MBE grown GaInNAs solar cells for multijunction applications

Triple-junction cells composed of III-V materials currently hold the world record for photovoltaic efficiency. In order to further increase cell efficiency in the future 4- and 5-junction cells incorporating a sub-cell with a bandgap of roughly 1.0 eV will be required. In this study 1.0 eV bandgap GaInNAs devices grown by solid source molecular beam epitaxy are investigated in terms of materials quality and device performance that show similar or better properties to the best MOVPE grown devices found in the literature. Deep-level transient spectroscopy measurements illustrate that the trap concentrations in the GaInNAs material are significantly lower than that of MOVPE grown material. The internal quantum efficiency (43%), open-circuit voltage (450 mV), short-circuit current density (25.76 mA/cm/sup 2/) and fill-factor (56.4%) of the GaInNAs devices under 1-sun power density 1064 nm radiation are similar to or surpass the properties of the best MOVPE GaInNAs devices found in the literature.