Spectroscopy of defects in neutron irradiated ammono-thermal GaN by combining photoionization, photoluminescence and positron annihilation techniques

In this work, pulsed photoionization as well as photoluminescence and positron annihilation spectroscopy were combined to detect different species of defects. The GaN crystals, grown by the ammono-thermal method, doped with Mn as well as Mg impurities and irradiated with different fluences of reactor neutrons, were examined to clarify the role of the technological and radiation defects. The evolution of the prevailing photoactive centres was examined by pulsed photoionization spectroscopy. Positron annihilation spectroscopy was applied to reveal vacancy-type defects.