ABSTRACT
GaAs MESFETs have been successfully fabricated with undoped GaAs layers up to 2000Å thick on the n-GaAs channels. Gate contacts are put on the channels, by boring through the undoped layers. It was found that the undoped layer eliminates a surface depletion layer for the channel, as well as suppresses channel reduction due to the GaAs surface trapping effect, even under high-voltage operations. Consequently, the undoped layer acts as an ideal passivation layer for the channel. The fabricated FET with 1000Å thick undoped GaAs layer and 0.69μ.m long and 16.128mm wide gate contact has shown 2dB gain compression output power as high as 39.6dBm(9.1W) at 12.575GHz. This FET has great potentials for use in extra high output power devices.
