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Julien Renard

Optical properties of GaN quantum dots and nanowires

Published on 28 September 2009
Thesis presented September 28, 2009

We studied the optical properties of wurtzite III-N heterostructures by means of various photoluminescence methods. Polarization resolved photoluminescence experiments allowed us to probe the combined effects of strain and confinement on the band structure of an heterostructure. We managed to perform the study of single GaN/AlN quantum dots on an original system: a quantum dot as a slice of a nanowire. This new system allowed us to identify the exciton and biexciton recombination. We also demonstrated that this structure behave as a single photon source thanks to a correlation experiment performed in the UV. We also studied the optical properties of III-N microdisks and measured quality factors up to 11000, which is promising to demonstrate the Purcell effect. Finally, we studied the carrier and spin dynamics in GaN/AlN heterostructures. The quantum dots are very efficient to inhibit the non radiative recombinations. The decay times are indeed not sensitive to temperature, even for lifetimes in the microsecond range. The quantum dots seem also to be very effective to reduce the spin scattering mechanisms for a localized exciton. Optical alignment experiments, performed under quasi resonant excitation, allowed us to show that the induced polarization was conserved on the lifetime of the exciton up to room temperature.

GaN, nanowires, quantum dots, photoluminescence, microcavities

On-line thesis.