Real time monitoring of PH/sub 3/ and AsH/sub 3/ induced exchange reactions on GaAs, InGaAs and InP during MOVPE

In this work we applied the optical reflectance anisotropy spectroscopy (RAS or RDS) technique to probe the change of surface structure which occurs during a MOVPE gas switching sequence. The exchange of group-V atoms was monitored in situ by RAS when GaAs, InGaAs and were exposed to PH/sub 3/ and InP to AsH/sub 3/. The resulting structure is compared with RAS spectra from reconstructed InP, InAs, GaAs and GaP surfaces. It is concluded that the c(4/spl times/4) reconstructed, As-terminated GaAs, as well as the As-terminated InGaAs surface, is replaced by a P-terminated (2/spl times/3)-like structure. For InP the (2/spl times/4)-like RAS spectra is replaced by a structure similar to that of (1/spl times/3) reconstructed InAs. At standard MOVPE growth temperatures and pressures the time constant for As by P exchange is of the order of 100 ms. The temperature and pressure dependence of this reaction is reported, and the activation energy was determined to be 1.64 eV on GaAs. It is concluded that PH/sub 3/ enhances the desorption of As from GaAs. The influence of the exchange process on interface properties of heterostructures is discussed.<
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