Theoretical prediction of strain-induced carrier effective mass modulation in 4H-SiC and GaN

We report the modulation of electron and hole effective masses under biaxial strain in 4H-SiC and GaN on the basis of first-principles calculations including the spin–orbit interaction. While the electron effective masses are insensitive to the strain, the hole effective masses manifest significant changes under moderate tensile strain in both 4H-SiC and GaN: more than two times increase in the (0001) in-plane directions and one-tenth decrease in the out-of-plane. We explain such substantial changes in the hole effective masses in terms of strain-induced hybridization, crossing, and reordering of the heavy-hole and light-hole bands.