A High-Efficiency Waveguide Photodiode for 40-Gb/s Optical Receivers

Takeshi TAKEUCHI  Takeshi NAKATA  Kiyoshi FUKUCHI  Kikuo MAKITA  Kenko TAGUCHI  

IEICE TRANSACTIONS on Electronics   Vol.E82-C    No.8    pp.1502-1508
Publication Date: 1999/08/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Joint Special Issue on Recent Progress in Optoelectronics and Communications)
Category: Optical Active Devices and Modules
photodiode,  optical waveguide,  optical receiver,  optical communication,  

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Waveguide photodiodes (WGPDs) are key devices for high-speed optical receivers in trunk lines because of their potential ability to provide both high efficiency and a high-speed response. We have designed a waveguide photodiode for 40-Gb/s-range optical receivers. The optical coupling characteristics were simulated in detail to optimize the waveguide structure, and the electrodes of the photodiode were designed to form a coplanar transmission line to match the system impedance, which minimized frequency-response degradation. A highly beryllium-doped, low-temperature-grown InGaAs contact layer grown by gas source molecular beam epitaxy was used to reduce the series resistance, and approximately 40% reduction of series resistance was achieved. The fabricated device exhibited both a very high external quantum efficiency of 81% for 1.55-µm light and a sufficient bandwidth of more than 40 GHz. Though we used a simple conventional fabrication process, excellent characteristics were achieved due to the optimized optical design and well suppressed parasitic parameters.