Berlin 2012 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 97: Quantum Dots and Wires: Optical Properties IV (mainly Nitrides)
HL 97.3: Talk
Friday, March 30, 2012, 10:30–10:45, ER 270
Strong dipole coupling in nonpolar nitride quantum dots due to Coulomb effects — •Kolja Schuh1, Steffan Barthel1, Oliver Marquardt2, Gerd Czycholl1, and Frank Jahnke1 — 1Institute for Theoretical Physics, University of Bremen, Germany — 2Tyndall National Institute, Lee Maltings, Cork, Ireland
Due to their wide-range of emission frequencies nitride-based optoelectronic devices are of current interest. However, a major drawback in nitrides is that the optical recombination is hindered by strong intrinsic fields that causes a separation of electrons and holes. In quantum wells, this effect can be avoided by enforcing a nonpolar growth direction, which ensures the absence of fields in the confined direction. However, since quantum-dot states are confined in all directions, there is always a separation of electrons and holes.
We show that in nonpolar nitride quantum dots the dipole transition between the single-particle ground states is only of minor importance for optical spectra. This spectra are dominated by many higher excited single-particle states which contribute to the ground-state transition when taking into account the Coulomb interaction. This finding may resolve existing discrepancies between theory and experiment, as theoretically only a weak ground state transition was obtained because of the spatial seperation of electron and hole ground state due to intrinsic fields, whereas experimentally fast recombinations were observed. Our treatment combines a continuum elasticity approach for the polarization potential, a microscopic tight-binding model for the electronic properties, and a many-body theory for the optical properties.