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Chapter 18: Problem 24

Define the following terms as they pertain to semiconducting materials: intrinsic, extrinsic, compound, elemental. Now provide an example of each.

Short Answer

Expert verified
Answer: Intrinsic semiconductors are pure materials, with electrical properties determined solely by their inherent characteristics. An example is undoped silicon (Si). Extrinsic semiconductors are doped materials with added impurities, altering their electrical properties. An example is phosphorus-doped silicon (Si:P). Compound semiconductors consist of two or more elements from the periodic table, resulting in distinct properties. An example is gallium arsenide (GaAs). Elemental semiconductors are composed of a single element from the periodic table, either intrinsic or extrinsic. An example is germanium (Ge).

Step by step solution

01

1. Define Intrinsic Semiconductors

Intrinsic semiconductors are pure or undoped materials, which have a balanced number of electrons and holes in the valence band. The electrical conductivity in intrinsic semiconductors is due to the thermal generation of electron-hole pairs. In other words, their electrical properties are solely determined by the inherent characteristics of the material and not influenced by any added impurities.
02

2. Example of an Intrinsic Semiconductor

An example of an intrinsic semiconductor is pure silicon (Si) that has not been doped with any impurities. It has a relatively low electrical conductivity at room temperature, which increases with increasing temperature.
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3. Define Extrinsic Semiconductors

Extrinsic semiconductors are materials that have been intentionally doped (i.e., impurities have been added) to alter their electrical properties. The added impurities introduce either extra electrons (n-type) or extra holes (p-type) to the semiconducting material, which subsequently increases its conductivity.
04

4. Example of an Extrinsic Semiconductor

An example of an extrinsic semiconductor is phosphorus-doped silicon (Si:P). Phosphorus has five valence electrons, and when it is added to silicon, it provides extra free electrons (n-type doping), which increases the electrical conductivity of the doped silicon material.
05

5. Define Compound Semiconductors

Compound semiconductors are composed of two or more elements from different groups in the periodic table. These materials tend to have properties that are distinct from those of pure, elemental semiconductors, such as improved optoelectronic and electronic performance.
06

6. Example of a Compound Semiconductor

An example of a compound semiconductor is gallium arsenide (GaAs). It has a high electron mobility and direct bandgap, making it useful for high-speed electronics and optoelectronic devices such as lasers and solar cells.
07

7. Define Elemental Semiconductors

Elemental semiconductors are composed of a single element from the periodic table. These materials can be either intrinsic or extrinsic depending on the presence of doping impurities, and they often serve as the foundation for understanding the properties of semiconducting materials.
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8. Example of an Elemental Semiconductor

An example of an elemental semiconductor is pure germanium (Ge), which has a similar crystal structure to silicon and is used in electronics and optoelectronics. In its undoped form, germanium is an intrinsic semiconductor; however, it can be turned into an extrinsic semiconductor by doping with other elements.

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Most popular questions from this chapter

(a) Using the data presented in Figure 18.16, determine the number of free electrons per atom for intrinsic germanium and silicon at room temperature \((298 \mathrm{~K})\). The densities for Ge and \(\mathrm{Si}\) are \(5.32\) and \(2.33 \mathrm{~g} / \mathrm{cm}^{3}\), respectively. (b) Now explain the difference in these freeelectron-per-atom values.

Cite the differences in operation and application for junction transistors and MOSFETs.

Consider a parallel-plate capacitor having an area of \(2500 \mathrm{~mm}^{2}\) and a plate separation of \(2 \mathrm{~mm}\), and with a material of dielectric constant \(4.0\) positioned between the plates. (a) What is the capacitance of this capacitor? (b) Compute the electric field that must be applied for \(8.0 \times 10^{-9} \mathrm{C}\) to be stored on each plate.

At room temperature the electrical conductivity and the electron mobility for copper are \(6.0 \times 10^{7}(\Omega \cdot \mathrm{m})^{-1}\) and \(0.0030 \mathrm{~m}^{2} / \mathrm{V} \cdot \mathrm{s}\), respectively. (a) Compute the number of free electrons per cubic meter for copper at room temperature. (b) What is the number of free electrons per copper atom? Assume a density of \(8.9 \mathrm{~g} / \mathrm{cm}^{3}\)

A charge of \(3.5 \times 10^{-11} \mathrm{C}\) is to be stored on each plate of a parallel-plate capacitor having an area of \(160 \mathrm{~mm}^{2}\left(0.25 \mathrm{in} .^{2}\right)\) and a plate separation of \(3.5 \mathrm{~mm}(0.14 \mathrm{in}\).). (a) What voltage is required if a material having a dielectric constant of \(5.0\) is positioned within the plates? (b) What voltage would be required if a vacuum were used? (c) What are the capacitances for parts (a) and (b)? (d) Compute the dielectric displacement for part (a). (e) Compute the polarization for part (a).
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