Model for Diode Shows Voltage Increase not Drop
You understanding is not wrong, but incomplete. You basically showed how a diode is "built", but not how it is used.







simulate this circuit &ndash; Schematic created using CircuitLab

If you have a circuit like the one above, for instance, the 3 V supply must overcome the built-in voltage of your diode (the one you drew in your picture) to generate an electric field (directed from anode to cathode) strong enough to push current from anode to cathode.