The surface composition of p‐type GaAsetched in HCl or Br2 in methanol, and n‐type InPetched in HCl, H2SO4, HNO3, or Br2 in methanol has been studied by means of x‐ray photoelectron spectroscopy(XPS). The surface compositions of GaAs and the binding energy of the surface As atoms vary with the etching solution and with the extent of oxidation of the surface. The full width at half‐maximum of the Ga(3p) photoelectron peak increases upon exposure of etchedGaAs to air. The XPS results are compared with Schottky barrier heights previously measured for similarly prepared surfaces with Pb contacts. The amount of oxidized P on InPsurfaces is higher after an HNO3etch than after HCl, H2SO4, or Br2/methanol treatments. An HCl etch leaves an unoxidized slightly In‐rich surface.