Hi,
I have a silicon photodiode and I am trying to characterize it. When I measured the currents generated in photovoltaic mode (PV) of operation (without applying a bias) and in photoconductive (PC) mode of operation (applying a 5V reverse bias voltage), I noticed that the Signal to noise (dark current) was much better for the photoconductive mode of operation.
Now, everywhere that I have read suggests that in the Photovoltaic mode of operation the circuit should be much more sensitive.
For examlple, in photovoltaic mode at some optical power, I get 0.044 nA of current being generated with a dark current of about 0.003 nA. In the photoconductive mode of operation, I get 3.98 nA of current generated when biased at 5V with a dark current (light off) of about the same 0.003 nA.
Also, shouldn't the dark current in photoconductive mode of operation increase with the applied reverse bias voltage? However, I noticed a constant dark current while varying my reverse bias voltage.
Also, I am using a picoammeter for my measurements.
Any help or suggestions would be greatly appreciated.
Thanks.