Extraction of the interface trap density through the differential subthreshold ideality factor technique in normally-off AlGaN/GaN MOSHFETs

Abstract

Normally-off AlGaN/GaN-on-Si metal-oxide-semiconductor heterojunction field-effect transistors (MOSHFETs) were fabricated combining a SiO2 gate insulator and recessed-gate etching. We have studied the extraction of the sub-bandgap interface trap densities of normally-off AlGaN/GaN MOSHFETs by using the differential subthreshold ideality factor (DIF) technique. This method allows threshold-voltage (V T )-independent extraction of interface states by using current-voltage data in the subthreshold region. The trap density is extracted to be D it (E) = 1 × 1012 ∼ 3 × 1013 [eV−1·cm−2] at the SiO2/GaN interface. An increase in the interface trap density was detected by the applying the DIF technique after the gate bias stress test.