E E 339 - CN2-crystals(1)

E E 339 - CN2-crystals(1) - 1 Semiconductor Crystals:...

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Unformatted text preview: 1 Semiconductor Crystals: properties and growth Semiconductor Crystals: properties and growth 1 Outline basic solid types crystal structure: general discussion crystal structure of most semiconductors Notation to denote planes and directions: “Miller indices” (jargon of the trade) Semiconductor crystal growth and wafer fabrication 2 2 There are three basic solid types: Crystalline (ordered) … as, for example, diamond Amorphous (disordered) … as, for example, window glass Solid types Polycrystalline (many small single crystalline/ordered regions randomly oriented to each other) … as, e.g., polysilicon Figure 1—1 Three types of solids, classified according to atomic arrangement: (a) crystalline and (b) amorphous materials are illustrated by microscopic views of the atoms, whereas (c) polycrystalline structure is illustrated by a more macroscopic view of adjacent single-crystalline regions, such as (a). 3 A semiconductor device may contain all three types as is the case for the “semiconductor” Industry workhorse, the m etal (actually typically highly conductive poly-Si) o xide (SiO 2 ) s emiconductor (Si) f ield-e ffect t ransistor (MOSFET). Figure 6—33* Cross section of a metal in this case … MOSFET. This high resolution transmission electron micrograph of a silicon Metal–Oxide Semiconductor Field Effect Transistor shows the silicon channel and metal gate separated by a thin (40Å, 4nm) silicon–dioxide insulator The inset amorphous SiO 2 crystalline Si … but more often poly Si insulator. The inset shows a magnified view of the three regions, in which individual rows of atoms in the crystalline silicon can be distinguished. (Photograph courtesy of AT&T Bell Laboratories.) 4 3 We will be principally, but not exclusively, interested in the properties of charge carriers in semiconductor crystals in this course. Metals or polysilicon are most often used simply as contacts (reservoirs of carriers) and amorphous materials are most often simply used as insulators (barriers to charge transport). 5 Hess, 2.4 modified: one view of a t ti f A crystal is, simply put, a periodic array of atoms. Crystal structure representation of, e.g., a GaAs cyrstal. However, to distinguish among the many possible types of crystal structures and the analyze their properties requires a bit more elaborate description of their structure … … employing terminology such as “Bravais lattice,” “atomic basis,” “translation/basis vectors,” “unit cells,” and “primitive” versions of all of the above. 6 4 Crystal structure is described via a “Bravais lattice ” and an “atomic basis ,” where … … a “ Bravais lattice ” is a periodic array of “points”—a mathematical construct—such that the lattice looks identical from each point....
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This note was uploaded on 09/03/2011 for the course E E 339 taught by Professor Leonardregister during the Fall '11 term at University of Texas.

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E E 339 - CN2-crystals(1) - 1 Semiconductor Crystals:...

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