A 0.1- mu m gate Al/sub 0.5/In/sub 0.5/As/Ga/sub 0.5/In/sub 0.5/As MODFET fabricated on GaAs substrates

Al/sub 0.5/In/sub 0.5/As/Ga/sub 0.5/In/sub 0.5/As MODFET structures have been successfully grown on lattice-mismatched GaAs substrates with a 3.8% difference of lattice constants. MODFETs fabricated with a 0.12- mu m T-shaped gate demonstrate DC and microwave characteristics comparable to those of Al/sub 0.5/In/sub 0.5/As/Ga/sub 0.5/In/sub 0.5/As MODFETs on lattice-matched InP substrates. A peak extrinsic DC transconductance of 585 mS/mm and a full-channel current of 370 mA/mm are achieved at room temperature. Parasitic substrate conduction, which may be the result of the threading dislocations under the FET bonding pads and the active FET channel, affects the device performance. The MODFET shows a high current-gain cutoff frequency of 117 GHz and a maximum available gain cutoff frequency of 125 GHz. The effects of substrate conduction on microwave performance are also investigated.<
>