Investigating nonlinear transport effects in GaAs using electro-optic probing

We have studied the potential profile of gateless MESFET devices using electro-optic probing. We have used smooth samples as previous work has shown how rough devices produce excessive noise generated from the Fabry-Perot effect. The profiles measured show non-linear behavior at low fields but high duty cycles. These non-linearities were more noticeable at the edges of the devices and we believe they are associated with device heating which would be prominent at the edges due to `edge effect'. To remove this effect we have used very low duty cycles and the resulting potential profiles are as expected. Using low duty cycles and applying high electric fields allows us to study non-linear transport behavior in these devices. The samples were designed to exhibit non-linear behavior due to the Gunn Effect. At high applied electric fields the current saturates and becomes noisy, indicative of non-linear behavior. We show the first reported device field profiles under these conditions measured using electro-optic probing. The observed non-linear behavior can be explained in terms of the Gunn Effect.