
576 Part 4 Functional Materials
This section deals with the physical properties of semi-
conductors. 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 rela-
tive 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 practi-
cally impossible to produce a reasonable relative change
by small changes of the absolute value of the carrier den-
sity. 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 tech-
niques, for instance by chemical doping, by temperature
changes, by the application of an electric field, or by
light. The electronic conductivity of a semiconduc-
tor can be changed intentionally by these techniques
by orders of magnitude; some techniques allow sta-
tionary 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 cur-
rent 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 world-
wide in research and development laboratories in the
field of semiconductor physics, semiconductor engi-
neering, and semiconductor chemistry. During this
time, semiconductor technology laid the foundations
for the development of data processing and of com-
munication technology and, more generally, for the
establishment of the information society. Today, semi-
conductor technology is a basic technology of our
economy, business practice, and daily life with its mod-
ern comforts.
We can give an account of only a very small part of
the empirical knowledge about semiconductors in this
Handbook. Thus, a very limited selection of semicon-
ducting substances and of physical properties is treated
here. Only three major groups of substances are consid-
ered. These are, first, the elements of the fourth group
of the Periodic Table, C, Si, Ge, and Sn, and binary
compounds between these (IV–IV compounds); second,
binary compounds between one element from the third
group of the Periodic Table, namely B, Al, Ga, or In, and
one element from the fifth group of the Periodic Table,
N, P, As, or Sb, the so-called III–V semiconductors; and
third, binary compounds between one element from the
second group of the Periodic Table, namely Mg, Ca, Sr,
Ba, Zn, Cd, or Hg, and one element from the sixth group
of the Periodic Table O, S, Se, or Te, the so-called II–VI
semiconductors.
In fact, these three major groups form a kind of ba-
sic set for the physical understanding of semiconductor
phenomena and for the wide field of semiconduc-
tor applications. It has to be kept in mind, however,
that ternary and higher compounds play a very im-
portant role in many semiconductor applications and,
furthermore, that a large number of semiconduct-
ing substances containing elements other than those
mentioned above have been developed for special
applications.
The limited number of pages of this Handbook
has forced us, furthermore, to be even more restric-
tive with regard to the properties of semiconductors,
which are considered as being of first-order im-
portance for this data collection. So, semiconductor
chemistry is beyond the scope of this Handbook.
The very broad and important field of semiconduc-
tor technology could not be included at all. Also,
the wide field of the influence of chemical dop-
ing, impurities, and defects on the properties of
semiconductors had to be left out. The Handbook’s
emphasis is on the physical properties of a re-
stricted number of most important pure semiconducting
materials.
All the data have been compiled from Landolt–
Börnstein, Numerical Data and Functional Relation-
ships in Science and Technology, New Series, Group III,
Vol. 41, Semiconductors, published in eight subvolumes
between 1998 and 2003 [1.1].
The CD-ROM and the online version of the Landolt–
Börnstein volume present a completely revised and
supplemented version of the older Landolt–Börnstein
volumes III/17 and III/22 on semiconductors. The
printed edition of Vol. III/41 contains only a supplement
to the earlier Volumes III/17 and III/22, but neverthe-
less the printed version of Vol. III/41 extends to more
than 4000 pages in the eight subvolumes. If, in addition
to the data in this Handbook, further or more detailed
information is needed, the reader is recommended to
consult [1.1].
Only a very restricted number of references is given
in this chapter to the original publications in journals.
Part 4 1