Fabrication and Performance of 0.25-$\mu$m Gate Length Depletion-Mode GaAs-Channel MOSFETs With Self-Aligned InAlP Native Oxide Gate Dielectric

The fabrication and performance of 0.25- mum gate length GaAs-channel MOSFETs using the wet thermal native oxide of InAlP as the gate dielectric are reported. A fabrication process that self-aligns the gate oxidation to the gate recess and metallization to reduce the source access resistance is demonstrated for the first time. The fabricated devices exhibit a peak extrinsic transconductance of 144 mS/mm, an on-resistance of 3.46 Omega-mm, and a threshold voltage of -1.8 V for typical 0.25 -mum gate devices. A record cutoff frequency of 31 GHz for a GaAs-channel MOSFET and a maximum frequency of oscillation f
_max
of 47 GHz have also been measured.