Question

In a forward-biased photo-diode with increase in incident light intensity, the diode current:

• A. increases
• B. remains constant
• C. decreases
• D. none of the above

Answer 1

The correct option is A increases

Light is a form of energy. So, if we allow light to fall onto the diode, we are transferring energy to the atoms in the diode. This additional energy is absorbed by the outermost layer of the atoms, and charges that were earlier bound to the atom now become free to move about in the semiconductor. So, light causes the number of free charge carriers in the semiconductor to increase significantly.

If we increase the intensity of falling light, the number of charges that cross the junction every second will increase. This is the same as saying that the current through the diode increases.