Semiconductors
The organization of this section follows a two-step approach. The first step corresponds to searching for the substance of interest, that is, the relevant group of substances. The second step corresponds to the physical property of interest.
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p IV Semiconductors and IV–IV Compounds ......................... 578 4.1.2 III–V Compounds ................................ 4.1.2.1 Boron Compounds ................... 4.1.2.2 Aluminium Compounds............ 4.1.2.3 Gallium Compounds ................ 4.1.2.4 Indium Compounds .................
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4.1.3 II–VI Compounds ................................ 4.1.3.1 Beryllium Compounds .............. 4.1.3.2 Magnesium Compounds ........... 4.1.3.3 Oxides of Ca, Sr, and Ba ........... 4.1.3.4 Zinc Compounds...................... 4.1.3.5 Cadmium Compounds .............. 4.1.3.6 Mercury Compounds ................
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References .................................................. 691
Part 4 1
Semiconducto 4.1. Semiconductors
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Part 4
Functional Materials
Part 4 1
This section deals with the physical properties of semiconductors. Semiconductors are substances which, like metals, are electronic conductors. In contrast to metals, however, the density of freely mobile charge carriers in semiconductors is, under normal conditions, smaller by orders of magnitude than it is in metals. Therefore, in semiconductors, a small change in the absolute value of the charge carrier density can induce a large relative change in this carrier density and in the electrical conductivity. In metals, on the other hand, the carrier density is so high from the beginning that it is practically impossible to produce a reasonable relative change by small changes of the absolute value of the carrier density. In conclusion, we can say that in semiconductors, and only in semiconductors, is it possible to manipulate the electronic conduction by small changes of the carrier density. Such changes can be effected by a number of techniques, for instance by chemical doping, by temperature changes, by the application of an electric field, or by light. The electronic conductivity of a semiconductor can be changed intentionally by these techniques by orders of magnitude; some techniques allow stationary changes, and some techniques also allow time-dependent changes on a very short timescale. Semiconducting materials are functional materials thanks to the above properties: they can be used as very small, robust, energy-efficient devices to control the current in electrical networks, either on the basis of external driving or on the basis of their internal, tailor-made device characteristics. During the last 50 years, a tremendous amount of knowledge and experience has been collected worldwide in research and development laboratories in the field of semiconductor physics, semiconductor engineering, and semiconductor chemistry. During this time, semiconductor technology laid the foundations for the development of data processing and of communication technology and, more generally, for the establishment of the information society. Today, semiconductor technology is a basic technology of our economy, business practice, and daily life with its modern comforts. We can give an account of only a very small part of the empiri
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