Energy gap semiconductors

Figure 7 shows Eq for GaAs and Ga 82 0.18 function of temperature T to about 900 K. Additional measurements on samples having differing A1 contents would generate a family of curves. The solid line is a least-squares fit to a semi-empirical relation that describes the temperature variation of semiconductor energy gaps ... 

Semiconductor Energy Gap (eV) Electron Mobility. ve (cm V ls l) Hole Mobility, v (etirV s-1)... 

The phase diagram of CuaTe-GagTeg has been determined. A compound CuaGa4Te7 is formed which is a defect sphalerite-type semiconductor (energy gap 1.08 0.05 eV). 

The most important point to note about Equation 2.30 is that ni depends exponentially with temperature on half of the semiconductor energy gap. Narrow-gap semiconductors will have large intrinsic carrier concentrations while wide-gap materials will have fewer mobile carriers at a given temperature. 

As discussed briefly in Section 6.1, observed semiconductor energy gaps he below what one would expect for a linear interpolation between the end-point compotmds. The direct energy gap can be written empirically as... 

Bechstedt F 1992 Quasiparticle corrections for energy gaps in semiconductors Adv. Solid State Phys. 32 161... 

Semiconductors are a class of materials whose conductivity, while highly pure, varies witli temperature as exp (-Ag//cg7), where is tlie size of a forbidden energy gap. The conductivity of semiconductors can be made to vary over orders of magnitude by doping, tlie intentional introduction of appropriate impurities. The range in which tlie conductivity of Si can be made to vary is compared to tliat of typical insulators and metals in figure C2.16.1. 

In an intrinsic semiconductor, tlie conductivity is limited by tlie tlieniial excitation of electrons from a filled valence band (VB) into an empty conduction band (CB), across a forbidden energy gap of widtli E. The process... 

Figure C2.16.3. A plot of tire energy gap and lattice constant for tire most common III-V compound semiconductors. All tire materials shown have cubic (zincblende) stmcture. Elemental semiconductors. Si and Ge, are included for comparison. The lines connecting binary semiconductors indicate possible ternary compounds witli direct gaps. Dashed lines near GaP represent indirect gap regions. The line from InP to a point marked represents tire quaternary compound InGaAsP, lattice matched to InP.

Semiconductors. The basic material employed in LEDs is the semiconductor, a soHd which possesses a conductivity intermediate between that of a conductor and an insulator. Unlike conductors, semiconductors and insulators possess an energy gap, E, between two energy bands, the... 

Direct and Indirect Energy Gap. The radiative recombination rate is dramatically affected by the nature of the energy gap, E, of the semiconductor. The energy gap is defined as the difference in energy between the minimum of the conduction band and the maximum of the valence band in momentum, k, space. Eor almost all semiconductors, the maximum of the valence band occurs where holes have zero momentum, k = 0. Direct semiconductors possess a conduction band minimum at the same location, k = O T point, where electrons also have zero momentum as shown in Eigure la. Thus radiative transitions that occur in direct semiconductors satisfy the law of conservation of momentum. 

Heterogeneous Photocatalysis. Heterogeneous photocatalysis is a technology based on the irradiation of a semiconductor (SC) photocatalyst, for example, titanium dioxide [13463-67-7] Ti02, zinc oxide [1314-13-2] ZnO, or cadmium sulfide [1306-23-6] CdS. Semiconductor materials have electrical conductivity properties between those of metals and insulators, and have narrow energy gaps (band gap) between the filled valence band and the conduction band (see Electronic materials Semiconductors). 

Trigonal selenium is a -type semiconductor with an energy gap of 1.85 eV (104) and a work function of about 6 eV (105), which is the largest value reported for all the elements. Accordingly, a Schottky barrier should be created at the contact of selenium with any metal. This is consistent with the... 

The equihbtium lever relation, np = can be regarded from a chemical kinetics perspective as the result of a balance between the generation and recombination of electrons and holes (21). In extrinsic semiconductors recombination is assisted by chemical defects, such as transition metals, which introduce new energy levels in the energy gap. The recombination rate in extrinsic semiconductors is limited by the lifetime of minority carriers which, according to the equihbtium lever relation, have much lower concentrations than majority carriers. Thus, for a -type semiconductor where electrons are the minority carrier, the recombination rate is /S n/z. An = n — is the increase of the electron concentration over its value in thermal equihbtium, and... 

Electronic and Optoelectronic Applications of TeUurides. Most metal teUurides are semiconductors with a large range of energy gaps and can be used in a variety of electrical and optoelectronic devices. AUoys of the form HgCdTe and PbSnTe have been used as infrared detectors and CdTe has been employed as a gamma ray detector and is also a promising candidate material for a thin-fUm solar ceU. 

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