Time-resolved photoluminescence (PL) spectroscopy was used to study the rad
iative recombination of free and donor-bound excitons in unintentionally do
ped GaN grown by hydride vapor phase epitaxy. Low temperature (4 K), time-i
ntegrated PL spectra identified the free exciton (A), the donor-bound excit
on peak similar to 6 meV below, and the acceptor-bound exciton similar to 2
0 meV below the free exciton peak. A radiative recombination lifetime of 29
5 ps for the free exciton and 530 ps for donor-bound exciton were found at
4 K. The decay of the free exciton remained single exponential to room temp
erature, with an increase in lifetime to 530 ps, consistent with the therma
l excitation of exciton states. (C) 1999 American Institute of Physics. [S0
003-6951(99)04032-2].