3. Connection terminals

The above developments apply, strictly speaking, only to laterally undefined flat junctions. In reality, edge effects can reduce the voltage withstand at the junction periphery to values much lower than the theoretical breakdown voltage. In particular, the electric field strength is increased at junction curvatures, precipitating localized breakdowns, and the crystal surface itself offers the possibility of the junction being bypassed by the surrounding medium.

To fully exploit the blocking capacity of a junction, it is therefore essential to use specific measures to reduce the electric field in critical areas. These measures are of two types:

• mesa" terminals, which are now rarely used except for high-power, high-voltage devices;

• planar" terminations, which are becoming increasingly...