Fabrication of depletion-mode GaAs MOSFET with a selective oxidation process by using metal as the mask

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 a transconductance of 90 mS/mm and a maximum drain current density larger than 350 mA/mm. In addition, a short-circuit current gain cutoff frequency f_T of 6.5 GHz and a maximum oscillation frequency f_max of 18.3 GHz have been achieved from the 1 μm×100 μm GaAs MOSFET.