Credit: CC0 Public Domain A discovery by two scientists at the Energy Department’s National Renewable Energy Laboratory (NREL) could aid the development of next-generation semiconductor devices. The researchers, Kwangwook Park and Kirstin Alberi, experimented with integrating two dissimilar semiconductors into a heterostructure by using light to modify the interface between them. Typically, the semiconductor materials used in electronic devices are chosen based on such factors as having a similar crystal structure, lattice constant, and thermal expansion coefficients. The close match creates a flawless interface between layers and results in a high-performance device. The ability to use different classes of semiconductors could create additional possibilities for designing new, highly efficient devices, but only if the interfaces between them can be formed properly. Park and Alberi A discovery by two scientists at the Energy Department’s National Renewable Energy Laboratory (NREL) could aid the determined that ultraviolet (UV) light applied directly to the semiconductor surface during heterostructure growth can modify the interface between two layers. Their paper, “Tailoring Heterovalent Interface Formation with Light,” appears in Scientific Reports. “The real value of this work is that we now understand how light affects interface formation, which can guide researchers in integrating a variety of different semiconductors in the future,” Park said. The researchers explored this approach in a model system consisting of a layer of zinc selenide (ZnSe) grown on top of a layer of gallium arsenide (GaAs). Using a 150-watt xenon lamp to illuminate the growth surface, they determined the mechanisms of light-stimulated interface formation by varying the light intensity and interface initiation conditions. Park and Alberi found the UV light altered the mixture of chemical bonds at the interface through photo-induced desorption of arsenic atoms on the GaAs surface, resulting in a greater percentage of bonds between gallium and selenium, which help to passivate the underlying GaAs layer. The illumination also allowed the ZnSe to be grown at lower temperatures to better regulate elemental intermixing at the interface. The NREL scientists suggested careful application of UV illumination may be used to improve the optical properties of both layers. Explore further:Scientists create ultrathin semiconductor heterostructures for new technologies More information:Kwangwook Park et al.Tailoring Heterovalent Interface Formation with Light,Scientific Reports(2017).DOI:10.1038/s41598-017-07670-2 Journal reference:Scientific Reports Provided by:National Renewable Energy Laboratory Source:PHYS For more information, please visit our website: http://www.semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com.
Abstract Secco etchant is conventionally used for delineation of flow pattern defects (FPDs) in lightly-doped Czochralski (Cz) silicon wafers. However, the FPDs in heavily doped p-type silicon wafers cannot be well delineated by Secco etchant. Herein, an etchant based on the CrO3HFH2O system, with an optimized volume ratio of V(CrO3):V(HF)=2:3, where the concentration of CrO3 is 0.25–0.35 M, has been developed for delineation of FPDs with well-defined morphologies for the heavily boron (B)-doped p-type silicon wafers. Keywords:Heavily doped p-type silicon,Flow pattern defects,Delineate,Preferential etching Source:ScienceDirect For more information, please visit our website: http://www.semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com.
Caption: Interdigitated back-contact silicon solar cells above 23% efficiency Imec together with its silicon photovoltaic industrial affiliation program partners Schott Solar, Total, Photovoltech, GDF-SUEZ, Solland Solar, Kaneka and Dow Corning, have demonstrated an excellent conversion efficiency of 23.3% on interdigitated back-contact (IBC) silicon solar cells. Interdigitated back contacts are introduced to increase the conversion efficiency of crystalline silicon soalr cells and allow for further reduction of the cell thickness, simplification of module fabrication and improved aesthetics of the final solar cell modules. Imec has developed a high-efficiency baseline process for small-area IBC cells within its multi-partner silicon solar cells industrial affiliation program that aims at increasing the efficiency well above 20% and decreasing the cost of silicon solar cells beyond the current state-of-the-art. Key aspects of the newly developed small-area (2×2 cm2) IBC Si solar cells are the n-type base float-zone (FZ) silicon substrates, a random pyramid texture, a boron diffused emitter, phosphorous diffused front- and back surface fields, a thermally grown silicon dioxide for surface passivation, a SiN single layer anti-reflective coating, lithography based patterning and Aluminum metallization. The realized IBC cells achieve a designated area conversion efficiency of 23.3% (Jsc = 41.6 mA, Voc=696 mV, FF=80.4%), certified by ISE-Callabs. Jef Poortmans, director of imec’s photovoltaic R&D program: “We are delighted to demonstrate these excellent efficiency results on IBC silicon solar cells. They prove the relevance of the IBC technology to our industrial partners. Such high efficiencies on small-area IBC silicon solar cells are a perfect base for further developing a large-area and industrially feasible IBC cell technology at imec.” ”As silicon photovoltaic industrial affiliation program partners of imec we are very happy with this new result”, says Dr. Martin Heming, CEO of SCHOTT Solar. This German solar manufacturer was the first industry partner to join imec’s program on silicon solar cells. “The test result confirms our confidence in imec’s excellent PV R&D capabilities and vision, and it allows us to acquire important know-how and IP as basis for our next generation solar cell products.” Source:PHYS For more information, please visit our website: http://www.semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com.
