Fig. 1. (Color online) (a) Schematic of AlGaN/GaN HEMT with different gate dielectric layers. Logarithmic coordinate transformation curve of (b) Sample A, (c) Sample B. (d) Results of other reported works on leakage current.

Fig. 2. (Color online) (a) XPS valence band spectra of GaN and TaN. (b) N 1s core-level spectra of TaN. (c) Band offset between TaN and GaN.

Fig. 3. (Color online) (a) The gate leakage curve of two samples. (b) TaN or Al₂O₃ as gate dielectric layer for MIS HEMT device breakdown voltage curve.

Fig. 4. (Color online) (a) The current collapse effect curve of two samples; (b) chamber environment of medium deposition using magnetron sputtering.

Fig. 5. (Color online) C−V measurement at 1 MHZ frequency of two samples.

Fig. 6. (Color online) (a) The pulse mode I_D−V_GS measurements of Sample A and Sample B are presented. (b) The interface trap charge density Q_it is determined for all samples with ∆E > x (eV).