Presentations

    Infrared absorption limits of femtosecond laser doped silicon – effect of dopant types and thermal treatments, at Black Silicon Symposium (Albany, NY), Friday, August 20, 2010
    Silicon doped with non-equilibrium concentrations of chalcogen exhibits strong sub-bandgap photon absorption. In this work, we investigate mid-infrared absorption of femtosecond laser doped silicon. Fourier transform infrared spectroscopy could shed light on energy levels of dopant states or bands. We study samples doped with sulfur, selenium and tellurium. In addition, we also investigate the effect of annealing temperature. Preliminary results suggest that near-unity absorption of sulfur doped silicon extends to mid-infrared. However, absorption decreases for photons with energy less than... Read more about Infrared absorption limits of femtosecond laser doped silicon – effect of dopant types and thermal treatments
    Femtosecond laser doped silicon for photovoltaic applications, at Photonics West 2011 (San Francisco, CA), Thursday, January 27, 2011:
    Doping silicon to concentrations above the metal-insulator transition threshold yields a novel material that has potential for photovoltaic applications. By focusing femtosecond laser pulses on the surface of a silicon wafe in a sulfur hexafluoride (SF6) environment, silicon is doped with 1% atomic sulfur. This material exhibits near-unity, broadband absorption from the visible to the near infrared (< 0.5 eV, deep below the silicon bandgap), and metallic-like conduction. These unusual optical and electronic properties suggest the formation of an intermediate band. We report on the... Read more about Femtosecond laser doped silicon for photovoltaic applications
    Femtosecond laser doped silicon for photovoltaic applications, at SPIE Optics & Photonics (San Diego), Friday, August 12, 2011:
    Doping silicon to concentrations above the metal-insulator transition threshold yields a novel material that has potential for photovoltaic applications. By focusing femtosecond laser pulses on the surface of a silicon wafer in a sulfur hexafluoride (SF6) environment, silicon is doped with 1% atomic sulfur. This material exhibits near-unity, broadband absorption from the visible to the near infrared (< 0.5 eV, deep below the silicon bandgap), and metallic-like conduction. These unusual optical and electronic properties suggest the formation of an intermediate band. We report on the... Read more about Femtosecond laser doped silicon for photovoltaic applications
    Femtosecond-laser hyperdoping: controlling sulfur concentrations in silicon for band gap engineering, at APS March meeting (Boston, MA), Tuesday, February 28, 2012:
    Doping silicon to concentrations above the metal-insulator transition threshold yields a novel material that has potential for photovoltaic applications. By focusing femtosecond laser pulses on the surface of a silicon wafer in a sulfur hexafluoride (SF6) environment, silicon is doped with 1% atomic sulfur. This material exhibits near-unity, broadband absorption from the visible to the near infrared (< 0.5 eV, deep below the silicon bandgap), and metallic-like conduction. These unusual optical and electronic properties suggest the formation of an intermediate band. We report on the... Read more about Femtosecond-laser hyperdoping: controlling sulfur concentrations in silicon for band gap engineering
    Infrared absorption of femtosecond laser doped silicon: effect of dopant types and thermal treatments, at 5th International Workshop on Crystalline Silicon Solar Cells (Boston, MA), Wednesday, November 2, 2011:
    Doping silicon to concentrations above the metal-insulator transition threshold yields a novel material that has potential for photovoltaic applications. By focusing femtosecond laser (fs-laser) pulses on the surface of a silicon wafer in a sulfur hexafluoride (SF6) environment, silicon is doped with 1% atomic sulfur. Similar concentration of heavy chalcogen dopants (Se and Te) is achieved by fs-laser doping with solid-phase dopant precursors. Fs-laser doped Si:chalcogen systems exhibit near-unity, broadband absorption from the visible to the near infrared (< 0.5 eV, deep below the silicon... Read more about Infrared absorption of femtosecond laser doped silicon: effect of dopant types and thermal treatments
    Mid-infrared absorptance of silicon hyperdoped with chalcogens via fs-laser irradiation, at Black Silicon Symposium (Albany, NY), Thursday, August 9, 2012:
    Silicon hyperdoped with heavy chalcogen atoms via femtosecond-laser irradiation exhibits strong broadband absorption. Understanding this absorption could enable applications for infrared detection and the intermediate band photovoltaic effect. In this work, we extend absorption measurements to wavelengths >14 μm using Fourier transform infrared spectroscopy and study sulfur-, selenium- or tellurium-hyperdoped Si before and after annealing. We find that the surface morphology of the sample significantly influences the extent of absorption into the mid-infrared wavelength range.... Read more about Mid-infrared absorptance of silicon hyperdoped with chalcogens via fs-laser irradiation
    The photovoltaic potential of femtosecond laser textured amorphous silicon, at Photonics West (San Francisco, CA), Thursday, February 7, 2013:
    Femtosecond laser texturing of silicon yields nanometer scale surface roughness that reduces reflection and enhances light absorption. In this work, we study the potential of using this technique to improve efficiencies of amorphous silicon-based solar cells by laser texturing thin amorphous silicon films. We use Ti:Sapphire femtosecond laser systems to texture amorphous silicon in either hydrogen or sulfur hexafluoride ambient gases and we also study the effect of laser texturing the substrate before depositing amorphous silicon. We adjust the thin-film thickness and laser fabrication... Read more about The photovoltaic potential of femtosecond laser textured amorphous silicon