Ames Laboratory scientist Paul Canfield removes a sample from a flux-growth furnace. Credit: Ames Laboratory When it comes to creating new materials, single crystals play an important role in presenting a clearer picture of a material’s intrinsic properties. A typical material will be comprised of lots of smaller crystals and the grain boundaries between these crystals can act as impediments, affecting properties such as electrical or thermal resistance. “Those boundaries can have profound effects, both good and bad,” said Ames Laboratory materials scientist and deputy director Tom Lograsso. “Generally, a material that has smaller and smaller crystals actually has improved mechanical properties.” An exception to this rule is that at high temperature, relative to the melting point, small crystals can have a tendency to slide past one another, a property called creep. It’s for this reason that turbine blades in some jet engines or generators are actually formed from single crystals of nickel-based alloy. A few other everyday applications using single crystals are semi-conductors, detectors, such as infrared or radiation sensors, and lasers. “The active component in a laser is a single crystal,” said Lograsso, who is also an Iowa State University adjunct professor of materials science and engineering, “because the crystal grain boundaries would scatter the light.” From a research viewpoint, especially when creating a new material, scientists want to remove as many variables as possible to best understand a material’s properties. A primary way to do this is to begin with raw materials that are as pure as possible and to produce the material as a single crystal. “You don’t want defects in the crystal structure and you don’t want impurities, which can be a source of extra nucleation,” Lograsso said. “New materials can have new physics, and we can determine what those are if we make measurements on a clean, pristine sample (i.e. single crystal). And if we do that consistently, we can make comparisons to other materials and see how it fits into our understanding of particular behaviors.” Ames Laboratory scientists employ a number of techniques to grow single crystals, with each suited to producing crystals from different types of materials. However, the basic premise is the same—oversaturate a solution, then precipitate out the crystal. “As kids, we’re familiar with adding rock salt or sugar to hot water until you supersaturate the liquid,” Lograsso said. “Then, as the water cools and eventually starts to evaporate, crystals of salt or sugar start to form and then grow. “You can do the same with about any two materials, using one as the solvent and then using heat or high temperatures to supersaturate the solvent,” he continued. “The tricky part is to get a single crystal to first form and then grow.” Ames Laboratory scientist Deborah Schlagel holds a graphite crucible (left) and a Bridgman-grown copper crystal (right). Credit: Ames Laboratory This “prac...
