2DMs are the layered materials in which the neighboring layers are weakly bound by van der Waals interactions instead of chemical bonds, including semi-metal 2DMs, semiconductor 2DMs, and insulator 2DMs.
Compared to the traditional bulk materials, 2DMs not only can be integrated flexibly with various material platforms such as silicon and silicon compounds but also avoid the surface recombination and the increment of the dark current caused by dangling bonds. In addition, silicon provides an excellent platform for PD read-out circuits based on microelectronics as well as high-performance photonic integrated circuits due to its complementary-metal-oxide-semiconductor (CMOS) compatibility. The combination of 2DMs and silicon offers unprecedented opportunities for photodetection.
In a new paper published in Light Science & Application, a team of scientists, led by Professor Daoxin Dai from State Key Laboratory for Modern Optical Instrumentation, Zhejiang University, China, and co-workers have reviewed the recent progresses of silicon/2DM PDs working for near-/mid-infrared wavelength-band.
The photodetection mechanisms of 2DM PDs are discussed, including the photovoltaic effect, the internal photon emission, the direct tunneling, the Fowler-Nordheim tunneling, the photoconductive effect, the photo-gating effect, the bolometric effect, as well as the photo-thermoelectric effect. Additionally, a systematic classification of the 2DM PDs is given in terms of the device configurations.
With the great enhancement of light-matter interaction, waveguide-integrated silicon-2DM PDs have attracted much attention for the potential applications in various functional photonic integrated circuits for e.g. optical communications and interconnects. Recent progresses are reviewed, including metal-2DM-metal PDs as well as 2DM-heterostructure PDs.
The state-of-the-art of surface-illuminated Si/2DM PDs is also reviewed, including metal-2DM-metal PDs, metal-2DM+X-metal PDs, as well as 2DM-heterostructure PDs. Several works on the image-sensing applications of Si/2DM PDs are introduced.
Finally the tasks, the goals, and the challenges are discussed from the perspectives of the material level, the device level, the circuit level, as well as the commercialization level. So far, great successes have been achieved at the levels of materials, devices, and circuits. It is desired to have more development at the system level.
These scientists summarize their work: "In this work, we discussed the operation mechanisms of 2DM PDs, focusing on their relationships and differences. In addition, we propose an idea for the device classification in terms of their configuration, including the metal-2DM-metal type, the metal-2DM+X-metal type , and the 2DM-heterostructure type. In this way, the mechanisms and the configurations are connected clearly."
"The waveguide-integrated PDs and the surface-illuminated PDs have different application scenarios and thus different evaluations. Recent work on imaging sensors based on Si/2DM PDs are also included." They added.
"We also give the perspective and outlook of Si/2DM PDs. To the best of our knowledge, Si/2DM PDs have not been commercialized yet. It is expected to happen in the following years with the great efforts from the groups working on materials, devices and circuits. In summary, we hope that this review work can shed light on this rapidly-growing area." They said.