Crystal growth and evaluation of nitrogen and aluminum co-doped N-type 4H-SiC grown by physical vapor transport

•N-Al co-doped n-type 4H-SiC crystals were grown using the PVT method.•The relation between impurity concentration and Al4C3 temperature was investigated.•The threading dislocation density of highly N-Al co-doped crystal was high.•The expansion velocities of the DSFs in the N-Al co-doped crystals were low. N-type 4H-SiC crystals were grown by the physical vapor transport (PVT) method with nitrogen and aluminum (N–Al) co-doping. By using aluminum carbide powder preannealed in nitrogen gas atmosphere as an aluminum doping source, we obtained highly N–Al co-doped crystals with a nitrogen concentration higher than that in nitrogen-only-doped crystals. The dislocation densities of N-Al co-doped crystals with a high aluminum concentration (>1 × 1019 cm−3) were found to become higher than those with a low aluminum concentration (