A high dielectric interface quality is the determining factor for high power GaN metal oxide semiconductor field‐ effect transistor (MOSFET) devices. We characterized 100 Å thick aluminum oxide (Al2O3) films deposited by ALD on MOCVD grown undoped GaN on sapphire. First we measured the leakage current and densification behaviour of the dielectric after annealing at different temperatures up to 900 °C and determined the polycrystalline phase change to be around 800 °C. Further we characterized the interface charges of both films according to the flatband shift, induced by over‐band gap UV light, showing the lowest interface charge density of 1.27 × 1011 cm–2 after thermal treatment at 850 °C. Additionally, we measured the AC conductivity and calculated the interface states density (Dit) of the upper half of the GaN bandgap, showing the lowest Dit of around 2×1010 cm–2 eV–1 at 2 eV above the valence band, while it remains higher around the band edge at 2.8×1011 cm–2 eV–1, after annealing at 750 °C. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

PACS : 73.40.Kp; 73.61.Ey; 81.15.Gh Crack-free Al x Ga 1--x N films with an Al mole fraction of up to 37% were successfuly grown on a sapphire substrate by introducing a 10 nm-thick low-temperature (LT) Al x Ga 1--x N interlayer. Three AlGaN layer structures were tested for application to solar-blind UV photodetectors. Among them, Schottky diodes with a Pt/0.5 mm thick Al 0.33 Ga 0.67 N/10 nm thick LT-Al 0.33 Ga 0.67 N interlayer/ 2 mm thick n + -GaN layer exhibited the best behavior with a reverse leakage current of 9 nA at À5 V, UV-visible extinction ratio of $10 4 , and responsivity of 0.15 A/W at 280 nm.

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