Copper gallium selenide thin films on Si by magnetron sputtering for photovoltaic applications: Composition, junction formation and metal contacts
Thin films of CuGaSe were deposited on n-Si (1 0 0) by rf magnetron sputtering from a stoichiometric CuGaSe2 target. The objective of this study was to characterize the thin film/Si heterojunction for potential photovoltaic applications, evaluate possible candidates for metal contacts and to establi...
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| Format: | Article |
| Language: | English |
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Taylor & Francis Group
2018-01-01
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| Series: | Cogent Engineering |
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| Online Access: | http://dx.doi.org/10.1080/23311916.2018.1514941 |
| _version_ | 1797726412034015232 |
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| author | M. A. Awaah U. Obahiagbon H. Mohammed O. Akpa I. Awaah T. Isaac-Smith N. Korivi J. B. Posthill K. Das |
| author_facet | M. A. Awaah U. Obahiagbon H. Mohammed O. Akpa I. Awaah T. Isaac-Smith N. Korivi J. B. Posthill K. Das |
| author_sort | M. A. Awaah |
| collection | DOAJ |
| description | Thin films of CuGaSe were deposited on n-Si (1 0 0) by rf magnetron sputtering from a stoichiometric CuGaSe2 target. The objective of this study was to characterize the thin film/Si heterojunction for potential photovoltaic applications, evaluate possible candidates for metal contacts and to establish whether heteroepitaxial growth could be achieved, particularly as the mismatch of lattice parameters corresponding to the base of the copper gallium selenide (CGS) tetragonal cell is quite close to that of Si, with a 2.9% mismatch. For this study, Si substrates were prepared by the standard Radio Corporation of America (RCA) cleaning procedure immediately followed by the deposition of CGS by sputtering at a substrate temperature of 600°C. The deposited thin-film stoichiometry and morphology were characterized by Rutherford backscattering spectroscopy (RBS) and transmission electron microscopy (TEM). Rutherford back scattering (RBS) analysis indicated a thin-film composition of Cu1Ga1Se1 indicating that the films were Se deficient, although channeling was not observed. The polycrystalline nature of the deposited thin film was established by cross-sectional TEM. An estimated 1.5-nm thick layer likely to be SiO x was observed at the CGS–Si interface. It is believed that this interfacial layer prevented heteroepitaxy CGS on Si. Additionally, circular metal contacts were deposited on the thin films and characterized by capacitance and current–voltage measurements. It was observed that Al and Ag contacts were rectifying, from which the thin-film carrier density was estimated to be ~5 × 1015 and ~7.68 × 1015 cm−3 with Al and Ag contacts, respectively. Au, Pt, W and Cr were ohmic, and Mo and Ni provided semi-ohmic contacts to CGS films. |
| first_indexed | 2024-03-12T10:44:59Z |
| format | Article |
| id | doaj.art-d319ac4e566648049a41986ee5c2ff29 |
| institution | Directory Open Access Journal |
| issn | 2331-1916 |
| language | English |
| last_indexed | 2024-03-12T10:44:59Z |
| publishDate | 2018-01-01 |
| publisher | Taylor & Francis Group |
| record_format | Article |
| series | Cogent Engineering |
| spelling | doaj.art-d319ac4e566648049a41986ee5c2ff292023-09-02T07:37:04ZengTaylor & Francis GroupCogent Engineering2331-19162018-01-015110.1080/23311916.2018.15149411514941Copper gallium selenide thin films on Si by magnetron sputtering for photovoltaic applications: Composition, junction formation and metal contactsM. A. Awaah0U. Obahiagbon1H. Mohammed2O. Akpa3I. Awaah4T. Isaac-Smith5N. Korivi6J. B. Posthill7K. Das8LithographyTuskegee UniversityTuskegee UniversityTuskegee UniversityTuskegee UniversityTuskegee UniversityTuskegee UniversityTuskegee UniversityTuskegee UniversityThin films of CuGaSe were deposited on n-Si (1 0 0) by rf magnetron sputtering from a stoichiometric CuGaSe2 target. The objective of this study was to characterize the thin film/Si heterojunction for potential photovoltaic applications, evaluate possible candidates for metal contacts and to establish whether heteroepitaxial growth could be achieved, particularly as the mismatch of lattice parameters corresponding to the base of the copper gallium selenide (CGS) tetragonal cell is quite close to that of Si, with a 2.9% mismatch. For this study, Si substrates were prepared by the standard Radio Corporation of America (RCA) cleaning procedure immediately followed by the deposition of CGS by sputtering at a substrate temperature of 600°C. The deposited thin-film stoichiometry and morphology were characterized by Rutherford backscattering spectroscopy (RBS) and transmission electron microscopy (TEM). Rutherford back scattering (RBS) analysis indicated a thin-film composition of Cu1Ga1Se1 indicating that the films were Se deficient, although channeling was not observed. The polycrystalline nature of the deposited thin film was established by cross-sectional TEM. An estimated 1.5-nm thick layer likely to be SiO x was observed at the CGS–Si interface. It is believed that this interfacial layer prevented heteroepitaxy CGS on Si. Additionally, circular metal contacts were deposited on the thin films and characterized by capacitance and current–voltage measurements. It was observed that Al and Ag contacts were rectifying, from which the thin-film carrier density was estimated to be ~5 × 1015 and ~7.68 × 1015 cm−3 with Al and Ag contacts, respectively. Au, Pt, W and Cr were ohmic, and Mo and Ni provided semi-ohmic contacts to CGS films.http://dx.doi.org/10.1080/23311916.2018.1514941copper gallium selenide filmscuingase2 cigscugasemagnetron sputteringcomposition of cuingase2 metal contacts to cuingase2 |
| spellingShingle | M. A. Awaah U. Obahiagbon H. Mohammed O. Akpa I. Awaah T. Isaac-Smith N. Korivi J. B. Posthill K. Das Copper gallium selenide thin films on Si by magnetron sputtering for photovoltaic applications: Composition, junction formation and metal contacts Cogent Engineering copper gallium selenide films cuingase2 cigs cugase magnetron sputtering composition of cuingase2 metal contacts to cuingase2 |
| title | Copper gallium selenide thin films on Si by magnetron sputtering for photovoltaic applications: Composition, junction formation and metal contacts |
| title_full | Copper gallium selenide thin films on Si by magnetron sputtering for photovoltaic applications: Composition, junction formation and metal contacts |
| title_fullStr | Copper gallium selenide thin films on Si by magnetron sputtering for photovoltaic applications: Composition, junction formation and metal contacts |
| title_full_unstemmed | Copper gallium selenide thin films on Si by magnetron sputtering for photovoltaic applications: Composition, junction formation and metal contacts |
| title_short | Copper gallium selenide thin films on Si by magnetron sputtering for photovoltaic applications: Composition, junction formation and metal contacts |
| title_sort | copper gallium selenide thin films on si by magnetron sputtering for photovoltaic applications composition junction formation and metal contacts |
| topic | copper gallium selenide films cuingase2 cigs cugase magnetron sputtering composition of cuingase2 metal contacts to cuingase2 |
| url | http://dx.doi.org/10.1080/23311916.2018.1514941 |
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