I think he has been answered now so just an aside.
I was told in Electronics 101 that electrons flow from neg to pos and that "holes" flow from pos to neg , just not so many of them . It wasn't until much later I realised this was a lecturers creation to cover conventional current flow . They obviously got it wrong at the start . They guessed at one way or the other .
Lately in my mental meanders I thought I should suggest that as holes are obviously different to electrons then it should be possible to block the flow of one and allow the flow of the other.
I wonder what we would get if it actually were true?
A holy stream ? Perhaps thats where religion comes from.