A GAAS FLOATED ELECTRON CHANNEL FIELD-EFFECT TRANSISTOR (FECFET) FABRICATED BY SELECTIVE METAL ORGANIC-CHEMICAL VAPOR-DEPOSITION

We have proposed and fabricated a new GaAs FET with very short channel, which we call Floated Electron Channel Field Effect Transistor (FECFET), using the Selective Metal Organic Chemical Vapor Deposition (SMOCVD) technique. The channel length of the proposed device is reduced by placing the channel layer on the top of the triangular void. The formation of the triangular void is well characterized by both the growth parameters of the SMOCVD and the mask orientation. The maximum extrinsic transconductance of 260 mS/mm is obtained for the gate length larger than 2-mu-m and the measured source resistance is 0.25-OMEGA.mm. It is also observed that the measured transconductance is almost independent of the gate length when the fabricated gate has a length between 2.0-mu-m and 4.0-mu-m. The effective channel length is mainly determined by the short distance between two n+ layers for source and drain rather than the gate length. This device structure is suitable for low noise FET and for the simple realization of direct coupled FET logic inverter.