Development of GaSb solar cells on GaAs by MOVPE via interface misfit technique

Current research in photovoltaics has pushed lattice matched triple junction solar cells on Ge to average efficiencies of 31% under one sun AM0. Further improvements are possible through an inverted metamorphic (IMM) design, departing from the lattice matching constraint to achieve improved current matching with a 1eV bottom cell. Even with these improvements the record one sun efficiencies fall short of the detail balance limit for three junctions of 48% largely due to the predominant use of two materials, (In)GaAs and InGaP, while neglecting the remainder of possible III-V semiconductor materials. It is proposed that including Sb-based materials will significantly expand the opportunities for high efficiencies. This is done through the development of an interfacial misfit (IMF) growth of highly mismatched materials with low defect densities by MOVPE. The development of IMF growth has led to the direct growth of GaSb on GaAs with a rocking curve FWHM of 307 arcsec, with the potential to reduce that further with alternate precursors. Single junction GaSb IMF and homoepitaxial solar cells have been grown and will be presented to demonstrate the potential of this technique. This enables triple and five junction solar cells with ideal bandgap combination that would result in efficiencies over 40% under 1 sun AM0.