Black Silicon Wafers Used By Researchers
An engineer researching high-power semiconductor lasers requested the following quote:
Please quote for all types of black silicon wafers that you can provide. It is not for epitaxial or device fabrication purpose. We are open to exploring this technology. Mostly interested in both anti reflective properties (low as possible near NIR) and high absorption as possible (at NIR). So pretty loose specs for now.
- I want to do a preliminary test to see if the idea will work. I will only need a small quantity for now. The volumes can be larger if it works. Please send me a formal quote for 5 wafers.
- Can you send me information on the reflectivity and absorption characteristics especially in 650 nm to 1000 nm range.
UniversityWafer, quoted High Absorption Silicon Wafers at NIR.
Refrence #253195 for specs and pricing.
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Why Use Black Silicon Substrates?
Black silicon is a semiconductor material, a surface modification of silicon with very low reflectivity and correspondingly high absorption of visible (and infrared) light. The modification was discovered in the 1980s as an unwanted side effect of Reactive Ion Etching (RIE). Another method for forming a similar structure was developed at Harvard University (1998).
Black silicon is a needle-shaped surface structure where needles are made of single-crystalline silicon and have a height above 10 microns and diameter <1 micron. Its main feature is an increased absorption of incident light – the high reflectivity of the silicon, which is usually 20–30% for quasi-normal incidence, is reduced to about 5%. This is due to the formation of a so-called effective medium by the needles. Within this medium, there is no sharp interface, but a continuous change of the refractive index that reduces Fresnel reflection.
What are Black Silicon Applications?
The unusual optical characteristics, combined with the semiconducting properties of silicon make this material interesting for sensor applications. The potential applications include:
- Image sensors with increased sensitivity
- Thermal imaging cameras
- Photodetector with high efficiency through increased absorption.
- Mechanical contacts and interfaces
- Terahertz applications
- Solar Cells - need to absorb the sun's light. Black silicon solar wafers provide higher efficiencies as the low reflectivity of the wafer surface capture more of the sun's energy.
- Satellites
High Light Absorption Black Silicon Used in Satellites
An aerospace engineer researching satellite solar power requested a quote for the following:
Black Silicon Wafer I am in the market for ideally a 50x50x0.5mm square black silicon disks. The 'black' is important as I intent using it for a light block or stop. Which of your other wafer would be optically black and ideally non reflective?
I want to ask does black silicon material reduce reflection in IR wavelength like 7-10um? since reflection reduced, does this mean there more IR transmitted? RFQ#267711
Reference #273432 for specs and pricing.
What Is Black Silicon Wafers?
The production method discovered by NREL will bring the use of black silicon in photovoltaic plants closer to commercial exploitation, as it will reduce production costs. Germany's sister plant PlanetSave has been pursuing the black silicon effort for several years, with a focus on the integration of black silicon surfaces in solar cells. We've known about it for about 30 years, But we are driving the first large-scale commercial production of this type of solar cell. [Sources: 0, 2, 3]
Eric Mazurs's research group at Harvard has found a way to produce black silicon by using femtosecond laser pulses to manipulate the surface. The ASG team has been working with black silicon for over a decade, and this article provides an insight into the technology that has been gained from this experience. Carey and his colleagues realized that, as explained in the article, they could absorb infrared light more efficiently by roughening the black silicone. Further tests of the black silicon revealed that it absorbs light at a wavelength of about 1,000 micrometers, or about one-tenth of a millimeter. [Sources: 3, 5, 6, 8]
Table 1 shows the thickness of the black silicon film at different deposition times and its absorption and absorption properties. When the deposition time is less than 500 s, the thicknesses are more even and the film covers its surface well. It is also obvious that there is no emission binding, as it only binds to the surface of a thin film, not to the entire film. [Sources: 1, 7]
The reflection, which is typically around 20 to 30 percent for standard silicon, is reduced to about 5 percent for black silicon, which means that more light is absorbed. The results of the IQE show that there are several factors that influence the absorption and absorption properties of a black silicon-based cell. Several teams have investigated the reactivity of black silicon detectors under various factors, including annealing temperature, doping agent and background gases. Although there is a remarkable reduction in IQe at shorter wavelengths, there is still a need to improve the sensitivity of the detector at longer wavelengths of light, such as visible and infrared wavelengths. [Sources: 1, 4]
Optimising the low reflection is therefore the key to realising the benefits of black silicon solar cells. Black silicon has various applications, but above all promising applications in the field of solar cell applications. Although the theory behind black silicon has been around for some time, various production methods have been developed in recent years, which have opened the door to the development of a wide range of new applications for the use of this powerful, cost-effective material. [Sources: 3, 5]
The Advanced Silicon Group has produced a device with millions of nanowires made of black silicon that allows the production of a highly sensitive detector for multiple biomarkers on a single chip. The sensitivity of the black silicon detector is comparable to that of commercial silicon-based PIN photodiodes, which use visible light. As shown in Fig. 1, the emissivity of black silicon decreases with annealing temperature, and the spectral responsiveness is significantly higher in the Black silicon component than in commercial silicon-based silicon photodiodes. [Sources: 1, 4]
The second photodiode transition, which forms on the black silicon surface of the silicon substrate, contributes significantly to the low-swelling voltage. [Sources: 1]
Black silicon nanotexture is preferred because of its anti-reflection properties, as it offers low reflections. However, there are several reflections on the surface of black silicon that lead to an improvement in the absorption of nanoscopic needles. [Sources: 1, 4]
Small changes on the nanoscale have a major influence on the macroscale, which is why the nanotexture is called black silicon. The geometry of a nanotexture can vary, and small changes in the microscale can cause significant changes in its properties, such as the size of the surface. Small changes At microscopic scale, nanotextures may refer to black silicon due to their anti-reflection properties and low reflections, but the geometries of these nanotextures may vary. A small change in the micro scale has a greater influence on the macro scale, The geometry of a nanoTEXURE can therefore vary, as can its size or the number of nanometers. [Sources: 5]
As black silicon does not have the exact properties of normal silicon, the exact application of silicon in solar cells has yet to be clarified. [Sources: 3]
Many black silicon methods have been developed, including chemical etching with the help of metal, reactive etching of ions and irradiation of the silicon surface with femtosecond laser pulses. However, graphene-based optoelectronic devices face significant challenges to this extent, including the absence of an anti-reflective layer on the surface of the material and the high cost of materials. As an alternative to graphene based on near-infrared detectors, there is also a possible competitor technology in black silicone. Since black silicon does not require an anti-reflective layer, it can allow the development of a high-performance, low-cost, non-reflective optical device instead of using only silicon dioxide or alumina as a passivating surface. Black silicon is cast from a polymer film that is spun on a wafer before the "black layer" is produced and then poured onto a silicon substrate. [Sources: 5, 6, 7]
Sources:
[1]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5908773/
[2]: https://cleantechnica.com/2014/09/05/low-cost-black-silicon-uses-copper-not-silver/
[3]: http://large.stanford.edu/courses/2010/ph240/haefele2/
[4]: https://www.asme.org/topics-resources/content/black-silicon-lowers-cost-increases-efficiency
[5]: https://www.pv-tech.org/guest-blog/black-silicon-theres-more-than-meets-the-eye
[6]: https://spie.org/news/spie-professional-magazine-archive/2019-april/black-silicon
[7]: https://www.hindawi.com/journals/ijp/2012/971093/
[8]: http:/newenergyandfuel/com/2008/10/14/what-is-that-black-silicon-stuff/
