Low bandgap GaInAsSb thermophotovoltaic cells on GaAs substrate with advanced metamorphic buffer layer

Thermophotovoltaic (TPV) devices based on GaInAsSb lattice matched to GaSb (100) substrates have demonstrated high external quantum efficiencies (EQEs) in the mid-infrared spectral range, making them promising candidates for waste heat recovery from high temperature “blackbody” sources. In this work, the GaInAsSb alloy has been integrated onto more cost-effective GaAs (100) substrates by using advanced metamorphic buffer layer techniques in molecular beam epitaxy (MBE), which included an interfacial misfit (IMF) array at the GaSb/GaAs interface followed by GaInSb/GaSb dislocation filtering layers. The threading dislocations in the GaInAsSb region can be efficiently supressed, resulting in high quality materials for TPV applications. To determine the performance of the GaInAsSb TPV on GaAs it was compared with a cell grown lattice matched onto GaSb substrate having the same structure. The resulting TPV on GaAs exhibited similar dark current-voltage characteristics with that on GaSb. Under illumination from an 800 °C silicon nitride emitter, the short circuit current density (Jsc) from the GaInAsSb TPVs on GaAs reached more than 90% of the control cell on GaSb, and the open circuit voltage (Voc) exceeded 80% of the cell on GaSb. The EQE from the TPV on GaAs reached around 62%, the highest value reported from this type of TPV on GaAs. With improved TPV structure design, large area GaInAsSb TPV panels on GaAs substrates can be realized in the future for waste heat energy recovery applications.