Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 3: Focus Session: Electron-phonon interaction and ultrafast processes in semiconductors

HL 3.1: Topical Talk

Monday, March 11, 2013, 09:30–10:00, H13

Exciton-Phonon Coupling in Wurtzite GaN Quantum Dots — •G. Callsen¹, A. Schliwa¹, G. Hönig¹, J. Settke¹, C. Kindel¹, J. Brunnmeier¹, S. Kalinowski¹, T. Markurt², M. Albrecht², S. Kako³, Y. Arakawa³, and A. Hoffmann¹ — ¹Technical University of Berlin, 10623 Berlin, Germany — ²Leibniz Institute for Crystal Growth (IKZ), 12489 Berlin, Germany — ³University of Tokyo, Tokyo 153-8505, Japan

Strongly polar quantum dot (QD) materials such as group III-nitrides are ideal candidates for the investigation of exciton-phonon interaction. Large excitonic dipole moments of around 2 e·nm inherent to GaN/AlN QDs amplify the coupling to acoustical and optical phonons, clearly observable in µPhotoluminescence (µPL) spectra. Using UV micro-PL spectroscopy, volumes of single-QD spectra are analyzed, and commonly obscured effects such as the QD-size dependence of the Huang-Rhys factor are revealed and compared to theory. Furthermore, the occurring strong excitonic electric dipole moments also influence the interaction of the QD-excitons with charged defects in the surrounding AlN matrix material, causing spectral diffusion induced emission line-width broadening. The extracted dependencies for the Huang-Rhys factor and the emission line-widths can be seen as general phenomena in strongly polar QD materials and reveal current device limitations with respect to applications at non-cryogenic temperatures. In conclusion we discuss the interrelation of the QD size, the built-in fields, the exciton energy and the dipole moment with the determined Huang-Rhys factors and emission line-widths, giving detailed new insight into the strong built-in piezo- and pyroelectric fields native to wurtzite GaN/AlN QDs.