Semiconductive compounds

Indium also combines with nonmetaUic elements and with metalloids such as N, P, Sb, As, Te, and Se. Many of the latter compounds ate semiconducting as ate the oxide and sulfide. Indium antimonide [1312-41 -0], InSb indium arsenide [1303-11-3], In As and indium phosphide [22398-80-7], InP, ate the principal semiconducting compounds. These ate all prepared by direct combination of the highly purified elements at elevated temperature under controlled conditions. 

We shall first review the basic principles of VASP and than describe exemplary applications to alloys and compounds (a) the calculation of the elastic and dynamic properties of a metallic compound (CoSi2), (b) the surface reconstruction of a semiconducting compound (SiC), and (c) the calculation of the structural and electronic properties of K Sbi-j, Zintl-phases in the licpiid state. 

The temperature at which this reaction is carried out is limited by considerations of the possibility of re-evaporation of AS2 molecules and gallium atoms from the GaAs film. The semiconducting compounds are less susceptible to this problem than the separate elements because of the thermodynamic stabilities of these compounds, as discussed above. 

Also, thin films of semiconducting compounds were formed on a gold electrode. To obtain them, a methodology called electrochemical ALE (electrochemical atomic layer epitaxy) has been developed. This procedure is based on the formation of individual atomic layers of particular elements, which may further form a compound. Accordingly, in each cycle, a controlled formation of a monolayer of the particular compound occurs. The advantage of this methodology is that three-dimensional growth of one-elemental deposit is inhibited. 

We briefly present below the papers dealing with deposition of S, Se, and Te on Au electrodes and with the formation of semiconducting compounds at their surfaces. 

To use templates or envelopes as a controlled reaction space was developed in the early 1980s, such as the use of inverse micelle technique (4). Another fundamental idea is to use the atomic periodicity of surfactant molecules by using them as surface ligands for sequential addition of anions and cations under the concept of semiconductive compounds like CdSe as a living polymer (3). 

Some semiconducting compounds can be of the II-VI type, which also has an average valence of four, but these have much more ionic character than Ill-V compounds. Their band gaps are thus larger, and in some cases they may even be viewed as insulators. For example, ZnS, with a band-gap energy of 3.6 eV, is an insulator, whereas ZnSe has an band gap of 2.8 eV, which is closer to a semiconductor. A wide variety of... 

The lithographic process is illustrated in Figure 7.46. The substrate, consisting of multiple layers of semiconducting compounds and metals, is covered with a crosslinkable... 

It has been shown in Section 1.3.7 that in semiconductors or insulators the lattice defects and electronic defects (electrons and holes), derived from non-stoichiometry, can be regarded as chemical species, and that the creation of non-stoichiometry can be treated as a chemical reaction to which the law of mass action can be applied. This method was demonstrated for Nii O, Zr Cai Oiand Cuz- O in Sections 1.4.5, 1.4.6, and 1.4.9, as typical examples. We shall now introduce a general method based on the above-mentioned principle after Kroger, and then discuss the impurity effect on the electrical properties of PbS as an example. This method is very useful in investigating the relation between non-stoichiometry and electrical properties of semiconductive compounds. 

Fig. 1.63 Kroger-Vink diagram of semiconductive compound MX for the case Kg < (see Table 1.6).

Thus, it has been shown that the electrical properties of semiconductive compounds depend on the chemical composition, viz. non-stoichiometry, and therefore the control of the composition is indispensable in the control of the semiconductive properties of the compounds. 

Semiconductive elements Si and Ge (Group IVB or 13 in the periodic table) have become very important electronic materials since development of a purification method. The electronic properties of semiconductive elements of high purity can be controlled by the species and concentration of defects and impurity elements. On the other hand, in the case of semiconductive compounds, that is, III-V and II-VI compounds, we have to consider not only control of the purity of constituent elements but also the nonstoichiometry, both of which have much influence on the electronic properties. In this sense, control of the electrical properties of semiconductive compounds is more difficult than that of semiconductive elements. 

Sadowski, J., Vanelle, D.S. Yee, D. Hrabovski, J. Kanski and L. liver, 2001c, presented at XXX International School on the Physics of Semiconducting Compounds Jaszowiec 2001 , June 1-8, 2001, Ustron-Jaszowiec, Poland. 

Figure 1-4. The A/AX interface during flow of A-cations across the boundary (g = 0) into the (semiconducting) compound AX. Point defect relaxation reaction between 0< < R reads V + A- = Aa. hit = width of relaxation zone.

Here, p 0i and pq2 are the oxygen pressures at the opposite surfaces of the spinel sample. If bA>i bB, the decomposed binary reactant AO will be formed at the high oxygen potential side (Fig. 8-4), whereas if bA< -bB, AO will be formed at the low oxygen potential side, provided that A/Uo2> Mo2 (max)- B203 will be formed at the respective opposite sides. Experiments have been performed that confirm this mode of decomposition [W. Laqua, H. Schmalzried (1983)]. In concluding, we point out that, in principle, kinetic decomposition occurs in all semiconducting compounds for which bA = bB, independent of their anionic transference. 

The above considerations referred to solid solutions of metals are also applicable to semiconducting compounds and microcrystalline one-component ceramics modified by admixtures (Table 5.3). It is seen from the example of corundum ceramics that the hardness of a material depends, when modified with elements of the second group in the periodic table, on the kind and quantity of admixtures, the best results being obtained for magnesium and strontium admixtures. 

Intermetallic and Semiconducting Compounds. Indium forms intermetallic compounds with a great many metals and combinations of metals including alkali metals, magnesium, the iron group, rare earths, and precious metals such as the platinum group. Carbon-free indium-based... 

Single crystals of transition-metal hydrides cannot be grown from the melt by the usual techniques because the hydrides dissociate at temperatures well below their melting points. The method used here is one of compound formation from saturated elemental melts. It is a modification of the technique used by Harman ct al.3 and Stambaugh et al.4 for growing crystals of III-V semiconducting compounds. 

A square-planar coordination is also met in the monoclinic PdP2 structure (58) of the semiconducting compounds NiP2, PdP2 and PdPAs (59). The anions are tetrahedrally surrounded by two cations plus two anions (Fig. 15). Here the anions form twisted zig-zag chains, so that these phases are also polycompounds and the cations are divalent. It is noteworthy that in the corresponding platinum compounds Pt is tetravalent like in the disulfide. Application of pressure may induce this valence state also... 

The mobility and resistivity data of single crystalline zinc oxide samples (measured at room temperature) from different authors, which were reported from 1957 to 2005, are displayed in Fig. 2.6 as a function of the carrier concentration (part of these data were taken from [67]). Undoped ZnO crystals exhibit carrier concentrations as low as 1015 cm-3, while indium-doped crystals reach carrier concentrations up to 7 x 1019cm-3. The mobility data show a large scattering between carrier concentrations of 1017 to 5 x 1018cm-3. This is caused by the fact that zinc oxide is a compound semiconductor that is not as well developed as other semiconducting compounds. For instance, only... 

Figure 6. The X-ray spectra firom 1.0 MeV proton bombardment of a) furnace black, b) mar resistant, and c) and d) two samples of the extra clean super smooth semiconductive compound. Note the improvement and the inhomogeneity of the remaining silicon and calcium.

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