High-quantum-efficiency 0.5 eV GaInAsSb/GaSb thermophotovoltaic devices

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Abstract
We report high-performance lattice-matched GaInAsSb/GaSb thermophotovoltaic (TPV) devices with a 0.5 eV band gap. The TPV structures were grown on GaSb substrates by organometallic vapor phase epitaxy at a lower temperature (525 °C compared to 550 °C) to improve the quality of the metastable GaInAsSb alloy. The 0.5 eV TPV devices exhibit external quantum efficiency as high as 60%, which corresponds to an internal quantum efficiency of 90%, assuming 35% reflection losses. This efficiency is comparable to the value measured for 0.53 eV devices. The ratio of the open circuit voltage to band-gap energy ratio decreases from 0.57 for 0.53 eV devices to 0.48 for 0.5 eV devices.