Ultimate Scaling and Performance Potential of MoS2 FETs

2D materials beyond graphene have gained enormous attention since a transistor with a two-dimensional (2D) molybdenum disulfide (MoS₂) channel was demonstrated in 2011. Currently,research on these materials for electronic applications is under way worldwide, in particular on the 2D transition metal dichalcogenides (TMD), with MoS₂ as the most prominent representative. MoS₂ possesses a sizeable band gap and therefore shows great promise for future digital electronics. The processing technology for MoS₂, however, is still in its infancy and many questions regarding the potential of MoS₂ transistors are still open. This makes it currently extremely difficult, if not impossible, to assess the performance and scaling limits of MoS₂ transistors and to judge the prospects of these devices for future electronics. This situation provides the motivation for the present project, which is focused on the fabrication technology, theory and simulation of ultimately scaled MoS₂ field effect transistors (FETs). The three project partners, two from Germany and one from Austria, with recognized and perfectly complementary expertise in 2D transistor theory and (nano-) fabrication will conduct systematic and exploratory research on MoS2 transistors and address the following objectives:

- Exploration of the scaling behavior of MoS₂ FETs by thorough and comprehensive in-depth experimental and theoretical studies.

- Demonstration of MoS₂ top-gate transistors with sub-10nm gate lengths.

- Critical assessment of the prospects of ultimately scaled single-and multilayer MoS₂ FETs considering processing constraints, switching speeds and non-idealities such as charge-trappingrelated issues.

- Assessment of p-type operation potential of MoS₂ FETs.

The partners will utilize state-of-the-art nanofabrication technology to explore the scaling limits of MoS₂ FETs. Extensive work on device theory and simulation will be performed to get better insights in the physics and in the performance and scaling limits of TMD MOSFETs. The theoretical work will be closely linked to the experiments and be used to elaborate suitable designs for MoS₂ FETs, taking into account the specifics of the processing environment as well as non-idealities such as charge trapping effects. Complete process flows for ultra-scaled MoS₂ FETs will be established, including modules for gate dielectric deposition, boron nitride encapsulation and Ohmic contact formation. The resulting range of test structures and transistors from chemical vapor deposited films, including high frequency transistors for extracting switching delays, will undergo thorough analysis and characterization whose results, in turn, will be fed back to the theoretical work. The project will result in significant enhancements of the understanding of the physics, the scaling behavior and the process integration of MoS₂ FETs and in a sound assessment of their merits and drawbacks.