CMOS Photodiode

Technology #18039

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Inventors
Professor Rajeev Ram
Department of Electrical Engineering and Computer Science, MIT
External Link (www.rle.mit.edu)
Luca Alloatti
Department of Electrical Engineering and Computer Science, MIT
Dinis Cheian
Department of Electrical Engineering and Computer Science, MIT
Managed By
Jim Freedman
MIT Technology Licensing Officer - Chemicals, Instruments, Consumer Products
Patent Protection

Waveguide-Coupled Silicon-Germanium Photodetectors and Fabrication Methods for Same

PCT Patent Application WO 2017-058319

Closed-loop Resonator Silicon Germanium Photodetector Apparatus and other Semiconductor Devices Including Curved-shape Silicon Germanium Structures

PCT Patent Application WO 2017-004418

Waveguide-Coupled Silicon-Germanium Photodetectors and Fabrication Methods for Same

US Patent Pending US 2017-0040469

Closed-loop Resonator Silicon Germanium Photodetector Apparatus and other Semiconductor Devices Including Curved-shape Silicon Germanium Structures

US Patent Pending US 2017-0040487

Applications

  • Chip-to-chip optical links for optical communications
  • Active optical circuits, e.g. switches, for electro-optical feedback
  • High performance computers

Problem Addressed

Monolithic integrated circuit with photonic components is predicted to be an enabling technology for the future high-performance computer (HPC) that can achieve higher data-processing speed and lower power consumption than existing ones. However, incorporating photonic components into the integrated circuit involves non-standard procedures that increase manufacturing costs and lower fabrication yields.

Technology

This technology uses existing design rules and the IBM 45nm CMOS process to create a waveguide-coupled photodetector. The photodetector consists of a ring resonator with silicon-germanium regions that generate photocarriers. The resonant structure increases the quantum efficiency compared to a straight photodiode along with having high Q factors  between 10000 and 50000. High bandwidth for the photodiode is obtained by forming a junction inside the silicon-germanium region. Good electrical contact is achieved by placing the anode and cathode of the diode directly on the silicon instead of silicon-germanium. 

Advantages

  • High bandwidth, e.g. 32 GHz at -1 V bias
  • Large dynamic range of more than 60 dB
  • Utilizes existing CMOS foundries and typical fabrication processes
  • High responsivity of 0.55 A/W at a wavelength of 1180 nm
  • Low dark current of less than 10 pA