HP Labs Technical Reports

Interfacial Gate Resistance in Schottky-Barrier-Gate Field-Effect Transistors

Rohdin, Hans; Moll, Nick; Su, Chung-yi; Lee, Gregg

HPL-98-93

Keyword(s): gate resistance; MODFET; MESFET; skin effect

Abstract: We discuss in depth a previously overlooked component in the gate resistance R(sub g) of Schottky-Barrier- Gate FETs, in particular 0.1-um gate-length AlInAs/GaInAs MODFETs. The high-frequency noise and power gain of these FETs depends critically on R (sub g). This has been the motivation for the development of T-gates which 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 3D 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) which 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 (power -7) (Omega)cm(power 2). Notes: Su is from the Communications Semiconductor Solutions Division, HP Santa Clara, CA

23 Pages

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