Reduced Cu concentration in CuAl-LPE-grown thin Si layers
- National Renewable Energy Lab., Golden, CO (United States)
Cu-Al has been found to be a good solvent system to grow macroscopically smooth Si layers with thicknesses in tens of microns on cast MG-Si substrates by liquid phase epitaxy (LPE) at temperatures near 900{degrees}C. This solvent system utilizes Al to ensure good wetting between the solution and substrate by removing silicon native oxides, and employs Cu to control Al doping into the layers. Isotropic growth is achieved because of a high concentration of solute silicon in the solution and the resulting microscopically rough interface. The incorporation of Cu in the Si layers, however, was a concern since Cu is a major solution component and is generally regarded as a bad impurity for silicon devices due to its fast diffusivity and deep energy levels in the band gap. A study by Davis shows that Cu will nonetheless not degrade solar cell performance until above a level of 10{sup 17} cm{sup -3}. This threshold is expected to be even higher for thin layer silicon solar cells owing to the less stringent requirement on minority carrier diffusion length. But to ensure long term stability of solar cells, lower Cu concentrations in the thin layers are still preferred.
- Research Organization:
- National Renewable Energy Lab., Golden, CO (United States)
- OSTI ID:
- 415124
- Report Number(s):
- NREL/SP--413-8250; CONF-9508143--Extd.Absts.; ON: DE95009278
- Country of Publication:
- United States
- Language:
- English
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