N-semiconductor

For a weU-designed, weU-made HgCdTe photoconductoi detector (76,77), g-r noise is dominant and may be expressed in terms of a minority carrier densityp and majority carrier density n. Semiconductor noise analysis for the HgCdTe photoconductor yields,... 

The heart of a light-emitting diode is a junction between a p-type semiconductor and an n-tyqje semiconductor. The different semiconductor types have different electron populations in their bands. The lower-energy band of a p semiconductor is deficient in electrons, while the upper-energy band of an n semiconductor has a small population of electrons. The band structure in the junction region is shown schematically in the figure below. 

Fig. 5.60 The semiconductor/electrolyte interface (a) before equilibration with the electrolyte, (b) after equilibration with the electrolyte in the dark, and (c) after illumination. The upper part depicts the n-semiconductor and the lower the p-semiconductor...

The photocurrent density (/ph) is proportional to the light intensity, but almost independent of the electrode potential, provided that the band bending is sufficiently large to prevent recombination. At potentials close to the flatband potential, the photocurrent density again drops to zero. A typical current density-voltage characteristics of an n-semiconductor electrode in the dark and upon illumination is shown in Fig. 5.61. If the electrode reactions are slow, and/or if the e /h+ recombination via impurities or surface states takes place, more complicated curves for /light result. 

The photocurrent is cathodic or anodic depending on the sign of the minority charge carriers injected from the semiconductor electrode into the electrolyte, i.e. the n-semiconductor electrode behaves as a photoanode and... 

Fig. 5.61 Current density-potential characteristics of n-semiconductor electrode in the dark and upon illumination...

Fig. 5.62 Scheme of a photovoltaic cell with n-semiconductor photoanode... 

The potential which controls the photoelectrochemical reaction is generally not the photopotential defined by Eqs (5.10.20) and (5.10.21) (except for the very special case where the values of v, REdox and the initial Fermi energy of the counterelectrode are equal). The energy which drives the photoelectrochemical reaction, eR can be expressed, for example, for an n-semiconductor electrode as... 

A phototransistor or photodiode may also be used to detect visible fight. Both devices have p-n junctions. In the photodiode the photon ejects an electron from the p semiconductor to the n semiconductor. The electron cannot cross back across the p-n junction and must travel through the circuitry, an ammeter to return to the p material. In a phototransistor, usually an npn type, the base (p-type semiconductor) is enlarged and photosensitive. Photons dislodge electrons that act as if a potential was applied to the base. This results in an amplified flow of electrons proportional to the number of photons striking the base (Fig. 5.11). 

Figures 2.13(a) and 2.13(b) illustrate the basis of a semiconductor diode laser. The laser action is produced by electronic transitions between the conduction and the valence bands at the p-n junction of a diode. When an electric current is sent in the forward direction through a p-n semiconductor diode, the electrons and holes can recombine within the p-n junction and may emit the recombination energy as electromagnetic radiation. Above a certain threshold current, the radiation field in the junction becomes sufficiently intense to make the stimulated emission rate exceed the spontaneous processes.

Figure 8-30 shows the normalized cathodic transfer current of redox electrons for several redox reactions as a function of the standard redox potential sbdox on n- semiconductor electrodes of zinc oxide in aqueous solutions. The bell-like curve observed in Fig. 8-30 is in agreement with the forgoing conclusion that the maximum current occurs at the electrode potential at whidi tox equals e. ... 

Maximization of the available energy for electrolysis with a given semiconductor seems to require use of the most heavily doped material together with a minimal band bending consistent with efficient charge separation so that in the n-semiconductor, Ep(n) is as high as possible while E (n, surface) is as low as possible and in the p-semiconductor 2 (p) is as low as possible... 

W. A. Bryden and T. J. Kistenmacher, Growth of Group III-A Nitrides by Reactive Sputtering N. Newman, Thermochemistry of III-N Semiconductors S. J. Pearton and R. J. Shul, Etching of III Nitrides... 

As described in Section 3 of Chapter 4, the stabilization of n-Si electrode by coating with poly(pyrrole) has attracted much attention. The stabilization of a small bandgap n-semiconductor electrode against oxidation is of great value not only to convert visible light into chemical energy, but also to construct liquid-junction solar cells operated under visible irradiation. The poly(pyrrole) film is usually electropolymerized on the semiconductor electrode dipped in the aqueous solution of pyrrole. The remarkable stabilizing effect of poly(pyrrole) film on polycrystalline n-Si is shown in Fig. 22 67). The photocurrent obtained under irradiation in the aqueous solution of... 

Nanotechnology, 1345 n-semiconductor, in thermal reactions, 1086 as cathode. 1087 n—pjunction, 1074, 1081... 

Fig. 7.24. The current-potential relation at a p-n semiconductor junction differs from that of an electrode/solution interface by being totally asymmetrical.

Figure 6. The energy level structure for an n-semiconductor-electrolyte interface as is appropriate for electron photoemission.

Rajh, T. Micic, O. I. Lawless, D. Serpone, N. Semiconductor photophysics. 7. Photoluminescence and picosecondcharge carrier dynamics in CdS quantum dots confined in a silicate glass, J. Phys. Chem. 1992, 96, 4633. 

Very little work has been performed on Schottky barrier contacts to the other III-N semiconductors, although a strong dependence of the Schottky barrier height of metal contacts to AIN on the electronegativity of the metal was reported in 1969 [35],... 

Hannay, N. Semiconductors, Eeinhold Publishing Co., Inc., New York (1959). Ward, R. Structure and Properties of Mixed Metal Oxides, in Cotton s Progress in Inorganic Chemistry, Vol. I, 465-536, Interscience Publishers, New York (1959). 

Figure 2.39a,b. Schematic picture of a solar cell with electron excitation and external circuit (a left) and current / vs. voltage V diagram under illumination (b above). 4, is short-circuit current, and is open-circuit voltage. The solar cell may consist of one or more p-n semiconductor junctions or of p-i-n amorphous junctions. 

Figure 6.22 Schematic energy digram of a metal/electrolyte interface (a) and n-semiconductor/ electrolyte interface (b) for equilibrium 6) and deposition (ii) conditions., and denote...

A variety of other systems have been suggested and some were also tested such as cells containing an n-semiconductor anode and a p-type cathode, photoelectrolysis cells integrated with photovoltaic configurations, and tandem and cascade type of cells (Nozik and Memming, 1996). 

Fig. 11.2 Current-voltage curves in the dark and under illumination for an electrochemical photovoltaic cell (with n-semiconductor)...

This synergetic effect can be explained by the presence of coherent boundaries whose first consequence is to lower the potential barrier for electron transfer between the n-semiconductor TiOo and 7 0. The resulting elastic strains on both sides of the and the transmission of this becomes rutile. When this last transformation is complete, the interface vanishes and the reaction stops. 

Electronic properties semiconductors (p, n) deg. seminconductors (TiS2) semimetallic semiconductors (p, n) semiconductors (n, P ( ))... 

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