Impact of Outer Shell Structure and Localization Effects on Charge Carrier Dynamics in GaAs/(In,Ga)As Nanowire Core–Shell Quantum Wells

Abstract

Herein, the charge carrier dynamics in GaAs/(In,Ga)As/(Al,Ga)As core–shell nanowires with different outer shell structures are studied. Localization of charge carriers in the minima of potential fluctuations is shown to govern the recombination processes at low temperatures. At higher temperatures, thermionic emission of carriers from the (In,Ga)As shell quantum well leads to a decrease of the luminescence efficiency for a sample with a GaAs outer shell. This effect can be reduced by introducing an AlAs barrier shell. However, the interfaces to this barrier act as an additional source for nonradiative recombination. These results will help in achieving high luminescence intensities at room temperature of light‐emitting devices based on nanowire shell quantum wells.

Drastic effect of sequential deposition resulting from flux directionality on the luminescence efficiency of nanowire shells

“…Such localization is more pronounced in these In 0.15 Ga 0.85 As/GaAs shell QWs than in conventional planar (100) In 𝑥 Ga 1−𝑥 As/GaAs QWs and occurs for low excitation density also in samples grown with cell As2, as we reported in a previous study. 26 Hence, both the lower PL intensity and the broad band of sharp lines indicate a much lower photogenerated charge carrier concentration in the sample grown with cell As1. Since light coupling is identical for the two samples, the difference between the integrated PL intensities reveals directly that the internal quantum efficiency must be more than two orders of magnitude lower in the As1 sample.…”

“…However, in a detailed analysis we showed for GaAs NWs with In 0.15 Ga 0.85 As shell QW that at 10 K an outer GaAs shell presents a sufficiently high barrier for charge carriers to suppress this channel. 26 There are still two possible explanations for the drastic influence of the deposition sequentiality on the luminescence efficiency demonstrated in Figure 1a. First, co-deposition as sketched in Figure 2c could result in a much higher density of deep point defects acting as non-radiative recombination centers, either throughout the QW shell or at its interfaces (or both).…”

“…For the sample grown with cell As2, we analyze the experimental transient with the coupled rateequation system for free and bound excitons used previously for similar samples in Ref. 26 and visualized in the inset of Fig. 1c.…”

Beam damage of single semiconductor nanowires during X-ray nanobeam diffraction experiments

“…The CL intensity is highly sensitive to the presence of non-radiative defects. The interface of the growing oxide shell to the NW core is likely to induce strong non-radiative recombination (Kü pers et al, 2019). However, the oxidation process may even introduce non-radiative centers deeper in the NW, for example by in-diffusion of O.…”

“…This makes it possible to access the same individual NWs both in nXRD and SEM/CL/EDX measurements. More details about the growth process and sample geometry can be found in the work of Kü pers et al (2018Kü pers et al ( , 2019.…”