850 nm GaAs P-i-N Photodiodes for 50 Gb/s Optical Links with Dark Current below 1 pA

Dufei Wu, University of Illinois at Urbana Champaign
Yu-Ting Peng, University of Illinois, Urbana-Champaign
Milton Feng, University of Illinois, Urbana-Champaign

Fabrication techniques and experimental data are presented for 850 nm GaAs P-i-N photodiodes designed for 50 Gb/s optical links. Optimizations in the device structure and the selective dry etching process reduce dark current below 1pA. Responsivity is shown to be comparable to commercial devices with similar dimensions. And microwave measurement shows a highest bandwidth of above 30 GHz, indicating potential for 60 Gb/s operation. Data rate testing is performed with a VCSEL up to 50 Gb/s, showing clear eye diagrams.

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