Comprehensive Study of Quasi-Ballistic Transport in High- $\kappa$/Metal Gate nMOSFETs

We study quasi-ballistic transport in nanoscale high-κ/metal gate nMOSFETs based on radio-frequency (RF)
S
-parameter analysis. An RF
S
-parameter-based simple experimental methodology is used for direct extraction of device parameters (i.e.,
L
_eff
,
R
_sd
, and
C
_inv
) and the effective carrier velocity v
_eff
from the targeted short-channel devices. Furthermore, an analytical top-of-the-barrier model, which self-consistently solves the Schrödinger-Poisson equations, is used to determine the ballistic carrier velocity
v
_inj
at the top of the barrier near the source. Based on the results of the experimental extraction and analytical calculations, backscattering coefficient
r
_sat
and ballistic ratio
BR
_sat
are calculated to assess the degree of the transport ballisticity for nMOSFETs. It is found that conventional high-κ/metal gate nMOSFETs will approach a ballistic limit at an effective gate length
L
_eff
of approximately 7 nm.