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