High mobility strained Si/SiGe heterostructure MOSFETs : channel engineering and virtual substrate optimization

High quality relaxed silicon-germanium graded buffers are an important platform for monolithic integration of high speed heterostructure field-effect transistors and III-V-based optoelectronics onto silicon substrates. In this thesis, dislocation dynamics in compositionally graded SiGe layers are explored and mobility enhancements in strained Si/SiGe metal-oxide-semiconductor field-effect transistors (MOSFETs) are evaluated. These results demonstrate the dramatic increases in microelectronics performance and functionality that can be obtained through use of the relaxed SiGe integration platform. By extending and modifying a model for dislocation glide kinetics in graded buffers to SiGe/Si, a complete picture of strain relaxation in SiGe graded buffers emerges. To investigate dislocation glide kinetics in these structures, a series of identical samples graded to 30% Ge have been grown at temperatures between 650ʻC and 900ʻC on (001)-, (001) offcut 6ʻ towards an in-plane <110>-, and (001) offcut 6ʻ towards an in-plane <100>-oriented Si substrates. The evolution of field threading dislocation density (TDD) with growth temperature in the on-axis samples indicates that dislocation nucleation and glide kinetics together control dislocation density in graded buffers. The TDD of samples grown on offcut substrates exhibits a more complicated temperature dependence, due to their reduced tendency towards dislocation pile-up formation at low temperature and dislocation reduction reactions at high temperature. Finally, by evaluating field threading dislocation density and dislocation pile-up density in a wide variety of SiGe graded buffers, a correlation between dislocation pile-up formation and increases in field threading dislocation density emerges.

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

• Leitz, Christopher W. (Christopher William), 1976-

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/1721.1/8440

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8440