Vacancy-type defects introduced by plastic deformation of GaN studied using monoenergetic positron beams

Vacancy-type defects in plastically deformed GaN were studied using monoenergetic positron beams. Dislocations with a Burgers vector of (1/3)[1 2 ̄10] were introduced by applying compressive stress at 950 °C. Measurements of Doppler broadening spectra of the annihilation radiation and positron lifetime spectra showed that both microvoids and Ga-vacancy-type defects were introduced into the deformed sample. The former defects are considered to be introduced through an agglomeration of vacancies introduced by dislocation motions. We observed a distribution of the mean positron lifetime along a long side of the deformed sample, which corresponds to the stress distribution during the deformation. In photoluminescence studies, yellow-band luminescence (2.2 eV) decreased due to the deformation. The suppression of this band was attributed to the vacancy-type defects and/or dislocations introduced by the deformation.