GaAs/AlGaAs atomic layer epitaxy in a commercial MOCVD reactor

Issues facing large area growth of GaAs by atomic layer epitaxy (ALE) are discussed. We have used a movable X-shaped mechanical barrier to divide the growth chamber into four zones. Alternate zones either supply source gas or mask the wafer from exposure to source gases. The substrate rotating beneath the barrier is alternately exposed to Group III and Group V sources. The thickness uniformity is affected by both the spatial variation of the TMG flux and the range of TMG flux in which self-limited growth is valid. Carbon incorporation can be reduced by using TBA and increasing TBA or AsH3 exposure time. GaAs epitaxial layers with hole concentration lower than 10(17) cm-3 and thickness uniformity less than 2% over a 50 mm diameter wafer grown at 580-degrees-C have been obtained. Preliminary 300 K photoluminescence measurement of ALE Al0.34Ga0.66As grown at 560-degrees-C has shown strong emission intensity which compares with no emission from MOCVD AlGaAs grown at 560-degrees-C.