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Register a new userHigh-performance silicon-graphene hybrid plasmonic waveguide photodetectors beyond 1.55 {mu}m
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A fast silicon-graphene hybrid plasmonic waveguide photodetectors beyond 1.55 {mu}m is proposed and realized by introducing an ultra-thin wide silicon-on-insulator ridge core region with a narrow metal cap. With this novel design, the light absorption in graphene is enhanced while the metal absorption loss is reduced simultaneously, which helps greatly improve the responsivity as well as shorten the absorption region for achieving fast responses. Furthermore, metal-graphene-metal sandwiched electrodes are introduced to reduce the metal-graphene contact resistance, which is also helpful for improving the response speed. When the photodetector operates at 2 {mu}m, the measured 3dB-bandwidth is >20 GHz (which is limited by the experimental setup) while the 3dB-bandwith calculated from the equivalent circuit with the parameters extracted from the measured S11 is as high as ~100 GHz. To the best of our knowledge, it is the first time to report the waveguide photodetector at 2 {mu}m with a 3dB-bandwidth over 20 GHz. Besides, the present photodetectors also work very well at 1.55 {mu}m. The measured responsivity is about 0.4 A/W under a bias voltage of -0.3 V for an optical power of 0.16 mW, while the measured 3dB-bandwidth is over 40 GHz (limited by the test setup) and the 3 dB-bandwidth estimated from the equivalent circuit is also as high as ~100 GHz, which is one of the best results reported for silicon-graphene photodetectors at 1.55 {mu}m.
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Silicon photonics is being extended from the near-infrared (near-IR) window of 1.3-1.5 {mu}m for optical fiber communications to the mid-infrared (mid-IR) wavelength-band of 2 {mu}m or longer for satisfying the increasing demands in many applications. Mid-IR waveguide photodetectors on silicon have attracted intensive attention as one of the indispensable elements for various photonic systems. Previously high-performance waveguide photodetectors on silicon were realized for the near-IR window of 1.3-1.5 {mu}m by introducing another semiconductor material (e.g., Ge, and III-V compounds) in the active region. Unfortunately, these traditional semiconductor materials do not work well for the wavelength of ~2 {mu}m or longer because the light absorption becomes very weak. As an alternative, two-dimensional materials provide a new and promising option for enabling active photonic devices on silicon. Here black-phosphorus (BP) thin films with optimized medium thicknesses (~40 nm) are introduced as the active material for light absorption and silicon/BP hybrid ridge waveguide photodetectors are demonstrated with a high responsivity at a low bias voltage. And up to 4.0Gbps data transmission is achieved at 2{mu}m.
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