Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 50: Poster II
HL 50.92: Poster
Donnerstag, 30. März 2006, 16:30–19:00, P3
Observation of Multi-exciton Transitions in Individual Quantum Dot Molecules — •Emily Clark1, Hubert J. Krenner1, Toshihira Nakaoka1,2, Matthias Sabathil1, Max Bichler1, Yasuhiko Arakawa2, Gerhard Abstreiter1, and Jonathan J. Finley1 — 1Walter Schottky Institut and Physik Department, Technische Universität München, Germany — 2University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo, 153-8505, Japan
We present investigations of single, charged and multi-exciton states in individual quantum dot molecules (QDMs). The samples investigated consist of pairs of self assembled, vertically stacked InGaAs-GaAs QDs embedded in an n-type Schottky photodiode. This device geometry enables us to control the coupling between excitonic states in the upper and lower dots via the electric field. Previously, we demonstrated an anticrossing of spatially direct (e,h in the same dot) and indirect (e,h in different dots) excitons with an average coupling energy of 2E=1.6±0.3meV. By comparing these findings with realistic calculations of the single exciton spectrum, we confirm that the observed anticrossing is due to hybridization of the electron component of the exciton wavefunction. New emission peaks emerge at higher excitation levels, the intensity of which increases quadratically on the excitation intensity, identifying them as biexcitons in the QDM. Both spatially direct (two excitons in upper dot) and separated (single exciton in upper and lower dot) biexcitons are identified. Comparison between quasi resonant and non-resonant excitation, separates between charged and neutral excitons.