Al+ implantation into epitaxial 6H-SiC: evolution of vacancy-type damage influenced by the substrate temperature


Al+ implantation into epitaxial 6H-SiC: evolution of vacancy-type damage influenced by the substrate temperature

Anwand, W.; Brauer, G.; Skorupa, W.

Slow Positron Implantation Spectroscopy (SPIS) is a nondestructive method whereby positrons of a predetermined energy are implanted into a solid. In a certain depth region they annihilate with electrons. The motion of the positron-electron pair prior to the annihilation causes a Doppler broadening of the photopeak. The Doppler broadening of the annihilation line, characterized by two lineshape parameters, is measured in dependence on the incident positron energy and thereby on the depth where the annihilation took place.
SPIS is well known for its sensitivity to vacancy-type defects in solids. For this reason, this method has been applied to investigate the damage created by implantation of Al+ ions into epitaxial 6H-SiC. Al+ was implanted at an energy of 200 keV and a fluence of 1x1015 cm-2. In order to minimize the implantation-induced damage the substrate temperature was varied from room temperature up to 800 oC in steps of 200 degrees. Depth dependent defect profiles were calculated from the measured lineshape parameters versus the incident positron energy using the software package VEPFIT [1]. These depth profiles show significantly deeper reaching defects as calculated by TRIM [2]: whereas TRIM calculations result in a maximum depth of vacancies of about 300 nm, the positron measurements show that multiple vacancy clusters can be found up to a depth of more than 1µm below the surface. In addition to the extraction of the depth distribution of the damage it was possible to estimate the size of the vacancy agglomerates from the positron data in dependence on the substrate temperature and the depth position. The size of the damage and its depth distribution will be compared for different substrate temperatures during implantation and it will be shown that the damage minimum is obtained at a substrate temperature of 190 oC.

[1] A. van Veen, H. Schut, J. de Vries, R. A. Hakvoort, and M. R. Ijpma, in Positron beams for solids and surfaces, edited by P. J. Schultz, G. R. Massoumi, J. P. Simpson (American Institute of Physics, New York, 1990), p. 171
[2] The Stopping and Range of Ions in Solids, eds. J. F. Ziegler, J. P. Biersack, and U. Littmark (Pergamon Press, NewYork, 1999)

Keywords: ion implantation; 6H-SiC; positron annihilation

  • Poster
    European Conference on Silicon Carbide and Related Materials, Linköping, Sweden, September, 1-6, 2002

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Publ.-Id: 4772