Observation of long photoluminescence decay times for high-quality GaN grown by metalorganic chemical vapor deposition

GaN epitaxial layers with different crystalline quality grown on sapphire s ubstrates by metalorganic chemical vapor deposition are investigated using time-resolved photoluminescence at 300 K. It is found that the time-depende nt photoluminescence of low-quality GaN decays faster than that of the high -quality GaN films. The time constants for the dual-exponential decay of th e photoluminescence are calculated to be 50 and 250 ps for high-quality und oped GaN and 30 ps for low-quality undoped GaN. For high-quality Si-doped G aN, time constants of 150 and 740 ps are extracted while corresponding time constants of 40 and 200 ps are measured for low-quality Si-doped GaN. We b elieve that the time constant of 740 ps measured for our high-quality Si-do ped GaN is the longest ever reported for thin GaN/sapphire films. (C) 2000 American Institute of Physics. [S0003- 6951(00)01942-2].