Two-dimensional (2D) semiconducting materials have the potential to revolutionize the field of electronic components due to their unique optoelectronic properties. However, interfacing these materials with gate dielectrics has been a major challenge, leading to the rapid degradation of transistor performance. Recent research by a team from King Abdullah University of Science and Technology (KAUST), Soochow University, and other institutions has introduced a promising approach to improve the performance of transistors based on 2D semiconductors.
The researchers proposed a novel design that involves using hexagonal boron nitride (h-BN) dielectrics and metal gate electrodes with a high cohesive energy. By utilizing platinum (Pt) as an anode, they discovered that the h-BN stack is less likely to trigger dielectric breakdown. This finding led them to fabricate transistors with Pt/h-BN gate stacks, which exhibited significantly lower leakage current and a high dielectric strength of at least 25 MV/cm.
The team fabricated over 1,000 devices using chemical vapor deposited h-BN as dielectrics. They employed a meticulous process that involved cleaning a SiO2/Si substrate, patterning Ti/Au source and drain electrodes using electron beam lithography, transferring MoS2 as the channel, and applying CVD h-BN film as the gate dielectric. The final step included patterning the Pt gate electrode using electron beam lithography and depositing it through e-beam evaporation.
The researchers discovered that the clean van der Waals interface between MoS2 and h-BN in their transistors significantly improved reliability and performance. Contrary to popular belief, they demonstrated that CVD h-BN can be an effective gate dielectric when paired with high cohesive energy metals like Pt and tungsten (W). These findings highlight the potential of 2D materials for creating reliable solid-state microelectronic circuits and devices.
The approach developed by the research team showed a significant reduction in current leakage and enabled a high dielectric strength, paving the way for the use of 2D semiconductor-based transistors in future electronic applications. The use of Pt and W-based gate electrodes resulted in a 500-fold decrease in leakage current across h-BN dielectrics compared to transistors with gold electrodes. This breakthrough could lead to the development of highly performing 2D semiconductor-based devices.
Future Outlook
Moving forward, the researchers plan to focus on developing ultra-small, fully 2D transistors to further advance the capabilities of 2D semiconductors and extend Moore’s Law. Their innovative approach opens up possibilities for other research groups to explore similar strategies and materials, ultimately driving the future of electronic devices towards smaller, more efficient designs.