The 1.8 eV luminescence band in GaN grown by molecular beam epitaxy is stud
ied by photo-luminescence (PL) and magnetic resonance. Optically detected m
agnetic resonance (ODMR) shows that deep centres with g = 1.98 and g = 2.01
are involved in the recombination. The results of the PL experiments indic
ate that the 1.8 eV recombination can be further fed by shallow centres lik
e shallow donors or excitons.