Vertical Transistors with Conductive-Network Electrodes: A Physical Image and What It Tells
Abstract
Vertical transistors with conductive-network electrodes composed of carbon- or metal-based nanowires or meshes are attractive because of their high current density, low operational voltage, and high degree of integration. However, the devices lack concise physical images to understand the operations and explicit design rules to achieve the necessary performance, such as sharp subthreshold swing and a large on:off ratio. Here, we develop a device theory with concise physical images, which are generally applicable for devices with organic or inorganic semiconductors. The simplified solution of Poisson's equation reveals that the electrostatic potential at the semiconductor-dielectric interface is controlled by both the gate and drain field, behaving like a plucked string. The spacing between electrodes and the capacitance ratio between semiconductors and dielectrics are critical for achieving strong gate tunability of the interfacial potential, and such gate tunability can be maximized to achieve a sharp turn-on property toward the Boltzmann limit in the subthreshold regime. Above the threshold, the conduction channels in devices with Schottky contacts can change from the "L type" to "I type", or vice versa, during scanning and the current-voltage relations can be well described by modifying classical transistor equations. The derived theories and equations agree well with the numerically simulated devices and reported experiments, revealing the physical images and providing explicit rules for designing, fabricating, and characterizing such transistors.
- Publication:
-
Physical Review Applied
- Pub Date:
- May 2020
- DOI:
- 10.1103/PhysRevApplied.13.054066
- Bibcode:
- 2020PhRvP..13e4066L