An approach to thin film oxide detection in GaAs substrate using Goos-Hanchen shift

Abstract

Commercial GaAs substrates form a thin layer of As₂O₃ when exposed to room conditions. The formation of As₂O₃ can introduce undesired experimental deviations in optical experiments, as well as in the deposition of thin films involving GaAs substrates. In this paper we perform a calculation to compare the resulting magnitude of the Goos-Hanchen (GH) shift of light striking an air/GaAs interface, as well as  air/As₂O₃/GaAs interface. The parameters consist of a monochromatic laser with 589.3 nm wavelength, while using a 500 mm and 200 mm lens separately, to vary the beam waist. Results indicate lower GH shifts for air/As₂O₃/GaAs interface, compared to the GH shifts resulting from air/GaAs interface. The difference in the GH magnitudes is calculated to be in the range of 6% to 6.5%, resulting in a GH measurement difference of 11 x 10^-5 m to 31 x 10^-5 m which is within the bounds of GH shift measurement resolution.