Bandgap materials

A more effective carrier confinement is offered by a double heterostructure in which a thin layer of a low-gap material is sandwiched between larger-gap layers. The physical junction between two materials of different gaps is called a heterointerface. A schematic representation of the band diagram of such a stmcture is shown in figure C2.l6.l0. The electrons, injected under forward bias across the p-n junction into the lower-bandgap material, encounter a potential barrier AE at the p-p junction which inliibits their motion away from the junction. The holes see a potential barrier of... 

Since IR detector materials are direct bandgap materials (with no change in electron momentum required), they are very efficient absorbers (and emitters) of light - all IR photons are absorbed within the first few /rm of material. The reason that infrared detectors are 10 to 15 ptm thick is for structural and fabrication reasons, not for light absorption reasons. 

Fink Y., Urbas A.M., Bawendi M.G., Joannopoulos J.D., and Thomas E.L. Block copolymers as photonic bandgap materials, J. Lightwave Tech., 17, 1963, 1999. 

Fujiyoshi, S., Ishibashi, T. and Onishi, H. (2005) Fourth-order Raman spectroscopy of wide-bandgap materials. J. Phys. Chem. B, 109, 8557-8561. 

While silicon is not the ideal solar cell material, it currently dominates the solar PV market due to its prevalence in the microelectronics industry. Crystalline silicon (c-Si) is an inorganic semiconductor, in which the valence-band maximum and conduction-band minimum are not directly aligned in Uspace, making c-Si an indirect bandgap material. The indirect nature of the bandgap in c-Si means that a considerable change in momentum is required for the promotion of an electron from... 

Other wide bandgap materials, such as GaN, AIN, and diamond, with band-gaps of 3.4, 6.3, and 5.5 eV, respectively, have also been explored by a number of... 

We recently published a chapter in the book Silicon Carbide Recent Major Advances by Choyke et al. [19] that describes SiC gas sensor applications in detail. In this book, we emphasize device properties applications are only briefly reviewed at the end. The device and gas sensing properties of various field-effect chemical gas sensing devices based on SiC are described, and other wide bandgap material devices are reviewed. The detection principle and gas response is explained, and the buried channel SiC-FET device is described in detail. Some special phenomena related to the high-temperature influence of hydrogen at high temperature are also reported. 

Schottky diode sensors based on other wide bandgap materials have also been investigated, as previously mentioned. GaN Schottky diodes processed on either the Ga or N face have been examined by Schalwig et al. [11,21]. A Pt/GaN Schottky diode with a barrier height of 1-eV has been shown to reversibly transform into an ohmic contact through exposure to [94]. Kokobun et al. have also investigated Pt-GaN Schottky diodes as hydrogen sensors up to 600°C [15]. 

Matsuo S, Kondo T, Juodkazis S, Mizeikis V, Misawa H (2002) Fabrication of three-dimensional photonic crystals by femtosecond laser interference. In Adibi A, Scherer A, Lin S-Y (eds) Photonic bandgap materials and devices. SPIE Proc 4655 327-334... 

Beginning with composite electrodes the simplest scheme here is to coat the surface of a small gap semiconductor that is well matched to the solar spectrum but which is electro-chemically unstable with a thin film of a wide gap, electrochemically stable semiconductor. To demonstrate the feasibility of using such a composite electrode, the film must be thin enough - of the order of 50-100 A or less - so that at least some of the photogenerated carriers in the small bandgap material can tunnel through to the electrolyte. Furthermore the film must not have any cracks or pinholes since these would... 

Donor-acceptor 7i-conjuga ted (D-rc-A) compounds have led to numerous theoretical and experimental studies to explore the origin of intramolecular charge-transfer (ICT) fluorescence. This property can be used in order to have low bandgap materials. 

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