Research

We are investigating optoelectronic materials for the next generation of infrared detectors, photovoltaics for solar energy generation and energy harvesting, and thin film electronics. Our emphasis is on the study of compound semiconductors materials and devices.

  • Materials Growth and Characterization
  • Simulation and Modeling of Optoelectronic Devices (Comsol, Sentaurus, Custom)
  • Device Fabrication and Testing

Infrared Detectors

HgCdTe nBn singe element detectors.

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. This narrow-bandgap II-VI compound semiconductor alloy is extremely challenging to grow and process. Though this material has been studied for decades, the ability to achieve and control the growth of high quality epitaxial HgCdTe material for FPA applications has only occured recently. Molecular beam epitaxy (MBE) has enabled the growth and control over sophisticated multilayer HgCdTe structures needed for detectors demanding high-performance, multi-spectral detection, and high operating temperature.

We are currently working on advanced materials studies and device architectures, in collaboration with industry, to enable the next generation of infrared imaging systems.

Next-Generation Solar Cell Technologies

Depiction of solar energy conversion in an intermediate band solar cell utilizing band to band, valence band to intermediate band, and intermediate band to conduction band optical transitions.

The growing importance of identifying renewable, clean energy sources has spurred increasing interest in photovoltaics. The viability of photovoltaics will depend on the solar cell cost, availability and hazards associated with solar cell materials/resources, and distributed overall cost of energy generation. The viability of photovoltaics may be improved with significant breakthroughs in solar cell efficiency, or through new methods to significantly reduce solar cell cost. We are currently investigating both new materials and device structures for high-efficiency, low- cost solar cells consisting of non-hazardous materials. Our current work includes the study of intermediate band solar cells based on oxygen doping and nanostructures in II-VI materials.

Photovoltaic Energy Harvesting for mm-Scale Systems

GaAs photovoltaic cell with reconfigurable series/parallel diode combinations for optimal energy harvesting in mm-scale computing systems

Low-power computing systems can enable pervasive sensor networks and the ‘internet of things’. Efficient energy-harvesting technologies are needed as a reliable energy source. Photovoltaics provide a means of harvesting energy from ambient lighting, or even infrared radiation for through-tissue implantable devices for medical applications. We are currently studying the application of photovoltaics to these systems and the optimization of material and device architectures to maximize energy harvesting.

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.