Failure mechanisms in Gunn diodes

Observations on electrical properties of planar Gunn diodes and on failure mechanisms using Sn¿Ag and In¿Au contacts are reported. A conducting channel of Sn(In) is proved to be responsible for the final catastrophic failure. Excess heat is generated at the anode, where also the breakdown is observed to start. Mechanisms starting the breakdown (hole injection and combined ion drift and diffusion of impurities) are discussed.