Optical quenching of the photoconductivity in n-type GaN

Results of optical quenching of photoconductivity measurements in undoped n-type and Se-doped GaN epitaxial thin films are presented. The spectral distribution of quenching phenomena shows a broadband centered around 1.26 eV. Transient changes in photoconductivity on application or removal of the quenching radiation are shown to exhibit a metastable behavior. The results reveal that the origin of the optical quenching phenomena is closely related to the defects corresponding to the persistent photoconductivity effects and the yellow luminescence band observed in most n-type GaN. In addition, this result indicates that these defects can have multiple charge states. It is found that the quenching ratio increases with increasing Se-doping concentration. We point out that the origin of the defects responsible for the optical quenching can be attributed to nitrogen antisite and/or Ga vacancy.