What is P-type Semiconductor : Doping & Its Energy Diagram
- May 25, 2022
The PN-junction diode is made up of two adjacent parts of two semiconductor materials like p-type and n-type. These materials are semiconductors like Si (silicon) or Ge (germanium), including atomic impurities. Here the type of semiconductor can be determined by the kind of impurity there. The procedure of adding impurities to semiconductor materials is known as doping. So semiconductors including impurities are known as doped semiconductors. This article discusses an overview of a P-type semiconductor and its working.
What is P-type Semiconductor?
Definition: Once the trivalent material is given to a pure semiconductor (Si/Ge) is known as a p-type semiconductor. Here, trivalent materials are Boron, Indium, Gallium, Aluminium, etc. Most frequently, semiconductors are made with Si material as it includes 4 electrons in its valence shell. To make a P-type semiconductor, extra material can be added to this like aluminum or Boron. These materials include only three electrons in their valence shell.
These semiconductors are made through doping the semiconductor material. The small amount of impurity is added compared with the amount of semiconductor. By altering the dopant amount which is added, the precise character of the semiconductor will be changed. In this type of semiconductor, the number of holes is larger compare with electrons. Trivalent impurities like boron/gallium are frequently used in Si like doping impurity. So the p-type semiconductor examples are gallium otherwise boron.
The process of adding impurities to the p-type semiconductor to change their properties is called p-type semiconductor doping. Generally, the materials used in doping for trivalent & pentavalent elements are Si & Ge. So this semiconductor can be formed by doping an intrinsic semiconductor using trivalent impurity. Here, ’P’ denotes Positive, where the holes in the semiconductor are high.
P-type Semiconductor Formation
The Si semiconductor is a tetravalent element and the common structure of crystal includes 4 covalent bonds from 4 outer electrons. In Si, group III & V elements are the most common dopants. Group III elements include 3 outer electrons that work like acceptors when used to dope Si.
Once an acceptor atom changes a tetravalent Si atom within the crystal, then an electron-hole can be created. It is one kind of charge carrier that is accountable for generating electric current within semiconducting materials.
The charge carriers in this semiconductor are positively charged and moves from one atom to another within semiconducting materials. The trivalent elements which are added to an intrinsic semiconductor will create positive electron holes within the structure. For instance, a-Si crystal that is doped with group III elements like boron will create a p-type semiconductor but a crystal doped with group V element like phosphorus will create an n-type semiconductor. The whole no. of holes can be equal to the no. of donor sites (p ≈ NA). The majority charge carriers of this semiconductor are holes whereas minority charge carriers are electrons.
Energy Diagram of P-type Semiconductor
The p-Type Semiconductor energy band diagram is shown below. The no. of holes within the covalent bond can be formed in the crystal by adding the trivalent impurity. A less amount of electrons will also be accessible within the conduction band.
They are generated once thermal energy at room temperature is imparted toward the Ge crystal to form the pairs of electron-hole pairs. However, the charge carriers are higher than the electrons within the conduction band due to the majority of holes compared with electrons. So this material is known as a p-type semiconductor where the ‘p’ denotes the +Ve material.
Conduction through P-type Semiconductor
In this semiconductor, the num. of holes can be formed through the trivalent impurity. The potential difference is given to the semiconductor is shown below.
The majority charge carriers are available within the valence band are directed in the direction of the -Ve terminal. When the flow of current through the crystal is done by the holes, then this kind of conductivity is called p-type or positive conductivity. In this type of conductivity, the outer electrons can flow from one covalent to others.
The conductivity of p-type is almost less to the n-type semiconductor. The existing electrons within the conduction band of the n-type semiconductor are more variable when compare to holes in the valence band of a p-type semiconductor. The hole’s mobility is less when they are more bound toward the nucleus. The electron-hole formation can be done even at room temperature. These electrons will be available in small quantities and carry less amount of current within these semiconductors.
1). What is the example of a p-type semiconductor?
Gallium or boron is an example of a p-type semiconductor
2). What are the majority charge carriers in p-type?
Holes are the majority charge carriers
3). How doping of p-type can be formed?
This semiconductor can be formed through doping process of pure Si using trivalent impurities like gallium, boron, etc
4). What is intrinsic & extrinsic semiconductor?
The semiconductor which is in pure form is known as intrinsic and when the impurities are added to semiconductor intentionally to make conductive is known as extrinsic.
5). What are the types of extrinsic semiconductors?
They are p-type and n-type
Thus, this is all about an overview of a p-type semiconductor which includes its doping, formation, energy diagram, and conduction. These semiconductors are used to manufacture various electronic components like diodes, lasers like heterojunction and homojunction, solar cells, BJTs, MOSFETs, and LEDs. The combination of p-type and n-type semiconductors is known as a diode and it is used as a rectifier. Here is a question for you, name the list of p-type semiconductors?