Drain current transient and low-frequency dispersion characterizations in AlGaN/GaN HEMTs

Abstract : This paper presents a detailed trap investigation based on combined pulsed I/V measurements, drain current transient (DCT) measurements and low-frequency dispersion measurements of transconductance (LF Y21) and output conductance (LF Y22). DCT characterization is carried out over a 7-decade time scale. LF Y21 and Y22 measurements are carried out over the frequency range from 100 Hz to 1 GHz. These combined measurements were performed at several temperatures for AlGaN/GaN high electron mobility transistors under class AB bias condition and allowed the extraction of the activation energy (Ea) and the capture cross section (σc) of the identified traps. Extensive measurements of these characteristics as a function of device bias are reported in this work to understand the dynamic trap behavior. This paper demonstrated a correlation between LF small-signal (LF Y21 and Y22) and large-signal voltage steps (DCT) results. These measurements allow identifying the same 0.64 eV deep level, attributed to a native defect of GaN, possibly located in the buffer layer.