# Question about built in voltage in p-n junction

If I have two materials, joined together to make a p-n junction, the $$V_{bi}$$ is found by calculating the difference between the conduction bands or LUMO levels. Should this be the same as the difference between the HOMO or valence bands? Often in diagrams it is drawn such that this difference looks the same.

Secondly, if a dopant is added to one of the two materials, lets say a p-type dopant to the already p-type material, would this change the $$V_{bi}$$?

Thanks for any help.