Bodové defekty pro kvantovou optiku

Vasilega, Richard

With the rise of quantum technologies, a demand for single-photon sources in quantum communication is growing. Point defects in wide-bandgap semiconductors have emerged as promising candidates for solid-state single-photon emission. This thesis investigates the spatial photocurrent response of a graphene-contacted semi-insulating 6H-SiC sam- ple to optical excitation across wavelengths from 355 nm to 1000 nm, complemented by Fourier transform photocurrent spectroscopy measurement. Spatially localized pho- tocurrent hotspots were observed exclusively under 355 nm and 405 nm illumination, at photon energies above the 6H-SiC bandgap. Quantitative analysis revealed carrier fluxes several orders of magnitude larger than expected from isolated point defects, indicat- ing collective contribution of defect ensembles forming localized electrostatic potentials that govern carrier collection via drift-diffusion transport. A photocurrent threshold of approximately 0.1 fA was established as a criterion for possible single point defect exci- tation. No photoluminescence signal was detected, attributed to low photoluminescence efficiency of 6H-SiC combined with limited detector sensitivity.

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