Semiconductor

Semiconductor, refers to room temperature conductivity in sulators. Semiconductor in radio, television and temperature on a wide range of applications.

introduction

Semiconductor: resistivity between metal and insulators and have negative resistance between temperature coefficient of the material. Semiconductor room temperature when resistivity in about 10-5 ~ 107 uefa · m, between the temperature rises resistivity index has decreased. Semiconductor materials many, according to chemical composition can be divided into element semiconductor and semiconductor compound two kinds big. Germanium or silicon is the most common elements semiconductor, Ⅲ - including semiconductor compound Ⅴ clan compounds (gaas, phosphating gallium, etc.), Ⅱ - Ⅵ clan compounds (cadmium sulphide, LiuHuaXin etc.), oxide (mn, chromium, iron, copper oxide), and by Ⅲ - Ⅴ clan compounds and Ⅱ - Ⅵ clan compounds composed of interstitial (gallium aluminum arsenic, gallium arsenic phosphorus, etc.). Besides the above-mentioned amorphous semiconductor outside, still amorphous glass semiconductor, organic semiconductor etc.

Intrinsic semiconductors does not contain impurities without lattice defects of semiconductor called intrinsic semiconductors. At extremely low temperatures, semiconductor valence band is filled with (see the band theory), subject to thermal excitation, the valence band part of electronic and cross the forbidden band into higher energy empty, empty belt with existing in the conduction band, electronic later became the lack of an electronic valence band formed after a positively charged open, called hole (figure 1). The conduction band of electrons and valence band of cavitation called electronic - hole on, all can move freely, namely carriers, they influenced by electric fields outside the generating directional movement and the formation of macro current, respectively called electron conductive and cavities conductive. As a result of the produce of electronic - hole formed hybrid conductive called this intrinsicall conductive. The conduction band of electrons will cavitation, electronic - hole to disappear, known as the compound. Compound when the energy released into the electromagnetic radiation (shine) or the lattice thermal vibration energy (heating). In certain temperatures, electronic - hole to the emergence and compound exist simultaneously and achieve the dynamic balance, then semiconductor has certain carriers density, which has certain resistivity. The temperature rises, will produce more of the electronic - hole right, carriers density increases, resistivity reduce. Without the lattice defects resistivity of pure semiconductor larger, actual application much.

Semiconductor of impurity in semiconductor impurities to the resistivity effect is very big. Semiconductor adding trace impurities, impurity atoms near the cycle of potential field interference and forming additional bound state, in the middle forbidden band with impurity level. For example four valence element germanium or silicon crystals adding pentavalent element phosphorus, arsenic, antimony impurities such as molecule, impurity atoms as a member of the lattice, four of five covalence with surrounding germanium or silicon atoms form () combine covalently, redundant an electronic be bound to impurity atoms of hydrogen level near, produce. Impurities level in forbidden band above near the conduction band bottom nearby. Impurities level of the electron easily stimulate to the conduction band became electronic charge carriers. This can provide electronic carriers impurities called benefactor, corresponding level called benefactor level. Benefactor level of the electron warp to the conduction band energy than required from the valence band inspired to the conduction band energy you need much smaller (figure 2). In germanium or silicon crystals adding trace trivalent element boron, aluminum, gallium impurities such as molecule, impurity atoms and around four germanium or silicon atoms form () combine covalently fashion lack an electron, consequently existence a space, and the space corresponding energy status is impurity level, usually located below forbidden band near valence band place. The valence band of electrons very easily stimulate to impurity fill in this space on level, make the impurity atoms becoming anion. The valence band due to lack of an electron and form a hole charge carriers (figure 3). This can provide cavitation impurities called recipient impurities. Existing recipient impurity in valence band formed in a hole charge carriers needed energy than intrinsic semiconductors situations are much smaller. Semiconductor doped whose resistivity dramatically reduced. Heat or light the heat generated by the stimulated or photoluminescence can make free carrier number increased and cause resistivity reduce, semiconductor thermistors and photoconductive resistance is according to this principle is made. For impermeability benefactor of impurities, semiconductor, conductive carriers is mainly the conduction band of electrons, belong to DianZiXing conductive, says n-type semiconductors. Incorporating recipient of impurity of cavitation type semiconductor conductive, called P type semiconductor. Semiconductor at all temperatures can generate electrons - hole on n-type in semiconductor, it can exist a few conductive cavitation, P type semiconductor can exist a few conductive electronic, which are called minority carriers. In semiconductor devices of various effects, the minority carriers are often play important roles.

