Explain the difference in photovoltaic and photoconductive modes as they relate to photodiodes.
What will be an ideal response?
In the photovoltaic mode, the photodiode will generate a voltage in response to light.When light strikes the photodiode, it creates electron-hole pairs. The negatively charged electrons that are generated in the depletion region are attracted to the positively charged ions in the N-type material. The holes are attracted to the negatively charged ions in the P-type material. The result is a separation of charges and a small voltage drop of about 450 mV is developed across the diode. In the photoconductive mode, the conductance of the diode changes when light isapplied. In this mode, the photodiode is reverse biased when no light is applied. In this state, there will be only a small reverse current through the diode. When light is applied to the photodiode, movement of electrons and holes causes an increase in the reverse current flow. When light is applied, the resistance of the photodiode is very low and decreases as the intensity of light increases. As the resistance continues to decrease, current flow increases.
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