SiGe electro-absorption modulators for applications at 1550nm

A novel SixGe₁-x, electro-absorption modulator design is experimentally demonstrated. The device is waveguide integrated, butt-coupled into high index contrast Si/SiO2 waveguides. 0.75% Silicon concentration in the alloy is optimized for 1550nm applications. With its 400nm height, 600nm width, and 50,pm length, the device has a footprint smaller than 30[mu]m². Low effective driving voltage, <2.5V, is needed to achieve an extinction ratio of 5.2dB in the broad 1510-1555nm wavelength operation range. At 1550nm, an extinction ratio of 6.5dB is achieved with an applied effective bias of -2.5V. High frequency measurements determine the device can reach a 3dB frequency of 1.2GHz. Electrical characterization of the device shows high series resistance (~15k[omega]) which is caused by fabrication over-etching during metal contact deposition. Series resistance reduction to ~100[omega] would allow the device to reach the predicted 3dB frequency of 100GHz with 10dB extinction ratio. A pseudo-linear relation is found between the achieved extinction ratio and the applied effective bias. The ratio between these two quantities, the modulation efficiency, can be considered as a new figure of merit of the device. The slope of this pseudo-linear relation measures 2.2dB/V for extinction ratio values ranging between 0 and 5.5dB. In terms of modulation depth it is equivalent to a slope of 40%/V in the range 0.5V-2V. Finally, an ultra-low power consumption per bit of 34fJ/bit is measured for a capacitance of 11fF and an effective applied reverse bias of 2.5V.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Materials Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Bernardis, Sarah

Advisor dc:contributor.advisor

• Lionel C. Kimerling and Jurgen Michel.

• Materials Science and Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/44385

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/44385