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HL: Fachverband Halbleiterphysik

HL 19: Quantum dots and wires: Transport properties

HL 19.1: Vortrag

Dienstag, 13. März 2018, 09:30–09:45, A 151

Tunnelling dynamics and hole storage of quantum dots measured by conductance spectroscopy — •Carsten Ebler, Arne Ludwig, and Andreas D. Wieck — Ruhr-Universität Bochum, Bochum, Deutschland

Approaching the goal of a memory, storing single charge quanta, especially in quantum dots are interesting. Therefore, we use epitaxially grown self-assembled InAs QDs (SAQD) as crystalline hosts compatible with coupling to photons. This is envisaged as a progress compared to amorphous indirect semiconductors used in today’s flash memories.

We establish the SAQDs in tunnel contact with an inverted GaAs/Al_0.3Ga_0.7As HEMT structure containing a 2-dimensional electron gas (2DEG), manipulate the system with electronical and optical pulses and perform time resolved conductivity measurements of the 2DEG to readout the charge occupation of the QDs.

The structure is appropriately biased, that the Fermi level is in electronical resonance with the X⁰state in the QD to store one single hole. This metastable hole state is read out over conductivity changes in the channel of the HEMT. Thereby it is possible to resolve electron tunnelling dynamics in and out of the quantum dots and furthermore the interaction with the holes trapped inside the QDs. It was possible to store the metastable hole for at least 4 s and to read it out during this time laps. Further experimentation with different voltage pulses provide information about tunnelling processes of the electron states and dynamics of non-equilibrium states.