Carbon 1s Core Level Shifts After Annealing the (100) Surfaces of InGaAsP, InP, and GaAs

The binding energy of the 1s core level of the surface contaminant carbon on InGaAsP, InP and GaAs decreases 0.7 eV upon heating in vacuum to temperatures of 560 to 635C. There is no significant decrease in the magnitude of the C1s signal as the temperature is increased, and the binding energies of other elements indicate that the decrease in the C1s level is not a result of surface charging. The core level change is accompanied by a loss of surface oxygen upon heating, and exposure to 3 x 10 sup t L oxygen re-establishes the original C1s binding energy with the concommitant increase in surface oxygen. The ion gauge is left on during the oxygen exposure, since it was found to accelerate the oxygen uptake after heating. The results suggest that the carbon observed on these surfaces is strongly chemisorbed, and consequently the C1s core level is affected by the electronic/chemical environment of the compound semiconductor surface.