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Chapter 12: Problem 73

If you want to dope GaAs to make an n-type semiconductor with an element to replace Ga, which element(s) would you pick?

Short Answer

Expert verified
To dope GaAs and make an n-type semiconductor by replacing Ga, suitable elements would be silicon (Si) and germanium (Ge) as they have 4 valence electrons and compatible lattice properties with GaAs.

Step by step solution

01

Determine the number of valence electrons in Ga

To determine a suitable dopant, we first need to know how many valence electrons Ga has. Gallium is in group 13 of the periodic table, so it has 3 valence electrons.
02

Identify elements with more valence electrons than Ga

We need to find elements that have one more valence electron than Ga to make an n-type semiconductor. Since Ga has 3 valence electrons, we are looking for elements with 4 valence electrons. Elements in group 14 of the periodic table have 4 valence electrons, such as C, Si, Ge, and Sn.
03

Choose suitable dopants

Not all elements in group 14 can be suitable dopants for GaAs. We should consider the lattice compatibility and chemical bonding properties. Carbon has a much smaller atomic radius and different chemical properties than Ga, so it is not a suitable dopant. Silicon and germanium are commonly used to dope GaAs, as their chemical properties and atomic radii are similar to Ga, which ensures good lattice compatibility. Tin is heavier than Ga and might introduce higher defect densities, so it is not as commonly used as Si and Ge.
04

Conclusion

To dope GaAs and make an n-type semiconductor by replacing Ga, suitable elements would be silicon (Si) and germanium (Ge), as they have 4 valence electrons and compatible lattice properties with GaAs.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

GaAs Doping
Gallium arsenide, commonly referred to as GaAs, is a compound semiconductor used in various electronic and photonic applications. Doping GaAs means introducing impurities intentionally to alter its electrical properties. Specifically, making GaAs an n-type semiconductor involves adding dopants to increase the number of free electrons for electrical conduction.
These dopants need to effectively replace gallium (Ga) atoms, without disrupting the GaAs crystal structure. Ideal dopants have similar atomic sizes and bonding habits to gallium. By choosing the right dopant, such as silicon or germanium, we can achieve efficient electron flow and enhance device performance.
Valence Electrons
Valence electrons are the outermost electrons of an atom and play a vital role in chemical bonding and semiconductor doping. The number of valence electrons determines how an element will interact or bond with others. Gallium, being in group 13 of the periodic table, has three valence electrons.
For creating an n-type semiconductor from GaAs, we need a dopant with four valence electrons. This extra electron from the dopant becomes free, contributing to the material's conductivity. Therefore, elements that can donate this additional electron, such as silicon and germanium, are prime candidates for doping GaAs.
Group 14 Elements
The periodic table's Group 14 elements are critical to the process of GaAs doping for n-type semiconductor fabrication. This group includes carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). Each element in this group possesses four valence electrons, one more than gallium鈥檚 three.
While all Group 14 elements theoretically could serve as dopants, not all are practical due to differences in atomic size and chemical compatibility with GaAs. Silicon and germanium stand out as favorable options due to their similar atomic radii and bonding behaviors to gallium, ensuring minimal disruption to the GaAs lattice structure.
Silicon Dopant
Silicon is a popular choice for doping GaAs to form n-type semiconductors. As a Group 14 element, silicon has four valence electrons. It efficiently introduces an additional electron into the GaAs crystal lattice, thus enhancing the material鈥檚 electrical conductivity.
Silicon's atomic size and chemical properties are compatible with gallium's, ensuring that the substitution maintains the integrity of the GaAs lattice. Silicon also offers excellent thermal and electrical stability, making it an ideal dopant for high-performance semiconductor devices.
Germanium Dopant
Germanium is another effective dopant for converting GaAs into an n-type semiconductor. Like silicon, germanium belongs to Group 14 and has four valence electrons, facilitating the release of an extra electron into the material鈥檚 structure.
Germanium shares similar physical and chemical characteristics with silicon and gallium, such as its atomic radius, which makes it another excellent choice for doping. When incorporated into GaAs, germanium maintains the crystal structure and ensures good electrical performance, making it a valuable option for various electronic applications.

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Most popular questions from this chapter

A particular form of cinnabar (HgS) adopts the zinc blende structure. The length of the unit cell edge is 5.852 A. (a) Calculate the density of HgS in this form. (b) The mineral tiemannite (HgSe) also forms a solid phase with the zinc blende structure. The length of the unit cell edge in this mineral is 6.085 A. What accounts for the larger unit cell length in tiemmanite? (c) Which of the two substances has the higher density? How do you account for the difference in densities?

GaAs and GaP make solid solutions that have the same crystal structure as the parent materials, with As and Prandomly distributed throughout the crystal. GaP As \(_{1-x}\) exists for any value of \(x .\) If we assume that the band gap varies linearly with composition between \(x=0\) and \(x=1,\) estimate the band gap for GaP \(_{0.5} \mathrm{As}_{0.5}\) . (GaAs and GaP band gaps are 1.43 \(\mathrm{eV}\) and 2.26 \(\mathrm{eV}\) , respectively.) What wavelength of light does this correspond to?

Covalent bonding occurs in both molecular and covalent network solids. Which of the following statements best explains why these two kinds of solids differ so greatly in their hardness and melting points? $$ \begin{array}{l}{\text { (a) The molecules in molecular solids have stronger covalent bonding than covalent-network solids do. }} \\ {\text { (b) The molecules in molecular solids are held together by weak intermolecular interactions. }}\end{array} $$ $$ \begin{array}{l}{\text { (c) The atoms in covalent-network solids are more polarizable than those in molecular solids. }} \\ {\text { (d) Molecular solids are denser than covalent-network solids. }}\end{array} $$

Classify each of the following statements as true or false: $$ \begin{array}{l}{\text { (a) Although both molecular solids and covalent- network }} \\ {\text { solids have covalent bonds, the melting points of molec- }} \\ {\text { ular solids are much lower because their covalent bonds }} \\ {\text { are much weaker. }} \\ {\text { (b) Other factors being equal, highly symmetric molecules }} \\ {\text { tend to form solids with highly symmetric molecules }} \\ {\text { asymmetrically shaped molecules. }}\end{array} $$

Pure iron crystallizes in a body-centered cubic structure, but small amounts of impurities can stabilize a face-centered cubic structure. Which form of iron has a higher density?
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