Increasing Biasing Voltage and Photocurrent Magnitude in a Photodiode

Introduction:
A photodiode is a semiconductor device that converts light energy into electrical current. It consists of a p-n junction with a reverse bias applied across it. When light strikes the photodiode, electron-hole pairs are generated, and the resulting photocurrent is proportional to the incident light intensity. Here, we will discuss the effect of increasing the biasing voltage on the magnitude of the photocurrent.

Effect of Increasing Biasing Voltage:
When a reverse bias voltage is applied to a photodiode, it creates a depletion region at the p-n junction. This depletion region acts as a barrier for the flow of photocurrent. As we increase the reverse bias voltage, the width of the depletion region increases, allowing more photons to be absorbed and generating more electron-hole pairs. This results in an increase in the magnitude of the photocurrent.

Initial Increase:
Initially, as the biasing voltage is increased, the photocurrent magnitude also increases. This is because more electron-hole pairs are generated due to the increased absorption of photons.

Saturation:
However, there comes a point where further increasing the biasing voltage does not significantly increase the magnitude of the photocurrent. This is known as saturation. Saturation occurs when all the available electron-hole pairs are already generated and any additional biasing voltage does not result in more photocurrent. At this point, the magnitude of the photocurrent remains constant and does not increase further.

Explanation:
The correct answer to the question is option 'D' - the photocurrent increases initially and saturates finally. This is because increasing the biasing voltage of a photodiode initially results in an increase in the magnitude of the photocurrent due to the generation of more electron-hole pairs. However, after reaching a certain point, further increasing the biasing voltage does not significantly increase the magnitude of the photocurrent as all the available electron-hole pairs are already generated. Hence, the photocurrent saturates and remains constant.

Overall, the magnitude of the photocurrent in a photodiode increases initially with increasing biasing voltage and eventually saturates, resulting in a constant photocurrent magnitude.