Properties of Silicon Carbide
Fully indexed with over 1000 references to published and unpublished sources, this book draws together the expert knowledge of numerous researchers from around the world to completely characterize the SiC system.
TABLE OF CONTENTS Properties of Silicon Carbide
Chapter 4: Energy Levels
4.1 Energy Levels of Impurities in SiC
I. Nashiyama
August 1993
A INTRODUCTION
This Datareview lists the energy levels of impurities from groups II, III, V and VI in several of the SiC polytypes. The most widely studied impurity is nitrogen as this is believed to cause the n-type character of high purity material. Boron, aluminium and gallium have also received a great deal of attention as acceptors in SiC. Reports of beryllium-doping and oxygen-doping have also been made. The standard techniques of Hall measurements and photoluminescence have mainly been used in these . studies.
B MULTIPLE DONOR AND ACCEPTOR LEVELS
Impurity atoms in SiC substitute on either the silicon or carbon sublattice. Nitrogen as well as other donor impurities, such as phosphorus, occupy the carbon sites [1 3]. Boron may substitute on the carbon sublattice or may occupy either the carbon or the silicon site (or both sites), in order to minimise the total free energy of the system. Aluminium atoms substitute only on the silicon sublattice [4]. The SiC polytype does not affect the site preference of these impurities, though energy levels of impurity atoms differ in the different polytypes. In addition, owing to the long unit cells of various SiC polytypes except 3C- and 2H-SiC, many inequivalent lattice sites exist, which are divided into two species: a cubic-like atomic configuration of the first- and second-neighbour atoms and a hexagonal-like atomic configuration. Stacking sequences in the c-axis direction and numbers of cubic-like and hexagonal-like sites in 2H-, 3C-,...
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