Identification of Semi-ON-State Current Collapse in AlGaN/GaN HEMTs by Drain Current Deep Level Transient Spectroscopy

A drain-controlled current-mode deep level transient spectroscopy (I-DLTS), was developed for investigation of Semi-ON-state current collapse in AlGaN/GaN high electron mobility transistors (HEMTs). By inserting a graded AlGaN back-barrier between the GaN channel and AlGaN buffer layer, hot-electron effect induced charging of buffer traps is effectively blocked, which contributes to a remarkable suppressed current collapse in AlGaN/GaN HEMTs under Semi-ON-state stress. A broad-distributed electron trap
${E}_{\text {T1}}$
, which features an energy level depth
${E}_{\text {C}}$
-
${E}_{\text {T}}$
and apparent capture cross section
${\sigma }_{\text {T}}$
of 0.25 ± 0.05 eV and
$9.0\,\, {\pm } 1.0 {\times } 10^{-18}$
cm
²
, was verified to locate in the AlGaN buffer layer by I-DLTS. A combination of pulsed
${I}$
-
${V}$
and I-DLTS measurements, could be an effective method for in-situ study of current collapse mechanism in AlGaN/GaN HEMTs.