A comparative study of bulk InGaAs and InGaAs/InGaAs strain-compensated quantum well cells for thermophotovoltaic applications

One of the main requirements for thermophotovoltaic (TPV) systems powered by fuel combustion is a low level of pollution. To achieve this, low combustion temperatures are needed. The most efficient narrow band emitters emit at long wavelengths, necessitating low band gap cells. Erbium oxide emits around 1500 nm and we report an InGaAs p-n cell which is well matched to this spectrum. Two more suitable emitters are thulium oxide and holmium oxide, which emit around 1700nm and 1950nm respectively, beyond the band gap of lattice matched InGaAs. To absorb this emission, lattice mismatched materials must be used. The technique of strain compensation can prevent the creation of dislocations within the structure. We present results of a strain-compensated InGaAs/InGaAs Quantum Well Cell (QWC) which demonstrates the success of this structure in allowing wavelength response to be extended whilst displaying a lower dark current.