Electron tube comprising a semiconductor cathode

An electron tube comprising a cathode, said cathode comprising a semiconductor device for generating electrons, said device having a semiconductor body with a first structure adjacent to a main surface in the semiconductor body, in which first structure, electrons to be emitted from the semiconductor body at the location of an emissive surface region can be generated by applying suitable voltages, and means for influencing the electrons, the semiconductor body comprising an electrode having an interconnecting portion, characterized in that said semiconductor body comprises adjacent to its main surface, below said electrode or its interconnecting portion, a second structure having a first surface region of a first conductivity type which is at least partly surrounded by a second surface region which is of a second, opposite conductivity type or is substantially intrinsic.