Diode construction follows a few very basic guidelines. In its simplest form, electricity moves into an anode through a semiconductor and out through a cathode. Due to the construction of the diode itself, electricity is unable to move back through the structure, which makes an average diode one way. While there are many versions of diodes, most of them are small variations on this base model.
When power flows through a diode, it can only go one way. This is typically from the anode to the cathode and out, but not always. In any situation where the device takes in power to operate, this is how the device functions. If the item is generating power, then the flow goes the other way. This second case is unusual and leads many people to believe that standard diodes are always unidirectional, a common misconception in diode construction.
In a normal situation and with a standard diode construction, the first area voltage would encounter would be the anode. This is a metallic connector, often made of zinc, on the outside of the diode. It attracts positively-charged anions and draws voltage into it.
Inside the diode, the current runs into a semiconductive material. This stage of diode construction typically uses silicon or germanium, but other materials are occasionally used as well. The semiconductor is comprised of two zones that have each been doped. Doping is a method of adding additional material to a semiconductor in order to change its properties.
The first area is called a p-type semiconductor. This area was doped with a metallic substance like boron or aluminum. This gives the area a slightly positive charge and helps pull electricity from the anode.
The second area of the semiconductor is the n-type. This section may be doped with a wide range of metals, mostly depending on what the base semiconductor is made of. Two of the more common dopants for an n-type are phosphorus and arsenic. These metals give the semiconductor a slight negative charge.
There is a gap in between the p-type and the n-type semiconductors, creating one of the main variances in diode construction. This zone may contain a small physical gap, secondary systems like those in a light emitting diode or simply materials that change the way the diode functions. A common additional material is a non-doped layer of the base semiconductor, called an intrinsic layer. This is the makeup of the PiN diode.
The last portion of diode construction is the cathode. This connector is the match for the anode. A cathode is metallic, often copper, and it draws in negatively-charged cations. This moves power out of the diode and into the attached system.