In situ time‐resolved monitoring of PH3 induced exchange reactions on GaAs 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 heterostructures in the technologically important GaAsP, InGaP, and InGaAsP material systems. The exchange of group‐V atoms was monitored in situ by reflectance anisotropy spectroscopy when GaAs is exposed to PH3. The c(4×4) reconstructed, As‐terminated GaAs surface is then replaced by a P‐terminated structure. At standard MOVPE growth temperatures and pressures the time constant for this reaction is of the order of 100 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. It is concluded that PH3 enhances the desorption of As.