A Schottky diode is constructed with two metal conductors bonded to a doped semiconductor. One of the metal-semiconductor junctions is a Schottky contact, and the other metal-semiconductor junction is an Ohmic contact. If the doping in the semiconductor is uniform, and the two metalic contacts are made of the same metal, I would presume the device would be symmetric, and would not be useful as a diode. If it had two Schottky contacts, they would be in opposing orientations. If it had two Ohmic contacts, it would just be a resistor composed of doped semiconductor.
My question is, how it the asymmetry between the two contacts achieved? Is there a doping gradient in the semiconductor? Are the two metal conductors composed of different metals? Is there some third alternative that I am missing?
(The common internet literature on Schottky diodes explains why the Schottky metal-semiconductor junction acts as a diode, but I have not seen an explanation of how the Ohmic contact in the same device is made to be different).