Inversion Layer in Enhancement Mode:

The inversion layer in an enhancement-mode transistor refers to the region within the channel where the carriers are inverted from their normal behavior. In an enhancement-mode transistor, the channel is initially non-conductive, and it needs to be enhanced or inverted to become conductive. This inversion layer is formed by applying a positive voltage to the gate terminal of the transistor.

Formation of Inversion Layer:

1. Applying Positive Voltage:
- In an enhancement-mode transistor, a positive voltage is applied to the gate terminal.
- This positive voltage attracts negative carriers towards the oxide layer, creating a depletion region.
- The depletion region near the oxide layer consists of immobile positive charges.

2. Formation of Negative Carriers:
- As the positive voltage increases, more negative carriers (electrons) are attracted towards the oxide layer.
- These negative carriers accumulate near the oxide layer, forming a region of excess electrons.
- This region is called the inversion layer.

3. Excess Negative Carriers:
- The amount of negative carriers in the inversion layer depends on the magnitude of the positive voltage applied to the gate terminal.
- The stronger the positive voltage, the greater the number of negative carriers in the inversion layer.
- The presence of excess negative carriers in the inversion layer allows current to flow through the channel, making it conductive.

Reason for Correct Answer:

The correct answer to this question is option 'B' - negative carriers. In an enhancement-mode transistor, the inversion layer is formed by attracting negative carriers (electrons) towards the oxide layer. These excess electrons in the inversion layer create the conductive channel in the transistor.

Option 'A' - positive carriers, is incorrect because positive carriers, such as holes, are not responsible for the formation of the inversion layer in an enhancement-mode transistor.

Option 'C' - both in equal quantity, is incorrect because the inversion layer consists of excess negative carriers, not both positive and negative carriers in equal quantities.

Option 'D' - neutral carriers, is incorrect because the inversion layer is formed by an excess of negative carriers, not neutral carriers.

In conclusion, the inversion layer in an enhancement-mode transistor consists of an excess of negative carriers (electrons) attracted towards the oxide layer by applying a positive voltage to the gate terminal.