Lateral carrier diffusion in InGaAs/GaAs coupled quantum dot-quantum well system

Abstract

The lateral carrier diffusion process is investigated in coupled InGaAs/GaAs quantum dot-quantum well (QD-QW) structures by means of spatially resolved photoluminescence spectroscopy at low temperature. Under non-resonant photo-excitation above the GaAs bandgap, the lateral carrier transport reflected in the distorted electron-hole pair emission profiles is found to be mainly governed by high energy carriers created within the 3D density of states of GaAs. In contrast, for the case of resonant excitation tuned to the QW-like ground state of the QD-QW system, the emission profiles remain unaffected by the excess kinetic energy of carriers and local phonon heating within the pump spot. The lateral diffusion lengths are determined and present certain dependency on the coupling strength between QW and QDs. While for a strongly coupled structure the diffusion length is found to be around 0.8 μm and monotonically increases up to 1.4 μm with the excitation power density, in weakly coupled structures, it is determined to ca. 1.6 μm and remained virtually independent of the pumping power density.

Correlated Nanoscale Analysis of the Emission from Wurtzite versus Zincblende (In,Ga)As/GaAs Nanowire Core–Shell Quantum Wells

“…Normally, even for QW structures, the IIIarsenides have a sufficiently large diffusivity that most carriers excited in the WZ segment should reach the lower energy ZB QW. 44,45 Nevertheless, we see a clearly blueshifted transition for the WZ QW. Apparently, the stacking defects in the transition region serve as a barrier limiting carrier diffusion to the lower energy segment.…”

Carrier dynamics in hybrid nanostructure with electronic coupling from an InGaAs quantum well to InAs quantum dots

“…Since 1993, self-assembled quantum dots (QDs) grown by the Stranski-Krastanow (S-K) strain relaxation have gained great attention due to their possible optoelectronic device applications, such as semiconductor lasers, amplifiers, modulators, photovoltaic, and infrared photo-detectors [1][2][3][4][5][6]. As examples, QD hybrid structures with QDs coupled to a quantum well (QW) have been exploited in various material systems and optoelectronic devices where additional excess carriers can be provided through carrier transfer from the QW [7][8][9][10][11][12][13][14]. There are at least two ways to fabricate such QD hybrid systems.…”