Frequency of Photocurrent

Hello,

Can anybody tell what is the frequency of Photocurrent?

Itotal = Id + Ip

Id = diode current
Ip = Photocurrent = R*P

P = incident light intensity
R = responsivity of diode

Thanks in advance.

There's no quantity related to frequency in the presented expression. If the light intensity would be time varying (P = P(t), originated from a modulated light source), frequency come's into play.

Photo current is, on a fine scale, a discrete phenomenon. One or a couple photons are absorbed in the diode, and they generate one electron. A lot of photons hitting the diode will generate a lot of electroncs. But there is no specific frequency involved in the detected current flowing out of the diode. There is an average DC current, with shot noise superimposed on top of it. I believe the shot noise is described by a poisson distribution, if my memory of school days is still intact.

If you vary the amplitude of the light hitting the diode, the amount of current coming out of the diode will also vary. If you change the color of the light hitting the diode, the diode efficiency can change (sometimes drastically).

Is that what you are asking about?

First of all thank you both of you for replying.

Biff@ you are absolutely correct
FVM@ Could you please refer any papers?

The thing is if you look at the IV curve for the photodiode (fig 8 http://www.optics.arizona.edu/palmer...cs/pd_char.pdf)

then you see if the light has a power P, it only shifts the curve. My question is can I actually vary the shape of the curve? By using a modulated light source?

Thanks for your cooperation

I my opinion, the datasheet explanation is somewhat long-winded. I see only one curve, which is basically a usual bipolar PN diode characteristic, and an overimposed photo current. The diode characteristic isn't changed by the light intensity.

A temperature variation will change the diode threshold voltage by some amount (about -1.9 mV/K).

There is not much that you can do to alter the IV curve. You can apply more or less reverse bias voltage. Not sure what a strong magnetic field would do, possibly something since electroncs are flowing in one direction.

Thank you both once again. Both of you are correct. Light does not change the characteristics of the diode. I can use the photo diode as a opto electronic mixer, this is what i was after

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Thanks again