Atomic-level charge transport mechanism in gate-tunable anti-ambipolar van der Waals heterojunctions

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.