Properties of a Free, Steadily Travelling Electrical Domain in GaAs

Experiments are described on the travelling domains of high electric field which can exist in n-type GaAs. A brief discussion of the appearance of stationary domains near the cathode and of the nucleation and transient behaviour of travelling domains is given, but the main topic is the steady-state behaviour of travelling domains. Measurements are reported on the dependence of domain velocity, and of the voltage drop across the domain, on the field E
∞
existing outside the domain. It is found that the velocity increases with E
∞
, but the voltage decreases. The resulting negative resistance is seen to have important consequences for the stability of the domain in real specimens.