What is N-type Semiconductor : Doping & Its Energy Diagram

The semiconductor materials include four electrons in their valence shell (external shell) like Ge (germanium) and Si (silicon). By using these electrons with semiconductor atom, bonds can be formed with its adjacent atoms. Similarly, some materials include five electrons in their valance shell is known as pentavalent materials like arsenic or phosphorus. So these materials are mainly used to make the n-type semiconductor. The four-electron impurities can form the bond using the adjacent silicon atoms. So this leaves one free electron and the resulting material includes no. of free electrons. When electrons are –Ve charge carriers, then the material is known as an n-type semiconductor. This article discusses an overview of n-type semiconductor.

What is N-type Semiconductor?

Definition: A N-type semiconductor material is used in electronics and it can be formed by adding an impurity to a semiconductor like Si and Ge is known as an n-type semiconductor. Here the donor impurities used in the semiconductor are arsenic, phosphorus, bismuth, antimony, etc.. As the name suggests, a donor gives free electrons to a semiconductor. By doing this, more charge carriers can be formed for conduction within the material.


The n-type semiconductor examples are Sb, P, Bi, and As. These materials include five electrons in their outer shell. The four electrons will make covalent bonds using the adjacent atoms and the fifth electron will be accessible like a current carrier. So that impurity atom is called a donor atom.

In this semiconductor, the flow of current will be there because of the movement of holes and electrons. Thus, the majority charge carriers in this semiconductor are electrons and minority charge carriers are holes.

N-type Semiconductor Doping

The n-type semiconductor is doped with a donor atom because the majority charge carriers are negative electrons. As silicon is a tetravalent element, then the structure of normal crystal includes four covalent bonds from 4 external electrons. The most frequently used dopants in Si are group-III & group-V elements.

N Type Semiconductor Doping
N-Type Semiconductor Doping

Here pentavalent elements are group-V elements. They include 5 valence electrons and they permit them to work as a donor. The count of these elements like antimony, phosphorus or arsenic donates free electrons so that the intrinsic semiconductor conductivity will be increased greatly. For instance, once a Si crystal is doped with a Group III element like boron, then it will create a p-type semiconductor but a Si crystal is doped with group V element like phosphorus then it will create an n-type semiconductor.

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The domination of conduction electrons can be done totally through the no. of donor electrons. Thus, the whole no. of conduction electrons can be equivalent to the no. of donor sites (n≈ND). The semiconductor material’s charge neutrality can be maintained when energized donor sites balance the electron’s conduction. Once the no. of electrons conduction is increased, then the number of holes will be decreased.

The carrier concentration imbalance in the respective bands can be expressed through the number of holes & electrons. In n-type, electrons are majority charge carriers whereas the holes are minority charge carriers.

Energy Diagram of N-type Semiconductor

The energy band diagram of this semiconductor is shown below. The free electrons are existing in the conduction band due to adding the Pentavalent material. In the covalent bonds of the crystal, these electrons did not fit. But, a small number of electrons can be available within the conduction band to form electron-hole pairs. The key points in the semiconductor are adding pentavalent material can cause the number of free electrons.

Energy Diagram
Energy Diagram

At room temperature, the thermal energy is passing on to the semiconductor, and then an electron-hole pair can be generated. Consequently, a small number of free electrons can be available. These electrons will leave after holes within the valence band. Here ‘n’ is the negative material when the no. of free electrons provided through the Pentavalent material is larger than the no. of holes.

Conduction through N-type Semiconductor

The conduction of this semiconductor can be caused by the electrons. When the electrons leave a hole, then space will be attracted by other electrons. Therefore the hole is considered as +vely charged. So this semiconductor includes two kinds of carriers like +vely charged holes & negatively charged electrons. The electrons are called majority carriers whereas the holes are called minority carriers because electrons are higher in number as compare with holes.

Once a covalent bonds smash & the electrons move away from a hole, then some other electron breaks away from its bond and gets attracted towards this hole. Therefore the holes & electrons will travel in reverse directions. The electrons will be attracted toward the +ve terminal of the battery whereas the holes are attracted to the -ve terminal of the battery.

FAQs

1). What is an n-type semiconductor?

A material that is designed by adding impurities to a semiconductor like silicon otherwise germanium is known as an n-type semiconductor.

2). What are the majority and minority charge carriers in this semiconductor?

The majority charge carriers are electrons and holes are minority charge carriers

3). What are extrinsic semiconductors?

They are p-type and n-type

4). What are semiconductor and their examples?

A material that has a property of conductor & insulator is known as a semiconductor. The examples are selenium, silicon & germanium.

5). What is the function of semiconductor?

It is used to manufacture electronic components like transistors, diodes, and ICs

Thus, this is all about an overview of n-type semiconductor. These are used to design different kinds of electronic devices like transistors, diodes & ICs (integrated circuits) due to their reliability, compactness, low cost, and power efficiency. Here is a question for you, what is a p-type semiconductor?

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