The noaradiative lifetime and spontaneous emission quantum efficiency in molecular-beam epitaxy grown bulk GaAs is determined using injection level dependent photoluminescence (PL) measurements. These measurements were performed at temperatures of 300, 230, 100, and 50 K using a HeNe pump laser with powers ranging from 0.3 to 40 mW. The quantum efficiency and lifetime is inferred from the power law relation linking pump power and integrated PL signal that is predicted by the rate equations. The nonradiative lifetime for bulk GaAs is determined to be 0.3 us, with an additional temperature dependent component attributed to the AlGaAs barriers that rapidly reduces the nonradiative lifetime at temperatures above 230 K. The peak quantum efficiency is > 0.96 at 300 K and > 0.99 at temperatures below 230 K. (c) 2007 American Vacuum Society.