Semiconductor silicon diodes

Semiconductor silicon diodes, called photodiodes, with special conductance properties are generally used in diode array spectrophotometers. Photodiodes are very useful because scan times of the order of a few milliseconds and thus many scans may be obtained in a very short time. In addition, the data obtained, being digital, can be further processed to generate spectra with a very high degree of resolution and accuracy. 

The exciter is an AC generator with a stator-mounted field. Direct cur rent for the exciter field is provided from an external source, typically u small variable voltage rectifier mounted at the motor starter. Exciter oui put is converted to DC through a three-phase, full-wave, silicon-diode bridge rectifier. Thyristors (silicon-controlled rectifiers) switch the cur rent to the motor field and the motor-starting, field-discharge resistors These semiconductor elements are mounted on heat sinks and assembled on a drum bolted to the rotor or shaft. 

Uses. In manufacture of transistors, silicon diodes, and similar semiconductors for making alloys such as ferrosilicon and silicon copper... 

The most common semiconductor detector for laboratory EDXRF systems is the lithium-drifted silicon diode, represented as Si(Li). (It is called a silly detector for short). A schematic diagram of a silicon lithium-drifted detector is shown in Fig. 8.30. A cylindrical piece of pure, single crystal silicon is used. The size of this piece is... 

Selenium has excellent light-conducting and light-converting properties. Until the 1970s, selenium semiconductors were more el3 cient than the previously used copper oxide rectifiers but could not stand the competition when cheaper silicon diodes came on the market. Now nearly all rectifiers are made with silicon components. Selenium is, however, currently enjoying a resurgence of interest as a possibly important component in electronics for solar cells. 

Semiconductor rectifiers contain at least two separate materials, a P-type and an N-type silicon semiconductor, joined together and held by conductors. With an alternating voltage across this combination, normally called a silicon diode, the electrons in the N-layer and the holes in the P-layer respond by moving in opposite directions. Figure 8.6 shows that during one half of the voltage cycle, the electrons and holes move toward the junction, and current flows. In the other half of the cycle, the electrons and holes move away from the junction, and current flow is impossible. 

Silicon diodes and other types of semiconductors have already been used for decades in radiation dosimetry for the measurement of dose and dose rate. There is a basic difference... 

Zhang L, Coffer JL, Gnade BE, DaXue X, Pinizzotto RF (1995) Effects of local ambient atmosphere on the stability of electroluminescent porous silicon diodes. J Appl Phys 77 5936 Zimin SP (2000) Classification of electrical properties of porous silicon. Semiconductors 34 353 Zimin SP (2006) Hopping conductivity in low-porosity mesoporous silicon formed on p -Si -B. Semiconductors 40(11) 1350... 

The thyristor is a semiconductor device made of germanium or silicon wafers and comprises three or more Junctions, which can be switched from the OFF state to the ON state or vice versa. Basically it is a ptipn junction, as shown in Figure 6.20(a) and can be considered as composed of two transistors with npn and pnpjunctions, as illustrated in Figure 6.20(b). It does not turn ON when it is forward biased, unlike a diode, unless there is a gate firing pulse. Thyristors are forced commutated (a technique... 

Silicon s atomic structure makes it an extremely important semiconductor. Highly purified silicon, doped with such elements as boron, phosphorus, and arsenic, is the basic material used in computer chips, transistors, sUicon diodes, and various other electronic circuits and electrical-current switching devices. Silicon of lesser purity is used in metallurgy as a reducing agent and as an alloying element in steel, brass, and bronze. 

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