Optical hyperdoping: black silicon

Serendipity and the quest for new materials, at 9th Science and Technology in Society Forum (Kyoto, Japan), Monday, October 8, 2012:
Throughout history, the development of new materials and serendipity have been tightly interwoven. I will illustrate the need for exploration and risk-taking with two anecdotes
Black silicon and the quest for intermediate band semiconductors, at Laser-Based Micro and Nano Processing VIII, Photonics West 2014 (San Francisco, CA), Thursday, February 6, 2014:
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 process has two effects: it structures the surface and incorporate dopants into the sample to a concentration highly exceeding the equilibrium solubility limit. This femtosecond laser "hyperdoping technique" enables the fabrication of defect- and bandgap engineered semiconductors, and laser texturing further enhances the optical density through excellent light trapping. Hyperdoped silicon opens the door for novel... Read more about Black silicon and the quest for intermediate band semiconductors
High sensitivity silicon-based VIS/NIR photodetectors, at CLEO 2004 (San Francisco, CA), Thursday, May 20, 2004:
We fabricate silicon-based photodiodes using a simple femtosecond-laser microstructuring technique. The detectors are ten times more sensitive than commercial silicon PIN photodiodes at visible wavelengths and can be used at wavelengths up to 1650 nm.
Femtosecond laser doping of silicon for photovoltaic devices, at MIT Energy Conference, MIT (Boson, MA), Friday, April 11, 2008:
Silicon is an abundant, stable, and efficient material for use in photovoltaic devices. However, it is costly to process, and is transparent at wavelengths longer than 1100nm, a spectral region containing 25% of solar energy. The limitations of silicon have spurred significant research into complex heterostructures that capture a greater fraction of sun’s energy. Engineering silicon to extend its effective spectral range, however, might offer a simpler way to increase the efficiency and decrease the cost of silicon-based photovoltaics. We report the creation of a thin, highly absorbing layer... Read more about Femtosecond laser doping of silicon for photovoltaic devices
Black silicon, at Huang Kun Forum on Semiconductor Sciences and Technologies, Institute of Semiconductors, Chinese Academy of Sciences (Beijing, China), Tuesday, December 22, 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, remote sensing, and photovoltaics.
Black silicon: engineering an intermediate band in silicon for optical sensing and photovoltaics, at G1 Faculty Lecture, Harvard University (Cambridge, MA), Monday, November 8, 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.
Femtosecond laser doping of TiO2 for photocatalysis, at Gordon Research Seminar on Renewable Energy: Solar Fuels (Barga, Italy), Saturday, May 12, 2012:
We present a novel method for femtosecond-laser doping of titanium dioxide (TiO2) for above bandgap absorptance by irradiating titanium metal in the presence of oxygen and dopants. With a bandgap of 3.2 eV for the anatase crystalline phase, TiO2 most strongly absorbs in the UV range (λ < 387 nm). However, doping with metals and nitrogen has been shown to create intermediate states in the bandgap. Using femtosecond laser doping techniques on titanium in a gaseous environment, we produce laser-induced periodic surface structures. Altering the gas composition and pressure does not change the... Read more about Femtosecond laser doping of TiO2 for photocatalysis
Pushing a physics discovery towards commercial impact, at REU Seminar, Harvard University (Cambridge, MA), Wednesday, July 24, 2013:
In 1997 my research group discovered that 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, making this 'black silicon' useful for a wide range of commercial devices, from highly-sensitive detectors to improved photovoltaics. Over the following ten years we investigated this material and developed a prototype detector. The prototype gave us the confidence to commercialize black silicon. Together... Read more about Pushing a physics discovery towards commercial impact
Black silicon: using lasers to make novel materials, at Condensed Matter Physics Seminar, Harvard University (Cambridge, MA), Friday, February 14, 2003:
Irradiating the surface of a crystalline silicon wafer with intense laser pulses in a reactive gas environment changes the structure and properties of the wafer dramatically: the formerly smooth, highly reflective surface becomes covered with a forest of sharp microspikes. In addition to changing the surface morphology, this microstructuring process also dramatically alters the optical properties of the silicon. The microstructured surface is highly absorbing even at wavelengths to which the original wafer is transparent. We find that the laser structuring process incorporates high... Read more about Black silicon: using lasers to make novel materials
Black silicon, at Zhejiang University (Hangzhou, China), Wednesday, March 28, 2007:
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 Research Seminar, University of Twente (Enschede, The Netherlands), Friday, June 12, 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.

Pages