Semiconductors are one of the most important topics in Electrical Engineering and Electronics Engineering. Questions related to Types of Semiconductor are frequently asked in SSC JE, RRB JE, GATE, State AE/JE, UPPCL JE, DRDO, ISRO, and other competitive exams.
In this detailed article, we will learn the definition, classification, working principle, characteristics, formulas, applications, examples, and exam-oriented concepts of semiconductors in a simple and easy language.
What is Semiconductor?
A semiconductor is a material whose electrical conductivity lies between that of a conductor and an insulator. Semiconductor materials can conduct electricity under certain conditions.
The conductivity of semiconductors can be controlled by temperature, light, electric field, and impurities. Because of this property, semiconductors are widely used in electronic devices.
Examples of Semiconductor Materials
- Silicon (Si)
- Germanium (Ge)
- Gallium Arsenide (GaAs)
- Carbon (in special forms)
Classification or Types of Semiconductor
Semiconductors are mainly classified into two types:
- Intrinsic Semiconductor
- Extrinsic Semiconductor
Intrinsic Semiconductor → Pure Semiconductor
Extrinsic Semiconductor → Doped Semiconductor
Intrinsic Semiconductor
Definition of Intrinsic Semiconductor
An intrinsic semiconductor is a pure semiconductor material without any impurity added to it. In intrinsic semiconductors, the number of free electrons is equal to the number of holes.
Characteristics of Intrinsic Semiconductor
- Pure semiconductor material
- No impurity added
- Number of electrons equals number of holes
- Low conductivity at room temperature
- Conductivity increases with temperature
Examples of Intrinsic Semiconductor
- Pure Silicon
- Pure Germanium
Working of Intrinsic Semiconductor
At absolute zero temperature, intrinsic semiconductors behave like insulators because there are no free electrons available for conduction.
When temperature increases, some covalent bonds break and free electrons are generated. These free electrons leave behind holes. Thus, conduction takes place due to both electrons and holes.
Charge Carriers in Intrinsic Semiconductor
| Charge Carrier | Description |
|---|---|
| Electron | Negative charge carrier |
| Hole | Positive charge carrier |
Important Formula of Intrinsic Semiconductor
For intrinsic semiconductor:
n = p = ni
Where,- n = Number of electrons
- p = Number of holes
- ni = Intrinsic carrier concentration
Extrinsic Semiconductor
Definition of Extrinsic Semiconductor
An extrinsic semiconductor is a semiconductor in which a small amount of impurity is added intentionally to increase its conductivity.
The process of adding impurity is called doping.
Types of Extrinsic Semiconductor
Extrinsic semiconductors are of two types:
- P-type Semiconductor
- N-type Semiconductor
P-Type Semiconductor
Definition of P-Type Semiconductor
A P-type semiconductor is formed by adding trivalent impurity atoms to a pure semiconductor material.
Trivalent Impurity Examples
- Boron (B)
- Gallium (Ga)
- Indium (In)
- Aluminium (Al)
Why it is Called P-Type?
In P-type semiconductor, holes are the majority charge carriers. Since holes carry positive charge, it is called P-type semiconductor.
Majority and Minority Carriers in P-Type Semiconductor
| Carrier Type | Charge Carrier |
|---|---|
| Majority Carrier | Hole |
| Minority Carrier | Electron |
Working Principle of P-Type Semiconductor
When trivalent impurity is added, one covalent bond remains incomplete due to the shortage of one electron. This incomplete bond behaves like a hole.
Thus, a large number of holes are created, which increases conductivity.
N-Type Semiconductor
Definition of N-Type Semiconductor
An N-type semiconductor is formed by adding pentavalent impurity atoms to a pure semiconductor material.
Pentavalent Impurity Examples
- Phosphorus (P)
- Arsenic (As)
- Antimony (Sb)
- Bismuth (Bi)
Why it is Called N-Type?
In N-type semiconductor, electrons are the majority charge carriers. Since electrons carry negative charge, it is called N-type semiconductor.
Majority and Minority Carriers in N-Type Semiconductor
| Carrier Type | Charge Carrier |
|---|---|
| Majority Carrier | Electron |
| Minority Carrier | Hole |
Working Principle of N-Type Semiconductor
When pentavalent impurity is added, four electrons participate in covalent bonding while one extra electron becomes free for conduction.
This increases the number of free electrons and improves conductivity.
