AbstractThe production of Gunn diodes with a planar architecture provides the ability to easily specify contact separation, and hence device transit region length, through lithographic processing. Beyond manufacturing and integration benefits, this also enables the production of devices whose contacts are intentionally and controllably non‐uniform over their width. Through such shaping of the contacts, the morphology of the Gunn domains may also be controlled. This has demonstrated potential for improving device performance, both with regard to operating frequency and oscillation amplitude, by at least ∼30% and ∼100% respectively. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)