SAW diagnostics of GaAs surface structure

Surface acoustic waves (SAW) are very sensitive to the properties of crysta l surfaces, so they find an application in crystal surface diagnostics. In this work GaAs (1 1 1) semi-insulating samples had SAW transducers formed a s Al thin-film interdigital structures that operated at a central frequency of 65 MHz. SAW parameters (amplitude and phase variations of the SAW outpu t signals) were measured during irradiation of the GaAs surface from a ligh t source. The results indicate that SAW propagation is sensitive not only t o the state of the natural oxide layers covering the GaAs surface, includin g oxide composition, surface morphology etc., but also to the crystalline s tate of the GaAs surface itself, particularly to the presence of stress def ormations within the GaAs. These deformations are most likely due to a modi fication of the oxide layer that changes the SAW maximum velocity direction , as indicated by changes in the SAW phase velocity. (C) 1999 Elsevier Scie nce B.V. All rights reserved.