Photonic devices of piezoelectric quantum dots

Abstract

Semiconductor Quantum Dots (QDs) are an ideal artifcial system to studyfundamental properties of matter and the ultimate component of quantum informationprocessing. Towards the implementation of a tunable source of singlephotons or entangled photon pairs, we present here a study on self-assembledInAs/GaAs QDs, grown on a high-index (211)B GaAs substrate. The system hasall the benefts of regular and well-studied (100) InAs/GaAs QDs, but additionallyhas a fascinating characteristic, which is the presence of a large vertical piezoelectric(PZ) feld inside the QDs, bringing in a number of signifcant advantages,which are illustrated in this work. First, the PZ feld along the growth directionpreserves the high symmetry of the confning potential, leading to negligible fnestructure splitting (FSS) values in the system, which is essential for entanglementapplications. By polarization resolved micro-photoluminescence experiments wededuce negligible FSS values of PZ QDs, which make them good candidates forquantum information applications. Second, the PZ feld generates large excitonbiexcitonenergy splittings, which is prerequisite for single photon applications athigh temperatures. This ability is demonstrated by cross-correlation experimentson single exciton emission lines, showing clear anti-bunching behaviour at elevatedtemperatures. Third, due to the pronounced PZ feld, the emission wavelength ofthese QDs should be very sensitive to an applied external electric feld, leading tosignifcant Stark shifts in this QD system. To explore this, a special dot-containingdiode structure has been fabricated and studied, and enhanced Stark tuning of theQD emission has been observed. Finally, our results provide a clear demonstrationof the importance of non-linear piezoelectric efects in Zinc-Blende semiconductors