In this article we are sharing knowledge on p type semiconductor, n type semiconductor, intrinsic semiconductors.
What are Semiconductors?
Semiconductors are substances that possess both conductivity and insulator characteristics. Intrinsic and extrinsic semiconductors are the two types of semiconductors. Pure semiconductors are those that have no doping and are hence intrinsic semiconductors. Impurity atoms are doped into the outside conductors.
Important semiconductor characteristics include:
- At zero kelvin, a semiconductor behaves like an insulator. It becomes a conductor as the temperature rises.
- D doping enhances semiconductors to create semiconductor devices suited for energy conversion, switches, and amplifiers due to their excellent electrical properties.
- Lower losses in power.
- Compared to other materials, semiconductors are smaller and lighter.
- They have a higher resistivity than conductors compared to insulators.
- When the temperature rises, semiconductor materials’ resistance lowers, and the opposite is true as well.
Types of Semiconductors
· Intrinsic Semiconductor
Intrinsic semiconductors, also known as pure or un-doped semiconductors, are faultless crystals devoid of the defects and impurities of other elements. All semiconductor materials, including those doped ones, have inherent properties. The doping components, however, introduce other desired properties.
Intrinsic refers to something inherent or natural, and intrinsic semiconductors exhibit the primary characteristics of the semiconductor compounds themselves, as opposed to impurities and dopants. Since silicon and germanium are intrinsic semiconductors, they are employed the most frequently. They were some of the earliest semiconductors to be extensively studied and used. The electrical structure of semiconductors forms the basis of their particular properties. One mechanism that distinguishes semiconductors as a specific form of material is their electrical structure, which controls their fundamental properties.
· Extrinsic Semiconductor
With the aid of a few appropriate atoms known as impurities, the conductivity of semiconductors can be increased. Doping is the process of introducing contaminants into a pure semiconductor. A doped semiconductor typically has one dopant atom for every 107 other atoms.
Two categories of extrinsic semiconductors exist:
Examples of extrinsic semiconductors are p- and n-type materials. While a free electron is produced whenever a covalent bond between two semiconductors breaks, a vacancy is always created in the broken link. These voids are referred to as holes. Each of these holes is thought of as a positive equal to a negative electron due to the loss of one electron. The leading mobile charge carriers in this system are electrons. In an n-type semiconductor, both free electrons and holes will exist.
- P-type semiconductor
- N-type semiconductor
P Type Semiconductors
In a pure (intrinsic) Si or Ge semiconductor, each valence electron forms four covalent links with its neighbors (see figure below). Each ionic core comprises a nucleus and non-valent electrons with a net charge of +4 and four valence electrons. There will always be the same number of electrons and holes because neither more nor more gaps exist in this situation.
Now, the electron-hole balance would alter if one of the atoms in the semiconductor lattice were replaced by an element with three valence electrons, such as group 3 elements like boron (b) or gallium (ga). This impurity can only contribute three valence electrons to the lattice, leaving one additional hole (see figure below). Because holes will “accept” free electrons, a group 3 impurity is also known as an acceptor.
“P type semiconductor” is a semiconductor doped with an acceptor; “P” stands for positive. This is because an acceptor adds more holes, which are believed to be positively charged. The substance itself remains electrically neutral, so keep that in mind. Most of the current in a p-type semiconductor is carried by the holes, which outnumber the free electrons. In this case, holes make up most carriers, while electrons make up the minority.
What exactly is an N-Type Semiconductor?
An extrinsic semiconductor known as an n-type semiconductor has been doped with a pentavalent impurity element with five electrons in its valence shell. To increase the number of electrons available for conduction, pentavalent impurities or dopant elements are added to n-type semiconductors. The p-type n-type semiconductor comprises the majority and minority charge carriers, the doping element, the nature of the doping element, the density of charge carriers, the Fermi level, energy level, the direction of movement of the dominant charge carriers, and other parameters.
When a modest quantity of pentavalent impurities is added to a pure semiconductor, the resultant abundance of free electrons creates an n-type of extrinsic semiconductor. In the n-type semiconductor, conduction is caused by the free electrons, which are symbolized by the pentavalent impurity atoms. These extra free electrons are not required to fill covalent bonds in semiconductors completely. Some examples of n-type semiconductors include SB, p, bi, and as. These materials have five electrons in their outer shell.
