Published online by Cambridge University Press: 21 February 2011
We apply the reflectance microwave probe (RMP) method to characterize the surface condition of the sulfur-treated GaAs. Undoped semi-insulating GaAs wafers are dipped in (NH4)2S or (NH4)2Sx [1<x≦3] after an etching. The intensity of the reflected microwave under He-Ne laser (λ=633nm) irradiation is proportional to the excess carrier density, which strongly depends on the surface condition. The (NH4)2Sx treatment increases the RMP signal intensity, while no significant change in the signal intensity is observed after the (NH4)2S treatment. The signal intensity of the (NH4)2Sx-treated samples is decreased by the annealingyhe results observed in this study are consistent with those previously found with other measurement methods. This method will be able to in-situ evaluate the surface condition of GaAs during the device fabrication process.