Semiconductors: Materials, Types, and the Periodic Table

Semiconductors are essential components of modern technology, bridging the gap between conductors and insulators. Found in group 14 of the periodic table, semiconductors like silicon and germanium exhibit unique electrical properties that enable their use in devices such as computers, smartphones, and solar cells. This guide explores the basics of semiconductors, their placement in the periodic table, the materials that make them, and the various types, offering a comprehensive overview of these indispensable materials.

What is a Semiconductor?

Semiconductors are materials whose electrical properties lie between conductors and insulators. For example: Silicon and Germanium.

Conductivity of insulators, semiconductors and conductors are as follows:

Semiconductor Materials

Semiconductor materials are categorized as follows, and they are shown in the periodic table of elements.

• Elemental semiconductors include Si and Ge. They are composed of single species of atoms.
• Compound semiconductors include combinations of atoms of column III and column V and some atoms from column II and VI. Combinations of two atoms result in binary compounds.
• There are three element (Ternary) compounds e.g. GaAsP and four element (quaternary) compounds e.g. InGaAsP.

• The wide variety of electronic and optical properties of these semiconductors provides the device engineer with great flexibility in the design of electronic and opto-electronic functions.
• Ge was widely used in the early days of semiconductor development for transistors and diodes.
• Si is now used for the majority of rectifiers, transistors and integrated circuits.
• Compounds are widely used in high-speed devices and devices requiring the emission or absorption of light.
• The electronic and optical properties of semiconductors are strongly affected by impurities, which may be added in precisely controlled amounts (e.g. an impurity concentration of one part per million can change a sample of Si from a poor conductor to a good conductor of electric current). This process is called doping.

Semiconductor Material Properties

Semiconductor Types

There are two main types of semiconductor viz. intrinsic and extrinsic.

Intrinsic Semiconductor

A semiconductor in which there is a balance between the number of electrons in the conduction band and the number of holes in the valence band is called an intrinsic semiconductor. Examples: pure carbon and germanium.

Extrinsic Semiconductor

Semiconductor material added with another element is known as an extrinsic semiconductor. For example, N-type and P-type materials.

P-type Material

When a trivalent element (e.g. indium, gallium) is added to a tetravalent semiconductor (germanium or silicon) then a deficit of electron is produced for each impurity atom; such type of material is known as P-type material. Example: Doping silicon or germanium with boron (having three valence electrons).

N-type Material

When a pentavalent element (e.g. arsenic, antimony) is added to a tetravalent semiconductor, then a surplus electron is produced by each impurity atom; such type of material is known as N-type material. Example: Doping silicon or germanium with phosphorus (having five valence electrons).

Conclusion

Semiconductors, positioned in group 14 of the periodic table, are the backbone of technological advancements. By understanding their basics, periodic table placement, materials, and types, we gain insight into their critical role in shaping the modern world. From intrinsic properties to extrinsic enhancements, semiconductors continue to drive innovation and play a pivotal role in technological progress.