Characterization of ZnSiP2 Films Grown on Si Substrate by Liquid Phase Epitaxy: Morphology, Composition, and Interface Microstructure

Abstract

The exploration and growth of novel cost-effective top cell materials is one of the great hot topics for the development of Si-based tandem solar cells. ZnSiP2 was thought to be a promising candidate of the top cell material for the Si tandem solar cell. In this work, ZnSiP2 single crystal film with the stoichiometric ratio was successfully grown on a Si substrate by the liquid phase epitaxy method for the first time. The surface morphology, thickness, composition, and the orientation of the film were characterized by SEM, EDS, EPMA, and the high-resolution XRD. The results show that a continuous epitaxial ZnSiP2 film with the thickness of 3 μm was grown on the Si substrate. In addition to this continuous film, many island single crystals were also observed on the surface of the film. The high-resolution XRD φ scan results indicated that the film as well as these isolated islands crystallized with the same orientation, c-orientation with respect to the (100) Si substrate, without any misoriented domains. The microstructure of the ZnSiP2/Si interface characterized by the high-resolution transmission electron microscopy image, as well as the selected area electron diffraction patterns of the ZnSiP2 thin films and Si substrates, also confirmed the epitaxial growth of ZnSiP2 on the Si substrate. The electrical conductivity σ, Hall mobility μH, and carrier concentrations n of the ZnSiP2 film were 1.38 × 10–5 Ω–1 cm–1, 94.5 cm–2 V–1 s–1, and 9.11 × 109 cm–3, respectively. Our work paves the way for the development of ZnSiP2 silicon-based tandem solar cell devices.