On the drain bias dependence of long-channel silicon-on-insulator-based tunnel field-effect transistors

Abstract

The drain bias dependence of tunnel field-effect transistors (TFETs) is examined on the basis of the measured characteristics and device simulation to understand the electrical behavior of TFETs. Our analyses focus on the long-channel silicon-on-insulator (SOI)-based TFETs as a good basis for further studies of short-channel effects, scaling issues, and more complicated device structures, such as multigate or nanowire TFETs. By device simulation, it is revealed that the drain bias dependence of the transfer characteristics of the measured TFETs is governed by two physical mechanisms: the density of states (DOS) occupancy factor, which depends on drain-to-source bias voltage, and channel electrostatic potential, which is limited by the drain bias through strong carrier accumulation. These mechanisms differ from the drain-induced barrier lowering (DIBL) of metal–oxide–semiconductor field-effect-transistors (MOSFETs), and cause a significant impact even in long-channel SOIs. Finally, the obtained insights are successfully implemented in a TFET compact model.

Enhancement of tunneling currents by isoelectronic nitrogen-atom doping at semiconductor pn junctions; comparison of indirect and direct band-gap systems

“…Here, we briefly comment on the potential slope at the pn junction. It is known by the device simulation 1,39) that, in an actual pn junction, the dopants cause a smooth change of potential with parabolic shapes at the left and right edges of pn junction. However, as a first-order approximation, we approximate the potential within the pn junction having a linear slope.…”

“…In addition, depending on the device structure, the external electric field is known to be applied nonuniformly within the device, not only to the pn junction. 39) However, since the p and n layers are characterized only by flat potentials and their electron occupation in the present model, the results of this paper can be applied to limited regions where strong electric fields are applied and tunneling currents occur.…”

“…26,27) Here, we briefly compare the current density values between experiments and calculations. Since the electric field in experiments depends on the device structures and is not uniformly applied, such as only to the pn-junction region as in the present model, 1,39) it is difficult to directly compare the absolute values of current density. Thus, we compare the current enhancement factor by the Al-N doping.…”