For Group IV semiconductors such as diamond, silicon, germanium, silicon carbide and silicon germanium, the most common dopants are Group III acceptors or donors from Group V elements. Boron, arsenic, phosphorus and sometimes gallium are used to boost silicon. Boron is the p-type dopant of choice for manufacturing silicon integrated circuits because it diffuses at a speed that makes connection depths easily controllable. Phosphorus is typically used for bulk doping of silicon wafers, while arsenic is used for transition diffusion because it diffuses more slowly than phosphorus and is therefore more controllable. (1) type n doping: Elements with five valence electrons are added to the semiconductor as impurities (pentavalent impurity or donor contamination). The semiconductor has four valence electrons, when doped with a pentavalent impurity, the four-valence electron forms a covalent bond and the rest is now free to move, so that n-type doping increases the conductivity of the semiconductor. Due to the surplus of electrons (e-) in the n-type semiconductor, it generates an overall negative charge and thus the name of the n-type semiconductor. As you can see in the image above (Figure: type P), we jumped into boron (trivalent element) in the silicon lattice. This created a hole that turns the semiconductor into a P-type material. By introducing a dopant with five external electrons, there is an electron in the crystal in n-doped semiconductors that is unbound and can therefore be moved into the conduction band with relatively little energy.
For example, in n-doped semiconductors, the energy level of the donor is close to the edge of the conduction band and the band gap to be overcome is very low. N doping is much rarer because the Earth`s atmosphere is rich in oxygen, creating an oxidizing environment. An electron-rich, n-doped polymer reacts immediately with elemental oxygen to detach the polymer (i.e., reoxidize it to the neutral state). Therefore, chemical n-doping must be performed in an inert gas environment (e.g. argon). Electrochemical n-doping is much more common in research because it is easier to exclude oxygen from a solvent in a sealed vial. However, n-doped conductive polymers are unlikely to be commercially available. In semiconductor production, doping refers to the process by which impurities are intentionally introduced into an extremely pure semiconductor (also known as intrinsic) to alter its electrical properties. Impurities depend on the type of semiconductor. Slightly and moderately doped semiconductors are called extrinsics. A semiconductor that is doped to values so high that it acts more like a conductor than a semiconductor is called degenerate. In most cases, many types of impurities will be present in the resulting doped semiconductor.
If an equal number of donors and acceptors are present in the semiconductor, the additional nuclear electrons provided by the former are used to fill the broken bonds due to the latter, so that doping does not produce free carriers of both types. This phenomenon is called compensation and occurs at the p-n junction in the vast majority of semiconductor devices. By doping pure silicon with V-group elements such as phosphorus, additional valence electrons are added that become unlimited by individual atoms and allow the compound to be an electrically conductive n-type semiconductor. Doping with group III elements lacking the fourth valence electron creates “broken bonds” (holes) in the silicon lattice that can move freely. The result is an electrically conductive p-type semiconductor. In this context, an element of group V is said to behave as an electron donor and an element of group III as an acceptor. This is a key concept in the physics of a diode. When we insert a pentavalent element into the grid. As you can see in the photo (Figure: type N), we doped the silicon lattice with phosphorus, a pentavalent element. Now the pentavalent element has five electrons, so it shares one electron with each of the four adjacent silicon atoms, so four electrons are connected to the silicon atoms in the lattice.
This leaves an extra electron. This excess electron can move freely and is responsible for conduction. Therefore, an intrinsic semiconductor (in this case silicon) of type N (negative type) is produced by doping the semiconductor with a pentavalent element. Conductive polymers can be doped by adding chemical reagents to oxidize or sometimes shrink the system so that electrons are pushed into the conductive orbitals into the already potentially conductive system. There are two main methods of doping a conductive polymer, both of which use an oxidation-control process (i.e. redox). Pure silicon or germanium are rarely used as semiconductors. A controlled amount of impurities should be added to practical semiconductors. The addition of impurities changes the conductivity and acts as a semiconductor. The process of adding an impurity to an intrinsic or pure material is called doping and contamination is called doping. After doping, an intrinsic material becomes an extrinsic material. Practically only after doping, these materials become usable.
A small number of doping atoms can impair a semiconductor`s ability to conduct electricity. When added on the order of one doping atom per 100 million atoms, doping is called weak or light. If many more doping atoms are added, on the order of one in ten thousand atoms, doping is called high or heavy. This is often displayed as n+ for n-type doping or p+ for p-type doping.(See the semiconductor article for a more detailed description of the doping mechanism.) A semiconductor that is doped to values so high that it acts more like a conductor than a semiconductor is called a degenerate semiconductor. A semiconductor can be considered a type i semiconductor if it has been doped in equal amounts of p and n. Partial compensation, in which the number of donors exceeds the number of acceptors or vice versa, allows device manufacturers to repeatedly reverse (reverse) the type of a particular layer below the surface of a mass semiconductor by successively dispensing or implanting higher doses of doping, called counterdopting. Most modern semiconductor devices are manufactured by successive steps of selective zone opening to create the necessary P and N type zones below the surface of the bulk silicon. [25] It is an alternative to the successive growth of such layers by epitaxy.
Atoms follow a rule called the byte rule. According to byte`s rule, atoms are stable when there are eight electrons in their valence layer. Otherwise, atoms easily accept or share neighboring atoms to reach eight electrons in their valence layer. In the silicon lattice, each silicon atom is surrounded by four silicon atoms. Each silicon atom shares one of its electrons in the valence layer with its neighboring silicon atom to satisfy the byte rule. A schematic diagram of an intrinsic semiconductor is shown in the figure on the right (Figure: Intrinsic silicon lattice). There are two types of doping: (1) type n doping (negative type) (2) p type doping (positive type) The number of dopant atoms needed to produce a difference in the capacity of a semiconductor is very small. When a relatively small number of doping atoms is added (on the order of 1 every 100,000,000 atoms), doping is called low or light. When much more is added (on the order of 1 in 10,000), doping is classified as serious or high. This is often displayed as n+ for type n doping or p+ for p-type doping. A more detailed description of the doping mechanism can be found in the article on semiconductors. Silicon is usually doped with a doping material between 1 and 106.
This means that material P has many more holes than electron-hole pairs of pure silicon. With the inclusion of an electron, the dopant is negatively charged, such doping substances are called acceptors (acceptare, lat. = add). Here too, the dopant is fixed in the crystal lattice, only positive charges can move. Due to positive holes, these semiconductors are called p-conductors or p-doped. Analogous to n-doped semiconductors, holes are the majority charge carriers, free electrons the minority charge carriers. At low degrees of doping, the relevant energy states are sparsely populated by electrons (conduction band) or holes (valence band). It is possible to write simple expressions for concentrations of electrons and hole carriers ignoring the Pauli exclusion (via Maxwell-Boltzmann statistics): (Note: When discussing groups of periodic tables, semiconductor physicists always use an older notation, not the current notation of IUPAC groups. For example, the carbon group is called “group IV” and not “group 14.”) The concentration of the dopant used influences many electrical properties. The most important is the concentration of the charge carrier of the material.
In an intrinsic semiconductor in thermal equilibrium, the concentrations of electrons and holes are equivalent. In other words, in semiconductor production, doping is the intentional introduction of impurities into an intrinsic semiconductor in order to modulate its electrical, optical and structural properties. The doped material is called an extrinsic semiconductor. Doping refers to the introduction of impurities into a semiconductor crystal for the defined change in conductivity.