Depending upon the type of impurity atoms added, an extrinsic semiconductor can be classified as n type or p type. In a p type conductivity the valence electrons move from one covalent to another. The electron in an n type semiconductor is called the majority carrier, whereas the hole in n type semiconductor is termed the minority carrier. Based on the type of doping material incorporated, semiconductor crystals are classified into two types particularly n type semiconductors and p type semiconductors. The fermi level for p type semiconductor is given as. Depending on the type of doping material used, extrinsic semiconductors can be subdivided into two classes. Four of the antimony atoms valence elec trons are used to form the covalent bonds with silicon atoms, leaving one extra electron. In a ptype semiconductor, the iii group element of the periodic table is added as a doping element, whereas in ntype the v group element is the doping element. Intrinsic semiconductor and extrinsic semiconductor energy. Semiconductor type intrinsic extrinsic ptype ntype. Semiconductors types, examples, properties, application. These are p type and n type semiconductors brought together in close contact, creating what is called the depletion region. A single semiconductor crystal can have many p and ntype regions.
Although the free electrons and holes drift in opposite directions, the current. As illustrated in figure 117, each pentavalent atom antimony, in this case forms co valent bonds with four adjacent silicon atoms. Ntype semiconductors are a type of extrinsic semiconductor where the dopant. Therefore along the junction between the p and n type silicon, a small natural potential is set up between the p and n semiconductor material with negatively charged electrons now on the p type side of the junction, and positively charged holes on the n side of the junction.
Semiconductors, diodes, transistors horst wahl, quarknet presentation, june 2001 electrical conductivity. The term p type refers to the positive charge of a hole. The resultant material is known as an ntype semiconductor. If a silicon or germanium atom in its pure form is doped with an element of group. A unique feature of the semiconductors is that they are bipolar in nature and in them, the current is transported by the electrons and holes. P type and n type semiconductor both are extrinsic semiconductors. As opposed to ntype semiconductors, ptype semiconductors have a larger hole concentration than. A n type semiconductor is defined as a type of extrinsic semiconductor doped with a pentavalent impurity element which has five electrons in its valence shell. When a small amount of impurity is added to a pure semiconductor. Difference between p type and n type semiconductor. A common p type dopant for silicon is boron or gallium. Because electrons under ordinary conditions will flow in only one direction through such barriers, p n junctions form the basis for creating electronic rectifiers and switches. Semiconductors ppt and pdf report free study mafia.
In p type semiconductors, holes are the majority carriers and electrons are the minority carriers. Extrinsic semiconductors are essentially divided into two types. P type and n type semiconductor doping pure semiconductor material is known as intrinsic material. The difference between p type and n type semiconductor are based on various factors like nature of doping element, majority and minority carriers etc. P type and n type semiconductor majority and minority.
The process of purposefully adding impurities to materials is called doping. Difference between p type and n type semiconductor circuit globe. Semiconductors made in this manner are called ptype. The mechanisms of conduction in a metal and in a semiconductor are compared. When pentavalent impurity uses for doping then it creates extra electrons in a semiconductor called n type semiconductor or donor. In a ptype semiconductor, there is an increase in the density of unfilled states. The principle of detailed balance tells us that each gr path is in balance. Extrinsic semiconductor is of two types p type and. They form a crystal lattice by having each atom share all of its 4. Such semiconductors are termed as n type semiconductors.
A semiconducting silicon bar is doped with a concentration of 4. Difference between n type and p type semiconductor quick. Lecture 2 n and p type semiconductors free download as powerpoint presentation. Photoelectrochemical experiments show that the cu 2 o thin films synthesized in acid and alkaline or neutral media present n type and p type semiconductor character, res. The semiconductor materials used in electronic devices are doped under precise conditions to control the concentration and regions of p and ntype dopants. So, the total electric charge of p type semiconductor is positive. Each type of atom has a certain number of electrons and protons that distinguishes it from the atoms of all.
Before intrinsic material can be used for device manufacture, impurity atoms must be added to improve its conductivity. We can define p type and n type semiconductor by their impurities added. The p and n type regions are referred to as anode and cathode respectively. In n type semiconductor, the population of free electrons is more whereas the population of holes is less. The charges depend on the hole concentration and the electron concentration. The conductivity of n type semiconductor is nearly double to that of p type semiconductor. Based on the type of doping material incorporated, semiconductor crystals are classified into two types particularly ntype semiconductors and ptype semiconductors. Doped semiconductors ntype materials ptype materials diodes and transistors. Conversely, in a p type semiconductor, holes are majority carriers and electrons are minority carriers. Trivalent impurity like aluminium, gallium and indium is added in the ptype semiconductor, while in ntype semiconductor pentavalent impurity like arsenic, antimony, phosphorus, bismuth, etc. Ptype, ntype semiconductors engineering libretexts.
