- #1
nonequilibrium
- 1,439
- 2
Hello,
If I put a voltmeter over a (pn-junction) diode, do I measure anything?
I would intuitively say "no".
Is the following picture correct?
So let's say the P-region is to the right, N-region to the left. If I were to attach a voltmeter across it, I'd have to attach a metal wire to the P-region. Won't this result into a new PN-junction? Or a P-metal conductor junction? Thermal diffusion would drive the metal conductor electrons into the P-junction, and the holes from the latter into the former, no? This would imply two things, it seems (if true...):
- the voltage difference is not measurable (because the netto effect is made zero by the new pn-junction due to the metal contacts as explained above?)
- when we close a diode with a metal wire, no current will flow, not even temporarily (or only in a selected region), and the netto voltage around the circuit will be zero due to two non-zero voltage differences
Am I way off? Is it impossible for a p-side and metal conductor to form such a junction? I've only had introductory courses on these matters, so I don't pretend to be knowledgeable on these things. I have tried googling a lot, but it's hard to find answers on these questions.
If I'm wrong, what is the right way to see these things? Or can you point me to a good source?
If I put a voltmeter over a (pn-junction) diode, do I measure anything?
I would intuitively say "no".
Is the following picture correct?
So let's say the P-region is to the right, N-region to the left. If I were to attach a voltmeter across it, I'd have to attach a metal wire to the P-region. Won't this result into a new PN-junction? Or a P-metal conductor junction? Thermal diffusion would drive the metal conductor electrons into the P-junction, and the holes from the latter into the former, no? This would imply two things, it seems (if true...):
- the voltage difference is not measurable (because the netto effect is made zero by the new pn-junction due to the metal contacts as explained above?)
- when we close a diode with a metal wire, no current will flow, not even temporarily (or only in a selected region), and the netto voltage around the circuit will be zero due to two non-zero voltage differences
Am I way off? Is it impossible for a p-side and metal conductor to form such a junction? I've only had introductory courses on these matters, so I don't pretend to be knowledgeable on these things. I have tried googling a lot, but it's hard to find answers on these questions.
If I'm wrong, what is the right way to see these things? Or can you point me to a good source?