Fabrication of spin-current field-effect transistor structures

It has been theoretically proposed that a narrow gap semiconductor field-effect transistor with ferromagnetic contacts for injection of spin-polarized electrons may be used for current modulation. This raises the possibility of electronic devices based on transport of spin-up and spin-down electrons biased and controlled by internal magnetic fields. As an initial step in this direction, we have fabricated GaAs/AlGaAs and InGaAs/AlInAs high electron mobility transistor structures, where the normal AuGeNi source and drain contacts are replaced by sputter-deposited Fe contacts. Mesa fabrication to allow the Fe to contact the two-dimensional electron gas formed at the interface between the doped AlGaAs or AlInAs and the lower bandgap (GaAs or InGaAs) undoped channel was achieved by either wet chemical etching or angled Ar+ ion milling. TiPtAu (I mu m gate width) was employed in both materials systems as a gate contact. The Fe is found to form a rectifying contact to the GaAs channel devices, preventing current injection, but produces a nearly ohmic contact to InGaAs. Improved, bilayer magnetic contacts are currently under investigation for the InGaAs/AlInAs high electron mobility transistor structures in order to produce complete ohmic behavior and establish the feasibility of polarized current injection in these devices. (C) 1997 American Vacuum Society.