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Title:An ultrasonic study of point defects in electron-irradiated P-type silicon
Author(s):Johnson, Ward Lewis
Doctoral Committee Chair(s):Granato, A.V.
Department / Program:Physics
Subject(s):ultrasonic waves
point defects in crystals
electron-irradiated P-type silicon
Abstract: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.
Issue Date:1987
Genre:Dissertation / Thesis
Rights Information:1987 Ward Lewis Johnson
Date Available in IDEALS:2011-06-02
Identifier in Online Catalog:1411696

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