The growth, fabrication, and radiation testing of InP solar cells grown heteroepitaxially on Si substrates is reported. Cells of both the n(+)p and p(+)n configuration have been made. The significant details of the cell growth are summarized, and important details of the cell design are described. The performance of the cells has been characterized through current-voltage measurements under one sun, air-mass zero simulated solar light. The radiation response of the cells has been measured under 3 MeV proton irradiation. Prior to irradiation, the n(+)p cells outperform the p(+)n cells because the n(+)p cells can be grown with a lower emitter resistivity and hence a better fill factor than the p(+)n cells. The causes and possible means of improvement of the high resistivity of the p(+) emitter are discussed. The open circuit voltage of the p(+)n cells, on the other hand, is higher than that of the n(+)p cells indicating a lower dark current in the p(+)n cells. Under irradiation, the cells showed 25 % degradation after a 3 MeV proton fluence of about 8 x 1012cm-2 which is equivalent to a 1 MeV electron fluence of about 2 x 1016cm-2. This result is used to show that the InP/Si cells are 20 times more radiation resistant than the best GaAs/Ge solar cells. For fluences < 8 x 1012cm-2, the n(+)p cells perform better than the p(+)n cells due to the higher beginning-of-life power of the n(+)p cells. However, as the fluence increases, the n(+)p cells degrade much more rapidly than the p(+)n cells so that there is a cross-over point in fluence where the p(+)n cell power output exceeds that of the n(+)p cells. Therefore, while the n(+)p cells display superior beginning-of-life characteristics, the p(+)n cells display superior radiation tolerance and, ultimately, superior end-of-life characteristics.
Heteroepitaxial InP/Si solar cells for space power systems
Heteroepitaxial gewachsene InP/Si-Solarzellen für den Einsatz in Satellitenleistungssystemen
1995
3 Seiten, 3 Bilder, 1 Tabelle, 7 Quellen
Conference paper
English
Sonnenbatterie , Indiumphosphid , Heterostruktur , Substrat , Silicium , Heteroepitaxie , Teilchenstrahlung , Protonenstrahl , Satellit , Stromversorgung , Schichtwachstum , Kurzschlussstrom , Leerlaufspannung , Wirkungsgrad , Konzentrationsprofil , Strahlungsfestigkeit , pn-Übergang , Diffusion , Zink
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