Clusters of vacancies in gallium nitride grown by MOCVD

Abstract We investigate the formation and characteristics of vacancy clusters (VCs) in gallium nitride (GaN) grown by metal–organic chemical vapor deposition. The research identifies vacancy-type defects, particularly V_Ga–H_i complexes, using positron annihilation spectroscopy, in as-grown sample which are transformed into VCs 2V_Ga–2V_N during low-energy electron beam irradiation. The study employs photoluminescence and cathodoluminescence spectroscopy to analyze the luminescence properties, demonstrating that yellow band and excitonic near-band-edge emission are greatly enhanced during the VC process. The results indicate that the luminescence spectra of the samples change significantly during electron beam irradiation, highlighting the dynamic behavior of defects in GaN under different conditions. The dominant change affecting the luminescence properties seems to be the elimination of a deep donor acting like a non-radiative centrum. The experimental evidence suggests that this deep donor is V_N. The findings contribute to a deeper understanding of the role of nitrogen vacancy, vacancy complexes and clusters in GaN, which is crucial for optimizing its applications in optoelectronic devices and their processing.