The number density of electrons and holes in pure silicon at $27 ^{\circ}C$ are equal and its value is $2.0 \times 10^{16}\, m^{-3}$.
On doping with indium the hole density increases to $4.5 \times 10^{22}\, m^{-3}$, the electron density in doped silicon is
- $10 \times 10^9\, m^{-3}$
- $8 .89 \times 10^9\,m^{-3}$
- $11 \times 10^9 \,m^{-3}$
- $16.78 \times 10^9\, m^{-3}$
The Correct Option is B
Approach Solution - 1
Approach Solution -2
Ans. When a little, controlled quantity of a chemical impurity is added to intrinsic semiconductors, extrinsic semiconductors are created. They go by the names doped or impurity semiconductors as well. Generally speaking, semiconductors are solids that can be either crystalline or amorphous and have the ability to conduct electricity between an insulator and a conductor. Doping, or the addition of impurities, modifies the semiconductor's electrical characteristics, making it appropriate for use in electronic devices such as transistors and diodes.
Doping is a process in an extrinsic semiconductor when a bandgap is controlled by specifically adding minor impurities to the material. Doping the semiconductor with some suitable impurity can also increase its conductivity by several times. These impurities are called dopants.
The selection of dopants is based on the application of the final semiconductor. A good Extrinsic Semiconductor can be made by adding just a small amount of dopant. Although we should always make sure to check and confirm the size of the dopant atom to be equal to that of the original atom. A Dopant’s presence should not disturb the original semiconductor’s shape as it occupies only some positions in the crystal lattice of the semiconductor. Silicon and Germanium have tetravalent crystals which can be doped with these two kinds of dopants:
- Pentavalent: These Atoms have a valency of 5. Examples: Phosphorous (Pi), Antimony (Sb), Arsenic (As), etc.
- Trivalent: These Atoms have a valency of 3. Examples: Aluminium (Al), Indium (In), Boron (B), etc.
The third and fifth groups of the periodic table consist of pentavalent and trivalent dopants respectively, and they are close to the fourth group. So, the size of the atoms is basically not so different from that of the fourth group of elements’ atoms. Extrinsic semiconductors can be further classified into two kinds:
- P-type semiconductor
- N-type semiconductor
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Notes on Semiconductor electronics: materials, devices and simple circuits
Concepts Used:
Semiconductors
Semiconductors are a crystalline solid materials, whose electrical conductivity lies between a conductor and an insulator. Semiconductors are mainly used in the manufacturing of electronic devices like capacitors, transistors, diodes, Integrated circuits, etc.
Properties of Semiconductor:
- Semiconductor acts like an insulator at Zero Kelvin. On increasing the temperature, it works as a conductor.
- Due to their exceptional electrical properties, semiconductors can be modified by doping to make semiconductor devices suitable for energy conversion, switches, and amplifiers.
- Lesser power losses.
Uses of Semiconductor:
- Semiconductors are widely used in manufacturing electronics devices like transistors, diodes, sensors, integrated circuits.
- Semiconductors are widely used in all electronic devices, like mobile phones, digital cameras, communication devices, trains, ATMs, etc.