Interfacial gate resistance in Schottky-barrier-gate field-effect transistors

We discuss in depth a previously overlooked component in the gate resistance R/sub g/ of Schottky-Barrier-Gate FETs, in particular, 0.1-/spl mu/m gate-length AlInAs/GaInAs MODFETs. The high-frequency noise and power gain of these FETs depend critically on R/sub g/. This has been the motivation for the development of T-gates that keep the gate finger metallization resistance R/sub ga/ (proportional to the gate width W/sub g/) low, even for very short gate length L/sub g/. R/sub ga/ increases with frequency due to the skin effect, but our three-dimensional (3-D) numerical modeling shows conclusively that this effect is negligible. We show that the always "larger-than-expected" R/sub g/ is instead caused by a component R/sub gi/ that scales inversely with W/sub g/. We interpret R/sub gi/ as a metal-semiconductor interfacial gate resistance. The dominance of R/sub gi/ profoundly affects device optimization and model scaling. For GaAs and InP-based SBGFETs, there appears to exist a smallest practically achievable normalized interfacial gate resistance r/sub gi/ on the order of 10/sup -7/ /spl Omega/ cm/sup 2/.