Résumé
We report CW and time-resolved optical investigations performed on two different InGaN/GaN multiple quantum well structures grown by MOVPE on sapphire substrates. In both cases, we find at low temperature (5K) strong "blue" luminescence bands, of which energy position does not change very much with temperature and corresponds with the low energy side of the. stimulated emission when exciting the sample with a pulsed nitrogen laser. From the time-resolved PL data, we show that these "blue" bands correspond with very long decay times, which can reach up to 4.5 ns at 8K. When increasing either the energy or the temperature, the decay time decreases and, at room temperature, we get for the lasing wavelength values in the range of 100 ps.