Germanium-rich silicon-germanium materials for field-effect modular application

The development of electric-field-induced optical modulation in the materials capable of monolithically integrated on silicon (Si) substrates offer the possibility of high-speed modulation in a pico second timeframe as well as low power consumption, key requirements for integrated modulator applications. This thesis presents a study of the Franz-Keldysh effect in germanium (Ge) layers epitaxially grown on Si substrates, by using free-space spectral responsivity measurement. Generalized Franz-Keldysh formalism and separately measured Ge material constants were used to calculate theoretical results, which were in agreement with experimental data. The Franz-Keldysh model predicts that the Ge layers on Si substrates will be the best material for phase modulation at nearly 2 [mu]m wavelength, with a value of L, of 3.8 mm and insertion loss of 0.4 dB. In addition, this thesis presents the design of silicon-germanium (SixGe1-x) electroabsorption and phase modulators at 1.55 pLm wavelength from the Franz-Keldysh model. The composition optimized for electroabsorption and phase modulator applications is SixGe1-x with a value of x~0.075 and 0.135, respectively. To achieve high-quality Ge-rich SiGe materials for the modulator applications, deposition of SixGe1-x (0.008<x<0.125) buffers at low temperature was performed, and the growth kinetic was studied. The films were deposited on SiGe buffers to reduce lattice mismatch between the buffers and the remainders of the films, and were in-situ annealed in the same condition as was used for similarly grown Ge films for a reduction of threading dislocation density. Si0.15Ge0.85 p-i-n diodes and Sio.15Geo.ss rib waveguides were fabricated.

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

• Jongthammanurak, Samerkhae

Advisor dc:contributor.advisor

• Lionel C. Kimerling.

• 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/1721.1/44314

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/44314