Interplay of morphology, composition, and optical properties of InP-based quantum dots emitting at the 1.55μm telecom wavelength

Abstract

Results for the development and detailed analysis of self-organized InAs/InAlGaAs/InP quantum dots suitable for single-photon emission at the 1.55 μm telecom wavelength are reported. The structural and compositional properties of the system are obtained from high-resolution scanning transmission electron microscopy of individual quantum dots. The system is composed of almost pure InAs quantum dots embedded in quaternary InAlGaAs barrier material, which is lattice matched to the InP substrate. When using the measured results for a representative quantum-dot geometry as well as experimentally reconstructed alloy concentrations, a combination of strain-field and electronic-state calculations is able to reproduce the quantum-dot emission wavelength in agreement with the experimentally determined photoluminescence spectrum. The inhomogeneous broadening of the latter can be related to calculated variations of the emission wavelength for the experimentally deduced In-concentration fluctuations and size variations.

Optical and electronic properties of symmetric InAs/InGaAlAs/InP quantum dots formed by a ripening process in molecular beam epitaxy: a promising system for broad-range single-photon telecom emitters

“…2 as a color map, where the two dotted lines distinguish the area of energies corresponding to the WL transition. As we do not expect very strong intermixing, this calculation allows us to determine that the average WL characteristics have to be between 4 ML (∼ 1.2 nm) of pure InAs and 5 ML (∼ 1.5 nm) of alloy with 𝑥 = 0.85, which resembles the recent transmission electron microscope images of similar QDs [39]. In the latter a rather soft interface with a gradient of composition was found.…”

“…The observed multimodal QD emission can be explained based on calculations of the QD ground state as a function of QD parameters (height, lateral dimensions, and chemical composition). The modeled QD geometry is a truncated pyramid with a square in the base and the angle between the side facets and the base of 25 degrees, in accordance with the structural studies of QDs grown under similar conditions [39]. The dot is settled on a 4-ML-thick WL, and the barrier material is In 0.53 Ga 0.23 Al 0.24 .…”

Telecom wavelength single quantum dots with very small excitonic fine-structure splitting

“…Furthermore, the biexciton binding energy values are nearly constant and all observed QDs have the same configuration where the X line is located at higher energies of the PL spectrum. This suggests that the structure, composition, and other QD parameters are nearly identical in this spectral range 23 . Biexciton binding energies in these QDs are lower than for earlier reported quantum dashes 24,25 or InAs/InP QDs grown by droplet epitaxy 13 and close to the Stranski-Krastanov InAs/InP QDs 26 .…”

Advances in Functional Nanomaterials Science

“…Therefore, the development of InP-based QD materials was reported as a means to address the 1.5 µm wavelength range and for application in classical optoelectronic devices, such as high-speed direct-modulated lasers, optical amplifiers and narrow-linewidth lasers [216][217][218] as well as single-photon emitters for quantum communication. [219][220][221][222] Furthermore, nearly circular InAs QDs with remarkably low fine-structure splitting values, which became comparable to the radiative exciton linewidth, were achieved on InP substrates. [222] Thus, Reithmaier's group identified these quantum emitters as ideal candidates for simple, pure, epitaxially grown polarization-entangled photon sources for core elements of far-reach quantum-communication systems, besides their use in fiber-based applications that were developed with regard to classical high-performance optoelectronic devices.…”