The Development of High-Speed (Beyond 25 Gbit/Sec) and High Linearity Avalanche Photodiode for the Applications of High-Capacity and Long-Reach Ethernet( I )

Avalanche photodiodes (APDs) which operate at the 1.55m wavelength have recently attracted a lot ofattention due to their superior performance in sensitivity to that of p-i-n photodiodes. Now APDs operatedat 10 Gbit/sec is very popular and has strong demanding in the market of passive optical network (PON).However, compared with the p-i-n PDs, APDs usually have a much slower internal speed, because of thesecondary-hole (or electron) drift-time and avalanche delay time inside its active layer. These bandwidthlimiting factors become obstacles to further boost the speed of APD to meet the requirement of nextgeneration (100) 400 Gbit/sec Ethernet. In (100) 400 Gbit/sec fiber communication system, receiver withhigh sensitivity and can be operated at the data rate as high as 25 or 50 Gbit/sec per channel are necessary.Furthermore, a high-linearity performance in such high-speed/-sensitivity APD is also required due to theappearance of burst-mode signal in the receiving end.In this work, we will demonstrate a novel p-side up mesa type In0.52Al0.48As based APD with partiallydepleted p-type absorber inside. By utilizing our proposed mesa structure, the high-E field would bestrongly confined in the bottom and center parts of device without exposing to the air. This should greatlybenefit its reliability performance. In addition, the partially depleted absorber in our structure caneffectively shorten the hole drift-time without sacrificing the efficiency performance.In order to pursue such high-speed performance (>25 Gbit/sec) in APD, a thin (< 100 nm) In0.52Al0.48Asbased multiplication (M-) layer is usually required. However, this would result in a tremendous increaseof dark current (and its induced short-noise) and may degrade the sensitivity performance of APD. In thisproject, we will also adopt a novel design of multiplication layer; “composite multiplication layer”, whichcan minimize the increase of dark current with the decrease of M-layer thickness.Overall, by combing with the above-mentioned device technology with advanced package technology,which is supported by Source Photonic Company, we will demonstrate a high-linearity/-sensitivity-/ andreliable APD based photo-receiver module for next-generation (100) 400 Gbit/sec Ethernet communicationsystem.