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

Abstract

gate resistance, MODFET, MESFET, skin effectWe discuss in depth a previously overlooked component in the gate resistance Rg of SchottkyBarrier-Gate FETs, in particular 0.1-µm gate-length AlInAs/GaInAs MODFETs. The high-frequency noise and power gain of these FETs depends critically on Rg. This has been the motivation for the development of T-gates which keep the gate finger metallization resistance Rga (proportional to the gate width Wg) low, even for very short gate length Lg. Rga 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-thanexpected" Rg, is instead caused by a component Rgi which scales inversely with Wg. We interpret Rgi as a metal-semiconductor interfacial gate resistance. The dominance of Rgi 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 rgi on the order of 10 -7 Ωcm 2 . AbstractWe discuss in depth a previously overlooked component in the gate resistance R g of Schottky-Barrier-Gate FETs, in particular 0.1-µm gate-length AlInAs/GaInAs MODFETs.The high-frequency noise and power gain of these FETs depends critically on R g . This has been the motivation for the development of T-gates which keep the gate finger metallization resistance R ga (proportional to the gate width W g ) low, even for very short gate length L g . R 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-thanexpected" R g , is instead caused by a component R gi which scales inversely with W g . We interpret R gi as a metal-semiconductor interfacial gate resistance. The dominance of R 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 gi on the order of 10 -7 Ωcm2 .

SIMPLE TECHNIQUES FOR DETERMINING THE SMALL-SIGNAL EQUIVALENT CIRCUIT OF MESFET’s

“…It must be noted that the specific resistances of the gate contact for three technologies have been chosen from the recently published works [10], [20], [21]. Several significant differences are found among the three MESFET technologies.…”

“…The origins of this resistance are the falls of tension produced in the metallization resistance (R ga ) and the metal-semiconductor interfacial gate resistance (R gi ) [10]. The global gate resistance can be expressed as gi ga g R R R (16) The gate metallization resistance clearly contributes to R g .…”

Scaling Rules for Multi-Finger Structures of 0.1-μm Metamorphic High-Electron-Mobility Transistors

“…This relationship can be obtained by assuming the gradual (linear) reduction in gate current (Ig) density as the open end is approached, as illustrated in Fig. 6, and an essentially uniform displacement current fed from the bottom of the gate to the channel region of the HEMTs [21]. In the open-ended gate structure shown in Fig.…”

“…Investigations have focused on Ro, Rg when w approaches zero [21,22]; however, the model for R o , is still not fully understood. In our case, the y-axis intercepts of the MHEMTs (N=2, 4, and 6) range from about 0.6 to 0.9 Ω, with the corresponding proportionality constants of about 0.0123, 0.0021, and 0.000515 Ω/μm, respectively, as shown in Fig.…”

Dispersion and tunneling analysis of the interfacial gate resistance in Schottky barriers

“…R gi is thus of practical importance to the performance, modeling, and optimization of high-speed SBGFETs, as discussed in Ref. 2. The origin of R gi was proposed to be an interfacial barrier between the gate metal and the semiconductor surface.…”