P-n junction transistors

W. Shockley, The theory of p-n junctions in semiconductors and p-n junction transistors, Bell Syst. Tech. J. 28 435H 89 (1949). 

Transistors eventually made their way into portable radios and other electronic devices, and are most prominently used today as building blocks of integrated circuits. Remarkably, the invention of the point-contact and p-n junction transistors,... 

A printed circuit has many n-p-n junction transistors. Fig. 10.33 illustrates the formation of one transistor area. The chip begins as a thin wafer of silicon that has been doped with an n-type impurity. A protective layer of silicon dioxide is then produced on the wafer by exposing it in a furnace to an oxidizing atmosphere. The next step is to produce a p-type semiconductor. To do this, the surface of the oxide is covered by a polymeric photoresist, as shown in Fig. 10.33(a). A template that only allows light to shine... 

Shockley W, Sparks M, Tetil GK (1951) p-n junction transistor. Phys Rev 83 151-162... 

In the case of the two prototype substances, water and silicon, mentioned at the beginning, we know that boundary layer effects frequently exceed the voliune effects in their importance one may think, on the one hand, of p-n junctions, transistors, photoelements, varistors, Schottky diodes, and, on the other, of electrode/liquid electrolyte junctions or colloid chemistry. First let los look at five particularly illustrative examples (Fig. 5.70). 

The bipolar junction transistor (BIT) consists of tliree layers doped n-p-n or p-n-p tliat constitute tire emitter, base and collector, respectively. This stmcture can be considered as two back-to-back p-n junctions. Under nonnal operation, tire emitter-base junction is forward biased to inject minority carriers into tire base region. For example, tire n type emitter injects electrons into a p type base. The electrons in tire base, now minority carriers, diffuse tlirough tire base layer. The base-collector junction is reverse biased and its electric field sweeps tire carriers diffusing tlirough tlie base into tlie collector. The BIT operates by transport of minority carriers, but botli electrons and holes contribute to tlie overall current. 

In addition to its use as a rectifier, the p—n junction (26) is the fundamental building block for bipolar, junction EFT (fFET), and MOSFET transistors. A thorough understanding of p—n junctions explains much of transistor behavior. The theory (5) of the p—n junction and its role in bipolar transistors was presented within a year of the discovery of the point-contact transistor. 

As Figure 10 shows, the n—p—n bipolar junction transistor (BJT) may be regarded as two back-to-back p—n junctions separated by a thin base region (26,32,33). If external voltages are applied so that the base-emitter (BE) junction is forward biased and the base-coUector (BC) junction is reverse biased, electrons injected into the base from the emitter can travel to the base-coUector junction within their lifetime. If the time for minority carrier electrons to... 

Eig. 10. The n—p—n transistor biased ia its active region, where 7 = current, (------) indicate depletion regions at the p—n junctions, and S is the electric field ... 

To achieve the lowest possible delay a bipolar switching transistor developed by IBM minimizes parasitic resistances and capacitances. It consists of self-aligned emitter and base contacts, a thin intrinsic base with an optimized collector doping profile, and deep-trench isolation (36). Devices must be isolated from each other to prevent unwanted interactions in integrated circuits. While p—n junctions can be used for isolation, IBM s approach etches deep trenches in the siUcon wafer which are filled with Si02 to provide electrical insulation. 

Secondary Ion Mass Spectroscopy (SIMS). When the p-n junction and the GaAs/GaAlAs heterojunction are not coincident, carrier recombination occurs, reducing the current and the performance of fabricated heterojunction bipolar transistors. 

A transistor, or n-p-n junction, is built up of two n-type regions of Si separated by a thin layer of weakly p-type (Fig. e). When the emitter is biased by a small voltage in the forward direction and the collector by a larger voltage in the reverse direction, this device acts as a triode amplifier. The relevant energy level diagram is shown schematically in Fig. f... 

Solid-state electronic devices such as diodes, transistors, and integrated circuits contain p-n junctions in which a p-type semiconductor is in contact with an n-type semiconductor (Fig. 3.47). The structure of a p-n junction allows an electric current to flow in only one direction. When the electrode attached to the p-type semiconductor has a negative charge, the holes in the p-type semiconductor are attracted to it, the electrons in the n-type semiconductor are attracted to the other (positive) electrode, and current does not flow. When the polarity is reversed, with the negative electrode attached to the n-type semiconductor, electrons flow from the n-type semiconductor through the p-type semiconductor toward the positive electrode. 

Judd-Hunter color difference scale, 7 321 Juglone, in skin coloring products, 7 847 Juglone derivatives, 21 264-265 Juice softening, 23 463 Junctional heart rhythm, 5 107 Junction capacitance, 22 244 Junction devices, 22 180-181 Junction FETs (JFETs), 22 163, 164. See also Field effect transistors (FETs) physics of, 22 241-245, 249 Junction potentials, 9 582 Junctions, stacking, 23 38-39. See also Josephson junctions p-n junction Just-in-Time technique, 21 172 Jute, 11 287, 288, 292, 293. See also China jute... 

K. Jdrrendahl and R. F. Davis, Materials Properties and Characterization of SiC V. A. Dmitriev and M. G. Spencer, SiC Fabrication Technology Growth and Doping V. Saxena and A. J. Steckl, Building Blocks for SiC Devices Ohmic Contacts, Schottky Contacts, and p-n Junctions M. S. Shur, SiC Transistors... 

If we place n- and p-type semiconducting crystals in contact (a p-n junction), we create a device that conducts electricity preferentially in one direction this is the basis of action of the semiconductor diodes used in the electronics industry, although specially refined silicon (Section 17.8.2) is usually employed rather than Ge. Transistors and electronic chips are designed using similar basic principles—typically with n-p-n or p-n-p junctions. We consider chemical aspects of electronic devices in more detail in Chapter 19. 

In solid state technology, some of the most important transport processes occur at junctions. Junctions are zones in which the disorder type changes. The best known junction is the (p-n) junction in a semiconductor, which is basic to the operation of a transistor. In Figure 4-8, the main features of a junction zone are presented. Although it illustrates the situation in a semiconductor, as we shall see later, its essential features explain other junctions as well. 

Solid-state electronic devices such as diodes, transistors, and integrated circuits contain p-n junctions in which a p-type semiconductor is in contact with an n-type semiconductor (Fig. 3.48). Because solar radiation can excite electrons into a conduction band, semiconductors can be used to generate an electrical current by the action of sunlight. 

MOSFETs. The metal-oxide-semiconductor field effect transistor (MOSFET or MOS transistor) (8) is the most important device for very-large-scale integrated circuits, and it is used extensively in memories and microprocessors. MOSFETs consume little power and can be scaled down readily. The process technology for MOSFETs is typically less complex than that for bipolar devices. Figure 12 shows a three-dimensional view of an n-channel MOS (NMOS) transistor and a schematic cross section. The device can be viewed as two p-n junctions separated by a MOS capacitor that consists of a p-type semiconductor with an oxide film and a metal film on top of the oxide. 

The operation of the NMOS transistor shown schematically in Figure 12 can be considered in the light of the previous discussion of a MOS capacitor. When no voltage is applied to the gate, the source and drain electrodes correspond to p-n junctions connected through the p region therefore only a small reverse current can flow from source to drain. On the... 

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