Do You Know About Semiconductor Lasers?( Part 2)

Semiconductor Lasers correlation Part 2.

Laser is one of the essential core components in modern laser machining systems. With the development of laser processing technology, laser is also constantly developing, there are many new lasers.

Doped semiconductor lasers

Semiconductors are widely used in today's digital world because they can alter their electrical properties by inserting impurities into their crystal lattices, a process known as doping.

Impurities in semiconductors have a significant effect on resistivity. When a trace impurity is added to a semiconductor, the periodic potential field near the impurity atom is disturbed and an additional bound state is formed, resulting in an additional impurity level in the band gap. For example, when impurity atoms such as phosphorus, arsenic, and antimony are added into a quaternary element germanium or silicon crystal, the impurity atom, as a molecule of the lattice, has four of its five valence electrons form a covalent bond with the surrounding germanium (or silicon) atom, and an extra electron is bound to the impurity atom, producing hydrogen-like energy level. The impurity level is located above the forbidden band and near the conduction band bottom. Electrons at the impurity level are easily excited to the conduction band as electron carriers. The impurity that provides the electron carrier is called the donor, and the corresponding energy level is called the donor level.

The impurity concentration and polarity of intrinsic semiconductors have a great influence on the conduction characteristics of semiconductors. The doped semiconductor is called an extrinsic semiconductor.

Doped semiconductor: The impurity semiconductor is obtained by the diffusion process by mixing a small number of suitable impurity elements into the intrinsic semiconductor.

P-type semiconductor lasers: A pure silicon crystal is formed by mixing a trivalent element (such as boron) in place of the silicon atoms in the crystal lattice.

Majority carriers: In P-type semiconductors, the concentration of holes is greater than the concentration of free electrons, known as majority carriers, or poly carriers for short.

Minority carriers: In P-type semiconductors, free electrons are minority carriers, or minority carriers for short.

Acceptor atom: A vacancy in an impurity atom absorbs electrons and is called an acceptor atom.

The conductive characteristics of a P-type semiconductor: it conducts electricity by holes. The more impurities are added, the higher the concentration of polygons (holes) and the stronger the conductive performance.

N-type semiconductor lasers: A pure silicon crystal is formed by mixing a pentavalent element (such as phosphorus) in place of the silicon atoms in the crystal lattice.

Many electrons: In N-type semiconductors, many electrons are free electrons.

Minority: In N-type semiconductors, the minority is the hole.

Donor atom: Impurity atoms that can contribute electrons are called donor atoms.

The conductivity of N-type semiconductors: The more impurities are added, the higher the concentration of polygons (free electrons) and the stronger the conductivity.

Semiconductor Lasers doping

According to the positive or negative charge of the doped material, the doped material can be divided into donors and acceptors. valence electrons (valence electrons) from the donor atoms are valence electrons covalent to the doped material atoms and thus tied up. An electron that is not covalently bonded to an atom of the doped material is weakly bound to the donor atom, also known as the donor electron.

Compared with valence electrons in intrinsic semiconductors, the energy required by the donor electrons to transition to the conduction band is lower, and it is easier to move in the lattice of semiconductor materials and generate current. Although the donor electron gains energy and jumps to the conduction band, it does not leave an electric hole as in the intrinsic semiconductor, and the donor atom is only fixed in the crystal lattice of the semiconductor material after losing the electron. Therefore, the semiconductor that obtains excess electrons to provide conduction due to doping is called an N-type semiconductor, where n stands for negatively charged electrons.

In contrast to the donor, when the acceptor atom enters the semiconductor lattice, because the number of valence electrons is less than that of the semiconductor atom, it will bring an equivalent vacancy, and this extra vacancy can be regarded as an electric hole. The doped semiconductor is called a P-type semiconductor, where p stands for positively charged holes.

The effect of doping is illustrated by an intrinsic semiconductor of silicon. Silicon has four valence electrons, and doping materials commonly used in silicon include trivalent and quinquevalent elements. When trivalent elements with only three valence electrons, such as boron, are doped into silicon semiconductors, boron plays the role of accepter, and silicon semiconductors doped with boron are P-type semiconductors. Conversely, if the pentavalent elements such as phosphorus (phosphorus) are doped to silicon semiconductor, phosphorus plays the role of donor, and the doped phosphorus silicon semiconductor becomes an N-type semiconductor.

A semiconductor material may be doped with donor and acceptor, and how to decide whether the semiconductor is N-type or P-type depends on the doped semiconductor, the acceptor brings the higher concentration of holes or the donor brings the higher concentration of electrons, that is, what is the "majority carrier" of the semiconductor. The opposite of the majority carrier is the minority carrier. For the analysis of the operating principle of semiconductor components, the behavior of a few carriers in semiconductors is very important.

Learn more about it from Part3

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