Photocapacitance Decay Technique for Interface Trap Characterization Near Inversion Band in Wide Bandgap MOS Capacitors

A technique to characterize interface traps near the minority carrier band for wide bandgap metal-oxide-semiconductor (MOS) capacitors at room temperature is presented. The method uses photogeneration of minority carriers and transient analysis of the subsequent photocapacitance decay to evaluate trap response times. The technique is demonstrated using n-type substrate 6H- SiC/SiO₂ MOS capacitors to extract interface trap density (D_it) ranging in energy from 0.2 to 0.8 eV above the valence band edge (E_v) and trap cross sections from 0.4 to 0.7 eV above E_v. For the given material system, traps near E_v exhibit significant differences between n-and p-type substrate MOS capacitors.