Abstract
We present the optical characterization of GaAs-based InAs quantum dots (QDs) grown by molecular beam epitaxy on a digitally alloyed InGaAs metamorphic buffer layer (MBL) with gradual composition ensuring a redshift of the QD emission up to the second telecom window. Based on the photoluminescence (PL) measurements and numerical calculations, we analyzed the factors influencing the energies of optical transitions in QDs, among which the QD height seems to be dominating. In addition, polarization anisotropy of the QD emission was observed, which is a fingerprint of significant valence states mixing enhanced by the QD confinement potential asymmetry, driven by the decreased strain with increasing In content in the MBL. The barrier-related transitions were probed by photoreflectance, which combined with photoluminescence data and the PL temperature dependence, allowed for the determination of the carrier activation energies and the main channels of carrier loss, identified as the carrier escape to the MBL barrier. Eventually, the zero-dimensional character of the emission was confirmed by detecting the photoluminescence from single QDs with identified features of the confined neutral exciton and biexciton complexes via the excitation power and polarization dependences.
Highlights
Publisher’s Note: MDPI stays neutralSemiconductor self-assembled epitaxial quantum dots (QDs) have been demonstrated to be suitable candidates for use in a wide range of optoelectronic devices, from lasers [1,2], optical amplifiers [1,3], or other broadband sources [4,5] to quantum computing and quantum information processing employing QD-based non-classical emitters [6,7,8,9,10]
PLspectra spectrafor for five five structures structures (A–E) with ing indium content in the top part of the layer, which show the emission from indium content in the top part of the metamorphic buffer layer (MBL) layer, which show the emission from QDsQDs at the atwavelengths the wavelengths below
We have investigated the optical properties of structures with InAs QDs on a graded
Summary
Semiconductor self-assembled epitaxial quantum dots (QDs) have been demonstrated to be suitable candidates for use in a wide range of optoelectronic devices, from lasers [1,2], optical amplifiers [1,3], or other broadband sources [4,5] to quantum computing and quantum information processing employing QD-based non-classical emitters [6,7,8,9,10]. The emission in the telecom range is typically obtained for QDs made of InAs material on an InP substrate. There exist many demonstrations concerning both the laser structures [1] and the non-classical quantum emitters [12,13,14,15,16,17,18]. The InP-based technology has its drawbacks—it is still relatively expensive and, in some aspects, less with regard to jurisdictional claims in published maps and institutional affiliations.
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