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HL: Fachverband Halbleiterphysik

HL 3: Quantum dots: Microcavities and photonic crystals

HL 3.5: Vortrag

Montag, 25. Februar 2008, 12:15–12:30, ER 270

Realization of Electrically Tunable Single Quantum Dot - Cavity Systems — Felix Hofbauer, •Jakob Angele, Michael Kaniber, Gerhard Böhm, and Jonathan J. Finley — Walter Schottky Institut, TU München, 85748 Garching, Germany

We present studies of the radiative coupling of single In_0.4Ga_0.6As self-assembled quantum dots to both extended and strongly localised optical modes in electrically contacted 2D photonic crystal (PhC) nanostructures. The samples investigated consist of a 180nm thick, free-standing GaAs membrane into which PhC are formed by etching a triangular lattice of air holes. Low mode-volume (V<(λ/n)³) and high Q ∼ 8000 nanocavities are realised by introducing point defects into the PhC and the structures are electrically contacted via 30nm thick p- and n- doped contact layers in the membrane. These structures enable us to apply static electric field perturbations to the dots in the nanocavity and continuously vary the detuning (Δ) between the exciton and cavity using the quantum confined Stark effect.

The structures were studied using spatially resolved photoluminescence (PL) and photocurrent (PC) absorption spectroscopy. Our results show that Δ can be tuned in-situ by ∼ 4 meV in the PL regime. Investigations of the PL intensity and spontaneous emission dynamics as a function of Δ reveal an increase in PL intensity by a factor of 1.5x and a twofold decrease of in spontaneous emission lifetime due to the Purcell effect. Using PC we observe enhanced optical in-coupling to the structures when exciting close to the cavity modes and can detect absorption from a single dot-cavity system.