Multi-channel RF-optical receiver enabled by a high performance p-i-n InP-InGaAs-based photodetector array

We propose an integrated back-illuminated InP/InGaAs p-i-n photodetector array (PDA) with high responsivity (R) and external quantum efficiency (EQE). The PDA was characterized and packaged for small-signal response and transmission experiments. At a bias voltage of -5 V, the dark current is below 17.5 μA/cm², and the average optical responsivity reaches up to 1 A/W for each ∅=50μm element at 1550 nm. The external quantum efficiency is as high as 81% at -5 V at 1550 nm. Under a photocurrent of 63 μA at -5 V bias, the proposed InP/InGaAs PDA exhibits an average 3 dB bandwidth of 3.6 GHz. We finally demonstrate a BER below 10^-12 at a 2.25 Gbit/s data rate. The compact size and large photosensitive area of the PDA will enable new applications for radio on free-space optical (RoFSO) communications.