The buried well and the active region form a clamping diode which positions a breakdown avalanche region between the buried well and the first terminal.

Electrons may be emitted by the photoemissive material in response to the provision of said photons, said electrons causing avalanche breakdown of the counter gas, indicating satisfactory operation of the radiation detector.

A switch using an improved method of optically-triggered avalanche breakdown which can produce pulses of 100 picoseconds duration that can deliver five kilovolts into 50 ohms using a standard laser diode.

By providing an optimized doping profile for the buried layer region, it is ensured that avalanche breakdown occurs at the buried layer region/body region.

With the body reverse biased, the electric field can be modulated to switch the structure (100) between a stable state and a current-conducting state in which an avalanche breakdown occurs in the intermediate region (114).

A semiconductor block (11) has electrodes coupled on opposing sides (11e, 11f) and a high voltage (V or V(t)) is applied across the electrodes which is less than the voltage required for avalanche breakdown.

Thanks to hard control technology, uniform switching increases the safe operation of the IGCT to the limits limited by avalanche breakdown, i.e. up to the physical capabilities of silicon.