Ultrafast avalanche photodiode exceeding 100 GHz bandwidth

Area of Science:

• Optoelectronics
• Materials Science
• Semiconductor Physics

Background:

• Avalanche photodiodes (APDs) require materials with a low ionization coefficient ratio (k) for high-speed and sensitive photodetection.
• Germanium/Silicon (Ge/Si) APDs offer CMOS compatibility but are limited to tens of gigahertz bandwidth due to dual-carrier multiplication in Germanium (Ge).

Purpose of the Study:

• To overcome the bandwidth limitations of Ge/Si APDs by introducing a novel uni-multiplication-carrier concept.
• To achieve high-speed and high-sensitivity photodetection beyond current technological barriers.

Main Methods:

• Designed a separated absorption-charge-cliff-multiplication structure.
• Engineered a gradient electric field distribution within a thin Ge region.
• Achieved electron-dominated carrier multiplication with a reduced k.

Main Results:

• Demonstrated a record-high bandwidth of 105 GHz at a gain of 7.
• Enabled 8×260 Gb/s signal reception, a feat previously requiring gainless detectors.
• Achieved a 9 dB improvement in sensitivity.

Conclusions:

• The uni-multiplication-carrier concept in Ge/Si APDs transcends previous material limitations.
• This advancement enables amplifier-free optical communications, ultra-precise optical sensing, and large-scale optical computing.
• The developed APD technology offers significant improvements in speed and sensitivity for optoelectronic applications.