Interpretation of low-energy Auger spectra from AlAs and GaAs(001): Applications to surface preparation

The relative positions of the low-energy Auger transitions for the III-V elements Ga, Al, In, As, P, and Sb have been estimated to enable selection of III-V compounds suitable for studies of CVV transitions. The surface-sensitive Auger spectra of GaAs and AlAs have been investigated in detail with emphasis on the CVV-type transitions. It is shown that a single-particle theory, using a bulk band structure, is sufficient to analyze the topmost (most intense) part of CVV transitions from the investigated group-III and -V elements. The As $M_{45}$VV peak line shape has been studied for different surface phases. Experimentally, it was found that the line shape of the peak is sensitive to the chemical surrounding of the As atom. Hence by studying an As-rich GaAs(001) surface (grown by molecular-beam epitaxy) during desorption, the As $M_{45}$VV line shape was found to change from mainly As to GaAs character as the polar surface changed phase. The As $M_{45}$VV line shape was found to be different for GaAs and AlAs, a fact that has been used to detect AlAs formation during Al adsorption on GaAs. Furthermore, the accuracy of the observable part of the As $M_{45}$VV peak as a measure of the As concentration is discussed. Upon comparison of the Ga $M_{23}$ $M_{45}$ $M_{45}$ peaks from metallic Ga and GaAs, it was seen that the intensity ratio between the $M_2$ $M_{45}$ $M_{45}$ and $M_3$ $M_{45}$ $M_{45}$ lines deviates from the expected value based on the statistical occupation of the $M_2$ and $M_3$ levels.