CMOS Photodiode

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