Time-dependent photo-induced electron paramagnetic resonance measurements

were made on high purity semi-insulating 4H-SiC to develop a more complete

understanding of the optical transitions of the positively charged carbon vacancy

VC

+. The single defect model originally proposed was given validity by

demonstrating that the time dependence of the photo-induced changes in VC

+ may

be fitted by a first order kinetic process. In addition, the photon energy dependence

of the optical cross sections for capture and emission of electrons from VC

+ was

extracted by incorporating both processes into one expression for charge transfer.

The data were interpreted by considering the role of the electronic density of states as well as participation of phonons. Analysis assuming only phonon participation

yields thermal and optical energies of 1.6 and 2.15eV, respectively, for charge

transitions between VC

+ and one of the band edges. Charge transfer between VC

+

and the opposite band edge was associated with a thermal and an optical energy of

1.9 and 2.45eV, respectively. An upper limit for the Franck–Condon shift of

0.55eV was extracted from the difference between the thermal and optical energies.

Measurements of Optical Cross Sections of the Carbon Vacancy in 4H-SiC by

Time-Dependent Photoelectron Paramagnetic Resonance. J.Dashdorj, M.E.Zvanut,

J.G.Harrison: Journal of Applied Physics, 2008, 104[11], 113707