CONTRASTS IN THE REACTIONS OF SULFUR FROM DIFFERENT SOURCES WITH GAAS-SURFACES

We have studied S2 and H2S adsorption on the GaAs (100) surface using low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and thermal desorption spectroscopy (TDS). We find that sulfur adsorption onto this surface proceeds to a much greater extent in the case of S2, involving amounts corresponding to several monolayers. A corrosion reaction probably occurs leading to the desorption of both disulfides and monosulfides of Ga and As. H2S adsorption is initially rapid, but sulfur uptake proceeds to an extent of only 1/5 the amount of S2. While GaH and AsH3 desorb at 100-degrees-C, only the monosulfides desorb on heating from a surface saturated with H2S. The loss of the hydrides plays a role in removing defects from the surface, and may contribute to the lowering of the Schottky barrier height seen by others.