Phonon-assisted radiative recombination of excitons confined in strongly anisotropic nanostructures

Abstract

The influence of acoustic phonons on the emission spectra of quantum dashes (QDashes), that are quasi-zerodimensional epitaxial nanostructures with significant shape anisotropy, is investigated both experimentally and theoretically. Photoluminescence (PL) spectra of single InAs/InGaAlAs/InP (001) QDashes exhibit sidebands of the main emission peak, clearly indicating the contribution of phonon-assisted emission to the exciton luminescence, which dominates the PL line shape at higher temperatures (between 50 and 100 K, usually). By utilizing the independent boson model we perform systematic and comprehensive studies of the influence of the overall geometry of quantum confinement on this spectral feature in an uncommon quantum system. A comparison of the experimental data and the results of modeling have confirmed the existence of two types of states differing in the spatial confinement and symmetry within one sample, i.e., typical for large elongated objects or characteristic for smaller and more symmetric structures. The latter are supposed to correspond to local widenings or zigzag bends present in some of the dashes and acting as additional localization centers, which confine excitons in a much smaller volume and decrease effectively the resulting in-plane anisotropy. Those observations evidence a nontrivial spatial character of the quantum confinement in these structures. They are consistent with our previous polarization-resolved study on the QDash ensemble and correlate well with the exciton decay times, and the spectral-diffusion-dominated line broadenings at low temperatures reflecting the effect of electric field fluctuations on the excitons of a different spatial extension. Finally, we demonstrate a pronounced suppression of phonon-induced decoherence for such strongly elongated nanostructures.

Single photon emission up to liquid nitrogen temperature from charged excitons confined in GaAs-based epitaxial nanostructures

“…While the energy shift is mainly driven by the change in the energy gap of the CQD material, the broadening of the emission line is related to the increase of the phonon reservoir and therefore enhanced the exciton-acoustic phonon coupling in the system. 33 The full picture of the temperature evolution of the X* emission line in the range of 5-80 K is presented in Fig. 3.…”

Optical Quality of InAs/InP Quantum Dots on Distributed Bragg Reflector Emitting at 3rd Telecom Window Grown by Molecular Beam Epitaxy

“…A temperature series were recorded and analyzed. Emission from single QDs is observed for temperatures in the range of 100 K, comparable to 80 K obtained in this spectral range for InAs/GaAs QDs on a metamorphic buffer layer [ 113 ], InAs/InGaAlAs/InP quantum dashes [ 114 ] and low-density InAs/InP QDs [ 88 ], as well as 100 K for InAs/InP quantum-LED [ 50 ]. For all the emission lines, typical thermally-induced behavior of the emission spectra is observed: a systematic redshift of the emission energy, linewidth broadening, and monotonic decrease of emission intensity (exemplary spectra presented in Figure 7 a).…”

Optical Properties of Site-Selectively Grown InAs/InP Quantum Dots with Predefined Positioning by Block Copolymer Lithography

“…However, with increasing temperature, the FWHM increases to the range of 55–68 meV at . This behavior is related to the carrier-phonon-induced broadening of an optical transition [ 55 ] without a strong signature of the carrier redistribution process, which typically results in a complicated functional form of the FWHM( T ) [ 53 , 54 , 56 ]. The indication of the carrier re-excitation process influencing the FWHM is possibly observed for the PL band A.…”