Electronic, optical and magnetic properties of Ti-doped and (Ti, VSi) co-doped 4H-SiC: A first-principles study

The electronic, optical and magnetic properties of both Ti-doped 4H-SiC and (Ti, V_Si) co-doped 4H-SiC are investigated using first-principles calculations based on the density functional theory (DFT). The energy calculations revealed that Ti atoms preferentially occupy Si lattice sites, characterized by the lowest formation energy and optimal structural stability. Ti doping reduces the bandgap of 4H-SiC from 2.22 eV to 2.13 eV, significantly enhancing its optical response to low energy photon fields. Upon (Ti, V_Si) co-doping, the bandgap of 4H-SiC decreases further to 0.89 eV and exhibits an indirect-to-direct transition, thereby improving optical absorption in the low energy spectral range. Detailed Analysis of magnetic properties reveals that the local magnetic moment in the co-doped system is primarily derived from electron spin splitting and redistribution in C atoms surrounding V_Si, elucidating the synergistic regulation mechanism of magnetism through defects and dopants. The findings give insights into Ti-doped and (Ti, V_Si) co-doped 4H-SiC and may be useful for their applications in optoelectronic and spintronic devices.