The n-channel depletion-mode GaAs MOSFETs with a selective liquid phase chemical-enhanced oxidation method at low temperature by using metal as the mask (M-SLPCEO) are demonstrated. The proposed process can simplify one mask to fabricate GaAs MOSFET and grow reliable gate oxide films as well as side-wall passivation layers at the same time. The 1 μm gate-length MOSFET with a gate oxide thickness of 35 nm shows the transconductance of 90 mS/mm and the maximum drain current density larger than 350 mA/mm. In addition, a short-circuit current gain cutoff frequency fT of 6.5 GHz and a maximum oscillation frequency fmax of 18.3 GHz have been achieved from the 1μm × 100 μm GaAs MOSFET.
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