Investigation of GaAs/InGaP superlattices for quantum well solar cells

Different heterostructures, MOVPE grown by TBAs and TBP, lattice-matched to GaAs and containing a sequence of InGaP/GaAs quantum wells (QWs), were studied for the development of novel photovoltaic devices. Their structural characterisation exhibited a low structural and compositional disorder with a low defect density, also in the case of a consistent number (30) of QW periods. The optical properties, characterised by excitonic features, show well resolved peaks ascribable to heavy and light hole to electron transitions, in good agreement with theory. The benefit role of the QW region was proved by an extension of the spectral response and a reduction of the reverse dark current. A main limitation to the conversion efficiency is discussed in terms of InGaP non-intentional impurity contamination.