Cryogenic operation of pseudomorphic AlGaAs/InGaAs single-quantum-well MODFETs

We have investigated the 77 K operation of AlGaAs/InGaAs MODFETs. The structures, grown by MBE, make use of a 200 Å undoped In0.15Ga0.85As quantum well for electron confinement and an Si-doped Al0.15Ga0.85As top barrier. The MODFETs with 1 μm gate lengths exhibit extrinsic transconductances of 360 mS/mm and maximum currents of 310 mA/mm at 77 K. The use of a low Al mole fraction AlGaAs/InGaAs heterojunction allows us to avoid the persistent trapping effects encountered in AlGaAs/GaAs MODFETs without sacrificing device performance.