A silicon wafer is doped with 2.50 × 1015 phosphorus atoms/cm3, 3.00 × 1017 boron atoms/cm3, and 3.00 × 1017 arsenic atoms/cm3. Calculate (a) the electron and hole concentrations (carriers per cubic centimeter), (b) the electron and hole mobilities (use Fig. 14.26), and (c) the electrical resistivity of the material.
(a)
The concentration of electrons and holes.
Answer to Problem 74AAP
The concentration of electrons is
The concentration of holes is
Explanation of Solution
Write the expression to calculate the concentration of holes.
Here, concentration of boron atoms is
Write the expression to calculate
Write the expression to calculate the concentration of electrons.
Here, the intrinsic carrier concentration is
Conclusion:
Substitute
Substitute
Substitute
Thus, the concentration of electrons is
Thus, the concentration of holes is
(b)
The electron and hole motilities.
Answer to Problem 74AAP
The mobility of electrons is
The mobility of holes is
Explanation of Solution
Conclusion:
Refer to the Figure-14.26, “The effect of total ionized impurity concentration on the mobility of charge carriers in silicon at room temperature.” to obtain the value of total impurity concentration as
Refer to the Figure-14.26, “The effect of total ionized impurity concentration on the mobility of charge carriers in silicon at room temperature.” to obtain the value of electron mobility at
Thus, the mobility of electrons is
Thus, the mobility of holes is
(c)
The electrical resistivity of the material.
Answer to Problem 74AAP
The electrical resistivity of the material is
Explanation of Solution
Conclusion:
Write the expression to calculate the resistivity for n-type semiconductor.
Substitute
Thus, the electrical resistivity of the material is
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Chapter 14 Solutions
Foundations of Materials Science and Engineering
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