Research

Optoelectronic devices are pervasive in our world, and are the basis for optical communications, imaging, sensors, and solar energy conversion. Our group explores optoelectronics based on new semiconductor materials and innovative device architectures. We have expertise and capabilities ranging from material synthesis and characterization, material and device modeling, and device fabrication and testing. Our work often uses capabilities in the Lurie Nanofabrication Facility and Michigan Center for Materials Characterization. Below are some examples of current activities in our group.  

Infrared Detectors

HgCdTe nBn single element detectors, demonstrating MWIR detection without p-type doping.

Infrared focal plane arrays (IR FPAs) are of high importance for a variety of defense, scientific, and commercial applications. HgCdTe is currently the premier material for high performance infrared detection applications, and continues to advance in performance, operability, and multi-spectral capabilities. We explore fundamental material properties and new device architectures to push the limits of HgCdTe performance. We are currently exploring quantum-confined structures such as type-II superlattices on InP to achieve extended-range SWIR detectors with potential to offer HgCdTe performance, but in a high-yield, low-cost InP-based technology.

Photovoltaic Energy Harvesting for mm-Scale Systems

Example of a GaAs photovoltaic module on a chip to power a Michigan Micro Mote, featured on the cover of Progress in Photovoltaics.

Low-power computing systems can enable pervasive sensor networks and the ‘internet of things’. Scaling to the mm-scale or smaller may enable transformative changes in how we interact with the world, detect and mitigate hazards, and monitor and control biological functions. These small systems require efficient energy harvesting, where we are exploring photovoltaic cells and modules to harvest sunlight, ambient indoor light, or infrared radiation through biological tissue. Through specially designed photovoltaic cells, modules on a chip, and co-design with circuit interfaces, we have achieved efficient energy harvesting to enable perpetual operation of these systems through solid state batteries or direct power transfer. 

Infrared Spectral Filters

Scanning electron microscope image of suspended silicon/air dielectric grating used for narrowband transmission filtering.

Narrow band spectral filtering is needed for a wide range of optical applications, where the achievement of such filters at the microscale could radically transform applications in spectroscopy and imaging. Microscale filters would provide dramatic reductions in system size and new functionality through localized specification of spectral response in linear or focal plane array formats. Dielectric gratings with high refractive index contrast, with dimensions near the optical wavelength, can provide unique optical behavior through photonic bandstructure engineering, where broadband reflection, focusing, and narrowband reflection can be achieved. We are investigating dielectric grating filters in the mid-wave infrared (MWIR, 3-5 microns) and long-wave infrared (LWIR, 8-12 microns) spectral region, and application to hyperspectral imaging.