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

The 77 K operation of AlGaAs/InGaAs MODFETs has been investigated. The structures, grown by MBE, make use of a 200 A undoped In(0.15)Ga(0.85)As quantum well for electron confinement and an Si-doped Al(0.15)Ga(0.85)As top barrier. The MODFETs with 1 micron 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 makes it possible to avoid the persistent trapping effects encountered in AlGaAs/GaAs MODFETs without sacrificing device performance.