the Si(100)/Al2O3 surface passivation known from experiments.