Question

The electrical resistance of depletion layer is large because (A) it contains electrons as charge carriers (B) it has holes as charge carriers. (C) it has no charge carriers. (D) It has large number of charge carriers

Short answer

The correct reason for the large electrical resistance in the depletion layer is option (C) because it has no charge carriers.

Step-by-step solution

Analyze the first option

Option (A) states that the electrical resistance of the depletion layer is large because it contains electrons as charge carriers. This is not the correct reason because the presence of electrons as charge carriers would actually lead to electrical conduction, not an increase in resistance.

Analyze the second option

Option (B) states that the electrical resistance of the depletion layer is large because it has holes as charge carriers. This is also not the correct reason because, like electrons, the presence of holes as charge carriers would also lead to electrical conduction, not an increase in resistance.

Analyze the third option

Option (C) states that the electrical resistance of the depletion layer is large because it has no charge carriers. This is the correct reason because, in the depletion layer, the recombination of electrons and holes leaves behind a region with no charge carriers, thus resulting in a large electrical resistance.

Analyze the fourth option

Option (D) states that the electrical resistance of the depletion layer is large because it has a large number of charge carriers. This is not the correct reason because having a large number of charge carriers would lead to an increase in electrical conduction, not an increase in resistance.

Conclusion

Based on the analysis of each option, the correct reason for the large electrical resistance in the depletion layer is option (C) because it has no charge carriers.

Key concepts

Electrical Resistance

Electrical resistance is a fundamental property of materials that indicates how much they resist the flow of electric current. In simpler terms, it tells us how difficult it is for electricity to pass through a material. Resistance is measured in ohms (\( \Omega \)). The formula to calculate resistance is given by \[ R = \frac{V}{I} \]where \( R \) is the resistance, \( V \) is the voltage, and \( I \) is the current. A higher resistance means less current flows for a given voltage, and vice versa.

• When a material has high resistance, it means that it does not easily allow the movement of charge carriers like electrons.
• Conversely, materials with low resistance allow charge carriers to move more freely, aiding the flow of electric current.

Electrically, the depletion layer in a semiconductor exhibits high resistance due to the absence of charge carriers, making it an insulator rather than a conductor.

Charge Carriers

Charge carriers are particles that carry electrical charge through a conductor or semiconductor. The most common charge carriers are electrons and holes.

• Electrons are negatively charged particles that move through a conductor, creating an electric current.
• Holes, although not particles themselves, represent the absence of an electron and act as positive charge carriers in semiconductors.

In semiconductors, charge carriers play a crucial role in determining the material's electrical properties. When no charge carriers are present, as in the depletion layer, the resistance is high because there is nothing to facilitate the movement of charge. This lack of charge movement is why the depletion layer acts as a barrier to current flow.

Semiconductor Physics

Semiconductor physics explores the properties and behavior of semiconductor materials, which are critical in electronic devices. Semiconductors have a conductivity that falls between conductors and insulators.

• They have a band structure that allows electrons to move from the valence band to the conduction band with some energy input, creating charge carriers.
• Doping is a process where impurities are added to a semiconductor, increasing its charge carrier concentration and altering its electrical properties.

The depletion layer is a unique feature in semiconductor devices, such as diodes and transistors.

• It is formed at the junction of p-type (positive) and n-type (negative) semiconductors, where electrons and holes recombine, leaving behind a region depleted of charge carriers.
• This layer acts as an insulator because of its high resistance, crucial for the function of electronic components by controlling the flow of current.

Understanding semiconductor physics is essential for the innovation and development of modern electronic devices.