For semiconductors used in photodetector we know the power law: Current(I)=Pa , where P is power density of incident illumination & a is power law coefficient. Generally a1?
Thank you sir for your guidance.I am talking about simple p-n junction diode or simple single crystaline detector
Ayon,
It seems that you forget the proportionality factor or the constant in your equation.
It must read Id= K P^a
Id in amperes and P in watts. So the incident light is measured in watt.
Normally this relation is linear such that a is normally equal one for normal pn junction or pin photo diode. Then Id= KP (1)
In case of avalanche photo diode multiplication of the generated photo electrons and holes occur so that the primary current will be multiplied by a multiplication factor M and the relation becomes Id= MK P (2)
The coefficient K or MK is called the sensitivity of the photo detector.
In fact the linear probability stems from that the generation G rate of the electrons and holes is proportional to photon flux which is proportional to P. The collection process is also proportional to G.
As a sought experiment, let us assume one incident photon it will generate one electron hole pairs and when phi=2 we will have G=2 not 4 if we have square relation ship. 3 photons will generate 3 e-h pairs in the linear case and 9 e-h in case of quadratic relation. How would this occur? Only the linear relationship is the possible.
Best wishes
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