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10
Beyond-CMOS Transistor
Models: Tunnel FETs
10.1 Introduction
As the CMOS (complementary metal-oxide-semiconductor) technology
approaches its ultimate scaling limit of MOSFET (metal-oxide-semiconductor
field-effect transistors) device miniaturization, extensive global search for
beyond-CMOS devices has been continued to rebooting computing. This
new device technology must be green (i.e., energy efficient) and continue to
increase packing density of devices as well as device functionalities in an IC
(integrated circuit) chip in the same rate as the CMOS technology. A number
of potential beyond-CMOS devices involving present as well as new state
variables and communication frameworks have been reported [1–3]. Among
the potential beyond-CMOS devices, the devices that compete directly with
the MOSFETs in power, area, and speed in the commercial temperature range
0°C–75°C and can utilize the existing CMOS facility are of special interest to
device technologists and IC manufacturers. These devices are aimed at supply voltages less than a 0.5 V with subthreshold swing (S) lower than that of
MOSFETs.
The scaled MOSFET devices, discussed in Chapter 5, are limited by short
channel effect (SCE) and S. As discussed in Chapter 9, the ultrathin-body
(UTB) MOSFETs are adopted to surmount the challenges of SCEs. However, S
in UTB-MOSFETs is still limited by the Boltzmann distribution of carriers to
a minimum value of 60 mV per decade of channel current at room temperature. Therefore, the devices that can achieve switching mechanisms less than
60 mV per decade are highly desirable for beyond-CMOS green IC technology.
The potential device structures with the desirable characteristics include
tunneling [4–6], impact ionization [7–10], ferroelectric dielectrics [11], and
mechanical gate [12–14] field-effect transistors (FETs). Among the emerging
devices, the tunnel FET (TFET) is one of the potential candidates for beyondCMOS technology that can be controlled at voltages well under a volt with
steep S and does not have the delays associated with positive feedback that
are intrinsic to impact ionization, ferroelectricity, and mechanical devices [15].
10
Beyond-CMOS Transistor
Models: Tunnel FETs
10.1 Introduction
As the CMOS (complementary metal-oxide-semiconductor) technology
approaches its ultimate scaling limit of MOSFET (metal-oxide-semiconductor
field-effect transistors) device miniaturization, extensive global search for
beyond-CMOS devices has been continued to rebooting computing. This
new device technology must be green (i.e., energy efficient) and continue to
increase packing density of devices as well as device functionalities in an IC
(integrated circuit) chip in the same rate as the CMOS technology. A number
of potential beyond-CMOS devices involving present as well as new state
variables and communication frameworks have been reported [1–3]. Among
the potential beyond-CMOS devices, the devices that compete directly with
the MOSFETs in power, area, and speed in the commercial temperature range
0°C–75°C and can utilize the existing CMOS facility are of special interest to
device technologists and IC manufacturers. These devices are aimed at supply voltages less than a 0.5 V with subthreshold swing (S) lower than that of
MOSFETs.
The scaled MOSFET devices, discussed in Chapter 5, are limited by short
channel effect (SCE) and S. As discussed in Chapter 9, the ultrathin-body
(UTB) MOSFETs are adopted to surmount the challenges of SCEs. However, S
in UTB-MOSFETs is still limited by the Boltzmann distribution of carriers to
a minimum value of 60 mV per decade of channel current at room temperature. Therefore, the devices that can achieve switching mechanisms less than
60 mV per decade are highly desirable for beyond-CMOS green IC technology.
The potential device structures with the desirable characteristics include
tunneling [4–6], impact ionization [7–10], ferroelectric dielectrics [11], and
mechanical gate [12–14] field-effect transistors (FETs). Among the emerging
devices, the tunnel FET (TFET) is one of the potential candidates for beyondCMOS technology that can be controlled at voltages well under a volt with
steep S and does not have the delays associated with positive feedback that
are intrinsic to impact ionization, ferroelectricity, and mechanical devices [15].