Van der Waals Multi-Heterostructures (PN, PIN, and NPN) for Dynamic Rectification in 2D Materials

Here, van der Waals multi-heterojunctions (PN, NP, PIN, and NPN) are fabricated by stacking of MoTe2, hexagonal boron nitride (h-BN), and MoSe2 nanoflakes using a mechanical-exfoliation technique where the dynamic rectification is examined. Low-resistance metal contacts Al/Au and Pt/Au are applied to MoSe2 and MoTe2, respectively, and gate-dependent rectifying behavior is achieved, with a rectification ratio of up to 105 in PN devices. It is found that the performance of the device is enhanced by placing an interfacial layer h-BN between two opposite layers of 2D materials where the rectification ratio is found to be >106 with the ideality factor ≈1.3 in the PIN devices. Also, using the conventional Richardson's plot, the barrier heights of PN and PIN diodes are calculated to be 260 and 490 meV at zero gate bias, respectively. As well, the devices exhibit good performance with a built-in electric field observed in both PN and PIN diodes, which gives rise to an open-circuit voltage (Voc) and short-circuit current (Isc) under zero external bias. Remarkably, it is found that the performance of the devices also gets better by forming double heterojunction (NPN) layer than PN or NP layers. The device is also tested for a rectification application, and it successfully rectifies an input alternating-current signal. These findings are important for the development of nano- and optoelectronics devices.