Transport properties, semiconductor

For bulk semiconductors and multiple quantum well structures (one-dimensional confined semiconductors), transport properties are of great interest and are important for practical applications such as transistors and detectors. Semiconductor nanoclusters are usually confined in three-dimensions by insulating matrices such as polymers and glasses, where the transport of carriers is not feasible. To explore transport-related applications of semiconductor clusters, a matrix that is capable of transporting carriers is needed, In addition, the redox properties of the matrix have to allow injection of carriers from semiconductor nanoclusters to the matrix. 

Table 2. Transport Properties of the Cubic Binary Compound Semiconductors...

Colloidal semiconductor nanocrystals are attracting growing attention as the building blocks for inexpensive, large-area, solution-processed solar cells. The advantages here are the scalable and controlled synthesis, an ability to be processed in solution, the broadband absorption, and the superior transport properties of traditional photovoltaic semiconductors. Solar cells that rely exclusively on colloidal nanocrystals have been anticipated theoretically58 and... 

Gamier, F. Hajlaoui, R. El Kassmi, A. Horowitz, G. Laigre, L. Porzio, W. Armanini, M. Provasoli, F. 1998. Dihexylquaterthiophene, a two-dimensional liquid crystal-like organic semiconductor with high transport properties. Chem. Mater. 10 3334-3339. 

Zinc antimonide, 3 44, 53—54 Zinc atomizing process, 26 598 Zinc baths, 9 828-829, 830t Zincblende semiconductors, 22 141 band structure of, 22 142-144 transport properties of, 22 148, 149t Zinc borates, 4 282-283 Zinc brass... 

We shall briefly discuss the electrical properties of the metal oxides. Thermal conductivity, electrical conductivity, the Seebeck effect, and the Hall effect are some of the electron transport properties of solids that characterize the nature of the charge carriers. On the basis of electrical properties, the solid materials may be classified into metals, semiconductors, and insulators as shown in Figure 2.1. The range of electronic structures of oxides is very wide and hence they can be classified into two categories, nontransition metal oxides and transition metal oxides. In nontransition metal oxides, the cation valence orbitals are of s or p type, whereas the cation valence orbitals are of d type in transition metal oxides. A useful starting point in describing the structures of the metal oxides is the ionic model.5 Ionic crystals are formed between highly electropositive... 

There have been many attempts to relate bulk electronic properties of semiconductor oxides with their catalytic activity. The electronic theory of catalysis of metal oxides developed by Hauffe (1966), Wolkenstein (1960) and others (Krylov, 1970) is base d on the idea that chemisorption of gases like CO and N2O on semiconductor oxides is associated with electron-transfer, which results in a change in the electron transport properties of the solid oxide. For example, during CO oxidation on ZnO a correlation between change in charge-carrier concentration and reaction rate has been found (Cohn Prater, 1966). 

All trap-spectroscopic techniques that are based on thermal transport properties have in common that the interpretation of empirical data is often ambiguous because it requires knowledge of the underlying reaction kinetic model. Consequently, a large number of published trapping parameters—with the possible exception of thermal ionization energies in semiconductors—are uncertain. Data obtained with TSC and TSL techniques, particularly when applied to photoconductors and insulators, are no exceptions. 

The results taken as a whole reveal the existence of at least three different trap species in the band gap of Sb(As)j Sei noncrystaUine semiconductors. These species are located at energies 0.22, 0.34, and 0.45 eV, respectively, below the conduction band edge and control the electron transport properties of the material. It seemed that Sb and As introduce a new set of detectable charge-carrier traps. 

It is appropriate to review the various major commercial applications of amorphous semiconductor devices and to indicate the extent to which the nsefnlness of amorphons semiconductors depends on an optimization of their electronic transport properties. 

The fabrication of active semiconductor devices from amorphous semiconductor films is a further application that offers considerable advantages. Thin-fihn transistors, based on amorphous films of hydrogenated silicon, are nnder intensive development. Other devices with monostable and bistable switching characteristics have also received considerable interest. Naturally enough, the performance of snch devices is intimately related to the transport properties of charge carriers in the materials employed. 

Bach et al. have successfully introduced the concept of a solid p-type semiconductor (heterojunction), with the amorphous organic hole-transport material 2,2, 7,7 -tetrakis (, V, V-di-/ -methoxyphcnyl-aminc)9,9 -spirobifluorenc [96]. This hole-conducting material allows the regeneration of the sensitizers after electron injection due to its hole-transport properties. Nevertheless, the incident photon-to-current conversion efficiencies using complex 22 as a charge-transfer sensitizer... 

While complexes in which the metal is coordinatively unsaturated frequently oligomerize utilizing bridging jS-diketonate ligands, a different mode of aggregation is believed to occur in M(CO)2-(MeCOCHCOMe) (M = Rh, Ir), The near planarity of the acetylacetonate permits these flat molecules to stack so that short (3.20 A for Ir) metal-metal contacts are formed. This leads to highly anisotropic DC electrical transport properties and these compounds are semiconductors. 

Poly- and oligothiophenes are generally p-type (hole-transporting) semiconductors. In thiophene-S,S-dioxide (98AM551 98JOC5497), this modification results in de-aromatization of the thiophene unit and increases the electron affinity and electron-transport properties of the... 

The catalytic activity of these simple oxides has been correlated [38,39] with its ability to chemisorb simple molecules such as CO and N20 via an electron transfer, which results in a change in the electron transport properties in the semiconductor solid oxide. In this sense, the catalytic activity of simple oxides has been correlated with the band gap, and the number of d-electrons for 3d metal oxides [22],... 

The classification scheme is particularly effective in arranging crystals by their charge transport properties. Integrated stack crystals (Sect. 2) and integral-oxidation state segregated stack crystals (Sect. 3) are invariably semiconductors, with typical room-temperature conductivities being a < 10 3 cm-1. In contrast, many of the non-... 

This process is obviously a natural scattering process in polycrystalline materials, since polycrystalline films exhibit a high concentration of crystallographic defects, especially dislocations [133,134]. However, this process is rarely used to explain experimental data of carrier transport in polycrystalline semiconductors and especially transparent conducting oxides [88], which is mainly due to the fact that in most works on transport properties of polycrystalline films the density of defects was not determined. Podor [135] investigated bended n-type Ge crystals with a dislocation density around 107 cm 2... 

---