Representative Photo C–V Measurement data are shown to illustrate the method. “Dark” and “After UV Exposure” curves are the measured C–V curves. The increase in capacitance during UV Exposure is shown in the adjoining time-axis plot. The “Shifted Dark Curve” is used to extract the interface state density and the trap concentration as shown.
(a) Schematic band diagram of SiN on GaN under depletion bias showing that the UV-generated holes can move out through the dielectric and the gate metal. (b) Band diagram of a dielectric with a positive valence band offset on GaN under depletion bias showing the barrier to the UV generated holes at the interface.
Schematic showing the epi layer structure of the samples used for the photo C–V characterization.
C–V Measurement data for MOCVD Al2O3 with the “Dark” and “After UV Exposure” curves. A large flat interface state ledge is obtained in the measurement after UV exposure. Inset: Band diagram of the structure, after UV illumination under depletion conditions.
Interface state density plots across the GaN bandgap for various dielectrics with a valence band barrier. All of them except for the unannealed Al2O3 exhibit a peak in the Dit curve.
C–V Measurement data for MOCVD Al2O3 with the “Dark” and “After UV Exposure” curves for varying UV exposure times. The interface state ledge increases with the UV exposure time.
Interface State Density (Dit) plot for MOCVD Al2O3 showing the contribution of charges from the interface states and the holes at the interface.
Table indicating the total charge, measured border trap, interface state density, and hole concentration for ALD and MOCVD Al2O3 along with MOCVD SiN on N polar AlGaN(5 nm)/GaN structure.
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