High-performance of 70 nm T-Gate InGaAs/InAlAs metamorphic HEMTs on GaAs substrates

We present a technology to fabricate 70-nm-gate-length In GaAs/InAlAs/GaAs metamorphic high electron mobility transistors (MHEMTs). This technology uses a ZEP520/P(MMA-MAA)/PMMA tri-layer and double exposure with 50-kV electron-beam lithography. The fabricated 70-nm MHEMTs with a 70-mum unit gate width and two fingers were characterized through DC, BF, and noise measurements. The maximum drain current density and extrinsic transconductance (g(m)) are 400 mA/mm and 1.02 S/mm, respectively. From the RF measurements, we obtained a current gain cutoff frequency (f(t)) of 320 GHz and a maximum oscillation frequency (f(max)) of 430 GHz. The noise figure was less than 1.5 dB across the measured frequency range of 56 to 60 GHz.