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7 April 2017 Plasma-enhanced chemical vapor deposition epitaxy of Si on GaAs for tunnel junction applications in tandem solar cells
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Abstract
We fabricated (n) c-Si/ (p) GaAs heterojunctions, by combining low temperature (175°C) RF-PECVD for Si and metal organic vapor phase epitaxy for GaAs, aiming at producing hybrid tunnel junctions for Si/III-V tandem solar cells. The electrical properties of these heterojunctions were measured and compared to that of a reference III-V tunnel junction. Several challenges in the fabrication of such heterostructures were identified and we especially focused in this study on the impact of atomic hydrogen present in the plasma used for the deposition of silicon on p-doped GaAs doping level. The obtained results show that hydrogenation by H2 plasma strongly reduces the doping level at the surface of the GaAs:C grown film. Thirty seconds of H2 plasma exposition at 175°C are sufficient to reduce the GaAs film doping level from 1×1020  cm3 to <1×1019  cm3 at the surface and over a depth of about 20 nm. Such strong reduction of the doping level is critical for the performance of the tunnel junction. However, the doping level can be fully recovered after annealing at 350°C.
© 2017 Society of Photo-Optical Instrumentation Engineers (SPIE) 1947-7988/2017/$25.00 © 2017 SPIE
Gwenaëlle Hamon, Nicolas Vaissiere, Romain Cariou, Raphaël Lachaume, José Alvarez, Wanghua Chen, Jean-Paul Kleider, Jean Decobert, and Pere Roca I. Cabarrocas "Plasma-enhanced chemical vapor deposition epitaxy of Si on GaAs for tunnel junction applications in tandem solar cells," Journal of Photonics for Energy 7(2), 022504 (7 April 2017). https://doi.org/10.1117/1.JPE.7.022504
Received: 14 January 2017; Accepted: 13 March 2017; Published: 7 April 2017
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