Structure of the DG-MOSFET. Current flow is along the direction and the confinement potential varies in the direction.
Saturation transconductance vs gate voltage for the scaled down DG-MOSFET. Note that the weak inversion region goes directly into the velocity saturation region. This is a common trend in ultrashort channel MOSFETs.
Saturation transconductance vs low field mobility (solid line). In dotted line the drift-diffusion limited transconductance is shown (no velocity overshoot). A saturation velocity has been assumed. The absolute upper bound for the transconductance is fixed by the thermal injection velocity (dashed line). In between, very high transconductance is reported due to velocity overshoot phenomena.
(a) Proximity of the saturation transconductance to the ballistic limit and reflection coefficient vs gate voltage. (b) Conduction subband edge vs position for the scaled down DG-MOSFET (high gate and drain bias). Note that the critical length is reduced relative to the mean free path , lowering the reflection coefficient near the ballistic limit .
Transconductance efficiency vs current in the ballistic regime. As the channel length is scaled down, the transconductance efficiency is degraded. In the weak inversion region, the bipolar limit is approached for the DG-MOSFETs due to its near ideal subthreshold slope.
Temperature effects on the transconductance efficiency.
Output characteristics of the DG-MOSFET for different low field mobilities. The ballistic limit is shown for comparison.
Output conductance vs drain voltage: (a) for a transistor considering several mobilities; (b) for different channel lengths in the ballistic limit.
(a) Early voltage vs drain voltage for a transistor considering several mobilities. The Early voltage is enhanced with electron mobility due to the increasing current; the output conductance in the saturation region is nearly constant [see Fig. 8(a)]; (b) Early voltage for different channel lengths in the ballistic limit.
Relevant digital parameters for a set of DG-MOSFETs with metallurgical gate lengths between 10 and . Values are specified for temperatures of (left values) and maximum operation temperature of (right values). The ITRS-2001 specifications for the off-state and on-state current are shown (in parentheses) as a reference.
Intrinsic gain and cutoff frequency for the DG-MOSFET near the ultimate scaling limits. A low field mobility of has been assumed for calculations. The ITRS-2001 specifications for radiofrequency applications are shown in parentheses for comparison.
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