RF performance limits of ballistic Si field-effect transistors

The continued advancement of digital system performance is arguably the primary reason for the longevity of Moore´s Law. However, the RF characteristics of the fundamental digital device, the Si FET, have also become increasingly important considerations for analog and mixed-signal applications. While deeply-scaled Si FETs are now approaching the (quasi-)ballistic regime, their RF performance in this condition has not been adequately studied. For the first time, we examine their intrinsic RF performance limits using the non-equilibrium Green´s function (NEGF) approach to account for ballistic and quantum effects. We find cutoff frequencies of several THz are possible provided parasitics and scattering are minimized.