70 GHz InGaAs metal-semiconductor-metal photodetectorsfor polarisation-insensitive operation

InGaAs metal-semiconductor-metal photodetectors with 0.2 µm feature size finger electrodes have been fabricated. A pulse response time of 3.8 ps for 1.55 µm light was measured by means of electro-optical sampling. A 3 dB bandwidth of 70 GHz was extracted from the time domain data. Polarisation-insensitive operation under front illumination was obtained by employing semicircular-type finger electrodes for the photodetectors with a 14 µm diameter active area.