Optical properties and Zeeman spectroscopy of niobium in silicon carbide
(English)Manuscript (preprint) (Other academic)
The optical signature of niobium in the low-temperature photoluminescence spectra of three common polytypes of SiC (4H, 6H and 15R) is observed and confirms the previously suggested concept that Nb occupies preferably the Si – C divacancy at hexagonal site. Using this concept we propose a model considering Nb-bound exciton, the recombination of which is responsible for the observed luminescence. The exciton energy is estimated using firstprinciples calculation and the result is in very good agreement with the experimentally observed photon energy in 4H SiC at low temperature. The appearance of six Nb-related lines in the spectra of the hexagonal 4H and 6H polytypes at higher temperatures is explained on the ground of the proposed model and the concept that the Nb center can exist in both C1h and C3v symmetries. The Zeeman splitting of the photoluminescence lines is also recorded in two different experimental geometries and the results are compared with theory based on phenomenological Hamiltonians. Our results show that Nb occupying the divacancy at hexagonal site in the studied SiC polytypes behaves like a deep acceptor.
IdentifiersURN: urn:nbn:se:liu:diva-117972OAI: oai:DiVA.org:liu-117972DiVA: diva2:812558