Electrons in donor states of gallium oxide exhibit a paradoxical behavior. On the one hand they exhibit free electron properties such as impurity band conduction and motionally narrowed ESR signals at liquid helium temperature, while on the other hand they are responsible for a blue luminescence characterized by a strong electron-phonon coupling. The time decay and the temperature dependence of the blue luminescence upon specific excitation of the acceptor defects were investigated and a model for the donor V X O and acceptor (V O , V G a )' microstructure is proposed. Donors would be assembled in shallow clusters responsible for delocalized electron behavior with minority acceptors between. The blue luminescence would result from the fast recombination of an exciton trapped at an acceptor site after a rate determining tunnel capture of an electron from a donor cluster.