A study is made of Gunn‐diode behavior for various lengths and doping densities. Emphasis is placed mainly on very short over‐critically doped diodes. Such diodes, when biased above threshold, are stable with a high‐field anode layer. The transition to this stable state occurs with or without the intermediary formation of Gunn domains. The relations between the various types of diode behavior and the nature of the small‐signal instability, convective or absolute, in the material is examined.