Photo-assisted capacitance-voltage characterization of high-quality atomic-layer-deposited Al2O3∕GaN metal-oxide-semiconductor structures

Abstract
The authors report on an Al 2 O 3 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 ) × 10 12 ∕ cm 2 eV on the as-grown films to 7 × 10 10 ∕ cm 2 eV on the same films after 800 ° 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.