The depletion layer width of Junction

The question asks about the depletion layer width in a junction (like a diode). Think of the depletion layer as a region with very few free charge carriers.

Let's look at each option:

Option A: Decreases with light doping
This is incorrect. Lighter doping means fewer charge carriers are available. To create the depletion region, more of the semiconductor needs to be depleted of its free carriers, so a lighter doping requires a *wider* depletion region.

Option B: Is independent of applied voltage
This is incorrect. The width of the depletion layer *definitely* changes with applied voltage. Applying a voltage will affect how easily charge carriers can move across the junction, and thus the size of the depletion region.

Option C: Is increased under reverse bias
This is correct. Reverse bias *widens* the depletion layer. Applying a reverse voltage pulls the charge carriers away from the junction, making the depletion region bigger and offering greater resistance to current flow.

Option D: Increases with heavy doping
This is incorrect. Heavier doping means more charge carriers are available. Only a *narrow* depletion region needs to be created to deplete the available carriers.

Therefore, the answer is Option C.