Difference Between Intrinsic and Extrinsic Semiconductor
| Parameter | Intrinsic Semiconductor | Extrinsic Semiconductor |
|---|---|---|
| Purity | Pure | Impurity added |
| Conductivity | Low | High |
| Charge Carriers | Equal electrons and holes | Unequal charge carriers |
| Doping | No doping | Doping present |
| Examples | Pure Silicon | P-type, N-type |
Difference Between P-Type and N-Type Semiconductor
| Parameter | P-Type Semiconductor | N-Type Semiconductor |
|---|---|---|
| Impurity Type | Trivalent | Pentavalent |
| Majority Carrier | Hole | Electron |
| Minority Carrier | Electron | Hole |
| Examples | Boron | Phosphorus |
| Charge Nature | Positive | Negative |
Energy Band Diagram of Semiconductor
Semiconductors have a small forbidden energy gap between valence band and conduction band. Because of this small energy gap, electrons can move to the conduction band at room temperature.
Important Points About Energy Gap
- Conductors have zero energy gap
- Insulators have large energy gap
- Semiconductors have small energy gap
Applications of Semiconductors
- Diodes
- Transistors
- Integrated Circuits (ICs)
- Solar Cells
- Rectifiers
- LEDs
- Microprocessors
- Voltage Regulators
- Digital Electronics
Advantages of Semiconductor Devices
- Small size
- Low power consumption
- High efficiency
- Long life
- Fast switching speed
- Reliable operation
Numerical Example Based on Semiconductor
Example 1
If a semiconductor has electrons concentration equal to holes concentration, identify the type of semiconductor.
Solution
Since:
n = p
Therefore, it is an intrinsic semiconductor.
Important Exam-Oriented Notes
- Intrinsic semiconductor is pure semiconductor.
- Extrinsic semiconductor is obtained by doping.
- Trivalent impurity creates P-type semiconductor.
- Pentavalent impurity creates N-type semiconductor.
- Majority carrier in P-type is hole.
- Majority carrier in N-type is electron.
- Conductivity of semiconductor increases with temperature.
Common Mistakes Made by Students
- Confusing majority and minority charge carriers
- Mixing trivalent and pentavalent impurities
- Assuming semiconductor behaves exactly like conductor
- Forgetting that conductivity increases with temperature
- Confusing intrinsic and extrinsic semiconductor definitions
Previous Year Question Insights
In SSC JE and RRB JE exams, questions are commonly asked from:
- Majority and minority carriers
- Types of impurities
- Intrinsic vs extrinsic semiconductor
- P-type and N-type semiconductor
- Energy band theory
- Semiconductor applications
Preparation Tips for JE Exams
- Remember impurity examples carefully
- Learn majority and minority carriers properly
- Practice previous year MCQs
- Understand energy band concept visually
- Revise definitions regularly
- Focus on conceptual clarity instead of rote learning
Short Revision Notes
- Semiconductor conductivity lies between conductor and insulator.
- Intrinsic semiconductor is pure.
- Extrinsic semiconductor is doped.
- P-type uses trivalent impurity.
- N-type uses pentavalent impurity.
- Hole is majority carrier in P-type.
- Electron is majority carrier in N-type.
- Conductivity increases with temperature.
Internal Linking Suggestions
- PN Junction Diode
- Energy Band Theory
- Zener Diode
- Transistor Basics
- Rectifier Circuits
- Semiconductor Devices MCQ
Conclusion
Types of Semiconductor is one of the most important topics in electronics and electrical engineering. Understanding intrinsic semiconductor, extrinsic semiconductor, P-type semiconductor, and N-type semiconductor is essential for SSC JE, RRB JE, GATE, and other competitive exams.
Semiconductors form the foundation of modern electronics and are widely used in almost every electronic device. Students should focus on impurity types, majority carriers, working principles, and energy band concepts for better exam preparation.
Frequently Asked Questions (FAQs)
What are the main types of semiconductor?
The main types of semiconductor are intrinsic semiconductor and extrinsic semiconductor.
What is intrinsic semiconductor?
An intrinsic semiconductor is a pure semiconductor without any impurity added to it.
What is extrinsic semiconductor?
An extrinsic semiconductor is a semiconductor in which impurity is added to increase conductivity.
What is P-type semiconductor?
A P-type semiconductor is formed by adding trivalent impurity to a pure semiconductor.
What is N-type semiconductor?
An N-type semiconductor is formed by adding pentavalent impurity to a pure semiconductor.
Which charge carrier is majority in P-type semiconductor?
Hole is the majority charge carrier in P-type semiconductor.
Which charge carrier is majority in N-type semiconductor?
Electron is the majority charge carrier in N-type semiconductor.
Why is silicon widely used as semiconductor?
Silicon is widely used because it is stable, easily available, and has suitable electrical properties.
What is doping in semiconductor?
Doping is the process of adding impurities to a pure semiconductor to increase conductivity.
Why are semiconductors important?
Semiconductors are important because they are used in diodes, transistors, ICs, computers, communication systems, and modern electronic devices.