Figure 1. Schematic of the waveguide-integrated van der Waals PN heterojunction photodetector. Credit: Light Publishing Center, Changchun Institute of Optics, Fine Mechanics And Physics, CAS
Photonic built-in circuits (PICs) use photons as info carriers and have ultra-high transmission pace, low delay, and anti-electromagnetic crosstalk. These benefits are anticipated to resolve the bottleneck issues of microelectronic chips by way of pace, energy consumption, and integration density. It is of key significance to selling breakthroughs in microelectronics expertise, quantum info expertise, and micro-sensing expertise within the “post-Moore era.”
Currently, pushed by the appliance of knowledge expertise, photonic built-in chips have made nice progress. For instance, silicon PIC is appropriate with the mature CMOS expertise for low-cost and large-scale manufacturing; Silicon nitride PIC may tolerate reasonably excessive optical energy and enormous fabrication errors; and Lithium niobate PIC may obtain excellent electro-optic modulations with low pushed voltage and excessive linearity.
However, one of many handicaps in these PICs is the monolithic integration of waveguides and photodetectors with a single materials. To assist the sunshine transmission within the waveguide, the PIC supplies can not soak up the optical sign, making it not possible to comprehend the built-in photodetector out of a single materials. To clear up this, hetero-integrations of absorptive bulk supplies (akin to Ge, III-V compound semiconductors, and so on.) on PICs have been carried out. Although it nonetheless presents open challenges such because the excessive prices, difficult fabrication processes, and materials interface points.
Figure 2. Band alignment of BP/MoTe2 PN heterojunction within the thermal equilibrium state (left panel); Optical microscope picture of the fabricated system (proper panel). Credit: Light Publishing Center, Changchun Institute of Optics, Fine Mechanics And Physics, CAS
Recently, two-dimensional (2D) supplies have emerged as a horny photon-absorption materials for chip-integrated photodetectors. 2D supplies don’t have any floor dangling bonds, which eliminates the lattice-mismatch constraints to hetero-integrate them with PICs. The household of 2D supplies has a wealthy number of digital and optical properties, together with semi-metallic graphene, insulating boron nitride, semiconducting transition metal dichalcogenides, and black phosphorus. As a consequence, chip-integrated photodetectors operating at various spectral ranges could be constructed by choosing appropriate 2D materials.
In a new paper published in the journal Light Science & Application on April 20, 2022, a research team, led by Professor Xuetao Gan from Key Laboratory of Light Field Manipulation and Information Acquisition, Ministry of Industry and Information Technology, and Shaanxi Key Laboratory of Optical Information Technology, School of Physical Science and Technology, Northwestern Polytechnical University, China have reported that integrating van der Waals PN heterojunctions of 2D materials on optical waveguides can provide a promising strategy to realize chip-integrated photodetectors with low dark current, high responsivity, and fast speed.
With the 2D layered structure and no dangling bonds, researchers can stack 2D materials with different properties in different orders by “stacking wood” to form van der Waals heterostructures with atomically flat interfaces. The “arbitrary combination” of van der Waals heterojunctions can not only give the advantages properties of a single material, but also generate novel properties, achieving a leap of 1+1>2, as shown in Figure 1.
In this research, the researchers made full use of natural p-doped BP and n-doped MoTe2 for hetero-stacking, and successfully fabricated an efficient van der Waals PN heterojunction.
Second, since there are no dangling bonds on the surface of 2D materials, compared with traditional semiconductors, 2D materials do not need to consider lattice mismatch when integrating with various photonic integration platforms.
Finally, the preparation of source-drain electrodes can also be integrated on the photonic platform through the “stacking wood” technology and placed on both sides of the material, without the cumbersome processes such as photolithography.
This also greatly simplifies the fabrication process of the device, avoiding the contamination of the device interface in processes such as photolithography, which greatly improves the performance of the device.
Reference: “Chip-integrated van der Waals PN heterojunction photodetector with low dark current and high responsivity” by Ruijuan Tian, Xuetao Gan, Chen Li, Xiaoqing Chen, Siqi Hu, Linpeng Gu, Dries Van Thourhout, Andres Castellanos-Gomez, Zhipei Sun and Jianlin Zhao, 20 April 2022, Light: Science & Applications.
DOI: 10.1038/s41377-022-00784-x
