Do You Know About Semiconductor Lasers?( Part 3)

Semiconductor Lasers correlation Part 3.

Semiconductor laser generally has the characteristics of lightweight, high modulation efficiency, small size, etc., and is widely used in civil, military, medical, and other fields. The research of high-power semiconductor lasers began in the 1980s and has never stopped. With the continuous development of semiconductor technology and laser technology, the high-power semiconductor laser has made great progress in the aspects of power output, power conversion, and reliability.

The effect of doping on structure

Doping the semiconductor's energy band changes. Depending on the doping, there are different energy levels between the band gaps of intrinsic semiconductors. The donor atom will produce a new energy level near the conduction band, while the recipient atom will produce a new energy level near the valence band. If boron atoms are doped into silicon, they ionize of boron atoms doped into silicon can be completely ionized at room temperature because the energy level between the boron and silicon valence band is only 0.045 electron volts, which is much smaller than the energy gap of silicon itself of 1.12 electron volts.

Another important effect of dopants on the band structure is to change the position of the Fermi energy level. The Fermi energy level remains constant in thermal equilibrium, and this property leads to many other useful electrical properties. For example, the band of a p-n junction can bend because the Fermi levels of a P-type semiconductor and an N-type semiconductor are at different positions, but the Fermi levels must remain at the same height to form the p-n junction. As a result, the conduction band or valence band of the P-type or N-type semiconductor will be bent to match the band difference at the junction.

The above effect can be explained by a band diagram. On a band chart, the horizontal axis represents position, and the vertical axis represents energy. intrinsicFermi level (intrinsicFermi level) of a semiconductor is usually expressed in Ei. Band maps are a very useful tool in interpreting the behavior of semiconductor components.

The relationship between semiconductors and integrated circuits

Semiconductors are materials whose electrical properties are intermediate between those of conductors and insulators. We know that a circuit has a function mainly because of the various variations of current within it and that current is formed mainly because of the flow (motion/migration) of electrons between the metal circuit and the electronic components. So how easily electrons move through a material determines its conductivity. In common metal materials at room temperature electrons are easy to obtain energy to move, so their conductive property is good; Due to the characteristics of the material itself, it is difficult for the electrons to obtain the energy required for conducting electricity. Few electrons can migrate inside the insulator, so it is almost non-conductive. Semiconducting materials, on the other hand, are somewhere in between, and can be altered by adding impurities, artificially controlling how easily it conducts electricity or not, and how easily it conducts electricity. This is called the dopable property of semiconductors.

As previously said, the basis of the integrated circuit is the transistor, the invention of the transistor is possible to create the integrated circuit, and the basis of the transistor is the semiconductor, so the semiconductor is also the basis of the integrated circuit. Semiconductors are to integrated circuits that land is to cities. Obviously, mountains and hills are not suitable for building cities, and places with sandy soil and limestone are not suitable for building cities. The "building" of a city requires a good site, and the "integrating" of a circuit requires the right basic material -- semiconductors. Common semiconductor materials are silicon, germanium, gallium arsenide (compounds), among which the widely used, commercial success of the push "silicon".

So why are semiconductors, and silicon in particular, good for making integrated circuits? There are several reasons. Silicon is an abundant element in the earth's crust, second only to oxygen. There are a lot of silicates or silica in nature in rocks and gravel, which is the cost of raw materials. The dopable nature of silicon is easy to control, making it easy to make transistors that fit the requirements, for reasons of circuit principle. The silicon dioxide formed by the oxidation of silicon is stable and can be used as an excellent insulating film needed in semiconductor devices, which is the reason for the device structure. The key point is the planar process of integrated circuits, silicon is easier to implement oxidation, lithography, diffusion, and other processes, easier to integrate, and its performance is easier to control. Therefore, the following is mainly introduced based on silicon integrated circuit knowledge, silicon transistor, and integrated circuit process understanding, it will be easier to understand this problem.

In addition to durability, semiconductor also has thermal sensitivity, photosensitivity, negative resistivity temperature, recyclability, and other characteristics, so in addition to manufacturing large-scale integrated circuits, semiconductor materials can also be used for power devices, optoelectronic devices, pressure sensors, thermoelectric refrigeration, and other purposes; Using the micromachining technology of microelectronics, it can also be made into MEMS (micromechanical electronic system), which can be used in electronic and medical fields.

The manufacture of semiconductor materials

In order to meet the needs of mass production, the electrical properties of the semiconductor must be predictable and stable, so both the purity of the doping and the quality of the semiconductor lattice structure must be strictly required. Common quality problems include dislocation in the lattice, twins, or stacking faults, affecting the characteristics of semiconductor materials. For a semiconductor component, the defects of the material lattice are usually the main factor affecting the performance of the component.

The most common method used to grow high-purity single-crystal semiconductor materials is called the Czochralski process. In this process, the seed of a single crystal is dropped into a dissolved liquid of the same material and slowly pulled upward in a rotating motion. As the seed is pulled up, the solute solidifies along the interface between the solid and the liquid, and rotation equalizes the temperature of the solute.

Semiconductor application

1. The first practical semiconductor was a Transistor/Diode. Used as a signal amplifier/rectifier in Radio and Television semiconductors.

2. Develop Solar Power, which is also used in Solar cells.

3. Semiconductors can be used to measure temperature, temperature range can reach production, life, medical health, scientific research, and teaching applications of 70% of the field, with high accuracy and stability, resolution up to 0.1℃, even up to 0.01℃ are not impossible, linearity 0.2%, temperature range -100~+300℃, It is a cost-effective temperature measuring element.

4. The development of semiconductor refrigerators, also known as thermoelectric refrigerators or thermoelectric refrigerators, use the Partier effect.

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