Interface properties of GaInP/Ge hetero-structure sub-cells of multi-junction solar cells

The interface properties of the GaInP/Ge hetero-structure solar cells were studied. It was found that an undesirable potential barrier for the majority carriers could occur at the n-GaInP/n-Ge hetero-interface during the growth of multi-junction solar cells. The potential barrier at the GaInP/Ge interface leads to S-shape behaviour of I-V curves at low temperatures, which was observed either for the single junctions or for the multi-junction solar cells containing the n-GaInP/n-Ge interface. The values of the effective barrier height and width as 0.12 +/- 0.05 eV and 45-55 nm, respectively, were estimated by admittance spectroscopy and by C-V profiling measurements.