Pentavalent Atoms as Donor Impurities

Oct 13, 2025 by talynt.org 18 views

Understanding Donor Impurity Atoms in Germanium (Ge)

Germanium (Ge) is a semiconductor material widely used in various electronic devices. The properties of Ge can be modified by introducing impurities into its crystal lattice. In this context, we will discuss the concept of donor impurity atoms and identify which of the given options is a suitable donor impurity atom for Ge.

What are Donor Impurity Atoms?

Donor impurity atoms are elements that, when introduced into a semiconductor material, donate excess electrons to the material. These excess electrons are free to move within the material, contributing to its electrical conductivity. Donor impurity atoms are typically elements from Group 15 of the periodic table, which have five valence electrons. When these elements occupy a position in the crystal lattice of a semiconductor material, they release one or more electrons, which become free carriers.

Pentavalent Atoms as Donor Impurities

Pentavalent atoms, such as phosphorus (P) and arsenic (As), are commonly used as donor impurities in silicon (Si) and other semiconductor materials. When a pentavalent atom occupies the position of an atom in the crystal lattice of Si, four of its electrons form covalent bonds with four silicon atoms, while the fifth electron is left free to move within the material. This excess electron is a free carrier that contributes to the electrical conductivity of the material.

Donor Impurity Atoms for Germanium (Ge)

Germanium (Ge) is a group IV element, and its crystal lattice is similar to that of Si. However, Ge has a larger atomic radius and a smaller electronegativity than Si. As a result, Ge has a higher electron mobility and a lower bandgap energy than Si. To modify the properties of Ge, donor impurity atoms are introduced into its crystal lattice. The following options are potential donor impurity atoms for Ge:

A. Boron (B): Boron is a group III element, and it is typically used as an acceptor impurity in Si and Ge. When B occupies a position in the crystal lattice of Ge, it accepts an electron from the material, creating a hole that is a free carrier.
B. Antimony (Sb): Antimony is a group V element, and it is a potential donor impurity atom for Ge. When Sb occupies a position in the crystal lattice of Ge, it releases one or more electrons, which become free carriers.
C. Aluminium (Al): Aluminium is a group III element, and it is typically used as an acceptor impurity in Si and Ge. When Al occupies a position in the crystal lattice of Ge, it accepts an electron from the material, creating a hole that is a free carrier.
D. Indium (In): Indium is a group III element, and it is typically used as an acceptor impurity in Si and Ge. When In occupies a position in the crystal lattice of Ge, it accepts an electron from the material, creating a hole that is a free carrier.

In conclusion, the correct answer is B. Antimony (Sb). Antimony is a group V element, and it is a potential donor impurity atom for Ge. When Sb occupies a position in the crystal lattice of Ge, it releases one or more electrons, which become free carriers. This excess electron is a free carrier that contributes to the electrical conductivity of the material.

Sze, S. M. (2007). Physics of semiconductor devices. John Wiley & Sons.
Streetman, B. G. (2005). Solid state electronic devices. Prentice Hall.
Ashcroft, N. W., & Mermin, N. D. (1976). Solid state physics. Holt, Rinehart and Winston.

Germanium (Ge) is a semiconductor material widely used in various electronic devices. The properties of Ge can be modified by introducing impurities into its crystal lattice. In this context, we will discuss the crystal lattice structure of Ge and its relationship with the properties of the material.

Crystal Lattice Structure of Germanium (Ge)

The crystal lattice structure of Ge is similar to that of Si. Ge has a diamond cubic crystal structure, which consists of a face-centered cubic lattice with a basis of two atoms. Each atom in the lattice is bonded to four neighboring atoms through covalent bonds. The crystal lattice structure of Ge is characterized by a lattice constant of 5.658 Å and a bandgap energy of 0.67 eV.

Relationship between Crystal Lattice Structure and Properties

The crystal lattice structure of Ge has a significant impact on its properties. The diamond cubic crystal structure of Ge provides a high degree of crystallinity and a low defect density, which are essential for the production of high-quality electronic devices. The lattice constant of Ge is larger than that of Si, which results in a higher electron mobility and a lower bandgap energy. These properties make Ge a suitable material for high-speed electronic devices.

In conclusion, the crystal lattice structure of Ge is a critical factor in determining its properties. The diamond cubic crystal structure of Ge provides a high degree of crystallinity and a low defect density, which are essential for the production of high-quality electronic devices. The lattice constant of Ge is larger than that of Si, which results in a higher electron mobility and a lower bandgap energy.

Sze, S. M. (2007). Physics of semiconductor devices. John Wiley & Sons.
Streetman, B. G. (2005). Solid state electronic devices. Prentice Hall.
Ashcroft, N. W., & Mermin, N. D. (1976). Solid state physics. Holt, Rinehart and Winston.
Q&A: Donor Impurity Atoms in Germanium (Ge) =============================================

Q: What is a donor impurity atom?

A: A donor impurity atom is an element that, when introduced into a semiconductor material, donates excess electrons to the material. These excess electrons are free to move within the material, contributing to its electrical conductivity.

Q: What is the typical group of elements used as donor impurities?

A: The typical group of elements used as donor impurities is Group 15 of the periodic table, which includes elements such as phosphorus (P) and arsenic (As).

Q: Why are pentavalent atoms used as donor impurities?

A: Pentavalent atoms are used as donor impurities because they have five valence electrons, which can form covalent bonds with the semiconductor material. When a pentavalent atom occupies a position in the crystal lattice of the semiconductor material, four of its electrons form covalent bonds with the material, while the fifth electron is left free to move within the material.

Q: What is the effect of introducing a donor impurity atom into a semiconductor material?

A: The effect of introducing a donor impurity atom into a semiconductor material is to increase its electrical conductivity. The excess electrons donated by the donor impurity atom are free to move within the material, contributing to its electrical conductivity.

Q: What is the typical concentration of donor impurity atoms used in semiconductor materials?

A: The typical concentration of donor impurity atoms used in semiconductor materials is in the range of 10^15 to 10^18 atoms per cubic centimeter.

Q: How do donor impurity atoms affect the electrical properties of a semiconductor material?

A: Donor impurity atoms affect the electrical properties of a semiconductor material by increasing its electrical conductivity. The excess electrons donated by the donor impurity atom are free to move within the material, contributing to its electrical conductivity.

Q: What is the relationship between the concentration of donor impurity atoms and the electrical conductivity of a semiconductor material?

A: The relationship between the concentration of donor impurity atoms and the electrical conductivity of a semiconductor material is a direct one. As the concentration of donor impurity atoms increases, the electrical conductivity of the material also increases.

Q: Can donor impurity atoms be used to modify the optical properties of a semiconductor material?

A: Yes, donor impurity atoms can be used to modify the optical properties of a semiconductor material. The introduction of donor impurity atoms can affect the absorption and emission spectra of the material, leading to changes in its optical properties.

Q: What are some common applications of donor impurity atoms in semiconductor materials?

A: Some common applications of donor impurity atoms in semiconductor materials include:

Solar cells: Donor impurity atoms are used to increase the electrical conductivity of solar cells, allowing them to convert sunlight into electrical energy more efficiently.
Transistors: Donor impurity atoms are used to modify the electrical properties of transistors, allowing them to switch on and off more quickly and efficiently.
Diodes: Donor impurity atoms are used to modify the electrical properties of diodes, allowing them to rectify electrical currents more efficiently.

In conclusion, donor impurity atoms play a critical role in modifying the electrical properties of semiconductor materials. By introducing donor impurity atoms into a semiconductor material, its electrical conductivity can be increased, allowing it to be used in a wide range of applications.