Oxygen migration enthalpy likely limits oxide precipitate dissolution during tabula rasa

• Published in: Applied physics letters 2017-09, Vol.111 (13)
• Main Authors: Looney, E. E., Laine, H. S., Youssef, A., Jensen, M. A., LaSalvia, V., Stradins, P., Buonassisi, T.
• Format: Article
• Language: English
• Subjects: Activation energy; Applied physics; Defect annealing; Dissolution; Enthalpy; Interstitials; Migration; Oxygen; Photovoltaic cells; Silicon; Solar cells
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4987144

In industrial silicon solar cells, oxygen-related defects lower device efficiencies by up to 20% (rel.). In order to mitigate these defects, a high-temperature homogenization anneal called tabula rasa (TR) that has been used in the electronics industry is now proposed for use in solar-grade wafers. This work addresses the kinetics of tabula rasa by elucidating the activation energy governing oxide precipitate dissolution, which is found to be 2.6 ± 0.5 eV. This value is consistent within uncertainty to the migration enthalpy of oxygen interstitials in silicon, implying TR to be kinetically limited by oxygen point-defect diffusion. This large activation energy is observed to limit oxygen precipitate dissolution during standard TR conditions, suggesting that more aggressive annealing conditions than conventionally used are required for complete bulk microdefect mitigation.