Strong Electron–Phonon Interaction in 2D Vertical Homovalent III–V Singularities

Abstract

Highly polar materials are usually preferred over weakly polar ones to study strong electron–phonon interactions and its fascinating properties. Here, we report on the achievement of simultaneous confinement of charge carriers and phonons at the vicinity of a 2D vertical homovalent singularity (antiphase boundary, APB) in an (In,Ga)P/SiGe/Si sample. The impact of the electron–phonon interaction on the photoluminescence processes is then clarified by combining transmission electron microscopy, X-ray diffraction, ab initio calculations, Raman spectroscopy, and photoluminescence experiments. 2D localization and layer group symmetry properties of homovalent electronic states and phonons are studied by first-principles methods, leading to the prediction of a type-II band alignment between the APB and the surrounding semiconductor matrix. A Huang–Rhys factor of 8 is finally experimentally determined for the APB emission line, underlining that a large and unusually strong electron–phonon coupling can be achieved by 2D vertical quantum confinement in an undoped III–V semiconductor. This work extends the concept of an electron–phonon interaction to 2D vertically buried III–V homovalent nano-objects and therefore provides different approaches for material designs, vertical carrier transport, heterostructure design on silicon, and device applications with weakly polar semiconductors.