We studied the performance of a new type of valved cracking cell which contains a separate condensing reservoir and is intended for molecular beam epitaxy of phosphide compounds. The cell was designed to operate with a white phosphorus source, derivedinsituby sublimation and subsequent condensation of red phosphorus vapor. The parameters investigated were stability of the beam flux, switching transients, and growth chamber recovery time. The data show that a properly constructed valved cell, which incorporates a valve where shut‐off and metering are independently controllable, provides for a rapidly switched, stable beam flux with a minimum chamber recovery time. Aninsitugenerated white phosphorus source was found to reduce the P4burst accompanying the use of a red phosphorus source by over 300%.