Carrier diffusion as a measure of carrier/exciton transfer rate in InAs/InGaAsP/InP hybrid quantum dot–quantum well structures emitting at telecom spectral range

Abstract

We investigate the diffusion of photo-generated carriers (excitons) in hybrid two dimensional–zero dimensional tunnel injection structures, based on strongly elongated InAs quantum dots (called quantum dashes, QDashes) of various heights, designed for emission at around 1.5 μm, separated by a 3.5 nm wide barrier from an 8 nm wide In0.64Ga0.36As0.78P0.22 quantum well (QW). By measuring the spectrally filtered real space images of the photoluminescence patterns with high resolution, we probe the spatial extent of the emission from QDashes. Deconvolution with the exciting light spot shape allows us to extract the carrier/exciton diffusion lengths. For the non-resonant excitation case, the diffusion length depends strongly on excitation power, pointing at carrier interactions and phonons as its main driving mechanisms. For the case of excitation resonant with absorption in the adjacent QW, the diffusion length does not depend on excitation power for low excitation levels since the generated carriers do not have sufficient excess kinetic energy. It is also found that the diffusion length depends on the quantum-mechanical coupling strength between QW and QDashes, controlled by changing the dash size. It influences the energy difference between the QDash ground state of the system and the quantum well levels, which affects the tunneling rates. When that QW–QDash level separation decreases, the probability of capturing excitons generated in the QW by QDashes increases, which is reflected by the decreased diffusion length from approx. 5 down to 3 μm.

Interplay of structural design and interaction processes in tunnel-injection semiconductor lasers

“…22 To benefit from the advantages of the TI design in telecommunication applications, InAs QDs within an InGaAlAs barrier lattice matched to the InP substrate are attractive due to their emission around the 1.55 µm wavelength and their re-duced size inhomogeneity. 8,[23][24][25][26][27][28] Further investigations of the InAs/InP material system include studies of the behavior of the QD ground state under the influence of varying QW parameters, as well as the carrier dynamics in TI structures at cryogenic temperatures. 28,29 For the simulation of carrier and laser dynamics in TI laser devices, the tunneling process is often described via rate equations, [30][31][32][33][34] using time constants extracted from experiments.…”

Persistent High Polarization of Excited Spin Ensembles During Light Emission in Semiconductor Quantum-Dot-Well Hybrid Nanosystems

“…In addition, this suggests that these QD-QW hybrid nano-spin-systems are of significance for future developments of spin-functional optical devices. Furthermore, the concept of laterally coupled high-density QDs with properly designed QWs could be useful for various promising devices such as a highperformance QD laser [34] and QD-based memory [35]. It is also worth noting that solid-state quantum information processing requires a QD-based two-spin-level system with a precisely controlled coupling of the electron wavefunctions.…”