Definitions [9]
The semiconductor with impurity added to it is called a doped semiconductor or extrinsic semiconductor.
The semiconductor in which silicon or germanium crystal is doped with trivalent impurity (acceptor), making holes the majority charge carriers, is called a p-type semiconductor.
The semiconductor in which silicon or germanium crystal is doped with pentavalent impurity (donor), making electrons the majority charge carriers, is called an n-type semiconductor.
A unique form of a bipolar device which permits the current flow in the reverse direction when the voltage applied is above a certain characteristic value called Zener voltage or breakdown voltage, most commonly used in voltage regulators to protect other semiconductor devices from fluctuations in voltage, is called a Zener Diode.
A special purpose junction diode that converts light energy into electrical current, works on the principle of the photoelectric effect, operates in reverse bias, and generates a current when exposed to light (proportional to the intensity of incident light), is called a Photodiode.
What is a solar cell?
It is a semiconductor device used to convert photons of solar light into electricity. It generates emf when solar radiation falls on the p-n junction. A p-type silicon wafer of about 300 μm is taken over which a thin layer of n-type silicon is grown on one side by the diffusion process.
With reference to a semiconductor diode, define the depletion region.
A semiconductor diode's depletion zone is the area surrounding the p-n junction where there are no mobile charge carriers, this area generates an electric field that allows the diode to conduct in one direction while blocking in another.
In semiconductor physics, what is meant by:
(i) rectifier
(ii) an amplifier
(iii) an oscillator
(i) Rectifier: It is a device which converts alternating current into direct current.
(ii) Amplifier: An amplifier is a device which increases the energy of a weak signal by supplying energy from an external source. An amplifier increases the amplitude of a input signal.
(iii) Oscillator: An oscillator is a device which produces electrical oscillations of adjustable frequency and constant amplitude. An oscillator is basically an amplifier. A part of the output energy is fed back into the L-C circuit to produce sustained oscillations.
With reference to a semiconductor diode, define the potential barrier.
The barrier that the repelling forces use to stop the mobile charge carriers (at the PN junction) is known as the potential barrier.
This results from the concentration of immobile charges close to the junction after electrons and holes diffuse across the function.
Key Points
-
Conductivity: Extrinsic semiconductors contain added impurities; conductivity increases depending on the valency of the impurity (p-type or n-type).
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n-type vs p-type carriers & formula
| n-type | p-type | |
|---|---|---|
| Majority carriers | Electrons ((n_e \gg n_h)) | Holes ((n_h \gg n_e)) |
| Dopant | Pentavalent — Sb, P, As | Trivalent — B, Al, In |
| Relation | ( n_i^2 = n_e \cdot n_h ) | ( n_i^2 = n_e \cdot n_h ) |
Both n-type and p-type semiconductors are electrically neutral; holes are not actual charges but behave like a positive charge.
Important Questions [28]
- If the Charge on the Condenser of 10°F is Doubled, Then the Energy Stored in It Becomes
- Explain the Formation of Energy Band Diagram in Case of Conductor and Semiconductor.
- Distinguish Between Intrinsic and Extrinsic Semiconductor. (Give Any Two Points).
- In a Semiconductor, Acceptor Impurity is
- Distinguish Between P-type and N-type Semiconductors.
- When a Hole is Produced in P-type Semiconductor, There is
- A Pure Semiconductor is ________.
- The Width of Depletion Region of P-n Junction Diode is _______.
- With the Help of a Neat Circuit Diagram, Explain the Working of a Photodiode.
- Colour of Light Emitted by Led Depends Upon
- State its any ‘two’ uses of photodiode.
- Explain the Working of P-n Junction Diode in Forward and Reverse Biased Mode
- With the Help of Neat Labelled Circuit Diagram Explain The Working of Half Wave Rectifier Using Semiconductor Diode.
- What is Zener Diode?
- Describe, with the Help of a Circuit Diagram, the Working of Zener Diode as a Voltage Regulator.
- Explain, with the help of a circuit diagram, the principle and working of a Zener diode as voltage regular.
- When a P-n-p Transistor is Operated in Saturation Region, Then Its
- What Are α And β Parameters for a Transistor? Obtain a Relation Between Them.
- Draw a circuit diagram for studying the input and output characteristics of a n-p-n transistor in common emitter configuration.
- Write the Functions of Three Segments of a Transistor.
- Explain the Working of Transistor as a Switch.
- Explain the Elementary Idea of an Oscillator with the Help of Block Diagram
- In Case of Transistor Oscillator, to Obtain Sustained Oscillations, the Product of Voltage Gain Without Feedback And Feedback Factor Should Be
- Draw the Schematic Symbols for And, Or, Not and Nand Gate
- The Logic Gate Which Produces Low Output When One of the Input is High and Produces High Output Only When All of Its Inputs Are Low is Called
- The Output of Nor Gate is High, When
- Name the Logic Gate Which Generated High Output When at Least One Input is High.
- Which Logic Gate Corresponds to the Truth Table Given Below?
Concepts [12]
- Energy Bands in Solids
- Extrinsic Semiconductor
- Applications of n-type and p-type Semiconductors
- Special Purpose P-n Junction Diodes
- Semiconductor Diode
- Zener Diode as a Voltage Regulator
- I-V Characteristics of Led
- Transistor and Characteristics of a Transistor
- Transistor as an Amplifier (Ce-configuration)
- Transistor as a Switch
- Oscillators
- Digital Electronics and Logic Gates
