Backward diodes VI curve
If you just need an IV-curve of a random backward diode, the German Wikipedia site has one:

(Unknown authorUnknown author, Public domain, via Wikimedia Commons)
There is a hint, that the diagram might be flipped by 180 ° compared to those of a tunnel diodes. So the right side of that picture is actually the reverse polarity side. Not sure why it was done like that.