Tuning the Excitonic Emission of GaAs Quantum Dots

Description

Quantum dots (QDs) have been studied intensively, as they are promising sources of single and entangled photons on demand. In this talk, I will show how the excitonic emission of GaAs QDs can be tuned in a wide range by combing flexible growth protocols and post-growth strain engineering. Highly symmetric GaAs QDs in Al0.4Ga0.6As matrix are obtained by an optimized local-droplet-etching technique. Compared with conventional InAs/GaAs QDs, the GaAs/AlGaAs QDs feature no complicated built-in strain and also their composition profile is better defined, making them an ideal platform for fundamental studies as well as for application in the red and near-infrared spectral range. Firstly, I will show the optimized growth of low density (<1μm-2) GaAs QDs on GaAs(001) substrates, which results in excitonic-emission linewidths down to 4 μeV and average fine structure splittings (FSSs) of less than 2 μeV under non-resonant excitation [1]. Then I will present a systematic study of FSS as a function of QD size and shape [1, 2]. Finally, I will show how the excitonic nature of our QDs can be swapped from the conventional heavy-hole (HH) like to light-hole (LH) like. Taking advantage of the negligible pre-strain, the ground state of the valence band in GaAs QDs can be switched using moderate tensile strains (~0.4%) provided by two InAlGaAs stressor layers. Different from HH excitons, the LH excitonic emissions show three orthogonally-polarized bright optical transitions with one polarized along the growth direction [3, 4].

Period	08 Sept 2015
Event title	Semicon Nano 2015
Event type	Conference
Location	Korea, Republic ofShow on map