How are the characteristics of a photodiode affected?

How are the characteristics of a photodiode affected?

All photodiode characteristics are affected by changes in temperature. They include shunt resistance, dark current, breakdown voltage, responsivity and to a lesser extent other parameters such as junction capacitance. Shunt Resistance and Dark Current: There are two major currents in a photodiode contributing to dark current and shunt resistance.

What should the RJ of a photodiode be?

An ideal photodiode will have an infinite RJ, but the actual value of R is typically on the order of thousands of MΩ, which depends on the photodiode material, and decreases by a factor of 2 for every 10°C rise in temperature. The high value of RJyields the low noise current of the photodiode.

How is the current generated from a photodiode related to the absorption coefficient?

The current generated is proportional to the incident light or radiation power. The light is absorbed exponentially with distance and is proportional to the absorption coefficient. The absorption coefficient is very high for shorter wavelengths in the UV region and is small for longer wavelengths (Figure 2).

How is junction capacitance used in a photodiode?

Junction capacitance is used to determine the speed of the response of the photodiode. The rise time and fall time of a photodiode is defined as the time for the signal to rise or fall from 10% to 90% or 90% to 10% of the final value respectively.

What is the rise and fall time of a photodiode?

The rise time and fall time of a photodiode is defined as the time for the signal to rise or fall from 10% to 90% or 90% to 10% of the final value respectively. This parameter can be also expressed as frequency response, which is the frequency at which the photodiode output decreases by 3dB.

Why are p-n photodiodes good for low light level?

Without added voltage across the junction, dark current can be extremely low (near zero). This reduces the overall noise current of the system. Thus unbiased P-N or PIN photodiodes are better suited for low light level applications compared to operation with reverse voltage bias.

Can a photodiode be operated without a voltage bias?

Photodiodes can be operated without any voltage bias. APDs are designed to be reversed biased, so this section will be relevant to the P-N and PIN photodiodes. Without added voltage across the junction, dark current can be extremely low (near zero).

How are PIN photodiodes used in the photoconductive mode?

PIN photodiodes are used in the Photoconductive Mode with a reverse bias applied, the relationship between the amount of light received and electric current produced is practically linear and they are also relatively stable over their normal temperature range.