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Published November 2018 | Published
Journal Article Open

Study of the Interface in a GaP/Si Heterojunction Solar Cell


We have investigated the GaP/Si heterojunction interface for application in silicon heterojunction solar cells. We performed X-ray photoelectron spectroscopy (XPS) on thin layers of GaP grown on Si by metal organic chemical vapor deposition and molecular beam epitaxy. The conduction band offset was determined to be 0.9 ± 0.2 eV, which is significantly higher than predicted by Anderson's rule (0.3 eV). XPS also revealed the presence of Ga–Si bonds at the interface that are likely to be the cause of the observed interface dipole. Via cross-sectional Kelvin probe force microscopy (x-KPFM), we observed a charge transport barrier at the Si/GaP interface which is consistent with the high-conduction band offset determined by XPS and explains the low open-circuit voltage and low fill factor observed in GaP/Si heterojunction solar cells.

Additional Information

© 2018 IEEE. IEEE Open Access. Manuscript received May 15, 2018; revised June 27, 2018; accepted July 25, 2018. Date of publication August 13, 2018; date of current version October 26, 2018. The authors would like to thank the Molecular Foundry for generously hosting the MOCVD growth and the Caltech MMRC for providing the XPS analytic tools and also L. Ding, S. Aloni, A. Nielander, N. Plymale, A. Shing, and L. Korte for helpful advice with measurements and data interpretation. This work was supported in part by the U.S. Department of Energy, Energy Efficiency and Renewable Energy Program, under Award No. DE-EE0006335 for band offset characterization and in part by the U.S Department of Energy and the National Science Foundation under grant EEC1041895 for other electrical and structural measurements and in part by the Molecular Foundry funded by the Office of Science, Office of Basic Energy Sciences, U.S. Department of Energy under Contract DE-AC02-05CH11231.

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August 19, 2023
October 19, 2023