"Which is the positive end of a diode?" is a seemingly silly question, but guess what. I've seen the answers to this question ( Yes, I do mean to be plural, not singular.) cause intense arguments among folks who should have known better.
The two opposing answers are illustrated here:
Yes, this inane semantic argument arose among some of the same crowd who were arguing about whether current flow goes from positive to negative or from negative to positive.
This is why I absolutely refuse to entertain that question. I reject the very phrase straight out of hand because I want to avoid this kind of nonsense.
Instead, I will only refer to the anode end (unbanded) and the cathode end (banded) of a diode, whether the discussion is about rectifier diodes, step recovery diodes, zener diodes, transient absorbing diodes, PIN diodes, varactor diodes, back diodes, light emitting diodes, 5U4GB diodes or any other kind of diodes whose existence might have slipped my mind at the moment.
The one exception I might make to this is for the late Bob Pease's invention, the "Mogen Diode":