High-Current Back-Illuminated Partially Depleted-Absorber p-i-n Photodiode With Depleted Nonabsorbing Region

We demonstrate a high-current back-illuminated InGaAs/InP p-i-n photodiode (PD), whose depleted region comprises partially depleted-absorbing, depleted-absorbing, and depleted-nonabsorbing layers to increase RF power output. The back-illuminated PD has an advantage of small thermal resistance between a photoabsorber and a heat sink for avoiding catastrophic thermal failure. The thermal resistance decreases with an increase in the detecting area; however, it simultaneously increases the capacitance, imposing a limitation on the RF response. To reduce the capacitance, we have incorporated a depleted-nonabsorbing layer into a partially depleted absorber PD structure that photogenerated electrons can drift trough. We have fabricated two samples, one with a detecting area of 50 μm, and the other with a detecting area of 70 μm in diameter. Both PDs show high RF power outputs of 28.7 and 29.0 dBm at a frequency of 5 GHz, and 25.7 and 26.7 dBm at each -3-dB frequency of 10.5 and 7 GHz, respectively.