Characterization of oxide layers on GaAs substrates

Oxide layers on undoped GaAs substrates have been assessed by grazing incid ence X-ray reflectivity (GIXR), spectroscopic ellipsometry (SE), surface ph otoabsorption (SPA) and atomic force microscopy (AFM). In addition to provi ding 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 estima ted oxide layer thickness of between 23-30 Angstrom and exhibit a surface r oughness of 2-3 Angstrom. Furthermore, a significant change in the oxide ch emical species through the film is indicated. An activation energy for deso rption of Ga2O3 of 2.0 eV is calculated, whilst partial deoxidation of acid -polished GaAs suggests oxide removal proceeds as island shrinkage of succe ssive oxide layers. (C) 2000 Elsevier Science S.A. All rights reserved.