Xiamen Powerway Advanced Material Co.,Ltd., a leading supplier of InGaP and other related products and services announced the new availability of size 3” is on mass production in 2017. This new product represents a natural addition to PAM-XIAMEN’s product line. Dr. Shaka, said, “We are pleased to offer InGaP layer to our customers including many who are developing better and more reliable for HEMT and HBT structures, but also for the fabrication of high efficiency solar cells used for space applications. Our InGaP layer has excellent properties, Ga0.5In0.5P is used as the high energy junction on double and triple junction photovoltaic cells grown on GaAs. The availability improve boule growth and wafering processes.” and “Our customers can now benefit from the increased device yield expected when developing advanced transistors on a square substrate. Our InGaP layer are natural by products of our ongoing efforts, currently we are devoted to continuously develop more reliable products.” PAM-XIAMEN’s improved InGaP product line has benefited from strong tech. support from Native University and Laboratory Center. Now it shows 2 examples as follows: Layer name Thickness (nm) Doping Remarks In0.49Ga0.51P 400 Undoped GaAs substrate (100) 2” Undoped or N-doped Layer name Thickness (nm) Doping Remarks In0.49Ga0.51P 50 Undoped In0.49Al0.51P 250 Undoped In0.49Ga0.51P 50 Undoped GaAs substrate (100) 2” Undoped or N-doped About Xiamen Powerway Advanced Material Co., Ltd Found in 1990, Xiamen Powerway Advanced Material Co., Ltd (PAM-XIAMEN) is a leading manufacturer of compound semiconductor material in China. PAM-XIAMEN develops advanced crystal growth and epitaxy technologies, manufacturing processes, engineered substrates and semiconductor devices. PAM-XIAMEN’s technologies enable higher performance and lower cost manufacturing of semiconductor wafer. About InGaP Indium Gallium Phosphide (InGaP), also called Gallium Indium Phosphide (GaInP), is a semiconductor composed of indium,gallium and phosphorus. It is used in high-power and high-frequency electronics because of its superior electron velocity with respect to the more common semiconductors silicon and gallium arsenide. It is used mainly in HEMT and HBT structures, but also for the fabrication of high efficiency solar cells used for space applications and, in combination with aluminium (AlGaInP alloy) to make high brightness LEDs with orange-red, orange, yellow, and green colors. Some semiconductor devices such as EFluor Nanocrystal utilise InGaP as their core particle. Indium gallium phosphide is a solid solution of indium phosphide and gallium phosphide. Ga0.5In0.5P is a solid solution of special importance, which is almost lattice matched to GaAs. This allows, in combination with (AlxGa1−x)0.5In0.5, the growth of lattice matched quantum wells for red emitting semiconductor lasers, e.g. red emitting(650nm) RCLEDs or VCSELs for PMMA plastic optical fibers. Ga0.5In0.5P is used as the high e...
Made of a single sheet of carbon atoms, graphene can be spun at the fastest rate of any known macroscopic object. Image credit: Wikimedia Commons. A CNST-led collaboration with the University of Maryland and the University of Texas has computed how electrostatic interactions between electrons in different layers of few-layer graphene affect the properties of the top layer [1]. Since graphene was first extracted from bulk graphite in 2004, it has been at the center of remarkable scientific advances and technological development. A particularly promising material is graphene grown on the surface of SiC crystals by sublimation of Si from the substrate, which typically grows in few-layer graphene sheets. Unlike graphite crystals, these layers are rotated with respect to each other so that the atoms do not line up. This rotation has surprising consequences, as found in recent scanning tunneling microscopy measurements done at the CNST [2]. In high magnetic fields and at low temperatures, the top layer behaves in many ways like an isolated graphene sheet, but a sheet in which charge could transfer to the other layers. The measurements also showed that at the highest fields in the study, the measured spectra had a gap that could not be explained by a simple single particle description of the system; electrons in the top layer were interacting with other electrons, either in the same layer or in the other layers. Explaining several aspects of the experimental data, the latest calculations reveal how electrons transfer between layers, and how under the right conditions a “correlated state” might develop between the electrons in the top layer and other layers. While additional experimental and theoretical research is needed to confirm this explanation, this work further demonstrates the variety of interesting phenomena that are emerging as the layers of graphene’s scientific puzzle are peeled away. Source:PHYS For more information, please visit our website: http://www.semiconductorwafers.net, send us email at angel.ye@powerwaywafer.com or powerwaymaterial@gmail.com.
