BGaInAs solar cells lattice-matched to GaAs

We have recently demonstrated the epitaxial growth of BxGa1-x-yInyAs on GaAs substrates by metal-organic chemical vapor deposition. This new material has a bandgap less than that of GaAs, and can be grown lattice-matched to GaAs. Such a material, used as the second or third junction in a strain-free multijunction III-V solar cell, has the potential to increase the total cell efficiency. We report here on the performance of single-junction solar cells with 1.36-eV carbon- and silicon-doped B0.03Ga0.91In0.06As bases and compare them with similar GaAs and Ga0.94In0.06As cells. The BGaInAs cells have exhibited less-than-ideal open-circuit voltages (Voc) and fill factors (FF) of 0.57-0.66 V and 69%-73%, respectively. Poor red response of the quantum efficiencies and low short-circuit currents (J(SC)) of 10-14 mA/cm(2) under AM1.5D conditions indicate that the minority-carrier diffusion lengths are short (< 0.1 mum). The n-on-p devices perform slightly better than the p-on-n devices.