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The authors report on an Al2O3 gate oxide deposited on n-type GaN by atomic layer deposition technique. The high-frequency C-V characteristic shows deep-depletion behavior at room temperature due to the wide band gap semiconductor nature of GaN. Systematic photoassisted C-V measurements demonstrate the importance of postdeposition-annealing process which could improve the average interface trap density D-it of (1-2)x10(12)/cm(2) eV on the as-grown films to 7x10(10)/cm(2) eV on the same films after 800 degrees C rapid thermal annealing in a N-2 ambient. The high-frequency C-V technique or Terman technique is also applied to estimate the mid-gap D-it and compare to the results from photoassisted C-V technique.

Current-voltage characteristics have been measured for an ultrathin atomic-layer-deposited Al2O3 on GaAs as a function of film thickness, ambient temperature, and electric field. Current transport measurements indicate direct tunneling for 12-25 A ultrathin films and typical Frenkel-Poole emission for 50-60 A thick films. The maximum dielectric strength, which is of considerable importance for metal-oxide-semiconductor device applications, is studied thoroughly in this letter. The square root of the maximum dielectric strength is found to be roughly reversely proportional to the temperature from 500 to 300 K, and becomes constant below 200 K. The enhancement in the dielectric field strength observed from 300 to 200 K for the ultrathin insulating films can be adequately described using classical models.

Atomic layer deposition