Elucidating the interfacial nucleation of higher-index defect facets in technologically important GaP/Si(001) by azimuthal angle-resolved polarized Raman spectroscopy

Structural complexities evolving at hetero-polar interface of III-V/Si have been critical obstacles to high-quality and cost-effective epitaxial integration of wide-bandgap GaP on closely lattice-matched Si. Unveiling the nature of interface-originated defect structures is quintessential for efficient integration of III-V semiconductors on Si. In this work, investigation of surface and interface of technologically important GaP/Si(0 0 1) hetero-structures is presented, through unique implementation of combining the information on variation in spatially resolved polarized Raman spectra and surface topography of grown epilayer. The mechanisms responsible for variation in ratio of Raman scattering cross-section of symmetry forbidden to allowed optical phonons of GaP are delineated using azimuthal angle-resolved polarized Raman measurements by allowing for the contribution of energetically favorable higher-index {1 1 1} and {1 1 2} crystallographic facets, nucleating near the hetero-interface, to light scattering. This is reasserted from polarized Raman spectroscopy performed on cross-sectional surface of GaP/Si(0 0 1) hetero-structures. To the best of our knowledge, this is first of it's kind work wherein angle-dependent polarized Raman measurements are employed for ascertaining the nature and orientations of interfacial defect facets in advanced hetero-structures. Non-invasive and expeditious nature of this optical technique open pathways for fabrication of efficient device structures of III-V semiconductors on Si and Ge platforms.