Investigation of interface state densities in SiC/SiO₂ probed by time-dependent second harmonic generation

In recent years, second-harmonic generation (SHG) is a preferred novel technique for interface characterization in semiconductor devices due to its non-destructiveness and high sensitivity. In this study, we investigate the application of time-dependent second-harmonic generation (TD-SHG) for probing interface state densities (D_it) in SiC/SiO₂ structures. SiO₂ films were deposited on SiC substrates via plasma-enhanced chemical vapor deposition (PECVD), followed by various annealing processes to modulate D_it. The samples were characterized by using TD-SHG, and the extracted characteristic parameters demonstrated a strong linear correlation with the D_it obtained from capacitance-voltage (C–V) measurements. Based on these results, we developed a semiconductor photoelectric effect model to explain the physical mechanisms of the interaction between light and interface traps. The results confirm that TD-SHG provides a highly sensitive, non-contact, and non-destructive approach for quantitative evaluation of D_it in SiC/SiO₂ systems, highlighting its potential for semiconductor device characterization and reliability assessment.