UV and Etching Treatment Improves Amorphous Silicon

Illuminating hydrogenated amorphous silicon with ultraviolet radiation and etching it with a sodium-hydroxide solution reduces subsequent light-induced degradation of its photosensitivity, report researchers from the National Renewable Energy Laboratory in Golden, Colo., in the Oct. 28 Applied Physics Letters. The treatment, which may drive mobile hydrogen into the bulk of the film, could lead to the development of inexpensive solar cells and photodiodes that display improved performance.

In the process, the film is exposed to approximately 330-nm radiation from a filtered mercury arc lamp. Soaking in sodium hydroxide removes the most damaged regions from the surface; etching the top 70 to 100 nm yields the best results. The treated semiconductors in the experiments displayed photoconductivities 25 to 30 percent higher than the untreated samples after 50 to 70 hours of light soaking.