Transient photoluminescence data with picosecond resolution is reported for homoepitaxial GaN layers grown with MOCVD. In the present: samples, with doping concentration in the 10(17) cm(-3) range, the free exciton (FE) decay time is less than 100 ps at 2 K, mainly due to capture to the shallow impurities. The donor bound exciton (DBE) decay time is also short, < 140 ps, influenced by excitation transfer to nonradiative defects. The shallow acceptor (probably Mg-related) bound exciton (ABE) has a well defined radiative decay time of about 800 ps.