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Detector types extrinsic

A variety of transducer configurations that has been employed in photometric sensor devices fall into two sensor types extrinsic sensors and intrinsic sensors. While in the former sensor type the optical fiber merely acts as a light guide, conveying the optical information between the optical source and the chemical transducer and between the chemical transducer and the detector, in the latter sensor type the optical fiber, probably in some modified form, would become a part of the transducer. [Pg.4401]

Impurity photoconductivity (extrinsic photoconductivity) is a type of absorption measurement where the detector is the sample itself. Classical photoconductivity occurs when the absorption of an electron or of a hole takes place between a discrete state and a continuum, where it can contribute to the electrical conductivity. When the final state of a discrete transition is separated from the continuum by an energy comparable to k T at the measurement temperature, the electron or the hole in this state can be thermally ionized in the continuum and give rise to photoconductivity at the energy of the discrete transition. This two-step process, which is temperature-dependent, is known as photo-thermal ionization spectroscopy (PTIS) and is discussed in more detail later in the section on extrinsic photoconductors. [Pg.88]

The largest applications for semiconductors use extrinsic material. The entire electronic materials industry is built around doped silicon. However, there are applications that require intrinsic semiconductors. One such application is X-ray detectors used on transmission electron microscopes (TEMs) and scanning electron microscopes (SEMs) for chemical analysis. Unfortunately it is essentially impossible to produce pure silicon. Even electronic grade silicon contains small amounts of boron (a p-type dopant). To create intrinsic material a dopant is added that produces an excess of electrons that combine with the holes formed by the residual boron. The process involves diffusing lithium atoms into the semiconductor. Ionization of the lithium produces electrons that recombine with the holes. It is possible to produce germanium crystals with much higher purity, and intrinsic Ge detectors are used on some TEMs. [Pg.537]

The left side of (4.88) is plotted vs N — N in Fig. 4.10 for several possible operating temperatures we have used the values of B and NJg given in Appendix F, as well as t = 5 x 10 cm to be consistent with condition 4 below. By comparing these curves with that for Hg gCd jTe in Fig. 4.10 and with the abscissa of Fig. 4.1, we see that this extrinsic Si photoconductive detector requires considerably lower operating temperatures than the intrinsic photoconductor for comparable performance. This result is a well-known disadvantage of an extrinsic photoconductor [4.31]. The curves for a p-type example would lie... [Pg.132]

Single crystals of Hg,, Cd Te are grown by several different methods [4.42]. Almost regardless of the growth method or composition x in the above range, undoped ( pure ) crystals which are n-type at low temperatures have an extrinsic electron concentration near 10 cm" this is a relatively low carrier concentration for a semiconductor, and it is one of the major reasons for the success of Hg, j.Cd Te as a photoconductive infrared detector material. However, undoped crystals often turn out p-type with or have... [Pg.139]


See other pages where Detector types extrinsic is mentioned: [Pg.193]    [Pg.379]    [Pg.379]    [Pg.193]    [Pg.345]    [Pg.39]    [Pg.8]    [Pg.216]    [Pg.305]    [Pg.8]    [Pg.216]    [Pg.273]   
See also in sourсe #XX -- [ Pg.8 , Pg.9 , Pg.11 , Pg.133 , Pg.135 , Pg.143 , Pg.155 , Pg.308 ]

See also in sourсe #XX -- [ Pg.8 , Pg.9 , Pg.11 , Pg.133 , Pg.135 , Pg.143 , Pg.155 ]




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Detectors types

Extrinsic detector

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