An ultrasonic study of point defects in electron-irradiated P-type silicon

The mechanisms of interaction of ultrasonic waves with point defects in crystals are reviewed and a perturbation approach is introduced which leads to general expressions for the resonance and relaxation strengths in terms of matrix elements of the ultrasonic perturbation. These expressions provide the basis for a discussion of the polarization dependence of resonance and relaxation. Selection rules for cubic crystals are presented. An exploratory ultrasonic study is performed on electron-irradiated Bdoped and Al-doped silicon. Neutral substitutional boron is detected before irradiation, as expected from previous ultrasonic studies on unirradiated silicon. This defect produces both resonance and relaxation. Similar effects are observed for substitutional aluminum. After irradiation, a relaxation is observed when the sample is exposed to 0.18-0.39 eV light. By comparison with previous EPR results, this relaxation is identified as the singly positively charged state of the vacancy, v+. Preliminary results on the relaxation time and strength of v+ suggest that it may have several populated vibronic levels. Another relaxation is observed in irradiated Al-doped silicon when the sample is exposed to white light. From its annealing behavior and dopant dependence, we identify it as a non-equilibrium charge state of interstitial aluminum. The most likely states appear to be Ali 0 and Ali-. Analysis of the polarization dependence of the relaxation leads to the conclusion that the aluminum atom rests at a Td interstitial site and the surrounding lattice is Jahn-Teller distorted with e-type (tetragonal or <100> orthorhombic) symmetry.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Johnson, Ward Lewis

Contributors dc:contributor

• Granato, A.V.

• ultrasonic waves
• point defects in crystals
• electron-irradiated P-type silicon

Statement dc:rights

• 1987 Ward Lewis Johnson

Language dc:language

en

Identifier

1411696

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/25224