Thinned and Back-side Illuminated Photodiodes

Featured Product from PREMA Semiconductor GmbH

Wireless Retina Implant Electrostimulates Ganglion Cells

Wafers with PREMA photodiodes consisting of pn-junctions close to the upper surface have been back-grinded to 20 µm, 35 µm, 60 µm and 100 µm. The spectral sensitivity of singulated photodiodes has been measured with back-side illumination. The spectral sensitivity is increased up to 0,18 A/W by a metal cap above the photodiodes. Here, photons that have not been absorbed are reflected. The retina implant consists of thinned photodiodes embedded in a foil substrate. While the light enters the photodiode at the back-side, the contact pads at the front-side can be utilized to electro-stimulate the ganglion cells.


  • Photodiodes with different thicknesses
  • Varied spectral responsibility
  • Additional metal cap for light reflexion
  • Efficiency is only reduced to about 35 %


  • Retina Implant
  • Photodiode-Arrays

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