Semiconductor optoelectronic properties

There is another class of amorphous semiconductors based on chalcogens which predate the developments that have occurred in i -Si. Because their use has been limited, eg, to switching types of devices and optical memories, this discussion is restricted to the optoelectronic properties of i -Si-based alloys and their role in some appHcations. 

Some of the major questions that semiconductor characterization techniques aim to address are the concentration and mobility of carriers and their level of compensation, the chemical nature and local structure of electrically-active dopants and their energy separations from the VB or CB, the existence of polytypes, the overall crystalline quality or perfection, the existence of stacking faults or dislocations, and the effects of annealing upon activation of electrically-active dopants. For semiconductor alloys, that are extensively used to tailor optoelectronic properties such as the wavelength of light emission, the question of whether the solid-solutions are ideal or exhibit preferential clustering of component atoms is important. The next... 

Molecular Group 3-5 compounds are currently of considerable interest for two reasons (a) they can serve as volatile low molecular weight single-source precursors for the CVD synthesis of binary and multinary group 3/5 semiconductors with remarkable optoelectronic properties (54), or (b) they are potentially useful cocatalysts for the polymerization reactions of unsaturated organic substrates (55, 56). Various strategies have been employed to synthesize well-defined aggregates. 

Nolte, D. D., Semi insulating semiconductor heterostructures Optoelectronic properties and applications, J. Appl. Phys. 1999, 85, 6259... 

Iron oxide (Fe Oj) and tungsten oxide (WO ) films have been studied and developed as candidate semiconductor materials for the PEC junction (photoanode). High-temperature synthesis methods, as reported for some high-performance metal oxides, have been found incompatible with multijunction device fabricatioa A low-temperature reactive sputtering process has been developed instead. In the parameter space investigated so far, the optoelectronic properties of WO3 films were superior to those of Fe Oj films, which showed high recombination of photogenerated carriers (Miller et al., 2004). 

It has been shown in Chapter 3 that electrodes (metals and semiconductors) interact with the electrolyte which strongly influences the optoelectronic properties of the junction. Frequently, it is very difficult to identify the microscopic and molecular nature of the states at the interface. Better scientific understanding demands a spectroscopic identification of the surface and the interface states. Several spectroscopic methods are available which allow the analysis of the chemical, structural and, also, electronic properties of the surface. 

S.E. Saddow, M. Mynbaeva, and M. MacMillan, Chapter 8 Porous SiC technology , in Silicon Carbide Materials, Devices and Applications, Zhe Chuan Feng and Jian H. Zhao (Eds), Optoelectronic Properties of Semiconductors and Superlattices, Taylor and Francis Engineering, New York, 2003. 

TABLE 8.1 Optoelectronic Properties of Common Inorganic, Polymer, and Small-Molecule Semiconductors... 

It is clear from this discussion that electrodeposition alone does not give high-quality p-type compound semiconductor layers with optoelectronic properties that are suitable for PV applications. ED therefore generally forms part of a multistage fabrication process. In the first step some or all of the elements of the semiconductor are deposited electrochemically to form a thin film, and in the subsequent steps the film is thermally annealed in an appropriate chemical environment to give it the desired properties. 

Lead Chalcogenides, in Optoelectronic Properties of Semiconductors and Superlattices, Vol. 18, Taylor Francis Inc., 2003 R 228 T. Story, Semimagnetic Semiconductors Based on Lead Chalcogenides ,... 

The quantum effect of reduction of particle size in reducing the band gap of semiconductors and so giving rise to novel optoelectronic properties has stimulated interest in quantum dot inclusion compounds of nanoparticles of semiconductors within zeolite pores.In a pioneering study, Herron and coworkers succeeded in introducing cadmium sulfide clusters within the pores of zeolite Y via the reaction of a cadmium-exchanged zeolite Y with hydrogen sulfide gas (Scheme 6.8). °... 

The first observation of intentional localized corrosion on semiconductors, other than Si, was purposely performed to corrugate the semiconductor surface, decrease the reflectivity, improve the optoelectronic properties, and consequently increase the performance of photoelectrochemical solar cells. 

Light-emitting ID nanomaterials made by conjugated potymers have unique features because they combine optoelectronic properties of semiconductors with structural properties of potymers. Organic nanowires, nanofibers, and nanotubes can be produced by different techniques, including template-assisted synthesis and vacuum sublimation. However, the lowthroughput of many of these approaches limits their application in photonic integrated systems. 

Semiconductor photorectifying cells absorb photons in the solar spectrum, and can convert some of the absorbed photon energy into electricity or chemical products, such as hydrogen. Different semiconductors are specifically sensitized to different parts of the solar spectrum dependent on optoelectronic properties related to bandgap and absorptivity. In general, the macroscopic light absorption process in a material follows the Beer-Lambert Law [89], here expressed as a function of photon wavelength, 1 ... 

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