Two-dimensional (2D) semiconducting materials have shown promise in the field of optoelectronics, offering unique properties that could revolutionize the development of ultra-thin and tunable electronic components. However, one major challenge has been the effective interfacing of these materials with gate dielectrics, which often leads to the degradation of transistor performance due to interfacial traps.
The Innovative Approach
Researchers at King Abdullah University of Science and Technology (KAUST), in collaboration with Soochow University and other institutions globally, have introduced a novel approach to address this challenge. By utilizing hexagonal boron nitride (h-BN) dielectrics and metal gate electrodes with high cohesive energy, they were able to develop a design that enhances the performance of transistors based on 2D semiconductors.
The study, published in Nature Electronics, highlighted the benefits of using platinum (Pt) as an anode in combination with h-BN stack, which significantly reduced dielectric breakdown. This led to the discovery that Pt/h-BN gate stacks exhibited a 500-times lower leakage current compared to Au/h-BN gate stacks, with a high dielectric strength of at least 25 MV/cm. These findings paved the way for the use of chemical vapor deposited h-BN as a gate dielectric in 2D transistors.
Device Fabrication Process
The team, led by first author Yaqing Shen and Prof. Mario Lanza, fabricated over 1,000 devices using CVD h-BN as dielectrics. The process involved cleaning a SiO2/Si substrate, patterning source and drain electrodes (Ti/Au), transferring MoS2 onto the electrodes to form the channel, and depositing CVD h-BN film over this structure. The final step included patterning the Pt gate electrode using electron beam lithography and depositing it using e-beam evaporation.
The clean interface between MoS2 and h-BN in the transistor improved its reliability and performance, minimizing defects and enhancing gate control. Contrary to previous beliefs, the researchers found that selecting the right metal electrodes, such as Pt and tungsten (W), enabled the effective use of CVD h-BN as a gate dielectric in field-effect transistors with MoS2 channels.
The team’s innovative approach has shown promising results in reducing leakage currents and achieving a high dielectric strength, opening up possibilities for the fabrication of reliable solid-state microelectronic circuits and devices using 2D materials. The use of high cohesive energy metals like Pt and W has been instrumental in improving the performance of transistors based on 2D semiconductors.
Future Prospects
The research conducted by Shen and her colleagues could potentially pave the way for the development of highly performing 2D semiconductor-based devices. As they continue their work, the team aims to further explore the fabrication of ultra-small (nanoscale), fully 2D transistors to contribute to the advancement of Moore’s Law in electronic technology.
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