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Research Progress in Silicon Photodetectors
Date:10/01/2018 Article: Photo:

Recently, the 2017 IEEE International Electron Devices Meeting was held in San Francisco, California, USA from 2017/12/2 to 2017/12/6. Our faculty member Yang Xu represented the research progress in silicon photodetectors, which was done by a collaborative team among ZJU-UIUC Institute, Tsinghua University, and CAS Shanghai Institute of Technical Physics. “High-Performance, Flexible Graphene/Ultra-thin Silicon Ultra-Violet Image Sensor” and “Graphene/Silicon-Quantum-Dots/Si Schottky-PN Cascade Heterojunction for Short-Wavelength Infrared Photodetection” have been published in this prestigious conference proceedings. In addition, the IEEE Spectrum Press also reported these research outcomes of our international collaboration; Yang Xu has been selected as a committee member of 2018 IEEE Electron Devices Technology and Manufacturing Conference.


Figure 1. Yang Xu’s group members presented the research work at 2017 IEDM conference (2017/12/2 – 2017/12/6) in San Francisco, USA; IEEE Spectrum Press also reported their results: click here
and their previous work published on Advanced Materials as Frontispieces showing West Lake, Hangzhou.


Owing to the mature complementary-metal-oxide-semiconductor (CMOS) device growth and fabrication techniques, Silicon has been widely used in almost all kinds of electronics applications. However, the device designed and fabricated only with Silicon cannot solve the key issues for photodetectors, due to its inefficient deep-ultraviolet (UV) light absorption. The unique crystal and energy-band structure of graphene make the fast conversion between optical and electrical signals in the waveband range from deep-UV even to terahertz possible.

Therefore, in this work, we proposed a novel ultrathin silicon/graphene flexible UV photodetector, as shown in Fig. 2. Compared with GaN and SiC Schottky photodetectors, our device showed better performance: 1010 Jones detectivity, 1 µs operation time, and 102 UV/ visible rejection ratio. In addition, the device is also semi-transparent with UV imaging capability, the performance of which is still stable after 1000 bending. 



Figure 2. (a) Schematics of PDMS assisted transfer printing of thin Si microstructures to flexible polyimide (PI) and (b-f) schematics of device fabrication process. (g) Photograph of real devices (photodetector arrays) on PI substrate. 


In recent years, this research group has been working on the integration of two-dimensional (2D) materials into the CMOS compatible image sensors, and trying to advance the performance of Silicon photodetector through the strategy namely “silicon + 2D”. The previous results have been published on journals such as Nature Communications, Advanced Materials and ACS Nano. This work might offer new ideas and methods for the development of future Silicon-based image sensors.

The series of work is supported by National Natural Science Foundation of China (Grant No. 61674127, 61474099), Zhejiang Natural Science Foundation (LZ17F040001), Zhejiang Key Laboratory for Advanced Microelectronic Intelligent Systems and Applications, ZJU-UIUI Institute, and State Key Laboratory of Silicon Materials.