Novel optoelectronics based on van der Waals heterostructures

Chang-Hua Liu^1*

¹Institute of Photonics Technologies, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Chang-Hua Liu, email:changhua@gapp.nthu.edu.tw

Two-dimensional (2D) materials, which possess a wide variety of optoelectronic properties,
can be used to develop atomically-thin nanoelectronics and optoelectronics operated at
different spectral regions. For instance, single layer transition metal dichalcogenides (TMDs)
materials are useful in the visible to near-infrared spectral regimes. The carriers in TMDs
have an extra valley degree of freedom (i.e., valley pseudospin), in addition to charge and
spin. These make TMD promising for spin-polarized devices or valleytronics applications.
Bulk black phosphorus (BP) owns the direct and narrow band gap (~0.33 eV), and thus is an
ideal candidate for mid-infrared devices applications. Furthermore, due to the weak van der
Waals (vdW) interactions, these materials can be assembled together to form the complex
vdW heterostructures, and the created heterostructures can be readily transferred onto
different device platforms without the issue of lattice mismatching. These features potentially
lead to the novel hybrid device platforms that could simultaneously exploit the advanced
semiconductor manufacturing technologies and exotic properties of vdW materials.
In this talk, we will demonstrate novel optoelectronics realized by using band-engineered
vdW heterostructures. Specifically, we will show BP-based mid-infrared light emitting diodes
and photodetectors that could exhibit excellent optoelectronic properties, including linear-
dichroic photoresponses, high speed, high quantum efficiency and long-term stability at room
temperature operation. Via leveraging the integrability of vdW heterostructures, we further
show our developed mid-infrared devices can be readily coupled with mid-infrared SOI
waveguides for on-chip sensing and light emissions. In addition, we will demonstrate the
electric control of the valley degree of freedom of TMDs using emerging vdW magnets and
discuss their potential applications on valleytronics.

Keywords: Mid-IR optoelectronics, Valleytronics, Two-dimensional materials, Van der Waals heterostructures