Photoinduced behavior of the V_cC_(Si)~- pair defect in 4H-SiC grown by physical vapor transport and halide chemical vapor deposition

摘要

Two different photothresholds of the carbon vacancy-carbon antisite pair defect (V_CC_(Si)~-) in 4H-SiC are observed using photoinduced electron paramagnetic resonance. The defect appeared after illumination with photon energy greater than 0.75 eV in two samples grown by halide chemical vapor deposition (HCVD) and one by physical vapor transport (PVT), all with activation energies (E_a) below 0.80 eV. In HCVD and PVT samples with higher activation energies, the defect was not detected with photon excitation less than 2.1 eV. The increase in V_CC_(Si)~- parallels changes in the negatively charged carbon vacancy V_C~- in the samples with low E_a. For SiC samples with high E_a, the concentration of the anitisite-vacancy pair also increases with V_C and, in addition, is accompanied by a simultaneous decrease in V_C~+. The results are interpreted in terms of two defect levels, one for the double negative-to-negative transition of V_CC_(Si) at 0.75 eV below the conduction band edge and another for the negative-to-neutral transition of the defect at 2.1 eV above the valence band edge. The model yielding these levels also suggests that the neutral-to-negative and negative-to-double negative transitions of the isolated carbon vacancy are within a few tenths of an eV of each other and are located close to the conduction band edge.