PN junction P type semiconductor and n-type semiconductor touch each other, its border area called PN junction. P area of freedom in cavitation and N area free electrons in other areas to spread, causing the positive and negative sides of accumulation in PN junction, forming electric dipole layer (figure 4). Electric dipole layer of the electric field in the direction of just stop diffusion. When due to the carrier number density caused by diffusion ranging with electric dipoles layer in the electric field effect reaches equilibrium, P area and N zone formed between certain DianShiCha, called contact DianShiCha. Due to the cavitation zone P N area and the N area after the diffusion, and electronic composite of electrons to P N area with P area area after the diffusion cavitation compound, which makes electric dipole layer free charge carriers reduction of the number and the formation of high resistance layer, reason electric dipole layer also called linings, linings resistance is often composed of PN junction of semiconductor original value several times and even hundreds of times.

PN junction has unilateral conductivity, semiconductor kozesnictvi is the use of PN junction this feature is made. PN junction is another important properties by light can produce emf, says pv effect, can use to create si-based ones. Semiconductor triode, SCR, PN junction photodetector and light-emitting diodes etc semiconductor devices are used the PN junction properties.

diversity

Matter exists in a variety of forms, solid, liquid, gas, plasma, etc. We usually pack electric conductivity and thermal conductivity of poor or bad materials, such as diamond and artificial crystal, amber, ceramics, etc., called insulators. The electric conductivity, thermal conductivity are better metals such as gold, silver, copper, iron, tin, aluminum etc called conductors. Can simply keep between insulators and conductors between semiconductor material called. Compared with insulators and conductors, semiconductor materials to find the latest, until the 1930s, when materials of purification technology to improve later, semiconductor existence truly be academic recognition.

classification

The classification of semiconductor, in its manufacturing technology can be divided into: integrated circuits, separation devices, photoelectric semiconductor, logic IC, simulation IC, packet other kinds, generally speaking these will be divided into small classes. In addition to application field, the design methods of classification, though not in common use, or according to the IC, LSI, DFM (LSI) and its large scale classification method. In addition, still in accordance with its handling signal, can be divided into analog and digital and analog and digital mix function classification method.

Semiconductor definition

Resistivity between metal and insulator [1] and the resistance between a negative temperature coefficient of the material.

Semiconductor room temperature when resistivity around 10E - 5 ~ 10E7 ohms · m, between the temperature rises resistivity index has decreased.

Semiconductor materials many, according to chemical composition can be divided into element semiconductor and semiconductor compound two kinds big.

Germanium or silicon is the most common elements semiconductor, Ⅲ - including semiconductor compound Ⅴ clan compounds (gaas, phosphating gallium, etc.), Ⅱ - Ⅵ clan compounds (cadmium sulphide, LiuHuaXin etc.), oxide (mn, chromium, iron, copper oxide), and by Ⅲ - Ⅴ clan compounds and Ⅱ - Ⅵ clan compounds composed of interstitial (gallium aluminum arsenic, gallium arsenic phosphorus, etc.). Besides the above-mentioned amorphous semiconductor outside, still amorphous glass semiconductor, organic semiconductor etc.

Semiconductor: refers to the transistor radio, because the transistor radio by the semiconductor material made its name.

Intrinsic semiconductors

Do not contain impurities without lattice defects of semiconductor called intrinsic semiconductors. At extremely low temperatures, semiconductor valence band is filled with (see the band theory), subject to thermal excitation, the valence band part of electronic and cross the forbidden band into higher energy empty, empty belt with existing in the conduction band, electronic later became the lack of an electronic valence band formed after a positively charged open, called cavities. The conduction band of electrons and valence band of cavitation called electronic - hole on, all can move freely, namely carriers, they influenced by electric fields outside the generating directional movement and the formation of macro current, respectively called electron conductive and cavities conductive. As a result of the produce of electronic - hole formed hybrid conductive called this intrinsicall conductive. The conduction band of electrons will cavitation, electronic - hole to disappear, known as the compound. Compound when the energy released into the electromagnetic radiation (shine) or the lattice thermal vibration energy (heating). In certain temperatures, electronic - hole to the emergence and compound exist simultaneously and achieve the dynamic balance, then semiconductor has certain carriers density, which has certain resistivity. The temperature rises, will produce more of the electronic - hole right, carriers density increases, resistivity reduce. Without the lattice defects resistivity of pure semiconductor larger, actual application much.