Low-Voltage Tunnel Transistors for Beyond CMOS Logic

Designing a low-voltage, high-current tunneling transistor

“…The tunneling probability, T, is [7]: For simplicity, we will assume that the electric field across the tunneling junction, F, is constant and equal to the peak electric field. The effective mass for tunneling [1,8,9] is * tunnel m 1 , and EG is the band gap. All of the parameters can be collected into a single constant, α.…”

“…However, in silicon and germanium the band gap is indirect and there are many interacting bands and so the WKB model breaks down [9]. Consequently, we use an experimentally fitted tunneling effective mass derived in [1]. While in [1] a single band tunneling model was used, we used a two band tunneling model and consequently we need to adjust the mass accordingly: (4.2.6) In the best case, As we can see from Eq.…”

“…Tunneling Field Effect Transistors (TFETs) have the potential to achieve a low operating voltage by overcoming the thermally limited subthreshold swing voltage of 60mV/decade [1], but results to date have been unsatisfying. The low voltage operation is parameterized by the voltage required to obtain a 10× change in output current, called the subthreshold swing voltage, SS.…”

“…While devices have been built that meet one or two of the three requirements, to date, no logic switch meets all three requirements [1,2]. No one has achieved a steep subthreshold swing voltage at a high conductance.…”

Magnitude of the current in 2D interlayer tunneling devices

“…This sharp turn-on permits usage of TFETs in circuits with reduced operating voltages, hence yielding digital devices and circuits that require relatively low amounts of energy to switch between on and off states. 19,20 In addition to this low-energy aspect of the devices, another critical requirement of TFETs is the amount of current that can be achieved in the on state. Typical values of 200 A per m length of channel are required for realistic circuit applications (for interlayer TFETs, this current is proportional to the width of the overlap region between source and drain, i.e.…”