The correct answer is option 'D' - leakage current does not flow.

An ideal power diode is a two-terminal electronic device that allows current to flow in only one direction and blocks current flow in the reverse direction. It is designed to have a very low leakage current when it is reverse biased.

Here is an explanation of why the leakage current does not flow in an ideal power diode:

1. Diode Structure:
- A diode is typically made of a P-N junction, where one side is doped with a P-type material and the other side is doped with an N-type material.
- The P-type material has an excess of positively charged holes, while the N-type material has an excess of negatively charged electrons.
- At the junction, the excess electrons from the N-type material diffuse to the P-type material, creating a depletion region with no free charges.

2. Forward Bias:
- When a forward bias voltage is applied across the diode, the positive terminal is connected to the P-side, and the negative terminal is connected to the N-side.
- The applied voltage reduces the width of the depletion region, allowing the majority carriers (holes in the P-side and electrons in the N-side) to flow across the junction.
- In this forward bias condition, the diode operates in its conducting region, and a significant amount of current flows from the anode (P-side) to the cathode (N-side).

3. Reverse Bias:
- When a reverse bias voltage is applied across the diode, the positive terminal is connected to the N-side, and the negative terminal is connected to the P-side.
- The applied voltage widens the depletion region, preventing the majority carriers from flowing across the junction.
- In this reverse bias condition, the diode operates in its blocking or non-conducting region, and ideally, no current should flow from the anode to the cathode.

4. Leakage Current:
- In reality, even in the reverse bias condition, there is a small amount of current that may flow through the diode, known as leakage current.
- The leakage current is caused by minority carriers (minority electrons in the P-side and minority holes in the N-side) that can cross the depletion region due to thermal excitation or other factors.
- However, in an ideal power diode, this leakage current is negligible and can be considered as zero for most practical applications.

In conclusion, an ideal power diode does not allow any significant leakage current to flow in the reverse bias condition. The small amount of leakage current that may exist is typically negligible and can be ignored for most engineering purposes.