20 NM metamorphic HEMT with 660 GHZ F(T)
A metamorphic HEMT MMIC technology with 20 nm gate length is presented, developed for the fabrication of terahertz-wave monolithic integrated circuits (TMICs) with operational frequencies beyond 500 GHz. The MBE grown transistor heterostructure comprises a strained In0.8Ga0.2As channel with high electron mobility and high electron density for proper device scaling. The realized mHEMTs achieve a source resistance R_S of 0.1 Omega_mm which is required to minimize resistive losses in combination with an extrinsic maximum transconductance gm_max of 2500 mS/mm. The output characteristics of the 20 nm devices show no short channel effects and demonstrate sufficient pinch-off behavior for analog applications. For a transistor with 2 x 10 µm gate width a cut-off frequency fT of 660 GHz was extrapolated which is to our knowledge the highest published fT for any HEMT device. The presented 20 nm mHEMT technology was employed for the design of a compact four stage lownoise amplifier (LNA). The total small signal gain of the LNA exceeds 20 dB from 115 - 175 GHz.