Scalable Tunneling diodes based on 2D materials – TUNNE2D

The huge increase in today`s information and data communication services imposes higher data rate transmission networks and processing, requiring high frequency (HF) operations. Tunneling devices (TDs) offer potentially superior performance than thermionic-based devices as they do not suffer from limitations due to thermal activation and can lead to negative differential resistance, a unique and differentiating feature for the development of HF sources and detectors. Unfortunately, as TDs are very sensitive to the chemical and electronic structure at the tunneling interface, their performance are hampered by a number of issues due to the covalent bonding at the interface when fabricated using Si, Ge or III-V semiconductors. It is then mandatory to explore emerging materials to improve the tunneling interface quality. The absence of surface dangling bonds in two-dimensional transition metal dichalcogenides (TMDs) alleviates the interface covalent bonding issue and allows the formation of van der Waals heterostructures rendering strain-free integration possible. In recent years several reports have confirmed the added value of TMDs for tunneling devices with band-to-band tunneling as the governing conduction mechanism. However, to date, TMD-based tunnel devices have been elaborated from exfoliated or transferred layers which raises severe issues regarding the interface integrity and process reliability.
The Tunne2D project aims at assessing the capabilities of TMDs for tunneling devices. To this end, different tunnel diodes will be fabricated at wafer scale and fully characterized at low and high frequency. The objectives are: i) the growth of TMD heterostructures using improved chemical vapor deposition (CVD) and molecular beam epitaxy (MBE) scalable growth techniques and their thorough characterization; ii) the design of tunnel diodes based on the simulation of material and transport properties; iii) the reliable fabrication of TMD-based tunnel diodes; iv) the comparison between tunneling devices fabricated with either CVD or MBE to get insights in the pros/cons of the two approaches; v) the benchmarking of the resulting TMD-based diodes versus conventional semiconductor-based ones. The success of TUNNE2D will not only pave the way for more complex tunneling devices, like Tunnel-FET for low power applications, but the resulting high-quality heterostructures will offer new opportunities for the development of optoelectronic devices like infrared photodetectors and photocatalytic cells for H2 production.
The project will focus on the Se-based TMD family offering the variety of materials, namely metallic, p- and n-type semiconducting layers with different electron affinities requested to fabricate these diodes. Our approach relies on the strong interaction between material issues, modeling and simulation and electrical investigation of the devices. It gathers 4 academic partners (IEMN, CINTRA, C2N, CP2M) with complementary skills and equipment in material elaboration and characterization, device processing and simulation. IEMN has launched a MBE system fully dedicated to TMD growth and is expert in the development of 2D-based devices with advanced fabrication techniques. Besides standard MBE, an original approach using single source precursors will be explored, in strong collaboration with CP2M, expert in the precursor design for gas-phase deposition techniques. CINTRA, very active in the field of TMD CVD growth, has demonstrated the versatility of the CVD technique for more than 30 materials and the interest of metalorganic precursors for large scale MoS2 continuous films. This approach will be extended to selenide ones. C2N has a long experience in tunneling device simulations and has recently focused on TMDs. The success of the consortium will rely on a long-term partnership between IEMN and CINTRA, a long running experience in joint projects of IEMN and C2N and the great habit of CP2M to work with material physicists.