Semiconductor p–n junctions are essential building blocks for electronic and optoelectronic devices1, 2. In conventional p–n junctions, regions depleted of free charge carriers form on either side of the junction, generating built-in potentials associated with uncompensated dopant atoms. Carrier transport across the junction occurs by diffusion and drift processes influenced by the spatial extent of this depletion region. With the advent of atomically thin van der Waals materials and their heterostructures, it is now possible to realize a p–n junction at the ultimate thickness limit3, 4, 5, 6, 7, 8, 9, 10. Van der Waals junctions composed of p- and n-type semiconductors—each just one unit cell thick—are predicted to exhibit completely different charge transport characteristics than bulk heterojunctions10, 11, 12. Here, we report the characterization of the electronic and optoelectronic properties of atomically thin p–n heterojunctions fabricated using van der Waals assembly of transition-metal dichalcogenides. We observe gate-tunable diode-like current rectification and a photovoltaic response across the p–n interface. We find that the tunnelling-assisted interlayer recombination of the majority carriers is responsible for the tunability of the electronic and optoelectronic processes. Sandwiching an atomic p–n junction between graphene layers enhances the collection of the photoexcited carriers. The atomically scaled van der Waals p–n heterostructures presented here constitute the ultimate functional unit for nanoscale electronic and optoelectronic devices.
At a glance
- 2006). & Physics of Semiconductor Devices 3rd edn (Wiley,
- 1982). Solar Cells: Operating Principles, Technology, and System Applications (Prentice-Hall,
- Atomically thin MoS2: a new direct-gap semiconductor. Phys. Rev. Lett. 105, 136805 (2010). , , , &
- Emerging photoluminescence in monolayer MoS2. Nano Lett. 10, 1271–1275 (2010). et al.
- Single-layer MoS2 transistors. Nature Nanotech. 6, 147–150 (2011). , , , &
- Electronics and optoelectronics of two-dimensional transition metal dichalcogenides. Nature Nanotech. 7, 699–712 (2012). , , , &
- Production and processing of graphene and 2D crystals. Mater. Today 15, 564–589 (December, 2012). et al.
- Strong light–matter interactions in heterostructures of atomically thin films. Science 340, 1311–1314 (2013). et al.
- Van der Waals heterostructures. Nature 499, 419–425 (2013). &
- Extraordinary sunlight absorption and one nanometer thick photovoltaics using two-dimensional monolayer materials. Nano Lett. 13, 3664–3670 (2013). , &
- Comparing organic to inorganic photovoltaic cells: theory, experiment, and simulation. J. Appl. Phys. 93, 3605–3614 (2003). &
- 2012). Principle of Semiconductor Devices (Oxford Univ. Press,
- Field-effect tunneling transistor based on vertical graphene heterostructures. Science 335, 947–950 (2012). et al.
- Cross-sectional imaging of individual layers and buried interfaces of graphene-based heterostructures and superlattices. Nature Mater. 11, 764–767 (2012). et al.
- Valley polarization in MoS2 monolayers by optical pumping. Nature Nanotech. 7, 490–493 (2012). , , , &
- Valley-selective circular dichroism of monolayer molybdenum disulphide. Nature Commun. 3, 887 (2012). et al.
- Tightly bound trions in monolayer MoS2. Nature Mater. 12, 207–211 (2013). et al.
- Optical generation of excitonic valley coherence in monolayer WSe2. Nature Nanotech. 8, 634–638 (2013). et al.
- Ultrasensitive photodetectors based on monolayer MoS2. Nature Nanotech. 8, 497–501 (2013). , , , &
- Electroluminescence in single layer MoS2. Nano Lett. 13, 1416–1421 (2013). et al.
- Band offsets and heterostructures of two-dimensional semiconductors. Appl. Phys. Lett. 102, 012111 (2013). , , , &
- Electron–hole transport and photovoltaic effect in gated MoS2 Schottky junctions. Sci. Rep. 3, 1634 (2013). et al.
- Highly efficient gate-tunable photocurrent generation in vertical heterostructures of layered materials. Nature Nanotech. 8, 952–958 (2013). et al.
- Optoelectronic devices based on electrically tunable p–n diodes in a monolayer dichalcogenide. Nature Nanotech. 9, 262–267 (2014). , , &
- Solar-energy conversion and light emission in an atomic monolayer p–n diode. Nature Nanotech. 9, 257–261 (2014). , &
- Electrically tunable excitonic light-emitting diodes based on monolayer WSe2 p–n junctions. Nature Nanotech. 9, 268–272 (2014). et al.
- High-performance single layered WSe2 p-FETs with chemically doped contacts. Nano Lett. 12, 3788–3792 (2012). et al.
- Two-dimensional electron–hole capture in a disordered hopping system. Phys. Rev. B 68, 245301 (2003). &
- Optical investigation of the natural electron doping in thin MoS2 films deposited on dielectric substrates. Sci. Rep. 3, 3489 (2013). et al.
- Photo-thermoelectric effect at a graphene interface junction. Nano Lett. 10, 562–566 (2010). , , , &
- Large and tunable photothermoelectric effect in single-layer MoS2. Nano Lett. 13, 358–363 (2013). et al.
- Exciton dynamics in suspended mono layer and few-layer MoS2 2D crystals. ACS Nano 7, 1072–1080 (2013). et al.
- Quasiparticle band structure calculation of monolayer, bilayer, and bulk MoS2. Phys. Rev. B 85, 205302 (2012). &
- One-dimensional electrical contact to a two-dimensional material. Science 342, 614–617 (2013). et al.
- Supplementary information (1,444 KB)