Optical hyperdoping: black silicon

We have developed a novel technique that creates highly doped and structured silicon. Focusing a train of femtosecond laser pulses on silicon wafers in the presence of heavy chalcogens (e.g. S, Se, or Te) dopes a thin layer of silicon at the surface to non-equilibrium levels. This optical hyperdoping process creates black silicon, a highly absorbing surface with extended spectral sensitivity. This material offers new opportunities for silicon-based optoelectronic devices. Black silicon is strongly light-absorbing. During hyperdoping, the polished surface of a silicon wafer is transformed from shiny gray to deep black. In addition to near-unity absorption in the visible, black silicon absorbs over 80 percent of below band-gap, infrared light for wavelengths as long as 2500 nm. This can be used to make photodiodes with remarkable responsivity in both the visible and infrared. It is also possible that this extended absorption range can improve the efficiency of silicon solar cells.
Black silicon and the quest for intermediate band semiconductors, at Siam Physics Congress 2015 (Krabi, Thailand), Thursday, May 21, 2015:
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
Black silicon: A new light absorber for solar cells and photodetectors, at OSA Annual Meeting (Baltimore, MD), Thursday, October 1, 1998
We demonstrate a new light absorber for solar cells and optical detection devices. Micron-sized spikes generated by irradiating a silicon surface with femtosecond laser pulses in SF6 enhance light absorption in silicon to near 100%. We observe an increase of more than 60% in photocurrent compared to a flat silicon surface.
Black silicon: Microstructuring silicon with femtosecond lasers, at Physics Colloquium, University of Massachusetts-Lowell (Lowell, MA), Wednesday, November 14, 2001:
Our research group has produced a novel form of microstructured silicon ("black silicon") with many surprising properties: near unity absorption, even below the band gap; production of photoelectrons in the visible and infrared; visible luminescence; and a strong field emission current. This talk will describe these properties and what is understood so far about their structural and chemical origin.
Black silicon: changing structure and properties with light, at Physics Colloquium, Haverford College (Haverford, PA), Monday, March 1, 2004:
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer changes its structure and properties dramatically: the formerly smooth, highly reflective surface becomes covered with a forest of sharp microspikes. This microstructured surface is highly absorbing even at wavelengths to which the original wafer is transparent. This talk will describe the properties of this microstructured surface and discuss why the microspikes form and what is responsible for the change in optical properties.
Femtosecond laser-nanostructured substrates for single molecule surface-enhanced Raman spectroscopy, at Photonics West (San Jose, California), Tuesday, January 22, 2008:
We present a new type of surface-enhanced Raman scattering (SERS) substrate that exhibits extremely large and uniform cross-section enhancements over a macroscopic (>25mm2) area. The substrates are fabricated using an extremely simple procedure: a train of femtosecond laser pulses is used to structure a silicon wafer with an array of submicron-sized spikes, and a silver film is subsequently deposited on the structured surface. SERS signals from adsorbed molecular dyes indicate a spatially uniform enhancement factor (ca. 10^7) that is consistently observed over a wide range of excitation... Read more about Femtosecond laser-nanostructured substrates for single molecule surface-enhanced Raman spectroscopy
Black Silicon Technology, at NATO SET Panel Business Meeting (Brussels, Belgium), Wednesday, October 28, 2009:
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
Thinking out of the box, at First Annual Scialog Conference, Biosphere 2 (Oracle, AZ), Wednesday, October 13, 2010:
What leads to innovation and how can we stimulate it?
Pushing materials research towards a commercial impact, at UTM Physics Seminar, Universiti Teknologi Malaysia (UTM) (Johor Bahru, Malaysia), Thursday, March 29, 2012:
The intersection of materials research and ultrafast optical science is producing many valuable fundamental scientific results and applications, and the trend is expected to evolve as new and exciting discoveries are made. Femtosecond laser micromachining presents unique capabilities for three-dimensional, material-independent, sub-wavelength processing. At the same time the surface processing of materials permits the creation of novel materials that cannot (yet) be created under other conditions.
Black silicon and the quest for intermediate band semiconductors, at iCone Seminar, University of North Carolina Charlotte (Charlotte, NC), Friday, February 15, 2013:
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
Early stages of femtosecond laser-induced formation of silicon microspikes, at Materials Research Society Fall Meeting (Boston, MA), Monday, December 2, 2002:
Arrays of sharp conical spikes form on crystalline silicon surfaces when irradiated with a train of femtosecond laser pulses in a background of sulfur hexafluoride (SF6); blunter, more irregular microstructures form in vacuum. The tips of the spikes are at the height of the original surface of the wafer, suggesting that the formation process predominantly involves removing material. The spikes are arranged in a quasi-ordered fashion with a characteristic nearest-neighbor separation of a few micrometers; the exact value of this characteristic separation depends on the laser fluence and number... Read more about Early stages of femtosecond laser-induced formation of silicon microspikes
Femtosecond laser-nanostructured substrates for surface enhanced Raman scattering (SERS), at Photonics West 2007 (San Jose, CA), Thursday, January 25, 2007:
We present a new substrate for efficient surface enhanced Raman scattering (SERS). Using a train of focused frequency-doubled femtosecond laser pulses from a regeneratively amplified Ti:Sapphire laser, we fabricate submicron surface structures on a silicon wafer. After irradiating the silicon wafer with 400nm, 100fs laser pulses in a cuvette of water, we observe the formation of an array of spikes, each approximately 500nm tall and 200nm wide. The wafer is scanned across the beam to form an arbitrarily-sized nanostructured area. When covered with a thin film of a noble metal, the structured... Read more about Femtosecond laser-nanostructured substrates for surface enhanced Raman scattering (SERS)
Black silicon briefing, at Night Vision Perspectives on Technology Lecture, Night Vision and Electronic Sensors Directorate (Ft. Belvoir, VA), Tuesday, May 26, 2009:
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
Black silicon: Engineering an intermediate band in silicon for sensing and energy harvesting, at Nanophotonics and Plasmonic Technologies Workshop, Harvard University (Cambridge, MA), Friday, May 7, 2010:
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
Black silicon, at Harvard Energy Innovation Showcase, Harvard University (Cambridge, MA), Tuesday, November 29, 2011:
Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of applications including improved solar energy harvesting.

Pages