By mixing different materials in appropriate amounts and in
appropriate ways in semiconductor materials, different electrical, optical and
magnetic properties can be created.
The composition of the mixed materials must be carefully controlled to determine which material to mix, in what amount, and in what way.
This control should not cause the semiconductor crystal
itself to be damaged. This is called the 'non-destructive control of the
composition' of the compound.
Semiconductors react to the mixed materials through changes
in the spectra of the multiple exciton complexes. Through this, a
non-destructive control method can be found.
Current in the crystal
Current in the Semiconductor crystals have two regions, the
conduction band and the valence band. The conduction band contains electrons.
In the valence band, there is an electron with a numerical value equal to the
electron's charge but with a positive sign. It is called a vacancy or hole.
This is because of these that an electric current can flow through the crystal.
The electron and hole attract each other.
Sometimes, they bind together and become electrically neutral quasi-particles called excitons. After World War II, the existence of such a structure in molecular structures and semiconductor crystals was discovered.
This is a great scientific achievement. The principles of
this were discovered as early as 1931 by the physicist Yakov Frenkel.
The structure of excitons is very similar to the structure of hydrogen atoms, but in excitons, there is a positive hole instead of a proton.
There are many similarities between hydrogen atoms and
excitons. So the question arises, do hydrogen atoms combine with other elements
to form many types of molecules, just as excitons do? Scientists have long
discovered that excitons behave in the same way as hydrogen.
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| Frenkel excitons, bound electron-hole pair |
Compound atoms
First, it has been discovered that two excitons combine to
form a bi-exciton molecule. It has also been discovered that if there are
compound atoms in semiconductor crystals, the exciton can combine with them to
form a compound multiple exciton system.
Such compound atoms are specially added to semiconductors to
give them certain properties. Multiple exciton compounds are multi-layered, with electron and hole layers alternating.
They are located in semiconductor films only due to the
strong properties of the conduction and valence bands. The existence of
such compounds was officially recorded in 1982.
When electrons and holes in multiple exciton compounds
collide, they push each other. During such collisions, rays with a specific
spectrum are emitted. With their help, the structure of these compounds can be
found.
They provide valuable information about the chemical elements
bound to the excitons and the amount of compounds in the solution. Analyzing
the emission spectra of multiple exciton complexes helps to create defects in
silicon layers that can be used to control the composition of the compounds
without damaging them.
Silicon crystals play a vital role in electronic
devices. Special devices for this purpose are very successful in the
non-ferrous metallurgy industry.
Multiple electron complexes have helped us understand how molecules behave in extreme conditions, such as strong
currents and strong magnetic fields.
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