Ultrafast multireflection- and transparent thinfilm silicon photodiodes

Thin-silicon-film mesa-shaped pin-photodiodes are presented, which exhibit high internal quantum efficiency at risetimes below 100 ps using a grated highly reflecting back contact and total reflection at the top. Theoretical and typical experimental data are given. Transparent photodiodes fabricated in a similar way are introduced, which can be inserted into an optical transmission path to take out a fraction of power without the need of an optical coupler.