A new valved source for evaporation of Ga or In has been demonstrated. Its performance in terms of controlling the group III flux has been shown to be very good to excellent in terms of response time (2-3 s), reproducibility (similar to 1%), stability (similar to 0.1%), and shut-off ratio (at least 30:1). In addition, this cell has produced GaAs, InGaAs, and InAlAs layers with material quality comparable to other state-of-the-ari sources in terms of uniformity, surface morphology, background doping, carrier mobility, and p-i-n device performance. Finally, it has been demonstrated that the graphite-based material used for the crucible and valve in this source does not generate any extra carbon doping compared to the usual pyrolytic boron nitride-based crucibles. (c) 2007 American Vacuum Society.