Temperature-dependent stacking fault energies of 4H-SiC: A first-principles study

Abstract

The stacking fault (SF) energy of 4H-SiC around room temperature is important for the quantitative investigation of bipolar degradation, which is a serious issue in 4H-SiC bipolar power devices. However, the experimental measurement of SF energy around room temperature is very difficult. We have theoretically estimated the dependence of 4H-SiC SF energy on temperature using a calculation of the free energy of phonons based on ab initio calculations. Calculations using both the harmonic vibration approximation and quasi-harmonic approximation are performed in order to account for the effects of thermal expansion. The SF energies of a single Shockley-type stacking fault (SSSF) at room temperature and at 1500 K are 14.5 mJ/m2 and 12.8 mJ/m2, respectively. The SF energy of an SSSF is not sensitive to temperature and at a high temperature agrees with the experimental value. The SF energy of a double Shockley-type stacking fault is about 8 mJ/m2 at room temperature, and the energy increases with temperature, reaching about 11 mJ/m2 at 1500 K. The critical minority carrier density at which SFs expand in bipolar degradation is estimated by applying the obtained SF energy to the quantum well action model. The estimated critical minority carrier density is 1.0 × 1016–1.0 × 1017 cm−3, which is consistent with the previous experimental value. Our estimated SF energy enables us to accurately estimate the critical conditions of SF expansion in bipolar degradation.