Luminescence decays following short current pulse excitation of an antireflection coated AlGaAs laser diode have been measured. Using an optical gating technique, decays in the high injection region (

threshold density of uncoated lasers) were measured with a 100 ps time resolution. The observed luminescence decay is shown to be strongly affected by net gain in the active region. It is also shown that both monomolecular and bimolecular carrier recombination must be considered. A model has been developed that takes these effects into account and is shown to accurately describe steady-state and decay spontaneous emission intensities from laser diodes. A procedure is outlined for determining the necessary device and material parameters for interpreting laser diode characteristics.