Sulfur passivation of GaAs metal-semiconductor field-effect transistor

A passivation technique consisting of a (NH4)(2)S dip followed by GaS deposition has been applied to a GaAs microwave-power metal-semiconductor field-effect transistor (MESFET). The breakdown characteristic of the MESFET is greatly improved upon the (NH4)(2)S treatment, and a stable passivation effect can be achieved by GaS film deposition. It is found that the FET current-voltage characteristics are closely related to variations in the pinning position of the GaAs surface Fermi level. With the surface passivated, a depletion layer can be properly formed and protected, which is of benefit to the control of the device parameters. (C) 2000 American Institute of Physics. [S0003-6951(00)04150-4].