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The main characteristics of semiconductors.


The five major characteristics of semiconductors: resistivity characteristics, conductivity characteristics, photoelectric characteristics, negative resistivity temperature characteristics, rectification characteristics.

In semiconductors that form a crystal structure, specific impurity elements are artificially doped, and the electrical conductivity is controllable.

Under the conditions of light and thermal radiation, its electrical conductivity changes significantly.

Lattice: The atoms in a crystal form a neatly arranged lattice in space, called a lattice.

Covalent bond structure: A pair of outermost electrons (that is, valence electrons) of two adjacent atoms not only move around their own nuclei, but also appear in the orbits to which adjacent atoms belong, becoming shared electrons, forming a covalent bond. key.

Formation of free electrons: At room temperature, a small number of valence electrons gain enough energy due to thermal motion to break free from covalent bonds and become free electrons.

Holes: valence electrons break free from covalent bonds and become free electrons, leaving a vacancy called holes.

Electron current: Under the action of an external electric field, free electrons move directionally to form an electronic current.

Hole current: The valence electrons fill the holes in a certain direction (that is, the holes also move in a direction) to form a hole current.

Intrinsic semiconductor current: electron current + hole current. Free electrons and holes have different charge polarities and move in opposite directions.

Carriers: Particles that carry charges are called carriers.

The characteristics of conductor electricity: The conductor conducts electricity with only one type of carrier, that is, free electron conduction.

Electrical characteristics of intrinsic semiconductors: Intrinsic semiconductors have two types of carriers, that is, free electrons and holes both participate in conduction.

Intrinsic excitation: The phenomenon in which semiconductors generate free electrons and holes under thermal excitation is called intrinsic excitation.

Recombination: If free electrons meet with holes in the process of movement, they will fill the holes and make the two disappear at the same time. This phenomenon is called recombination.

Dynamic equilibrium: At a certain temperature, the number of free electron and hole pairs generated by intrinsic excitation is equal to the number of free electron and hole pairs that are recombined to achieve dynamic equilibrium.

The relationship between the concentration of carriers and temperature: the temperature is constant, the concentration of carriers in the intrinsic semiconductor is constant, and the concentrations of free electrons and holes are equal. When the temperature increases, the thermal motion intensifies, the free electrons that break free from the covalent bond increase, the holes also increase (that is, the concentration of carriers increases), and the electrical conductivity increases; when the temperature decreases, the carrier As the concentration decreases, the electrical conductivity deteriorates.