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(a) Typical transfer curves Ids (Igs ) vs Vgs curve for the HEMT and the MIS-HEMT gate architectures. (b) Three terminals gate-source leakage current (for different temperatures) during the off-state reverse bias. (c) Two terminal gate-bulk reverse current showing severe degradation for T > 160 °C. (d) Poole-Frenkel plot of the gate-bulk reverse current at varying T. (e) Arrhenius plot for the reverse gate current at Vds = −150 V with an activation energy of Ea = 0.4 eV.
(a) SEM image of the HEMT device. The FIB partial etch shows the depth of the GaN buffer (GaN). (b) 3D topographic image of the HEMT surface. (c) Topography and (d) current map of HEMT’ gate surface taken with the CAFM for the 10 × 10 μm2 scan.
Conductive AFM scans of the HEMT surface in the drain-gate spacing with (a) topography and (b) current map of surface taken with the CAFM for the 2.8 × 2.8 μm2 scan; (c) Respective cross-sectional profiles along the solid lines marked in (a) and (b) biased at −2 V (top) and −10 V (bottom).
CAFM (a) topographic and (b) current map (Vtip = −10 V) showing the scan lines for the investigation of the correlation depressions vs leakage spots. (c) Cross-sectional TEM image of the MBE GaN grown on AlN. (d) Detailed scan through L7 showing the relative peaks (Δ1, Δ2, and Δ3). (e) Detailed scan through line L10 where four high current spots are found (e1-e4).
Conductive AFM scans of the MIS-HEMT surface in the drain-gate spacing with (a) topography and (b) current map of surface taken with the CAFM for the 2.8 × 2.8 μm2 scan; (c) Respective cross-sectional profiles along the solid lines marked at −2 V.
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