A study was made of semi-insulating 4H-SiC grown by physical vapor transport (PVT) and high-temperature chemical vapor deposition (HTCVD) using electron paramagnetic resonance and infra-red photoluminescence (IR-PL) in order to understand better the defects which were responsible for the semi-insulating behavior. Although intrinsic defects such as the isolated C vacancy and in some cases the isolated Si vacancies had previously been observed by electron paramagnetic resonance in undoped semi-insulating SiC, their concentrations were an order of magnitude too low to be responsible for the semi-insulating behavior. It was possible to observe the electron paramagnetic resonance signature of the C vacancy–C antisite pair (VC–CSi) pair defect in an excited state of its 2+ charge state in all PVT samples and some HTCVD samples. It was also established that the IR–PL signature of this electron paramagnetic resonance center was the UD2 spectrum: a set of 4 sharp lines between 1.1 and 1.15eV, previously observed in neutron-irradiated 4H–SiC. Also observed was the UD1 line, a pair of sharp IR–PL lines at ~1.06eV and UD3, a single sharp line at ~1.36eV. A simple model was proposed for the SI behavior in material in which the (VC–CSi) pair defect was the dominant deep defect.

Optical and Magnetic Resonance Signatures of Deep Levels in Semi-Insulating 4H SiC. W.E.Carlos, E.R.Glaser, B.V.Shanabrook: Physica B, 2003, 340-342, 151-5