Carrier thermalization

All the CO resulting from the pseudo solid-solid reaction is conducted, together with entrained char, from the top fluidized section through a constriction, in which the high-velocity gas flow prevents backflow, to a transport combustor, where the CO is burned to C02 with preheated air, along with as much of the char as is called for by heat balance to maintain the endothermic FeO-C reaction. The heated recycled char is separated from the off gas at the top of this transport combustor in a hot cyclone and is returned as a thermal carrier to the lower part of the lowest j igged section, while the hot flue gas from the transport combustor is used to preheat the incoming air in a recuperator. 

At very low voltage the injected effective carrier density may be lower than the background thermal carrier density and the current is then ohmic. The voltage at which SCLC begins to dominate is given by,... 

Expression (221) allows us to solve the problem only in the approximation of the one-dimensional Onsager model but not in the approximation of the strong gradient js(x). But, even in the first case, an approximated solution becomes expressed by a first order modified Bessel functions and requires summation procedures (see Ref. 361). However, to describe the one-dimensional motion of thermal carriers near the injecting contact, we can define the transition probability from a position x to a position x +1 and x — l, corresponding to the carrier motion in and against the external electric field direction, respectively. Assuming the carrier to realize a... 

A very important EL mechanism—in fact, the most important today in practice—is radiative recombination (by any of several possible processes) of thermal carriers in a forward-biased p-n junction. This process is not important in CPs today because attempts at making stable p-n junctions have essentially failed, probably because, as mentioned above, the dopants are only intercalated between the chains and are therefore mobile in an electric field. 

The diffusion of carriers in the imdoped layer against the internal field also reduces the collection efficiency. A thermalized carrier can, on average, diffuse over a potential of kT. Backward diffusion can therefore occur over a distance, Xj, of approximately... 

Therefore, the photoconductor must not only be free of thermal carriers but it must be protected against the dark injection of external charge, as well. Injection from the base electrode may be avoided by a thin blocking dielectric—typically 50 A.U. of a dense oxide or polymer--thin enough to allow any accumulated residual charge to leak off between cycles. 

Passively and actively quenched single-photon APDs must normally be cooled. Except for diodes of extremely small area the thermal carrier generation rate at... 

At higher temperatures, neutralization of space charge also occurs due to the recombination with thermally generated carriers. These are uniformally distributed in the entire specimen and are responsible for the conductivity of the material. The loss of space charge owing to recombiimtion with thermal carriers is not always noticeable. 

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