SiC Research Group: Theory of SiC doping and graphite overlayers on SiC surfaces

Project description

Theory of doping

A semiconductor's necessary properties for the production of electronic devices are obtained by doping, that is insertion of impurity atoms and thereby manipulation of its electronic characteristics. A high concentration of impurity atoms results in a high conductivity, which is technically required. On the path to technological success of the material there are obstacles such as the low doping efficiency and the appearance of distinctive diffusion effects. Our goal is to obtain a basic understanding of the occuring physical processes during the doping of SiC, by using ab initio methods based on density functional theory. We analyse two fundamental aspects of doping: on the one hand solubility of the impurity atoms (including impurity complexation and impurity atom compensation) and on the other hand the mechanisms of impurity atom diffusion. We want to illuminate the nature of substitutional bound doping atoms such as Boron, Phosphorus and Nitrogen and the deep defects connected with these impurity atoms. Thereby the premises for a microscopic understanding of the central aspects mentioned above are accomplished. By comparing hyperfine data from ENDOR/ESR-spectra and phonon replica from photoluminescence spectra with calculated hyperfine parameters and defect oscillation modes we are able to verify the models for the observed intrinsic and extrinsic defect centers.

Graphite overlayers on SiC surfaces

In the new funding period the interaction of graphite layers on top of SiC surfaces is studied in addtion to the theory of doping. There are strong experimental indications that the graphite aggregates play a key role in the formation of Ohmic contacts on SiC. Ohmic contacts are an important preequisite for the manufacturing of p-n diodes. It was observed that with annealing temperatures above 1000˚C SiC/nickel contacts always show an Ohmic behaviour, although the pure nickel/SiC interface has a Schottky barrier. This significant and technologically important change in the behaviour was recently attributed to the catalytic formation of graphite inclusions at the interface. It is well known that under high temperatures the SiC(0001) surface evaporates silicon, so that thin graphite layers with hiqh quality form. It is the goal of this project to understand the interaction between the graphite layer and the underlying substrate. The structural properties are investigated as well as the electronic interface states by efficient ab initio methods. This information will support the development of Ohmic contacts on SiC as well as the interaction of graphite inclusions with SiC in general, which were recently proposed as nanowires buried within the SiC crystal.


project data
project managementDr. Michel Bockstedte, Prof. Dr. Oleg Pankratov
participantsDipl.-Phys. Alexander Mattausch
keywordssemiconductors, SiC, diffusion, defects, doping
duration2002-01-01 - 2005-12-31
sponsorsGerman Research Foundation
contactphone +49 9131 8528830
fax +49 9131 8528833

Lehrstuhl für Theoretische Festkörperphysik - Institut für Theoretische Physik IV - Staudtstr. 7-B2 - 91058 Erlangen
Contact our webmaster