Abstract
We have seen in Chapter 7 that metals are characterized by partially filled valence bands and that the electrons in these bands give rise to electrical conduction. On the other hand, the valence bands of insulators are completely filled with electrons. Semiconductors, finally, represent in some respect a position between metals and insulators. We mentioned in Chapter 6 that semiconductors have, at low temperatures, a completely filled valence band and a narrow gap between this and the next higher, unfilled band. The latter one is called the conduction band. We discuss this now in more detail.
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- 1.
See Appendix 3.
- 2.
The integration should actually be done over the states in the conduction band only. However, since the probability factor F(E) is rapidly approaching zero for energies E > E F, the substitution of infinity for the upper limit does not change the result appreciably. This substitution brings the integral into a standard form, namely:
$$ \int_{ 0}^{ \infty } {{x^{1/2}}{e^{ - nx}}dx = (1/2n)\sqrt {{\pi /n}}.} $$ - 3.
Note that m = m 0, see Section 6.7 and Footnote 17 in Section 6.7.
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For numerical values, see the tables in Appendix 4.
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See the tables in Appendix 4.
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- 7.
The superscript plus means heavily doped region.
- 8.
The term impedance is used to describe the a.c. resistance, which may consist of ohmic, capacitive, and inductive parts.
- 9.
The depletion layer width in GaAs varies with impurity concentration between 3 μ m for 1014 cm–3 and 0.05 μ m for 1018 impurity atoms per cubic centimeter.
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© 2011 Springer Science+Business Media, LLC
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Hummel, R.E. (2011). Semiconductors. In: Electronic Properties of Materials. Springer, New York, NY. https://doi.org/10.1007/978-1-4419-8164-6_8
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DOI: https://doi.org/10.1007/978-1-4419-8164-6_8
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