Dongbu HiTek today announced that it has begun volume production of Ambient Light Proximity Sensor (ALPS) chips for Clairpixel Co., Ltd., a Korean company specializing in single-chip image and motion sensor solutions for mobile, automotive, medical and security applications. Leveraging Dongbu HiTek’s specialized mixed-signal process, Clairpixel’s advanced ALPS chip is expected to target the growing Chinese smartphone market.

“Clairpixel’s ALPS chip highlights the system-on-chip attributes of our specialized 0.18um mixed-signal process,” said Jae Song, Dongbu HiTek EVP of marketing. “We look forward to expanding our collaboration before year end to add a color sensor function to this highly integrated chip design.” He credited the rapidly rising adoption rate of ALPS chips to their ability to extend battery life by optimizing screen brightness against ambient light. “With the addition of a color sensor, ALPS will also be able to automatically optimize color on large mobile screens while conserving battery power.”

According to recent market research from Gartner, Inc., worldwide smartphone shipments are expected to more than double from about 718 million units last year to more than1.6 billion units in 2016. Over this same period, Chinese smartphone shipments are forecast to rise from 25 percent to 33 percent of the total. Smart phone manufacturers such as Huawei and ZTE Corporation are expected to lead the expanding share of Chinese shipments. During the fourth quarter of 2012, some estimates report that Huawei shipped nearly 5 percent the worldwide total giving them the third largest market share worldwide

Dongbu HiTek Co., Ltd. specializes in developing s analog and mixed-signal processing technologies. The company processing portfolio encompasses Analog CMOS, BCDMOS, High Voltage CMOS, CMOS RF, CMOS Image Sensor (CIS), Display Driver IC (DDI), Touch Screen Controller IC and NOR Flash technologies.

When a team of University of Illinois engineers set out to grow nanowires of a compound semiconductor on top of a sheet of graphene, they did not expect to discover a new paradigm of epitaxy.

The self-assembled wires have a core of one composition and an outer layer of another, a desired trait for many advanced electronics applications. Led by professor Xiuling Li, in collaboration with professors Eric Pop and Joseph Lyding, all professors of electrical and computer engineering, the team published its findings in the journal Nano Letters.

Nanowires, tiny strings of semiconductor material, have great potential for applications in transistors, solar cells, lasers, sensors and more.

“Nanowires are really the major building blocks of future nano-devices,” said postdoctoral researcher Parsian Mohseni, first author of the study. “Nanowires are components that can be used, based on what material you grow them out of, for any functional electronics application.”

A false-color microscope image of a single nanowire, showing the InAs core and InGaAs shell. | Graphic by Parsian Mohseni

Li’s group uses a method called van der Waals epitaxy to grow nanowires from the bottom up on a flat substrate of semiconductor materials, such as silicon. The nanowires are made of a class of materials called III-V (three-five), compound semiconductors that hold particular promise for applications involving light, such as solar cells or lasers.

The group previously reported growing III-V nanowires on silicon. While silicon is the most widely used material in devices, it has a number of shortcomings. Now, the group has grown nanowires of the material indium gallium arsenide (InGaAs) on a sheet of graphene, a 1-atom-thick sheet of carbon with exceptional physical and conductive properties.

Thanks to its thinness, graphene is flexible, while silicon is rigid and brittle. It also conducts like a metal, allowing for direct electrical contact to the nanowires. Furthermore, it is inexpensive, flaked off from a block of graphite or grown from carbon gases.

“One of the reasons we want to grow on graphene is to stay away from thick and expensive substrates,” Mohseni said. “About 80 percent of the manufacturing cost of a conventional solar cell comes from the substrate itself. We’ve done away with that by just using graphene. Not only are there inherent cost benefits, we’re also introducing functionality that a typical substrate doesn’t have.”

The researchers pump gases containing gallium, indium and arsenic into a chamber with a graphene sheet. The nanowires self-assemble, growing by themselves into a dense carpet of vertical wires across the surface of the graphene. Other groups have grown nanowires on graphene with compound semiconductors that only have two elements, but by using three elements, the Illinois group made a unique finding: The InGaAs wires grown on graphene spontaneously segregate into an indium arsenide (InAs) core with an InGaAs shell around the outside of the wire.

“This is unexpected,” Li said. “A lot of devices require a core-shell architecture. Normally you grow the core in one growth condition and change conditions to grow the shell on the outside. This is spontaneous, done in one step. The other good thing is that since it’s a spontaneous segregation, it produces a perfect interface.”

