It is assessed in detail both experimentally and theoretically how the interlayer coupling of transition metal dichalcogenides controls the electronic properties of the respective devices. Gated transition metal dichalcogenide structures show electrons and holes to either localize in individual monolayers, or delocalize beyond multiple layers -depending on the balance between spin-orbit interaction and interlayer hopping. This balance depends on layer thickness, momentum space symmetry points and applied gate fields. The design range of this balance, the effective Fermi levels and all relevant effective masses is analyzed in great detail. A good quantitative agreement of predictions and measurements of the quantum confined Stark effect in gated MoS2 systems unveils intralayer excitons as major source for the observed photoluminesence.
van der Waals p–n heterojunctions using both 2D–2D and mixed-dimensional systems have shown anti-ambipolar behavior. Gate tunability in anti-ambipolar characteristics is obtained in special heterojunction geometries, such as self-aligned black phosphorus/MoS2 p–n heterojunctions. Although the device physics of anti-ambipolar characteristics has been investigated using finite-element or semi-classical device models, an atomic-level description has not yet been developed. This work models the interface physics with quantum transport including incoherent scattering and carrier recombination. Densities of electrons and holes are calculated in DFT-based maximally localized Wannier functions with 2% strain. Qualitative agreement with our experiments is found for both the anti-ambipolar (or Gaussian) behavior and the tunability of Gaussian function in a dual-gated geometry. Carrier recombination is found to determine the overall current density. The two gates control the recombination by regulating the density of electrons in MoS2 and holes in black phosphorus reaching the heterojunction area.
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