PN junction is the most basic single – guide – pass principle in diode

  • Chemical bonds
    • Ionic bond
    • Covalent bond
  • Periodic table
  • P-n junction
    • The principle of
    • The formation of
    • Forward biased
    • Reverse biased

P-n junction

Chemical bonds

There are three types of chemical bonds: ionic, covalent, and metallic (hydrogen is not a chemical bond, it is an intermolecular force).

– Baidu

Ionic bond

Interactions between ions with opposite charges are called Ionic bonds. Bonding is essentially an electrostatic interaction between anions and anions.

– Baidu

Cations and anions form chemical bonds through electrostatic action called ionic bonds. When the electronegativity of two atoms is very different, it is usually a metal and a nonmetal, such as chlorine and sodium. If they combine, the more electronegative chlorine will steal an electron from the less electronegative sodium to fit the octet. Then chlorine will have a minus 1 valence, and sodium a plus 1 valence, and the two are bound together by coulomb electrostatic force of positive and negative attraction.

– a Wiki

Na is 11 on the periodic table, which means it has 11 protons, 2, 8, 1, depending on the electron configuration, so Na tends to lose electrons, plus 1, and F tends to gain electrons, and the resulting NaF forms an ionic bond.

Covalent bond

Covalent bonds are interactions between atoms caused by shared electron pairs (cloud overlap)

– Baidu

Chemical bonds formed by sharing electrons between atoms are called covalent bonds. It is bonded by two atoms of similar electronegativity, such as two oxygens, sharing their outer electrons in an octet bond, which is also said to be nonmetallic.

– a Wiki

Metallic bonding

A type of chemical bond found mainly in metals. It’s a combination of free electrons and electrostatic attraction between metal ions arranged in a lattice. Because of the free movement of electrons, metal bonds have no fixed orientation and are therefore nonpolar.

– Baidu

Polar bond

Polar bond is a covalent bond formed by different kinds of atoms in a compound molecule. Due to the different ability of two atoms to attract electrons, the shared electron pair must be biased towards the atom with stronger ability to attract electrons, so the atom with weaker ability to attract electrons is relatively positive. Such covalent bonds are called polar covalent bonds, or polar bonds.

– Baidu

Periodic table

Single elements can be formed by covalent bonds, such as H2, O2

NaCl consists of ionic (polar) bonds. Na shell configuration: 2-8-1, Cl shell configuration: 2-8-7, one easy to lose electrons, one easy to gain electrons.

Isotopes: Since the periodic table ranks elements by the number of protons, not by the number of neutrons, elements with different numbers of neutrons but different numbers of protons are isotopes.

PM”

One side of a semiconductor crystal is doped into a P-type semiconductor, and the other side is doped into an N-type semiconductor. The contact surface between the two connected is called PN junction. PN junction is the material basis of many components in electronic technology, such as semiconductor diodes, bipolar transistors.

– a Wiki

Basic principles of PM junction

Boron doped with a small amount of impurity elements (or indium element) of silicon crystal (or germanium crystals), due to the semiconductor atoms (such as the silicon atoms) replaced by impurity atoms, the boron atoms around the outer three outer electrons and semiconductor atoms form a covalent bond, will produce a “hole”, the hole may attract bound electron to “fill”, make the boron atom becomes negatively charged ions. Thus, such semiconductors are conductive materials because of their high concentration of “holes” (” equivalent “to a positive charge).

Si electron layer configuration: 2-8-4, pure Si shares 4 outer electrons with 4 Si elements around, forming 4 covalent bonds, forming a stable structure of 4 + 4 with 8 electrons. On this basis, B (electron configuration: 2-3) is added to create a hole.

Mixed with a small amount of impurity phosphorus antimony (or elements) of silicon crystal (or germanium crystals), due to the semiconductor atoms (such as the silicon atoms) replaced by impurity atoms, phosphorous outer five outer electrons of the four of them with the surrounding semiconductor atoms form covalent bonds, more of an electron bound, hardly is relatively easy to become a free electron. Thus, the N-type semiconductor becomes a semiconductor with a higher concentration of free electrons, and its conductivity is mainly because free electrons conduct electricity.

Formation of PN junction

When the PN level is combined, the excess N electrons will expand to the P pole, forming an internal electric field, which is called the PN junction, also known as the barrier layer, depletion layer, space charge region.

Electrons will drift to the N level under the electric field force, but if there are too many electrons in the N level, they will still spread to the P level. The two motions form a dynamic equilibrium, of course, but not necessarily a stable circular current as shown in the following animation.

Forward biased

The positive electrode of the power supply is connected to P and the negative electrode to N, and the charge will be redistributed

Because there are many carriers and PN junction is narrow, it will form a relatively large current.

The inflow of negative electrons (applied electric field) leads to the narrowing of the PN junction, thus enhancing the diffusion motion of electrons and forming a forward current

Reverse biased

Reverse bias widens the PN junction

Because there are fewer carriers and the PN junction is too wide, the current will be small.

QA

  • isotope

    Isotopes are the divisions of a particular chemical element under which all isotopes have the same atomic number and have the same number of protons but different numbers of neutrons. These isotopes occupy the same place on the periodic table, hence their name.

    For example, deuterium and tritium in hydrogen have a proton in their nuclei, but they have zero neutrons, one neutron and two neutrons in their nuclei, so they are isotopes of each other.

  • Industrial system of silicon

    In industry, it is usually made by reducing silica from carbon in an electric furnace:

    SiO2 + 2C → Si + 2CO

  • semiconductor

    A Semiconductor (English: Semiconductor) is a material whose electrical conductivity can be controlled from an insulator to a conductor. Common semiconductor materials include silicon, germanium, gallium arsenide, etc. Silicon is the most influential semiconductor material in commercial application.

  • diode

    A Diode is a two-electrode electronic device with asymmetric conductance. The ideal diode has zero resistance between the two electrodes (anode and cathode) in the forward direction and infinite resistance in the reverse direction, i.e. current is only allowed to flow through the diode in a single direction.

References

  • P-n junction animation
  • Working principle of PN junction

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