Improvements of photodiodes structures for communication applications

Photogenerated carriers in a photodiode drift in the junction before joining the circuit. We must use a quite thin depletion region so that their transit time does not penalize the microwave response of the devices. However, when the depletion region decreases the component capacity increases, which highly limits the microwave response of this latter. Replace the completely absorbent depletion region by a mixed depletion region increases the pure transit cut-off frequency for the same thickness of the depletion region. We use this property in what follows to optimize the performance of PIN photodiode based on InP/InGaAs, adapted for the photodetection at the wavelength of 1.55 μm. The obtained results show that the maximum area of photodiodes with mixed depletion regions with thin absorbent exceeds by 64% that of the photodiodes with completely absorbent depletion regions for the same bandwidth. Their maximum absorption volume exceeds by 8% that of the photodiodes with completely absorbent depletion regions for the same bandwidth. Both types of components are also compared on the abacuses when the thickness of the absorbent and the surface are imposed.