DYNAMICS OF BOUND-EXCITON LUMINESCENCES FROM EPITAXIAL GAN

Free- and bound-exciton luminescences of GaN epitaxial layers grown by a sublimation technique on 6H-SiC substrates were investigated using time-integrated and time-resolved photoluminescence measurements at lo w temperatures. Lifetimes were determined for the donor-bound exciton at 3.4722 eV and for two acceptor-bound excitons with energies of 3.46 72 eV and 3.459 eV. On the basis of our results we obtain an upper Lim it of the free-exciton oscillator strength of 0.0046 for GaN. Luminesc ences between 3.29 eV and 3.37 eV are identified as due to excitons de eply bound to centers located near the substrate-epilayer interface. F ree excitons are captured by these centers within 20 ps. (C) 1996 Amer ican Institute of Physics.