An antireflection coating of a germanium subcell in GaInP/GaAs/Ge solar cells

Spectral characteristics of the Ge subcell of triple-junction GaInP/GaAs/Ge solar cells have been simulated. It was shown that using a GaInP nucleation layer that creates a shallow diffusion $p$–$n$ junction in Ge can raise the photogeneration current of the Ge subcell by $\sim$4.5 mA/cm$^2$ as compared with the value in the case of a GaAs nucleation layer. The optimal thickness of the GaInP layer (170–180 nm) makes it possible to additionally raise the photocurrent by $\sim$1.5 mA/cm$^2$. It was experimentally demonstrated that the photogenerated current of the Ge subcell of GaInP/GaAs/Ge solar cells increases by 3.9 mA/cm$^2$ on replacing the GaAs nucleation layer with GaInP and there is an additional gain by 0.9 mA/cm$^2$ on using the optimal thickness of the GaInP nucleation layer.