![]() Shunt resistance is the slope of the current-voltage curve of the photodiode at the origin, i.e. For best photodiode performance the highest shunt resistance is desired. Shunt resistance is used to determine the noise current in the photodiode with no bias (photovoltaic mode). Experimentally it is usually obtained by applying ☑0mV, measuring the current and calculating the resistance. Although an ideal photodiode should have a shunt resistance of infinite, actual values range from 10s to 1000s of Mega ohms. Shunt Resistance, R sh Shunt resistance is the slope of the current-voltage curve of the photodiode at the origin, i.e. The typical spectral response curves of Silicon photodiodes are shown in Figure, The P and N-sides of the junction have metal pads, which make an electrical contact through dielectric layers. The active area is coated with an Anti-Reflection coating to reduce the reflection of the light for a specific predefined wavelength. ![]() To form an ohmic contact, another impurity diffusion into the backside of the wafer is necessary. The diffused area defines the photodiode active area. A P-N junction can be formed by diffusing either a P-type impurity, such as Boron, into a N-type bulk or epitaxial silicon wafer, or a N-type impurity, such as Phosphorus, into a P-type bulk or epitaxial wafer. Planar diffused silicon photodiodes are P-N junction diodes. Photodiodes operate by absorption of photons or charged particles and generate a flow of current in an external circuit, proportional to the incident power. Photodiodes are semiconductor devices responsive to high energy particles and photons.
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