  Absence of an efficient technology of GaAs passivation limits the use of
III-V semiconductors in modern electronics. The effect reported here can
possibly lead to a solution of this long standing problem. We found that an
electrically conducting interfacial channel is formed when insulating metal
oxide dielectrics are deposited on untreated semi-insulating GaAs wafers by
reactive RF sputtering in argon/oxygen plasma. The conducting channel is n-type
with the surface charge density of 10^7 to 10^10 cm^-2 and Hall mobility as
high as 6000 cm^2/Vsec, depending on the RF plasma excitation power and oxygen
content during the deposition. The conducting channel is formed by depositing
any of the tested metal oxide dielectrics: MgO, SiO2, Al2O3 and HfO2.
