Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 79: Photovoltaics: Mainly Silicon

HL 79.1: Vortrag

Donnerstag, 17. März 2011, 14:30–14:45, FOE Anorg

Microstructuring of silicon with femtosecond laser pulses — •Waldemar Freund, Jan P. Richters, Tobias Voß, and Jürgen Gutowski — Institute of Solid State Physics, Semiconductor Optics Group, University of Bremen

Silicon structured with ultrashort laser pulses which is called "black silicon" due to its dark appearance has been a field of intense studies in recent years. It exibits a nearly uniform absorptivity beyond 90% in the whole visible to near-infrared spectral region. Therefore, it is a promising material for applications in solar cells and photo diodes.

In this talk a brief introduction of microstructuring of silicon with ultrashort laser pulses will be given. Structuring is carried out in a sulfurhexafluoride (SF₆) atmosphere, which simultaneously allows doping of the silicon with sulfur far above the solubility limit. The structuring leads to a specific quasiperiodic surface morphology at which incident light is reflected multiple times. Thus light absorption in the silicon is considerably enhanced. The extremely high doping with sulfur results in the formation of a distinct defect band which is the origin of high absorptance in the near infrared. Furthermore, sulfur acts as a donor in silicon. Hence, microstructuring of p-doped silicon in SF₆ atmosphere leads to the formation of a p-n⁺ junction. This is an important step towards the fabrication of efficient solar cells and photo diodes with increased infrared sensitivity on base of easy-to-produce black silicon.