Generation-recombination process

Specific features of corrosion processes at semiconductors (as against to metals) are caused by the fact that charge carriers of both signs, namely conduction band electrons and valence band holes, take part in charge exchange between a solid and a solution. Therefore, the condition of Eq. (43) is insufficient, so account should be made of charge balance for each type of the carriers because equilibrium between the bands, which is established via generation-recombination processes, may not be reached. 

Many stochastic processes are of a special type called birth-and-death processes or generation-recombination processes . We employ the less loaded name one-step processes . This type is defined as a continuous time Markov process whose range consists of integers n and whose transition matrix W permits only jumps between adjacent sites,... 

Thus the random distribution of the particles among the boxes in the generation-recombination process leads to an equiprobable distribution, cardinally different from the Poisson distribution, of boxons (sets of a given number of particles of the same colour) over the boxes and to the macroscopic magnitude of the fluctuations of the number of particles in the boxes of (7.4.5). 

These characteristic features are manifested also in the generation-recombination processes of the Frenkel defects in real crystals. However, in contrast to the box model, in a crystal statistical screening of the recombing particles occurs in coordinate space that leads to a complex spatial distribution of vacancies v and interstitial atoms i. This distribution depends on the law whereby the probability of recombination varies with the distance r between complementary particles. Usually one approximates this law by the step-distribution cr(r) = 1 (r ro), er(r) = 0 (r > ro), ro is a recombination radius. 

We stress an important feature of the generation-recombination process being discussed. The lifetime of a vacancy v, owing to the competition for capture of an i that has fallen at some site a with other vacancies that also lie within the sphere of recombination of i, depends on the concentration of vacancies N-y a) in the sphere with its centre at the site a. Yet the quantity N-y(a) depends analogously on for the sites a of the recombination... 

Shockley-Read (SR) [55] or Shockley-Read-Hall [56] generation-recombination processes proceed via imperfections ( traps ), i.e., centers of capture in semiconductor crystal lattice. Acceptor levels capture electrons and donor levels holes, or they emit them at rates dependent on the nature and the concentration of traps, as well as on the occupancy of energy levels. At that, within the bandgap there may be one or more impurity levels. SR mechanisms are more marked in technologically lower-quality material (with a larger concentration of defects and impurities), i.e., this mechanism is not fundamental. 

The main (but not the only) reason for the appearance of carrier number fluctuations are generation-recombination processes, i.e., the same processes that enable the very operation of the device and define both the dark current of the device and its optically generated signal. 

Since Johnson noise is much lower than g-r noise in the operating frequency range of photonic detectors, from the point of view of noise optimization it is most important to minimize generation-recombination processes. 

The photon management methods also represent a pathway toward a decrease of generation-recombination processes and the related noise phenomena and pose a viable way to overcome obstacles that until recently appeared insurmountable. The mechanism of photon recycling by cavity enhancement ensures direct suppression of radiative noise, while the possibility to localize fields at a subwavelength level ensures vastly smaller photodetector volumes, thus helping overcome problems with Auger and Shockley-Read phenomena as well. 

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