A semiconductor is a material product usually composed of silicon, which has a higher electrical conductivity than insulators such as glass, but a lower conductivity than pure conductors such as copper or aluminum. Its conductivity and other properties can be altered by the introduction of impurities, called doping, to meet the specific needs of an electronic component.

A look at the atomic structure diagram of copper metal shows that it has only one valence electron in its outermost layer.semiconductor system Because of the low attraction between the nucleus and the valence electron, this electron can easily break away from the atom to become a free electron once it is attracted by an external force. This is the main reason why copper can be a conductor. Similarly, looking at the atomic structure of insulators reveals that they are usually very stable with eight valence electrons. As the name suggests, semiconductors should be somewhere between conductors and insulators. So, what is the atomic structure of a semiconductor?

A look at the periodic table reveals that the element near the dividing line between conductors and insulators is the element silicon, an important material for making semiconductors. Of course, silicon is the most influential one. A look at the atomic structure diagram of silicon reveals that it has four valence electrons in its outermost layer. In order to achieve a state of equilibrium, silicon atoms either give up four electrons or pull in four electrons even more. And silicon atoms in the arrangement of cleverly shared up and down the left and right four electrons, hand in hand to form a stable 8-electron structure, that is, covalent bonding.semiconductor test system So where does silicon's electrical conductivity come from? When the temperature is greater than absolute zero, the electrons in the valence band may undergo a jump into free electrons, while the original position will form a hole. In other words, there will be an equal number of free electrons and holes within the silicon crystal, and they can all play a role in conducting electricity. This is the structure of a pure semiconductor, also called an intrinsic semiconductor. Although it is perfect, there are other elements that need to be doped in order to increase the semiconductor's ability to conduct electricity.

When we replace silicon atoms with 5-valent phosphorus atoms, we can increase the concentration of free electrons and get an N-type semiconductor. Similarly, if we replace a silicon atom with a boron atom, which has only three electrons in its outermost layer, and increase the concentration of holes, we get a P-type semiconductor. So what happens when you join these two types of semiconductors together is that the electrons in the N region desperately want to diffuse into the P region, and the holes in the P region desperately want to diffuse into the N region. This creates an "internal electric field" pointing from N to P, preventing diffusion.semiconductor solutions In the two to reach dynamic equilibrium, it will be in the interface to form a space charge area, which is the PN junction. PN junction has a unidirectional conductivity. Our common diode is made using this feature. And the use of sunlight irradiation PN junction will be excited to produce electron - hole pairs through the interface layer of charge separation, it will form a photogenerated electric field from P to N. This is the photovoltaic effect, the PN junction has a unidirectional conductivity. This is the photogenerated volt effect, the basic principle of solar cells.

The classic dilemma facing semiconductor companies is whether technology drives the market or the market drives technology. Investors should recognize that both are valid for the semiconductor industry.