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and gaas and alp the data table

And gaas and alp the data table

Electrical resistivity (10–8 �– m)

7 Composition (at% Zn) Questions and Problems 395

FIGURE 12.35 Room-temperature

10 20 30

alloys. (Adapted from Metals


Handbook: Properties and


1979, p. 315.)



10 20 30 40
are 1.5 free electrons per gold atom. The electrical conductivity and density for Au
are 4.3 � 107(�-m)�1and 19.32 g/cm3, re- this alloy given the following data:
spectively. (b) Now compute the electron
From Figure 12.35, estimate the value of A in Equation 12.11 for zinc as an impurity



in copper–zinc alloys.

1.88 � 10�8 8.94
(a) Using the data in Figure 12.8, determine 5.32 � 10�7 8.25
the values of �0 and a from Equation 12.10 for pure copper. Take the temperature T 12.19 The room-temperature electrical resistivit-ies of pure lead and pure tin are 2.06 �

composition for all compositions between

Figure 12.8. (c) Using the results of parts a and b, estimate the electrical resistivity of

pure lead and pure tin.

Determine the electrical conductivity of a
Cu-Ni alloy that has a yield strength of 125
MPa (18,000 psi). You will find Figure

(c) Explain the shapes of these two curves, as well as any differences between them.

Tin bronze has a composition of 92 wt% Cu and 8 wt% Sn, and consists of two phases

12.20 A cylindrical metal wire 2 mm (0.08 in.) in diameter is required to carry a current of 10 A with a minimum of 0.03 V drop per

at room temperature: an � phase, which is copper containing a very small amount of
tin in solid solution, and an � phase, which



(a) Compute the number of free electrons and holes that exist in intrinsic germanium

tion involving an acceptor impurity atom.

sume that the impurity elements are substi-

for Ge and Si, which are 5.32 and 2.33 g/ cm3, respectively.

N Si
B Ge

ature as follows:
n, p � exp��Eg 2kT

Zn GaAs
S InSb
In CdS
As ZnTe

or, taking natural logarithms,

12.23 12.30
Thus, a plot of the intrinsic ln n (or ln p)

tor? (c) Make a schematic plot of Fermi energy versus temperature for an n-type

semiconductor up to a temperature at

trinsic, compound, elemental. Now provide an example of each.

(a) The room-temperature electrical con-ductivity of a silicon specimen is 103(�-


hole mobilities for silicon in Table 12.2,


your answer.

For each of the following pairs of semicon-
ductors, decide which will have the smaller

Using the data in Table 12.2, compute the electron and hole concentrations for intrin-

12.26 12.32

sic InSb at room temperature.

free electrons in numbers in excess of those

ductor at room temperature, and virtually all the Sb atoms may be thought of as being

ionized (i.e., one charge carrier exists for each Sb atom). (a) Is this material n-type or p-type? (b) Calculate the electrical con-

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