Doping-dependent electrical properties of threading dislocations in 4H-SiC

Electron beam induced current experiments are employed to quantitatively characterize the local electronic properties of threading dislocations (TDs) in 4H-SiC epitaxial layers. Combining with the Shockley–Read–Hall recombination theory, the local dopant concentrations and local Fermi levels of TDs are evaluated. At room temperature, the local Fermi levels of threading screw dislocations (TSDs) and threading edge dislocations (TEDs) are 14 and 29 meV higher than that of perfect region of n-type 4H-SiC with concentration of 4.76 × 1016 cm−3. As the doping concentration decreases to 1.83 × 1014 cm−3, the Fermi-energy difference between TSDs/TEDs and perfect region decrease to 1/18 meV, respectively. This is caused by the nitrogen accumulation at TD cores in n-type 4H-SiC, with the effect being more prominent for TEDs. Whereas, in p-type 4H-SiC, the local Fermi levels of TSDs and TEDs are 11 and 1 meV higher than those of the perfect region of 4H-SiC with a doping concentration of 3.08 × 1016 cm−3. As the doping concentration decreases to 2.55 × 1015 cm−3, the Fermi-energy differences between TSDs/TEDs and perfect 4H-SiC region increase to 22/3 meV, respectively. In p-type 4H-SiC, aluminum tends to be incorporated in perfect lattice sites, which is more prominent for TSDs. As the doping concentration decreases, the Fermi-energy difference decreases in n-type 4H-SiC, but increases in p-type 4H-SiC. The effect of dopants on the electronic properties of TDs increases with the increase in temperature, indicating that the adverse effect of TDs during the application of power devices based on 4H-SiC aggravates.