IN-SITU TIME-RESOLVED MONITORING OF PH3 INDUCED EXCHANGE-REACTIONS ONGAAS UNDER METALORGANIC VAPOR-PHASE EPITAXY CONDITIONS

Exposure of GaAs and InGaAs to PH3 is a standard step in gas switching sequences for metalorganic vapor phase epitaxy (MOVPE) growth of hete rostructures in the technologically important GaAsP, InGaP, and InGaAs P material systems. The exchange of group-V atoms was monitored in sit u by reflectance anisotropy spectroscopy when GaAs is exposed to PH3. The c(4 X 4) reconstructed, As-terminated GaAs surface is then replace d by a P-terminated structure. At standard MOVPE growth temperatures a nd pressures the time constant for this reaction is of the order of 10 0 ms. The temperature and pressure dependence of the As by P exchange is reported, and the activation energy was determined to be 1.64 eV. I t is concluded that PH3 enhances the desorption of As.