Q&A with materials innovator Luke Mawst

Posted on 27. Sep, 2013 by in Academic Departments, Annual Report, Chemical and Biological Engineering, Electrical and Computer Engineering, Features, Materials Science and Engineering, People, Research

Luke Mawst

Luke Mawst

Professor, electrical and computer engineering
Co-founder, Alfalight / Co-founder, Intraband

Talk about your research. What, simply, do you study?
The main thrust of my research is really looking at new semiconductor compounds and the application of these compounds into optoelectronic devices. Most people are familiar with the most common semiconductor material, silicon. But there’s a whole other class of materials for opto-electronics (like semiconductor lasers), materials that emit or detect light. They’re more complex materials in a sense that we take multiple elements from the periodic table and combine them, things like gallium and arsenic, for example, to form gallium arsenide.

And then we can keep adding elements. We’re synthesizing materials with as many as five or six elements all combined together into a crystalline structure. These additional elements give us a lot of added flexibility to design the electronic and optical properties of the materials, which is advantageous for devices. We call them multinary materials.

What are the key technical issues you focus on and how do youcollaborate with others on campus to develop solutions?
Some of our research occurs under the umbrella of the interdisciplinary, National Science Foundation-funded Materials Research Science and Engineering Center (MRSEC) at UW-Madison. It involves collaborations with Chemical Engineering Professor Tom Kuech, and Materials Science and Engineering Professor Sue Babcock and Associate Professors Dane Morgan and Izabela Szlufarska, as well as collaborators at Duke and Michigan.

Under the MRSEC, we look at multinary compounds that have never been produced before, so there are challenges in combining these elements in a controllable manner such that we can produce a material system with the desired optical properties.

An example of the applications of these materials is in high-efficiency photovoltaics, or solar cells. We’ve been the first to successfully grow these five-element materials using metalorganic vapor phase epitaxy, or MOVPE. We’ve integrated the materials into solar cells in collaboration with our industrial partner, MicroLink Devices.

Industry also is working closely with us on virtual substrates. With commercially available substrates, you’re limited to a certain lattice constant, the atomic spacing, and that limits what materials you can grow on top and what devices you can make. Many devices require thick layers of materials with uniform composition. Here, we grow virtual substrates in a growth system called hydride vapor phase epitaxy, or HVPE, which allows us to grow very thick layers in tens of minutes. It’s potentially a low-cost growth technique for these virtual substrates. Tom Kuech, Sue Babcock and I recently won an NSF Partners for Innovation grant that involves three industrial partners looking at transitioning the materials research and processes we have developed here into commercial products, specifically in high-efficiency solar cells and high-performance semiconductor lasers.

What impact, both technically and in application, do you think your work has for the state and the nation?
One end application is high-efficiency solar cells for renewable energy. There are efforts in the United States to develop these high-efficiency technologies. We’re working with Ajou University to try to realize the higher-efficiency cells.

Another application is homeland security—for example, detection of dangerous toxic materials or explosives. Very-high-power lasers in the mid-infrared range can be used in applications such as remote infrared sensing. Those detection schemes use lasers in the mid-infrared range, wavelengths from 3 to 10 microns. But there’s a lack of reliable high-output-power devices. I collaborate with Electrical and Computer Engineering Professor Dan Botez on quantum cascade lasers. The expertise we have in designing and developing very high power semiconductor lasers, we rely on that now for producing these quantum cascade lasers, so we’re pushing the envelope and taking them to higher powers.

Tell us about what you find promising about the federal Materials Genome Initiative.
It will foster collaborations, very similar to what we’re doing, but at a much larger-scale coordination. These multi-university, industrial collaborations are key to driving the technology. We’re not experts on everything. We focus our research, say, on one aspect of materials development, but things like looking at reliability of devices, it’s hard for us to do that in a university setting, so we need collaborations with industry to do that, and that provides feedback for our materials research. The initiative may foster more of these interdisciplinary collaborations, and I think that’s key to moving materials technology and manufacturing forward.

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