Dynamics of excitons in GaN-AlGaN MQWs with varying depths, thicknesses and barrier widths

Picosecond time-resolved photoluminescence is used to investigate the recom bination dynamics of excitons in samples which ail contain four GaN-AlxGa1- xN quantum wells of respective widths of 4, 8, 12 and 16 molecular monolaye rs, grown by molecular beam epitaxy. The compositions and thicknesses of th e barriers have been varied, in order to change the electric fields induced by piezo- and pyro-electric effects. The dependences of experimental decay times with barrier characteristics indicate the presence of efficient inte r-well carrier escaping. Calculations of electronic tunneling times versus barrier width show that the present carrier escaping is enhanced by some ad ditional process, such as scattering by impurities or composition fluctuati ons in the barriers.