A comparison of S-passivation of III-V (001) surfaces using (NH4)2Sx and S2Cl2

Soft X-ray photoelectron spectroscopy has been applied to compare the effect of two S-passivating etchants (S2Cl2 and (NH4)(2)S-x) on the (001) surfaces of GaAs and InP. Detailed analysis of substrate and adsorbate core level emission peaks reveal the similar nature of S-III-V bonding in each case. Prior to in-situ annealing, the semiconductor surface is covered by an amorphous layer, and above around 400 degrees 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 S-Ga(In) bonding. The S 2p core level spectra contain two components related to the surface and sub-surface S atoms. As-S bonding on the annealed GaAs-S surface is not present above 400 degrees C. (C) 1998 Elsevier Science B.V.