We can substitute one of the lattice atoms with either a group 3 atoms or an element with five valence electrons, such as the group 5 atoms arsenic (as) or phosphorus, in addition to doing the former (p). In this instance, the impurity increases the lattice’s capacity from four to five valence electrons. Consequently, the lattice contains one more electron (see figure below). A group 5 impurity is referred to as a donor since it gives away one electron. Note that the substance maintains its electrical neutrality.
An n-type semiconductor has undergone donor doping; the letter “n” stands for negative. Electrons with a negative charge are added to the lattice by donor impurities. As a result, free electrons are more prevalent than holes in n-type material, making them the dominant carrier and holes the minority carrier.
N-Type Semiconductor Doping
The n-type semiconductors are doped with pentavalent impurity elements. The valence shell of the pentavalent elements contains five electrons. Examples of pentavalent impurities include antimony (a), phosphorus (p), and arsenic (as) (SB). To avoid disrupting the crystal structure of the original intrinsic semiconductor, the pentavalent impurity is added to the n-type semiconductor in a minimal amount. As a result, one electron is not linked to silicon atoms, while the pentavalent impurity atom forms covalent bonds with four silicon atoms. Pentavalent impurities are known as donor impurities because each bit provides one electron to an n-type semiconductor. Therefore, the n-type semiconductor has a greater quantity of electrons.
The number of donor electrons can control the dominance of conduction electrons completely. As a result, the total number of conduction electrons may be equal to the total number of donor sites. When energetic donor sites balance the conduction of the electrons, the charge neutrality of the semiconductor material can be preserved. The number of holes will decrease as the number of electrons conducting rises. The ratio of holes to electrons in each band can be used to describe the imbalance in carrier concentration. For example, in the n-type, electrons make up most of the charge carriers, while holes make up the minority.
The N-Type Semiconductor’s Charge
Many people think there are many free electrons in n-type semiconductors. The outcome is a negative total electric charge on the n-type semiconductor. But this presumption is untrue. Despite their abundance, the free electrons in an n-type semiconductor come from electrically neutral pentavalent atoms. As a result, the total electric charge of the n-type semiconductor is zero.
Conduction through an N-Type semiconductor:
Electrons are primarily responsible for conduction through an n-type semiconductor. The lattice structure has received additional electrons from the pentavalent donor impurity. The electrons gain energy as a voltage is applied, or the semiconductor is exposed to outside heat. In addition, more electrons are released into the conduction band due to the electrons’ breaking of covalent bonds. When an electron detaches from a covalent link, a hole or vacuum is left in its place.
The hole created by the negatively charged electron draws in other electrons. The hole is therefore thought to be positively charged. Because of this, the n-type conductor has two carriers: ultimately arrested holes and negatively charged electrons. Because there are more electrons than holes in an n-type semiconductor, the latter is referred to as the minority carriers and the former as the majority carriers. In an n-type semiconductor, the current created by electrons is known as the majority carrier current, and the current created by holes is known as the minority charge current.
Another electron breaks free from its covalent bond and is drawn to the hole created when a covalent bond breaks and an electron leaves a hole in its stead. As a result, the motion of the electron and spots is opposing. The positive battery terminal attracts the electrons, while the negative one attracts the holes. Current begins to follow the electrons and holes as they move through the crystal’s lattice in the n-type semiconductor.
N-Type Semiconductor Energy Diagram
Below is a picture of this semiconductor’s energy band diagram. Due to the addition of the pentavalent substance, the free electrons are present in the conduction band. These electrons did not fit in the covalent bonds of the crystal. However, a few electrons may be present in the conduction band to create electron-hole pairs. One of the crucial components of a semiconductor is that adding pentavalent material might affect how many free electrons there are.
An electron-hole pair can be produced at room temperature by the semiconductor transferring thermal energy to it. As a result, a tiny number of free electrons can be available. These electrons will depart from the valence band following the holes. When more free electrons are produced by the pentavalent material than there are holes, the material is said to be negative, or “n.”
The Difference between P-Type and N-Type Semiconductors
In p-type semiconductors, the periodic table’s iii group element is employed as a doping element, whereas the v group element is used in n-type semiconductors.
Trivalent impurities like aluminum, gallium, and indium are added to the p-type semiconductor. However, pentavalent contaminants, including arsenic, antimony, phosphorus, bismuth, and others, are still added to n-type semiconductors.
An impurity contributes extra holes, or acceptor atoms, to a p-type semiconductor, whereas an impurity adds more electrons, or donor atoms, to an n-type semiconductor. In a p-type semiconductor, holes make up most carriers, while electrons make up the minority. In an n-type semiconductor, electrons make up most airlines, while holes make up the minority.