Skip to main content
Pearson+ LogoPearson+ Logo
Ch.12 - Solids and Modern Materials
All textbooksBrown 14th EditionCh.12 - Solids and Modern MaterialsProblem 123
Previous problem
Next problem
Chapter 12, Problem 123

When you shine light of band gap energy or higher on a semiconductor and promote electrons from the valence band to the conduction band, do you expect the conductivity of the semiconductor to (a) remain unchanged, (b) increase, or (c) decrease?

Verified step by step guidance
1
Step 1: Understand the structure of a semiconductor. Semiconductors have a valence band filled with electrons and a conduction band that is typically empty. The energy gap between these two bands is known as the band gap.
Step 2: Consider what happens when light with energy equal to or greater than the band gap is shone on the semiconductor. This energy can excite electrons from the valence band to the conduction band.
Step 3: Recognize that when electrons are promoted to the conduction band, they leave behind holes in the valence band. Both the electrons in the conduction band and the holes in the valence band can contribute to electrical conductivity.
Step 4: Analyze the effect of increased charge carriers. With more electrons in the conduction band and more holes in the valence band, the number of charge carriers increases, which typically enhances the material's ability to conduct electricity.
Step 5: Conclude that the conductivity of the semiconductor is expected to increase when light of band gap energy or higher is shone on it, due to the increased number of charge carriers.
Previous problem
Next problem
Related Practice
Textbook Question

In their study of X-ray diffraction, William and Lawrence Bragg determined that the relationship among the wavelength of the radiation 1l2, the angle at which the radiation is diffracted 1u2, and the distance between planes of atoms in the crystal that cause the diffraction (d) is given by nl = 2d sin u. X rays from a copper X-ray tube that have a wavelength of 1.54 Å are diffracted at an angle of 14.22 degrees by crystalline silicon. Using the Bragg equation, calculate the distance between the planes of atoms responsible for diffraction in this crystal, assuming n = 1 (first-order diffraction).

457
views
Textbook Question

Germanium has the same structure as silicon, but the unit cell size is different because Ge and Si atoms are not the same size. If you were to repeat the experiment described in the previous problem but replace the Si crystal with a Ge crystal, would you expect the X rays to be diffracted at a larger or smaller angle u?

826
views
Textbook Question

(a) The density of diamond is 3.5 g>cm3, and that of graphite is 2.3 g>cm3. Based on the structure of buckminsterfullerene, what would you expect its density to be relative to these other forms of carbon?

2395
views
Textbook Question

The karat scale used to describe gold alloys is based on mass percentages. (a) If an alloy is formed that is 50 mol% silver and 50 mol% gold, what is the karat number of the alloy? Use Figure 12.18 to estimate the color of this alloy.

684
views
Textbook Question

The karat scale used to describe gold alloys is based on mass percentages. (b) If an alloy is formed that is 50 mol% copper and 50 mol% gold, what is the karat number of the alloy? What is the color of this alloy?

721
views
Open Question
Spinel is a mineral that contains 37.9% Al, 17.1% Mg, and 45.0% O, by mass, and has a density of 3.57 g/cm³. The unit cell is cubic with an edge length of 8.09 Å. How many atoms of each type are in the unit cell?