GaP films grown on Si by liquid phase epitaxy

Abstract

High efficiency multijunction solar cells are usually grown on expensive III-V or germanium semiconductor substrates. Growing thin layers of III-V semiconductors on a low cost silicon substrate can reduce the cost. The low lattice constant mismatch between gallium phosphide (GaP) and Si (0.37%) is favorable for epitaxial growth. In this paper, we will demonstrate that gallium phosphide has been epitaxially grown on silicon and briefly outline the photovoltaics applications of GaP growth on Si. Thin films of GaP have been grown on single crystalline p-type Si(111) substrates by liquid phase epitaxy and characterized by scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), rocking curve x-ray diffraction (XRD). The film composition showed a Si concentration of 15% in the GaP. The lattice constant mismatch between the epitaxial films and substrate was 0.58%. These samples were further processed into diodes and IV curve measurements were made under a solar simulator. Photovoltaic effect and an open circuit voltage of 486mV were observed.