How do you bias photodiode?
As the applied reverse bias increases, the photodiode current increases sharply. The blocking voltage applied at this point is called the breakdown voltage. This is the maximum applied reverse voltage under which the photodiode should operate (also referred to as the maximum reverse voltage).
If you connect a photodiode with direct polarization (forward bias), it works like a normal diode. However, when a reverse-biased photodiode is used, the amount of electrons flowing through the PN junction is proportional to the amount of light incident on the diode.
In a depletion region, a current is generated due to the absorbed light. This is the amount of electricity proportional to the light intensity. This amount of current corresponds to the leakage current (dark current) + current generated by the photodiode. The dark current is defined depending on how much reverse voltage is applied to the photodiode.
What happens if you forward bias a photodiode?
When a photodiode is forward biased, it means that the voltage is applied in a way that allows current to flow from the p-side (anode) to the n-side (cathode) of the photodiode. In this state, the photodiode operates in a similar manner to a regular diode.
Forward biasing a photodiode leads to an increase in the width of the depletion region, which reduces the barrier potential. As a result, the photodiode becomes more conductive, allowing current to flow more easily through it. When exposed to light, the incident photons can generate electron-hole pairs in the depletion region of the photodiode. The electric field due to the forward bias helps separate these charge carriers, allowing the electrons to flow towards the anode and the holes towards the cathode, contributing to the photocurrent.
Forward biasing a photodiode can increase its sensitivity and responsiveness to light. It enables the photodiode to produce a larger photocurrent for a given level of illumination. This property is commonly utilized in various applications such as optical communications, light detection, and sensing systems where high sensitivity and fast response times are required.