Thus, accommodating more electrons at the lower energy levels. As the current flow through the crystal is by holes, which are carrier of positive charge, therefore, this type of conductivity is known as positive or p type conductivity. They are named as such due to the charge that they carry. Examples of pentavalent impurities are phosphorus or. Difference between p type and n type semiconductor p. Jun 16, 2017 semiconductors ppt and pdf report free. Types of doped semiconductors there are two different ways of adding an impurity to the semiconductor atom. The formation of a pn semiconductor junction is described and its conduction properties are discussed. A doped semiconductor as opposed to an intrinsic semiconductor is one that has had specific impurity atoms introduced into it to shrink the band gap. As conduction is due to a large number of free electrons, the electrons in the n type semiconductor are the majority carriers and holes are the minority carriers. As the number of electrons and holes is greater in extrinsic conductor it exhibits greater conductivity than intrinsic semiconductors. Lecture 2 n and p type semiconductors pn junction doping.
Ntype semiconductors are a type of extrinsic semiconductor where the dopant atoms are capable of providing extra conduction electrons to the host material e. The semiconductors have the conductivity which is between the conductors and the insulators. Jul 30, 2017 in this physics digital electronics video lecture in hindi for class 12 we described different type of semiconductor intrinsic and extrinsic. Based on the dopants used the extrinsic semiconductors are further classified as ntype semiconductor and ptype semiconductor. Group v elements such as phosphorus, antimony and arsenic are usually classified as ntype impurities. As opposed to n type semiconductors, p type semiconductors have a larger hole concentration than electron concentration. What is the difference between ntype and ptype semiconductor. A barrier forms along the boundary between p type and n type semiconductors that is known as a p n junction. Where n v is the effective density of states in the valence band. The types of doped semiconductors formed after the addition of the impurity are.
The resultant material is known as an n type semiconductor. This extra electron contributes to electrical conductivity, and with a su. N and p type semiconductors neither pure siliconsi nor germaniumge are great conductors. If an abrupt change in impurity type from acceptors p type to donors n type occurs within a single crystal structure, a p n junction is formed see parts b and c of the figure. Therefore, the fermi level in the p type semiconductor lies close to the valence band. This creates an excess of negative ntype electron charge carriers. Extrinsic semiconductors definition, types and properties. The p type and n type are two different types of semiconductors. But since boron only offers 3 of the four electrons that a silicon atom needs, each silicon center is left with a hole. Hence in n type semiconductor free electrons are called majority carriers and holes are called minority carriers. Apr 01, 2019 these impurity atoms are known as dopants.
Group v elements such as phosphorus, antimony and arsenic are usually classified as n type impurities. On the p side, the holes constitute the dominant carriers and so are called majority carriers. Perhaps the most important current use of n type semiconductors is in p n junctions. This process, called doping, increases the number of current carriers electrons or holes. If a silicon or germanium atom in its pure form is doped with an element of group three in a small amount, such as indium, gallium or boron, these elements having 3 electrons in their. The difference between a p type semiconductor and n type semiconductor are given below in tabulated form. Semiconductors can be broadly classified into intrinsic and extrinsic semiconductors. Jul 06, 2016 since semiconductors are generally poor conductors, their conductivity can be drastically increased by the controlled addition of impurities to the intrinsic pure p. The importance of this contact or junction is the creating of a region between the p and n layers where p type holes can recombine with. The density of electrons and holes, energy level and fermi level, the direction of movement of majority carriers, etc. An extrinsic semiconductor is one that has been doped. Oct, 2012 semiconductors, electrons and holes as charge carriers n type semiconductors p type semiconductors. The p positive side contains an excess of holes, while the n negative side contains an excess of electrons in the outer shells of the electrically neutral atoms there. Mar 16, 2019 the impurity elements used are termed as dopants.
However, in an ntype semiconductor, the density of states increases, therefore, accommodating more electrons at higher energy levels. The two categories of impurities are n type and p type. The p type semiconductor has a larger hole concentration, which results in the positive charge. Semiconductor doping an overview sciencedirect topics. The p type carries a positive charge, while the n type carries a negative charge. Difference between p type and n type semiconductor circuit.
When a small amount of pentavalent impurity such as arsenic is added to a pure germanium semiconductor crystal, the resulting crystal is called n type semiconductor. So many people think that p type semiconductor has large number of holes and current conduction is mainly due to these holes. Neither pure siliconsi nor germaniumge are great conductors. A pn junction is a boundary or interface between two types of semiconductor materials, ptype and ntype, inside a single crystal of semiconductor. Semiconductors types, examples, properties, application, uses. Crystal as a whole is neutral, but the donor atom becomes an immobile positive ion. Determine its n or p character if the intrinsic carrier concentration of ge at room temperature is n i 2. They form a crystal lattice by having each atom share all of its 4 valence electrons with neighbouring atoms.