Hrg. Dominik Gruber,
"Electric-field-dependent light-emission of sin-gle GaAs quantum dots grown by local droplet etching"
Electric-field-dependent light-emission of sin-gle GaAs quantum dots grown by local droplet etching
Sprache des Titels:
Improving the performance of photon sources for future quantum cryptography and quan-tum computing is of significant interest. Semiconductor quantum dots are among the most promising candidates as sources of "quantum light" for such applications. Therefore, unique semiconductor sample structures have been developed to improve the optical quality of the quantum dots. This thesis reports on the first charge-tunable quantum dot device based on GaAs quantum dots grown at the Johannes Kepler University. The purpose of the charge-tunable device is to serve as a photon source for quantum cryptography with better perfor-mance compared to the current sources. As a part of the thesis several samples have been grown with molecular beam epitaxy with di?erent thicknesses of the tunnelling barriers. After the growth, samples have been characterized with atomic force microscopy and photolumines-cence measurements to get first information about the sample qualities. Afterwards, samples have been processed to create the functional charge-tunable device out of the raw structures. The fabricated devices have been examined through polarization-resolved photoluminescence measurements as a function of the applied-gate voltage. We find that in the presence of a high vertical electric field the light emission of confined excitons have a significant Stark shift. By increasing the vertical electric field the line-width of the excitons increases. The fine structure splitting of the neutral exciton is barely not a?ected by the electric field. De-pending on the tunnelling barrier thickness the excitons vanish after a specific gate voltage. Clear charging plateaus are not observed in any of the examined structures. We expect that this will be possible by further reducing the tunnelling barrier.