Consider the potential distribution across a PN junction. The difference in the Fermi levels between the differently doped semiconductors leads to a 'built-in' voltage across the semiconductor junction.
What happens to the potential distribution if we short-circuit the device i.e. connect the two contacts together?
Given there is a difference in the potential values does a current flow until the potentials at the contacts match up? Then it feels like we're getting current from nothing.
Or does the external circuitry instead not see the potential difference? After all if no current is flowing across the device, how can it suddenly start flowing if we short circuit.
Thanks in advance for any help.