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 electron-phonon interaction to 2D vertically buried III-V homovalent nanoobjects and therefore provides different approaches for material designs, vertical carrier transport, heterostructure design on silicon and device applications with weakly polar semiconductors.

Epitaxial III–V/Si Vertical Heterostructures with Hybrid 2D‐Semimetal/Semiconductor Ambipolar and Photoactive Properties

“…While some APBs follow the [110] or [−110] directions (blue lines), and are thus expected to follow the 𝜎°charge configuration, numerous other APBs are lying along other directions (red lines), and are thus expected to follow the 𝜎 +/− charge configuration or intermediate ones. This is in good agreement with the atomically-resolved observations performed in previous works [19,21] and is not fully surprising as the APBs naturally result from the coalescence of monodomain islands. [16] The simplified picture given here does not take into account the possible charge compensation effects which could occur during the growth.…”

“…Beyond materials developments, physical properties of the specific stoichiometric APBs (with equal numbers of III–III and V–V bonds within the same APB) were recently clarified. [ 21 ] It was demonstrated that the electronic bandgap is reduced by 2D electronic localization, and that, an intrinsic and strong electron‐phonon coupling arises in stoichiometric APBs and impacts the photoluminescence properties. [ 21 ] Therefore, APBs should no longer be considered as usual non‐radiative recombination centers, but as a 2D homovalent singularities with specific symmetry properties in a bulk semiconducting matrix.…”

“…[ 21 ] It was demonstrated that the electronic bandgap is reduced by 2D electronic localization, and that, an intrinsic and strong electron‐phonon coupling arises in stoichiometric APBs and impacts the photoluminescence properties. [ 21 ] Therefore, APBs should no longer be considered as usual non‐radiative recombination centers, but as a 2D homovalent singularities with specific symmetry properties in a bulk semiconducting matrix. Due to the insertion of a local translational symmetry breaking, a III–III (V–V) bond also adds two free holes (two free electrons) in the semiconductor.…”

“…In addition, compared to the zinc‐blende bulk materials (Figure S24, Supporting Information), stoichiometric σ 0 APB structures also introduce several localized states on the top of valence bands, shifting VBM upward and reducing the bandgap (Figure S25, Supporting Information). [ 21,51 ] The IPCE data shows a weak signal in the 550–750 nm range for the bi‐domain GaP/Si sample (Figure 2c), which might correspond to the absorption of stoichiometric APB structures. These σ 0 APBs may also contribute to the transport through strong electron‐phonon coupling related processes, [ 21 ] but it is not considered to be the main origin of the efficient ambipolar transport properties evidenced in the present work.…”

Crystal Phase Control during Epitaxial Hybridization of III‐V Semiconductors with Silicon

“…These so-called anti-phase boundaries (APBs) consist of III-III and/or V-V bonds, [23,24] resulting locally in an excess or a lack of charges, and in a significant modification of the electronic band structure and vibrational properties. [25,26] Threading APBs are therefore a critical issue as far as they introduce efficient vertical electrical path within the III-V heterostructure, thereby killing the performances of any p-n junction device. [25,27] Engineering the APBs generation and propagation at the early stages of the III-V growth on Si is thus the only way to fully benefit from the ultimate properties of integrated III-V semiconductors and a major prerequisite for the successful monolithic integration of III-V optoelectronic devices on Si photonic platforms [28,29] or III-V/Si energy harvesting devices.…”