Tetrahedrally bonded semiconductors

In LCAO1 theory the valence band maximum of a tetrahedrally bonded semiconductor is derived from the anion p-levels and its energy given by [89] ... 

J.B. Goodenough and A. Hamnett, in 0. Madelung (Ed.), Non-tetrahedrally Bonded Semiconductors, Landolt-Bornstein Neue Serie Vol. XVII/g, Springer-Verlag, Berlin, 1984. 

Fig. 2. Correlation of the metallization pressure as calculated from Hertzfeld s theory and the Vickers indentation hardness for tetrahedrally bonded semiconductors. The initial structures are cubic diamond and zincblende the final structures are of the j -tin and rocksalt types. After Reference [10].

In his analysis of this situation, Rapoport first considered the melting behavior of metallic elements such as Cs, Ba, and Eu, as well as chalcogenide semiconductors (Te), and ionic salts such as KNO3. Aptekar applied the two-species thermodynamic model to Si and Ge, that form tetrahedrally bonded semiconductors at low pressure but transform into densely packed octahedrally coordinated metallic... 

Mercuric sulfide (HgS) is dimorphic. The more common form, cinnabar (red a-form), has a distorted RS, trigonal structure which is unique among the monosulfides, for the crystal is built of helical chains in which Hg has two nearest neighbors at 2.36 A, two more at 3.10 A, and two at 3.30 A. Bulk a-HgS is a large-gap semiconductor (2.1 eV), transparent in the red and near IR bands. The rare, black mineral metacinnabarite is the 3-HgS polymorph with a ZB structure, in which Hg forms tetrahedral bonds. Upon heating, 3-HgS is converted to the stable a-form. The ZB structure of HgS is stabilized under a few percent admixture of transition metals, which replace Hg ions in the lattice. 

Beyer, W. (1985). Tetrahedrally Bonded Amorphous Semiconductors, ed. by D. Adler and H. Fritzsche. Plenum Press, New York, 129. 

The bond order for tetrahedral elemental semiconductors at equilibrium may, therefore, be written as... 

All three elements can crystallise in the tetrahedrally bonded diamond structure. Si and Ge are semiconductors. Carbon has... 

Semiconductors Physics of Non-tetrahedrally Bonded Binary Compounds II, edited by O. Madelung, Landolt-Bomstein New Series, Group III, Vol 17, Part f. Springer Verlag, Berlin, 1984. 

Doping can be done by adding altervalent impurities to the intrinsic semiconductor. For example, P (a Group 15 or VA element) will act as a donor in Si (a Group 14 or IVA element). This can be rationalized on chemical terms by noting that P needs only four valence electrons for tetrahedral bonding (as in the Si lattice) —the fifth electron is available for donation by each P atom. The donor density,... 

The choice of the diamond cubic structure (FC-2) as the initial configuration to be randomized is a natural one. It is the most common structure for group IV elements and related semiconductors with tetrahedral bonding and it is the one of highest symmetry. It has periodicity built in from the outset and it allows for the possibility that the randomized structure can in principle return to the initial crystal structure. Indeed, with insufficient randomization, the nearly-randomized structure will sometimes return to the perfect FC-2 crystal structure [34]. Without exactly N = Sn atoms this option is precluded. 

Oconnor P, Tauc J (1982) Photoinducedmidgap Absorption in Tetrahedrally Bonded Amorphous-Semiconductors. Phys Rev B 25(4) 2748-2766... 

Defects that introduce extra electrons, or that give missing electrons or holes , have a large influence on electronic conduction in nonmetallic solids. Most semiconductor devices use doped or extrinsic semiconductors rather than the intrinsic semiconduction of the pure material. Doping Si with P replaces some tetrahedrally bonded Si atoms in the diamond lattice (see Topic D2) with P. Each replacement provides one extra valence electron, which requires only a small... 

All three elements can crystallize in the tetrahedrally bonded diamond structure (see Topic D2). Si and Ge are semiconductors (see Topic D7). Carbon has other allotropes. Graphite is the thermodynamically stable form at ordinary pressures, diamond at high pressures. More recently discovered forms include buckminsterfullerene C60, higher fullerenes such as C70, and nanotubes... 

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