Role of Vacancy Defects in Reducing the Responsivity of AlGaN Schottky Barrier Ultraviolet Detectors.

Abstract

The spectral response properties of AlGaN Schottky barrier detectors with different Al content were investigated. It was found that the responsivity of AlGaN detectors decreases with increase in Al content in AlGaN. It was found that neither dislocation density nor the concentration of carbon and oxygen impurities made any remarkable difference in these AlGaN devices. However, the positron annihilation experiments showed that the concentration of Al or Ga vacancy defects (more likely Ga vacancy defects) in AlGaN active layers increased with the increase in Al content. It is assumed that the Al or Ga vacancy defects play a negative role in a detector’s performance, which increases the recombination of photogenerated carriers and reduces the detector responsivity. It is necessary to control the concentration of vacancy defects for the high performance AlGaN detectors.