Defect study of N-type 6H silicon carbide using positron lifetime spectroscopy

by Lam, Chi-hung

Abstract (Summary)
(Uncorrected OCR) Abstract of thesis entitled DEFECT STUDY OF N-TYPE 6H SILICON CARBIDE USING POSITRON LIFETIME SPECTROSCOPY submitted by LAM CHI HUNG for the Degree of Master of Philosophy at The University of Hong Kong in August 2002 Vacancy-type defects in as-grown nitrogen doped n-type 6H Silicon Carbide (SiC) were studied using positron lifetime spectroscopy in the temperature range of 10 K to 300 K. Samples were annealed at temperatures of 400, 650, 900, 1200 and 1400 ? and the annealing behaviour of the material was investigated. For the as-grown n-type 6H-SiC samples, a positron trapping centre with a lifetime value of 200 ?9 ps was observed. In addition, another positron trapping centre with a lifetime value very close to that of bulk (~ 148 ps) was found to compete with the 200-ps lifetime component. This lifetime component predominates at low temperatures (less than 100 K). It is suggested that the long lifetime positron trapping site was attributed to the co-existence of the VCVSi divacancy defect and the VSi monovacancy defect. The low temperature trap is suggested to be either a Rydberg state formed by binding the positron with a negative impurity centre or a carbon vacancy defect VC. In the annealing study of the n-type 6H-SiC samples, the VCVSi divacancy defect, which has a lifetime of 232 ?6 ps, was thermally stable at the annealing temperature of 1400 ?. The VSi monovacancy defect was observed to anneal out in the temperature range of 400 to 650 ?.
Bibliographical Information:


School:The University of Hong Kong

School Location:China - Hong Kong SAR

Source Type:Master's Thesis

Keywords:positrons silicon carbide spectra semiconductors defects


Date of Publication:01/01/2003

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