Understanding the Atomic Structure of Semiconductors and Their Role in Electronic Components

Observing the atomic structure diagram of a metallic copper conductor reveals that its outermost layer only has one electron. We call this electron a valence el...

Nov 22,2023 | Lareina

Semiconductor is a material product typically composed of silicon, with higher conductivity than insulators such as glass, but lower conductivity than pure conductors such as copper or aluminum. Impurities (known as doping) can be introduced to alter their conductivity and other properties to meet the specific needs of the electronic components they reside in.

Observing the atomic structure diagram of a metallic copper conductor reveals that its outermost layer only has one electron. We call this electron a valence electron because the attraction between the nucleus and the valence electron is relatively small. Once attracted by external forces, this electron is easily detached from the atom and becomes a free electron. This is also the main reason why copper can become a conductor, Similarly, observing the atomic structure of insulators reveals that they typically have 8 valence electrons and are extremely stable. As the name suggests, semiconductors should be somewhere between the two. So what is their atomic structure like?

Observing the periodic table of elements reveals that the elements near the boundary between conductors and insulators are important materials for making semiconductors, such as silicon, Of course, the most influential observation of an atomic structure diagram reveals that its outermost layer has four electrons. To achieve equilibrium, either the four electrons are discarded or the four electrons are pulled closer together, while silicon atoms cleverly share the four electrons in the arrangement, forming a stable 8-electron structure, known as covalent bonds, So where does the conductivity of silicon come from? When the temperature is greater than absolute zero, electrons in the valence band may undergo a transition to free electrons, and a hole will be formed in the original position. That is to say, there will be an equal amount of free electrons and holes in the silicon crystal, which can all play a conductive role. This is the structure of pure semiconductors, also known as intrinsic semiconductors, Although perfect, to increase the conductivity of semiconductors, other elements need to be doped.

When we replace silicon atoms with 5-valent phosphorus atoms, we can increase the concentration of free electrons to obtain N-type semiconductors. Similarly, if we replace silicon atoms with boron atoms with only three electrons on the outermost layer and increase the concentration of holes, we can obtain P-type semiconductors. So what happens when we connect these two types of semiconductors together? The electrons in the N region urgently want to diffuse to the P region, and the holes in the P region desperately want to diffuse to the N region. At this point, an "internal electric field" from N to P will be formed to prevent diffusion. After the two reach dynamic equilibrium, a space charge region will be formed at the interface. This is why PN junctions have unidirectional conductivity, which is a common diode, It is made by utilizing this characteristic, and using sunlight to irradiate the PN junction will stimulate the generation of electron holes. The separation of charges passing through the interface layer will form a photo generated electric field from P to N. This is the photo generated volt effect and the basic principle of solar cells.

The classic challenge faced by semiconductor companies is whether the market is driven by technology or by market driven technology. Investors should recognize that both are effective for the semiconductor industry.

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