SBIR Phase I: Epitaxially Grown GaSb Thin Films on GaAs Substrates For Near-Field Conversion of Heat to Electricity

This Small Business Innovation Research (SBIR) Phase I project aims to develop strain-relieved GaSb thin films grown directly on GaAs for near-field thermophotovoltaic (TPV) devices. Thin films of direct low-bandgap materials will outperform germanium, an indirect bandgap material, in both power density and efficiency. In this project, TPV devices will be fabricated and tested in the near-field using thin films of GaSb grown directly on GaAs via molecular beam epitaxy (MBE). It has been shown that the well-behaved 90-degree misfit dislocations at the heterojunction result in strain-relieved, low defect density thin films of GaSb grown on relatively inexpensive GaAs substrates. These substrates also have the optical and electrical properties required for fabrication of monolithically integrated TPV devices that are compatible with operation in the near-field of a hot thermal radiator. The broader/commercial impact of this project will be the potential to provide an economically viable solution in waste heat harvesting. Of all power produced in the world, over half is rejected in the form of waste heat. This has led research teams worldwide to search for solid state solutions to waste heat recovery, but with very limited success. This project will develop the TPV devices, and demonstrate that their operation in the near field of hot objects may lead to more than a tenfold increase in power density over existing technologies. This technology is expected to be used for industrial waste heat, methane flaring, solar, vehicle power, satellite power, and personal portable power applications.