Ionic liquid gel gate tunable p-Si/MoS2 heterojunction p-n diode

Monolayer MoS2 crystals investigated in this work were grown via chemical vapor deposition on Si/SiO2 substrates. Using a wet KOH etch, these crystals were transferred onto the edge of a freshly cleaved p-Si/SiO2 wafer where they formed mechanically robust heterojunctions at the p-Si/MoS2 interface. Electrical characterization of the device across the junction yielded an asymmetric I–V response similar to that of a p-n diode. The I–V response was electrostatically tunable via an ionic liquid gel gate. This is the first report demonstrating reversible gate control of the p-Si/MoS2 diode current by several orders of magnitude while lowering its turn-on voltage. Fermi energy level shifts within the MoS2 bandgap by the gate was believed to be responsible for the observed effects. The ease of fabrication, low operating voltages (<±2 V), and moderately high throughput currents (∼1 µA) are attractive features of this diode, especially for use in sensors and power saving electronics.