Germanium diodes can be point contact, grown junction, alloy junction, diffused junction, or surface barrier; each type is made differently.
- point contact, a sharp pointed metal wire is pressed against the surface of a piece of germanium
- grown junction, as a boul of germanium is being pulled a quantity of the opposite dopant is added to the molten germanium, the boul is then sliced on opposite sides of the junction and diced into individual diodes
- alloy junction, a pellet of alloy containing the opposite dopant is placed on a piece of germanium and heated until it alloys into the surface of the germanium
- diffused junction, dopant of the opposite type of a piece of germanium is applied and heated to allow it to diffuse into the germanium
- surface barrier, a piece of germanium is carefully cleaned then metal is electroplated on a small spot on its surface
Note: these are significantly over simplified descriptions (other than the grown junction method only one device can be made at one time).
Note: all of these methods have also been used to make germanium transistors.
