Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 48: Quantum Dots and Wires: Growth

HL 48.6: Talk

Thursday, March 21, 2024, 16:15–16:30, EW 202

Wafer-Scale Emission Energy Modulation of Indium Flushed Quantum Dots — •Nikolai Spitzer, Nikolai Bart, Hans-Georg Babin, Marcel Schmidt, Andreas D. Wieck, and Arne Ludwig — Ruhr-Universität Bochum, Lehrstuhl für Angewandte Festkörper- physik, Universitätsstraße 150, 44801 Bochum, Germany

We explore a novel approach for fine-tuning the emission wavelength of quantum dots (QDs) by building upon the indium flush growth method: Submonolayer variations in the capping thickness reveal a non-monotonic progression, where the emission energy can decrease even though the capping thickness decreases. Indium flush, a well-known technique for inducing blue shifts in quantum dot emissions, involves the partial capping of QDs with GaAs followed by a temperature ramp-up. However, our findings reveal that the capping layer roughness, stemming from fractional monolayers during overgrowth, plays a pivotal role in modulating the emission energy of these QDs. We propose increased indium interdiffusion between the QDs and the surrounding GaAs capping layer for a rough surface surrounding the QD as the driving mechanism. This interdiffusion alters the indium content within the QDs, resulting in an additional emission energy shift, counterintuitive to the capping layers thickness increase. We utilize photoluminescence spectroscopy to generate wafer maps depicting the emission spectrum of the QDs. Using thickness gradients, we produce systematic variations in the capping layer thickness on 3-inch wafers, resulting in modulations of the emission energy of up to 26 meV.

Keywords: molecular beam epitaxy; quantum dots; indium flush method; photoluminescence spectroscopy