Optical hyperdoping: black silicon

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, from highly-sensitive PIN photodetectors to photovoltaics.

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

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 Laser-processing of semiconductors for solar energy harvesting applications

Ultrafast-laser hyperdoped semiconductors have begun to be utilized for optoelectronic applications, but there is a need to better understand their fundamental physical properties. In this presentation, we discuss recent work on the basic science of ultrafast-laser structuring, time-resolved melting, resolidification, and hyperdoping, and the optical and electronic properties hyperdoped silicon. These aspects of ultrafast-laser hyperdoped semiconductors are central to hyperdoped materials science and device design.

Poster presented at the 2001 MRSEC visit

Arrays of sharp, conical microstructures are obtained by texturing the surface of a silicon wafer using femtosecond laser-assisted chemical etching. The one step, maskless texturing process drastically changes the optical and electronic properties of the original silicon wafer. These properties make the textured silicon viable for use in a wide range of commercial devices. Near-unity absorption of light, from visible to infrared wavelengths, offer opportunities for use in optically active devices such as solar cells and detectors. Significant enhancement of below-band-gap photocurrent... Read more about Femtosecond laser-assisted microstructuring of silicon for novel detector, sensing, and display technologies

Arrays of sharp, conical microstructures are obtained by stucturing the surface of a silicon wafer using femtosecond laser-assisted chemical etching. The one step, maskless structuring process drastically changes the optical, material and electronic properties of the original silicon wafer. These properties make microstructured silicon viable for use in a wide range of commercial devices including solar cells, infrared photodetectors, chemical and biological sensors, and field emission devices.

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.

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.

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

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

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.

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.

Arrays of sharp, conical microstructures are obtained by texturing the surface of a silicon wafer using femtosecond laser-assisted chemical etching. The one step, maskless texturing process drastically changes the optical, material and electronic properties of the original silicon wafer. These properties make the textured silicon viable for use in a wide range of commercial devices. First, near-unity absorption of light, from visible to infrared wavelengths, offer opportunities for use in optically active devices such as solar cells and detectors. Significant enhancement of below-band-gap... Read more about Laser-assisted microstructuring of silicon surfaces for novel detector, sensing, and display technologies

Arrays of sharp, conical microstructures are obtained by texturing the surface of a silicon wafer using femtosecond laser-assisted chemical etching. The one step, maskless texturing process drastically changes the optical, material and electronic properties of the original silicon wafer.