Characterization of oxide layers on GaAs substrates

Oxide layers on undoped GaAs substrates have been assessed by grazing incidence X-ray reflectivity (GIXR), spectroscopic ellipsometry (SE), surface photoabsorption (SPA) and atomic force microscopy (AFM). In addition to providing a comparison between different measurement techniques, these new data improve the understanding of the structure and thermal desorption of oxides typical to GaAs substrates. Epi-ready GaAs wafers typically have an estimated oxide layer thickness of between 23-30 angstroms and exhibit a surface roughness of 2-3 angstroms. Furthermore, a significant change in the oxide chemical species through the film is indicated. An activation energy for desorption of Ga sub(2)O sub(3) of 2.0 eV is calculated, whilst partial deoxidation of acid-polished GaAs suggests oxide removal proceeds as island shrinkage of successive oxide layers.