Very high speed operation of planar InGaAs/InP photodiode detectors.

Planar, diffused, InGaAs/InP pin detectors have been optimized for high speed operation. In order to minimize the junction capacitance the p-n junction diameter was reduced to 25microns, resulting in operating chip capacitance as low as 20 fF. The relationship between the bandwidth and quantum efficiency was investigated by varying the thickness of the n-InGaAs absorbing layer, from 8microns down to 0.4microns. Using optical heterodyning techniques, a response bandwidth (-3 dB) in excess of 20 GHz was demonstrated. The quantum efficiency of the fastest devices is 38% at 1.3micron wavelength.