Cryogenic performance of a high-speed GaInAs/InP p-i-n photodiode

The cryogenic performance of a high-speed GaInAs/InP p-i-n photodiode, with graded bandgap layers at the heterostructure interfaces, was investigated for the first time. DC measurements show that the dark current of the diode decreases sharply as the temperature decreases from 300 to 200 K. A factor of 1000 in dark current reduction was found for this photodiode, when it was cooled from room temperature to about 150 K. Similar modulation bandwidths were found for this device for temperatures between 9 and 300 K, with a bandwidth greater than 20 GHz. No degradation was found in performance at cryogenic temperature compared to room temperature. This enables direct integration of high-speed photodiodes with superconductive and other cryogenic electronics.