Abstract :
Soft X-ray photoelectron spectroscopy has been applied to compare the effect of two S-passivating etchants (S2Cl2 and (NH4)2Sx) on the (001) surfaces of GaAs and InP. Detailed analysis of substrate and adsorbate core level emission peaks reveal the similar nature of Ssingle bondIIIsingle bondV bonding in each case. Prior to in-situ annealing, the semiconductor surface is covered by an amorphous layer, and above around 400°C, a stable S-terminated surface is obtained in each case. Variations in the relative intensities of spectral features are more sensitive to process and temperature differences than to the etchants used. For S-terminated GaAs and InP surfaces, a high binding energy component is observed in the substrate Ga 3d and In 4d core level emission spectra corresponding to surface Ssingle bondGa(In) bonding. The S 2p core level spectra contain two components related to the surface and sub-surface S atoms. Assingle bondS bonding on the annealed GaAssingle bondS surface is not present above 400°C.
