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Ga 3d (a) and Al 2p (b) core-level photoemission spectra with curve-fitting results for Al2O3 films on GaN layers. Annealing-temperature dependence of the core-level spectra in Al2O3 films and the referenced spectra for bare GaN layers are also shown.
Valence-band spectra of Al2O3 films on GaN layers normalized by that of a bare GaN layer. The valence band densities of states derived from the Al2O3 film are obtained by subtracting valence-band spectra of the GaN layers from those of the Al2O3 films. The intensity of valence-band spectrum of GaN has been rescaled before it is subtracted from that of the films.
O K-edge XAS spectra of Al2O3 films on GaN layers. First derivative XAS spectra are also shown. Vertical bars indicate absorption edges determined by the maxima of first derivative XAS spectra.
Cross-sectional TEM images of as-grown (a) and annealed at 800 °C (b) samples for Al2O3 films on GaN layers. (c) Out of plane x-ray diffraction patterns for as-grown, annealed at 700 and 800 °C samples. (d) Rocking curves measured at Al2O3 and GaN(002) conditions for the Al2O3 film annealed at 800 °C.
Summary for the values of ΔE v, ΔE c, and E g in Al2O3 gate insulator films, depending on annealing temperature.
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