So what causes this spontaneous core-shell structure? By coincidence, the distance between atoms in a crystal of InAs is nearly the same as the distance between whole numbers of carbon atoms in a sheet of graphene. So, when the gases are piped into the chamber and the material begins to crystallize, InAs settles into place on the graphene, a near-perfect fit, while the gallium compound settles on the outside of the wires. This was unexpected, because normally, with van der Waals epitaxy, the respective crystal structures of the material and the substrate are not supposed to matter.

“We didn’t expect it, but once we saw it, it made sense,” Mohseni said.

In addition, by tuning the ratio of gallium to indium in the semiconductor cocktail, the researchers can tune the optical and conductive properties of the nanowires.

Next, Li’s group plans to make solar cells and other optoelectronic devices with their graphene-grown nanowires. Thanks to both the wires’ ternary composition and graphene’s flexibility and conductivity, Li hopes to integrate the wires in a broad spectrum of applications.

“We basically discovered a new phenomenon that confirms that registry does count in van der Waals epitaxy,” Li said.

New research led by University of Cincinnati physics professors Howard Jackson and Leigh Smith could contribute to better ways of harnessing solar energy, more effective air quality sensors or even stronger security measures against biological weapons such as anthrax. And it all starts with something that’s 1,000 times thinner than the typical human hair – a semiconductor nanowire.

UC’s Jackson, Smith, recently graduated PhD student Melodie Fickenscher and physics doctoral student Teng Shi, as well as several colleagues from across the US and around the world recently have published the research paper “Optical, Structural and Numerical Investigations of GaAs/AlGaAs Core-Multishell Nanowire Quantum Well Tubes” in Nano Letters, a premier journal on nanoscience and nanotechnology published by the American Chemical Society. In the paper, the team reports that they’ve discovered a new structure in a semiconductor nanowire with unique properties.

“This kind of structure in the gallium arsenide/aluminum gallium arsenide system had not been achieved before,” Jackson says. “It’s new in terms of where you find the electrons and holes, and spatially it’s a new structure.”

These cross-sectional electron microscope images show a quantum well tube nanowire’s hexagonal facets and crystal quality (left), and electron concentration in its corners.

By using a thin shell called a quantum well tube and growing it – to about 4nm thick – around the nanowire core, the researchers found electrons within the nanowire were distributed in an unusual way in relation to the facets of the hexagonal tube. A close look at the corners of the tube’s facets revealed something unexpected – a high concentration of ground state electrons and holes.

“Having the faceting really matters. It changes the ballgame,” Jackson says. “Adjusting the quantum well tube width allows you to control the energy – which would have been expected – but in addition we have found that there’s a highly localized ground state at the corners which then can give rise to true quantum nanowires.”

The nanowires the team uses for its research are grown at the Australian National University in Canberra, Australia – one partner in this project that extends to disparate parts of the globe.

The team’s discovery opens a new door to further study of the fundamental physics of semiconductor nanowires. As for leading to advances in technology such as photovoltaic cells, Jackson says it’s too soon to tell because quantum nanowires are just now being explored. But in a world where hundreds of dollars’ worth of technology is packed into a 5-by-2.5 inch iPhone, it’s not hard to see how small but powerful science comes at a premium.

The team at UC is one of only about a half dozen in the US conducting competitive research in the field. It’s a relatively young discipline, too, Jackson says, and one that’s moving fast. For such innovative science, he says it’s important to have a collaborative effort. The team includes scientists from research centers in the Midwest, the West Coast and all the way Down Under: UC, Miami University of Ohio and Sandia National Laboratories in California here in the US; and Monash University and the Australian National University in Australia.

 “We’re training students in state-of-the-art techniques on state-of-the-art materials doing state-of-the-art physics,” Jackson says. “Upon completing their education here, they’re positioned to go out and make contributions of their own.”

Additional contributors to the paper are Jan Yarrison-Rice of Miami University, Oxford, Ohio; Bryan Wong of Sandia National Laboratories, Livermore, Calif.; Changlin Zheng, Peter Miller and Joanne Etheridge of Monash University, Victoria, Australia; and Qiang Gao, Shriniwas Deshpande, Hark Hoe Tan and Chennupati Jagadish of the Australian National University, Canberra, Australia.