Hey there,
I'm currently studying pn-junctions and think I somewhat understand whats going on on a basic level. However there is one question I just can't wrap my head around. So considering an ideal PN-junction where a depletion region is formed between the p-type and n-type substrate. An electric field forms inside the depletion region to counter the diffusion current based on the concentration difference between n- and p-type.
Now in my textbooks it says that outside the depletion region the E-field is negligible if the dotation is high enough. If I now were to calculate the voltage across the diode (so, integral over the E-field across the whole diode) I must get *some* voltage right? Because in the depletion region there is a purely negative (or purely positive, depending on which way you look at it) E-field and outside of it the E-field is basically zero.
However if I connect a multimeter to any diode I of course will *not* measure a voltage. So, what gives?
My current theory is that there is nothing to sustain an ongoing current, so the internal resistance of my voltmeter is causing a reading of 0V. Is that correct or am I missing something?
Were I to connect an ideal voltmeter to an ideal pn-junction, would I actually measure its diffusion voltage?