Integration of III-V optical devices and interconnects on Si using SiGe virtual substrates

Because of the limitations to the functionality that Si can provide, integration of light emitting materials such as GaAs and other III-V materials provides the promise for the combination of electrical and optical devices onto a Si platform. Monolithic integration, compare to hybrid integration, is the more cost effective and reliable way to combine these dissimilar materials. However, materials compatibility issues such as lattice mismatch, polar-on-non-polar epitaxy, and thermal mismatch make the direct growth of high quality GaAs-based material on Si difficult. However, with the use of SiGe virtual substrates, Si substrates that have the Ge lattice constant, this goal can be achieved since Ge and GaAs have a small lattice mismatch of only 0.07%. High quality GaAs on Si having a threading dislocation density lower than 3x 106 cm'2 on offcut SiGe virtual substrates has been demonstrated. While utilizing SiGe virtual substrate technology to enable high quality GaAs on Si, we have studied the crack formation in GaAs layers on SiGe resulting from the thermal mismatch between the film and the substrate. GaAs has a thermal expansion coefficient of 5.8x10-6 /ʻC while the value for Si and the SiGe substrate is 2.6x10-6 /C. The thermal expansion coefficient of the SiGe virtual substrate is mainly dictated by the underlying Si substrate. As a result of the thermal mismatch, crack arrays can form in GaAs layers grown over a critical thickness after a temperature change. These cracks can act as electrical shorting paths and can also limit the usable area for device fabrication, and therefore need to be eliminated.

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

2002

Author dc:creator

• Yang, Vicky Kung-Fan, 1975-

Advisor dc:contributor.advisor

• Eugene A. Fitzgerald.

• 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/1721.1/8446

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8446