Question

the nature of avalanche mulplication processes
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Answer 1

Avalanche multiplication is based on a high electric field on the order of several volts per micrometer within the APD that accelerates the electrons. If the electron's energy is high enough, it is able to generate further electron-hole pairs by impact ionization.

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Answer 2

Answer:

B Theory of Avalanche Multiplication

Avalanche multiplication is based on a high electric field on the order of several volts per micrometer within the APD that accelerates the electrons. If the electron's energy is high enough, it is able to generate further electron-hole pairs by impact ionization. The probability of generating new electron-hole pairs within the path length dx is expressed by the ionization probabilities for electrons α and for holes β. The ionization probability depends on the electric field E:

(8)

For linear amplification and optimized noise, only one charge type—electron or holes—should be multiplied in the APD. Because α >> β for silicon-based APDs, the electrons are the charge type that should be amplified. If α = β, even small electric fields would cause a high current that destroys the diode. The ratio between the ionization probabilities of electrons and holes is called the ionization coefficient k:

(9)

The gain M of an APD expresses the number of multiplied electron-hole pairs caused by one original charge pair. The multiplication process is started at position x within the depletion layer (length w). After McIntyre (1966), the APD gain can be calculated by the following integral:

(10)

Differentiation of Eq. (10) leads to a first-order linear differential equation. The solution of this equation is the gain of an APD as a function of the ionization probabilities:

(11)

Junctions

RICHARD H. BUBE, in Electrons in Solids (Third Edition), 1992

QUANTUM WELLS AND SUPERLATTICES

In recent years major steps have been made toward what might be called “band gap engineering” by the development of highly controllable deposition systems for thin films, such as molecular beam epitaxy and organometallic chemical vapor deposition, that make it possible to deposit multilayer heterojunctions with atomically abrupt interfaces and controlled composition and doping in individual layers that are only a few hundreds of Angstroms thick. These layers are so thin that the energy