Optical spectroscopy under varying temperature is used to investigate samples containing planes of self-assembled Ga1-xInxN quantum dots (0.15 < x < 0.20), embedded in a GaN matrix. The samples have been grown by molecular beam epitaxy on sapphire substrates and the nano-islands have been obtained by the Stranski-Krastanov growth mode transition. Half-widths at half maximum as small as 0.05 eV are obtained for photoluminescence (PL) lines at T = 2 K. Increasing the growth time decreases the PL energy and drastically increases the PL decay time, as a result of the increasing of the average dot height. Time-resolved PL measurements with variable temperature allow us to observe the competitive influence of several mechanisms, namely the usual radiative and nonradiative recombination processes, plus the carrier feeding from random fluctuations, which plays a crucial role in the case of the larger dots. (C) 2001 Elsevier Science B.V. All rights reserved.