Trap investigation under class AB operation in AlGaN/GaN HEMTs based on output-admittance frequency dispersion, pulsed and transient measurements

This paper presents a detailed trap investigation based on combined pulsed I/V measurements, Drain Current Transient (DCT) measurements and Low Frequency output-admittance (LF Y₂₂) dispersion measurements. DCT characterization is carried out over a 7-decade time scale. LF Y₂₂ measurements are carried out over the frequency range from 10 Hz to 10 MHz. These combined measurements were performed for AlGaN/GaN HEMTs under class AB operation and allowed the extraction of the activation energy Ea and the capture cross section σ_a of the identified traps. Low-frequency small-signal, (LF Y₂₂) and large-signal voltage steps (DCT) results for trap characterization were found to be correlated. They allow identifying the same 0.64 eV deep level, attributed to a native defect of GaN, possibly located in the buffer layer.