Computer Application


A substance (such as silicon or germanium) that lies between a conductor and a non-conductor, so that its conductivity lies between a metal and an insulator and increases with temperature. Semiconductor materials that are moderately to highly resistive (depending on the substance doped at the time of manufacture). Pure semiconductor materials (called endoplasmic semiconductors) with low electrical conductivity; If a specific type of impurity atom is added to it (to become an exoplasmic semiconductor), its electrical conductivity can be greatly increased. The donor impurity (5 valence) can greatly increase the number of electrons and produce a negative semiconductor. The acceptor impurity (3-valence) greatly increases the number of holes and produces a positive semiconductor. The electrical conductivity of such a semiconductor depends on the type and total amount of impurities in it. Semiconductors with different conductivity can form various junctions if they are gathered together. This is the basis of a semiconductor device (for use as an electronic component). The term semiconductor often refers to the device itself (e.g., transistor, integrated circuit, etc.).

In terms of conductivity, we should know that there are so-called conductors and insulators; And between the two, the conductivity is much less than the metal conductor, but better than the insulator, is called "semiconductor" or "semi-metal".

In general, silicon (Si) is a commonly used semiconductor material, adding a trace amount of arsenic (As), phosphorus (P) or boron (B) to silicon, it can change the conductive characteristics of silicon, forming an N-type (negative) or P-type (positive) semiconductor. Type n? Type p? What does that mean? The following is a brief explanation:

Silicon atoms have four electrons in the z outer layer, and pure silicon atoms form a fairly stable state in a covalent (electron sharing) manner. Due to the lack of free electrons, pure silicon is extremely poor in electrical conductivity. However, if we add a little arsenic or phosphorus to pure silicon (z has five electrons in the outer layer), we will have one more free electron, and thus form an N-type semiconductor; If we add a little boron (z has three electrons in the outer layer) to pure silicon, one electron is missing, and a hole is formed, so that a P-type semiconductor is formed (one negatively charged electron is missing, and one positive charge is seen as more). At this time, if a voltage is applied to both ends of the silicon crystal, the electrons can be generated to move freely and significantly increase their conductivity.

In addition to N-type and P-type semiconductors, if the two are connected, there will be a special situation at their joint surface, which is called the p-n junction. Generally known electronic components such as transistors and diodes are formed by using p-n junction.

The importance of semiconductors is that we can use capacitors that change semiconductors to make a variety of semiconductor components, which makes the electronics industry, optical industry and energy systems produce major improvements (such as lasers, solar cells), and have been more widely used in computer chips in recent years.

A semiconductor (semicondcctor), as its name suggests, is a substance that conducts electricity between a conductor, such as metal, and a flying conductor, such as glass. In terms of conductivity, the semiconductor is roughly located in the range of 1e3-10(ohm-cm) < this is just a rough breakdown >. The resistivity of aluminum at temperature is 2.5e-6 ohm-cm, while that of glass is almost infinite. This phenomenon is because the electrons inside the material are distributed in different energy ranges < or bands >, in which the band that allows the electrons to move freely is called the conductive band, unless the electrons in the conductive band are free to move, otherwise the material will not be able to conduct current through the electrons. The electrons of other energy bands must overcome the energy barrier to jump into the conduction band before they can become conducting electrons. Glass, for example, is a non-conductor because the gap is too large, so that electrons can not jump to the conductive band after the temperature is free to move.

As for semiconductors, their energy barriers are not very large, lower than non-conductors, so at high temperatures, lighting and other conditions that give energy or add some elements that can reduce energy barriers, you can change its resistance value and become a good conductor of electricity. The electronics industry uses the characteristics of semiconductors, which can change their conductive capacity with the addition of environment and reference materials, to develop a number of application products.
Semiconductor materials can be divided into elemental semiconductors and compound semiconductors. Elemental semiconductors are semiconductors composed of one element, such as Si,Ge, etc. Compound semiconductors are semiconductors composed of more than two elements, such as GaAs,Zns, etc., often used in optoelectronic or high-speed components.