Inverted GaAs/AlGaAs modulation-doped field-effect transistors with extremely high transconductances

Inverted GaAs/AsGaAs MODFET's with transconductances as high as 1810 mS/mm at 77 K and 1180 mS/mm at 300 K are fabricated using a self-aligned process. The devices have the gate-heterojunction interface spacing of only 100 Å, and the observed values of the transconductance are limited primarily by the source series resistance and by the gate current. The MODFET characteristics are interpreted using the charge control velocity saturation model which takes into account the gate current. The obtained results show a great potential of inverted MODFET's for ultrahigh-speed applications.