Abstract:
Wrap around CNTFET has gate around it except the bottom portion. Wrap
around gate carbon nanotube field effect transistor (CNTFET) has the advantage
of more accurately controlled channel than top gated CNTFET. 3-D simulation is
performed using Finite Element Method (FEM) to model wrap around CNTFET
with multi-CNT channel. For predicting the device speed, capacitance modeling is
necessary. Along with gate to channel capacitance, there are fringing capacitance as
well. Analytical expressions to model various capacitances of the same device are also
derived from capacitances for 1-D FET with multiple cylindrical conducting channels
incorporating screening effect due to multiple CNT. Various capacitances thus obtained
exhibit remarkable improvement over planar top gate device with multiple
conducting channels. This is attributed to the charge enhancement and better charge
confinement in the channel of the wrap around CNTFET with multi-CNT channel.
Capacitances are also extracted from the proposed FEM model. The extracted capacitances
are in excellent agreement with the capacitances obtained from the analytical
model presented in this study.
Temperature distribution of wrap around CNTFET with multi-cnt is presented
in this paper. For predicting the device characteristics, temperature modeling is
necessary. Temperature distribution is changed due to multi-cnt as voltage of adjacent
cnt affects temperature of mid cnt. Again it is also changed by temperature dependent
thermal conductivity of single walled carbon nano tube (SWCNT). Current flow is
changed both due to multi-cnt wrap around structure and due to the temperature
change. So, temperature has a great impact on current modeling and thus on device
characteristics. All these issues are considered in this paper using finite element
method.
