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.