Ingaas/ingaas strain-compensated quantum well cells for thermophotovoltaic applications

Strain-compensated layers in photovoltaic devices can yield unique
advantages as the absorption threshold can be extended towards longer
wavelengths beyond that of the lattice-matched material, which is
particularly important for thermophotovoltaic (TPV) applications. In such a
nanostructure, where InGaAs barriers and InGaAs quantum wells of
appropriate compositions are strain compensated on an InP substrate, the
absorption of a quantum well cell (QWC) can be extended to about 2 microns.
Due to the higher band-gap barriers, the dark current remains at a low
level more appropriate to lattice-matched InGaAs. Great care has to be
taken in design and growth to achieve a situation that is close to strain
balance with zero stress. Results are presented on a strain-compensated QWC
that absorbs out to 1.77 microns. Predictions show that strain-compensated
InGaAs/InGaAs QWCs have superior performance when compared with bulk InGaAs
on InP monolithic interconnected modules and GaSb TPV cells.