InAs Thermophotovoltaic Cells with Low Reverse Saturation Current

To efficiently convert heat from sources < 1000 °C to electricity with thermophotovoltaic cells, low-bandgap devices < 0.7 eV with good electrical characteristics are required. III-V semiconductors are the best material system for these applications due to their high quality and compatibility with a variety of cell architectures. However, low-bandgap III-V cells operating at ambient temperatures suffer from challenging nonradiative losses, including Auger recombination and diffusion current from the contacts. We report the modeling, fabrication, and characterization of low-bandgap InAs (0.35 eV) thermophotovoltaic cells with good electrical characteristics as evidenced by low reverse saturation currents < 20 mA/cm2. Auger losses are mitigated with a double-heterojunction p-i-n architecture that minimizes minority carrier densities in the central intrinsic InAs layer. Our results should provide strategies to design efficient thermophotovoltaic systems for solar thermal energy, waste heat recovery, and other low-temperature heat sources.