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Is there any way to determine whether an unidentified photodiode is a regular PIN photodiode or is an avalanche diode? The photodiode is part of a small scintillation detector unit.

Eric Slighton
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  • Unless I make an error, PIN diodes are used in RF circuits as "variable resistors" or 'switches'. – Antonio51 Jul 04 '21 at 10:25
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    @Antonio51 the PIN structure is also used for (some) photodiodes, though you are correct that common "PIN diodes" are used for (HF) switching. –  Jul 04 '21 at 11:14
  • Avalanche photodiodes have built in gain. Should be easy enough to test. Are running some simple tests an option? You say "part of scintillation detector unit". Can the diode be tested on its own? If not, more information about the unit is probably needed. – Matt Jul 04 '21 at 14:06
  • @Matt APDs have gain if they are biased with a few 10s of volts, at a value that varies from device to device, and needs to be carefully controlled to avoid blowing up the device. A pin diode will also have some reverse breakdown behavior. If you bias the device on the edge of breakdown and it turns out to be a PIN rather than an APD it may well be blown by the time you have determined its not providing photocurrent gain. – The Photon Jul 04 '21 at 14:58
  • Can you say anything about the machine specs for pulse width and bias voltage? It could be Si or InGaAs and (PIN or APD) – Tony Stewart EE75 Jul 04 '21 at 16:39
  • @ThePhoton Yes, while testing dont put so much current through it that you destroy the device. – Matt Jul 04 '21 at 22:44
  • I can test the diode on its own as it is simply glued to a small scintillation crystal. The pulse length is somewhere between 10 and 100 microseconds. Someone else tested it at 30V reverse bias as if it is a regular PIN photodiode and it worked, but when I look at specs of things I think might be similar, most are avalanche photodiodes. I think 30V reverse bias is relatively high for regular PIN photodiode, but still possible. – Eric Slighton Jul 06 '21 at 01:38
  • I could apply a variable voltage through a high value resistor to see how it breaks down, but I have no idea how much breakdown current is acceptable without causing damage. The photodiode is about 4mm square. – Eric Slighton Jul 06 '21 at 01:40

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