Velocity Enhancement in Cryogenically Cooled InP-Based HEMTs on (411)A-Oriented Substrates.

An extremely high maximum transconductance gm max of 2.25 S/mm and a cutoff frequency ƒT of 310 GHz was achieved at a cryogenic temperature (16 K) in a 195-nm-gate In0.75Ga0.25As/In0.52Al0.48As high electron mobility transistor (HEMT) fabricated on a (411)A-oriented InP substrate by molecular beam epitaxy, compared with room temperature values (fro max = 1.78 S/mm and ƒT = 245 GHz). These significantly enhanced gm max and ƒT values are attributed to a high electron velocity of up to 4.9 × 107 cm/s due to suppressing phonon scattering in the In0.75Ga0.25As/In0.52Al0.48As HEMT with (411)A super-flat InGaAs/InAlAs interfaces (effectively atomically flat heterointerfaces over a wafer-size area). [ABSTRACT FROM AUTHOR]