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Interdisziplinäres Zentrum für Materialwissenschaften
Nanotechnikum Weinberg
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F. Redmann
Untersuchung von Siliziumkarbidkristallen mit Hilfe der Positronen-Annihilations-Spektroskopie
Dissertation (2003),

In the center of this work the characterisation of vacancies-like defects in the silicon carbide is located, as they are to be found after the crystal growth or by irradiation or ion implantation. Vacancies do not possess an influence on the electrical and optical characteristics of semiconductors, which can be neglected. Element structures on SiC basis are accomplished exclusively by ion implantations. The crystal defects arising with it were examined with the positron annihilations spectroscopy and compared with other research methods, like DLTS and EPR. Starting point of the work is the investigation of substrate crystals. In them carbon vacancies and double vacancies with the positron lifetime spectroscopy could be proven. After the irradiation with 2 MeV electrons additionally silicon vacancies were detected. Annealing studies and positron lifetime measurements under monochromatic lighting show similar behaviour of the silicon vacancy with the E1/E2-Defekt, detected with DLTS at electron-irradiated 6H SiC. A further emphasis is the investigation of layer systems, as they are present with epitaxial wafers on SiC basis. 4H and 6H-SiC epitaxial films were examined after electron irradiation and ion implantation (He, B, SI, C) with the Doppler broadening spectroscopy and the positron lifetime spectroscopy. The moreover one the validity of existing diffusion models for boron in SiC was examined.

Keywords: silicon carbide; irradiation; positron annihilation; implantation; annealing; lifetime

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