Fabrication and characterization of single junction GaAs solar cells on Si with As-doped Ge buffer

A single junction gallium arsenide (GaAs) solar cell on silicon (Si) substrate with energy conversion efficiency of 11.88% under the AM1.5 G spectrum at 1 sun intensity without an anti-reflection coating (ARC) has been developed. This development was enabled by utilizing an intermediate, thin arsenic-doped germanium (As-doped Ge) buffer layer. The thin epitaxial Ge layer (< 2 mu m) grown on the Si substrate created a virtual Ge-on-Si (Ge/Si) substrate for subsequent growth of the GaAs solar cell, providing low threading dislocation density (TDD) of < 5 x 10(6) cm(-2). The energy conversion efficiency could be further improved to 16% upon optimizing the ARC and metal coverage. Hence, a manufacturable photovoltaic on a large-area Si substrate has become possible.