SCR vs diode VI characteristics
Is an SCR VI curve the same as a diode? Look at some curves from datasheets. I tried to pick components with similar current capabilities.
I would say that the VI curve is similar, but not the same. At very low currents, a diode voltage drop is smaller than an SCR, and the drop seems to be approaching zero faster.
In the &quot;on&quot; state, an SCR has two series P-N junctions conducting, that is part of the reason. Why an SCR voltage drop approaches zero slower, I don't know.
There may be someone here who knows semiconductor physics well enough to explain the technical reasons.

https://diotec.com/tl_files/diotec/files/pdf/datasheets/1n4148.pdf
https://media.digikey.com/pdf/Data%20Sheets/Solid%20State%20INC%20PDF's/2N2322-29-22A-29A-C5U-C5D-TO39-ssi.pdf
Note that since the current is on a log scale, the shape is not the upward turning curve that most of us are more familiar with.