Downscaling 2D Transition Metal Dichalcogenide FETs Reveals Classical-to-Quantum Crossover

Two-dimensional materials hold immense promise for building the next generation of energy-efficient transistors, but shrinking these devices to incredibly small sizes presents significant challenges. Yu-Chang Chen and Ken-Ming Lin, from National Yang Ming Chiao Tung University, along with their colleagues, investigate the behaviour of these materials as channel lengths scale down to just a few nanometres. Their research reveals a fundamental shift in how electrons travel through these tiny transistors, moving from a classical flow to a quantum-dominated tunnelling effect. This crossover, governed by specific temperature thresholds, allows the shortest devices to outperform traditional limits on energy efficiency, potentially paving the way for a new era of ultra-low-power computing and overcoming the constraints of conventional transistor technology. The team’s atomistic modelling provides critical insights for designing these advanced transistors and harnessing the power of quantum mechanics for future electronic devices.

Scaling two-dimensional transition metal dichalcide field-effect transistors (TMD FETs) into the sub-10 nanometer regime presents significant technical challenges. Understanding how these devices behave at such small scales remains a key hurdle. This work investigates the transport properties of platinum, tungsten diselenide, platinum nanojunctions, examining channel lengths ranging from 12 nanometers down to 3 nanometers, using advanced computational methods. The simulations reveal a fundamental shift in electron transport as transistors shrink, governed by critical temperatures that define the transition from classical to quantum behavior.

WSe2 Nanotransistors, Quantum Transport, Contact Resistance

This research explores the potential of two-dimensional materials, specifically tungsten diselenide (WSe2), for building ultra-small, high-performance transistors, overcoming the limitations of traditional silicon-based devices. The study focuses on understanding electron behavior at the nanoscale, minimizing resistance at the metal-2D material interface, and potentially exceeding the performance limits imposed by conventional physics. Researchers also investigate the transition between quantum and classical behavior in these nanoscale devices. The research demonstrates the promise of WSe2 as a channel material, offering advantages like high carrier mobility and the ability to create extremely thin devices. Contact resistance is a major limiting factor in WSe2 transistor performance, emphasizing the importance of optimizing the metal-2D material interface. The authors developed a computational framework combining effective medium theory with quantum transport simulations to accurately model these nanoscale devices, allowing for efficient and accurate predictions of device behavior.

Electron Transport Shifts at Nanoscale Dimensions

Researchers are investigating two-dimensional materials for future electronic devices, specifically field-effect transistors, with the goal of creating components that use less power and operate at higher speeds. A significant challenge lies in scaling these transistors down to extremely small sizes, below 10 nanometers, and fully understanding their behavior at that scale. This work presents a detailed study of these materials, focusing on how electrons move through nanojunctions with channel lengths ranging from 3 to 12 nanometers. The research reveals a fundamental shift in how electrons travel through these tiny transistors as they become smaller.

At larger sizes, electron transport resembles a classical process, where electrons gain enough energy to overcome barriers. However, as the channel length shrinks, electron transport increasingly relies on quantum tunneling, where electrons pass through barriers even if they don’t have enough energy to go over them. This transition is governed by critical temperatures, influencing how efficiently the transistor switches on and off. Notably, the shortest 3-nanometer junction demonstrates tunneling effects up to 500 Kelvin, and achieves a subthreshold swing that surpasses the theoretical limit imposed by conventional physics. This means these ultra-small transistors have the potential to operate more efficiently than previously thought, potentially leading to significant energy savings in future computing technologies. The study also identifies how the dominant transport mechanism changes with channel length, with shorter junctions relying heavily on quantum tunneling and longer junctions exhibiting classical thermionic emission.

Quantum Tunneling Beats Classical Limits in Nanojunctions

This study investigates the electron transport properties of two-dimensional transition metal dichalcogenide nanojunctions, exploring how performance changes as channel length scales down to the 3 nanometer regime. Researchers demonstrate a transition from classical to quantum electron transport, governed by critical temperatures that define the crossover between tunneling and thermionic emission. The findings reveal that shorter channels exhibit dominant quantum tunneling, while longer channels increasingly rely on classical thermionic emission, offering insights into optimizing device performance at different length scales. Notably, the 3-nanometer junction surpasses the classical limit of the subthreshold swing, effectively exceeding conventional performance limits due to a steep energy dependence in the transmission coefficient. This enhanced switching efficiency suggests that quantum tunneling can be a beneficial mechanism for ultra-scaled field-effect transistors, potentially enabling energy-efficient computing technologies.