a UNIPRESS, High Pressure Research Center, Polish Academy of Sciences, ul. Sokolowska 29, 01-142 Warsaw, Poland
b Laboratory of Physics, Helsinki University of Technology, FIN-02150 Espoo, Finland
Abstract:
Highly resistive GaN : Be was obtained by means of synthesis of Ga+Be with atomic nitrogen under high nitrogen pressure. Activation energy of resistivity is about 1.5 eV. This material exhibits features very different from those observed in highly resistive bulk GaN : Mg. Up to 300 K strong yellow band dominates photoluminescence spectrum in resistive GaN : Be crystals. Positron annihilation studies point to the presence of gallium vacancies, VGa. In highly resistive GaN:Mg neither yellow band with considerable intensity, nor detectable concentration of VGa was found. We also discuss the puzzling findings in highly resistive bulk GaN : Be of morphological features typical for highly conducting bulk n-GaN material.