Xiamen Powerway Advanced Material Co.,Ltd., a leading supplier of AlGaP and other related products and services announced the new availability of size 2” is on mass production in 2017. This new product represents a natural addition to PAM-XIAMEN’s product line. Dr. Shaka, said, “We are pleased to offer AlGaP layer to our customers including many who are developing better and more reliable for a platform for optical light communication, specifically an air-bridged waveguide. Our AlGaP layer has excellent properties, a crystalline solid used as a semiconductor and in photo optic applications. American Elements produces to many standard grades when applicable, including Mil Spec (military grade); ACS, Reagent and Technical Grade; Food, Agricultural and Pharmaceutical Grade; Optical Grade, USP and EP/BP (European Pharmacopoeia/British Pharmacopoeia) and follows applicable ASTM testing standards. Typical and custom packaging is available. Additional technical, research and safety (MSDS) information is available as is a Reference Calculator for converting relevant units of measurement. The availability improve boule growth and wafering processes.” and “Our customers can now benefit from the increased device yield expected when developing advanced transistors on a square substrate. Our AlGaP layer are natural by products of our ongoing efforts, currently we are devoted to continuously develop more reliable products.” PAM-XIAMEN’s improved AlGaP product line has benefited from strong tech. support from Native University and Laboratory Center. Now it shows an example as follows: About Xiamen Powerway Advanced Material Co., Ltd Found in 1990, Xiamen Powerway Advanced Material Co., Ltd (PAM-XIAMEN) is a leading manufacturer of compound semiconductor material in China. PAM-XIAMEN develops advanced crystal growth and epitaxy technologies, manufacturing processes, engineered substrates and semiconductor devices. PAM-XIAMEN’s technologies enable higher performance and lower cost manufacturing of semiconductor wafer. About AlGaP Aluminium gallium phosphide, (Al,Ga)P, a phosphide of aluminium and gallium, is a semiconductor material. It is an alloy of aluminium phosphide and gallium phosphide. It is used to manufacture light-emitting diodes emitting green light. Q&A Q: Can you supply epi-wafer as follow? wafer size: 2 inchThe below structure will be used as a platform for optical light communication,specifically an air-bridged waveguide. The thickness tolerance of each layer is as follows: capping layer, sacrificial layer: thickness is not important. The given number (50 nm,1000 nm) is just a minimum requirement for the layers to provide their roles. waveguide layer: it should be kept as “100 nm” since the wavelength of guiding lightand propagation efficiency are determined by its thickness. So the tolerance of waveguide layer should be in less than 5%, or “100 ± 5 nm”. A: We can not offer GaP with epi layers, what we can offer GaAs epi wafer or InP epi...
Schematic of the electrically pumped quantum dot micro-ring laser. Credit: Department of Electronic and Computer Engineering, HKUST Decades ago, the Moore’s law predicted that the number of transistors in a dense integrated circuit doubles approximately every two years. This prediction was proved to be right in the past few decades, and the quest for ever smaller and more efficient semiconductor devices have been a driving force in breakthroughs in the technology. With an enduring and increasing need for miniaturization and large-scale integration of photonic components on the silicon platform for data communication and emerging applications in mind, a group of researchers from the Hong Kong University of Science and Technology and University of California, Santa Barbara, successfully demonstrated record-small electrically pumped micro-lasers epitaxially grown on industry standard (001) silicon substrates in a recent study. A submilliamp threshold of 0.6 mA, emitting at the near-infrared (1.3?m) was achieved for a micro-laser with a radius of 5 μm. The thresholds and footprints are orders of magnitude smaller than those previously reported lasers epitaxially grown on Si. Their findings were published in the prestigious journal Optica on August “We demonstrated the smallest current injection QD lasers directly grown on industry-standard (001) silicon with low power consumption and high temperature stability,” said Kei May Lau, Fang Professor of Engineering and Chair Professor of the Department of Electronic & Computer Engineering at HKUST. “The realization of high-performance micron-sized lasers directly grown on Si represents a major step toward utilization of direct III-V/Si epitaxy as an alternate option to wafer-bonding techniques as on-chip silicon light sources with dense integration and low power consumption.” The two groups have been collaborating and has previously developed continuous-wave (CW) optically-pumped micro-lasers operating at room temperature that were epitaxially grown on silicon with no germanium buffer layer or substrate miscut. This time, they demonstrated record-small electrically pumped QD lasers epitaxially grown on silicon. “Electrical injection of micro-lasers is a much more challenging and daunting task: first, electrode metallization is limited by the micro size cavity, which may increase the device resistance and thermal impedance; second, the whispering gallery mode (WGM) is sensitive to any process imperfection, which may increase the optical loss,” said Yating Wan, a HKUST PhD graduate and now postdoctoral fellow at the Optoelectronics Research Group of UCSB. “As a promising integration platform, silicon photonics need on-chip laser sources that dramatically improve capability, while trimming size and power dissipation in a cost-effective way for volume manufacturability. The realization of high-performance micron-sized lasers directly grown on Si represents a major step toward utilization of direct III-V/Si...
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