Characterization of Semi-insulating SiC
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0911-B06-03
Characterization of Semi-insulating SiC Nguyen Tien Son1, Patrick Carlsson1, Björn Magnusson1,2, and Erik Janzén1 1 Department of Physics, Chemistry and Biology, Linköping University, Linköping, SE-581 83, Sweden 2 Norstel AB, Ramshällsvägen 15, Norrköping, SE-602 38, Sweden
ABSTRACT Electron paramagnetic resonance was used to study defects in high-purity semi-insulating (HPSI) substrates grown by high-temperature chemical vapor deposition and physical vapor transport. Deep level defects associated to different thermal activation energies of the resistivity ranging from ~0.6 eV to ~1.6 eV in HPSI substrates are identified and their roles in carrier compensation processes are discussed. Based on the results obtained in HPSI materials, we discuss the carrier compensation processes in vanadium-doped SI SiC substrates and different activation energies in the material. INTRODUCTION In recent years, high-purity semi-insulating (HPSI) SiC substrates for high-frequency power devices have become commercially available. In HPSI SiC materials grown by physical vapor transport (PVT) [1-3] and by high-temperature chemical vapor deposition (HTCVD) [4-6], intrinsic defects were used to compensate the residual shallow N donors and B acceptors [1-6]. It has been shown that the concentration of intrinsic defects is enough to create the SI properties in PVT material with the concentrations of shallow N donors and B acceptors in the mid and low 1016 cm–3 ranges, respectively [1,2]. Different activation energies, as determined from the temperature dependence of the resistivity, in the range Ea~0.8-1.6 eV were observed in substrates grown by PVT [1-3] and HTCVD [5,6]. Many defects have been observed by electron paramagnetic resonance (EPR) and optical techniques in HPSI substrates [1-11] and by deep level transient spectroscopy (DLTS) in n-type and p-type as-grown PVT material [1-3]. However, the defects associated to different activation energies in HPSI material have not been identified. The reduction in the resistivity by several orders of magnitude (to ~105 Ωcm) after high-temperature annealing was observed for PVT substrates with the N concentration of ~2×1016 cm–3 [8]. Despite a lower N concentration of mid 1015 cm–3 in the HTCVD material a similar instability of the SI properties also occurred in some of the HPSI substrates and Ea changed from ~0.8 eV to ~0.6 eV [5]. Identifying the defects that are responsible for the SI behavior is important for a better defect control during the crystal growth in order to achieve high-quality and stable HPSI substrates. In this work we identify the dominating defects in different types of HPSI 4H-SiC substrates. Combining EPR data with reported DLTS levels we determine donor and acceptor levels of dominant defects and correlate with different activation energies. Recent studies of Vdoped SI SiC are reviewed and the role of V in carrier compensation is discussed.
EXPERIMENTAL DETAILS In our study, we used many n-type and HPSI samples grown by PVT and HTCVD from different producer
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