Abstract: An improved semiconductor device, particularly a gate controlled switch is provided by optimally fitting an involute spiral cathode-gate structure into a substantially square device. 4N cathode-gate branches radiate from a central gate portion and intersect the perimeter of the square device region at predetermined locations, N per side, where N is an integer. Four of the branches tangentially intercept the square perimeter at a distance R from a centerline where R is the radius of the central gate portion. The origin of the branches is angularly displaced from the line connecting the die center to the tangential intercept point by (L/R)- arctan (L/R) radians where L is half the edge length of the square device region. Improved thermal performance is obtained by thermally coupling the cathode heat spreader to the gate as well as cathode portions of the device.

Abstract: Light-controlled transistor, including a semiconductor body having a surface including a given area intended for the incidence of light, a collector zone, and a base zone and an emitter zone each having a smaller area than the semiconductor body, each of the base and collector zones having at least a part thereof emerging to the surface, a pn-junction disposed between the base and emitter zones and a pn-junction disposed between the base and collector zones, each of the pn-junctions emerging to the surface at the given area, and at least one auxiliary electrode disposed on and electrically insulated from the surface, the auxiliary electrode covering at least the parts of the base and collector zones emerging to the surface, the auxiliary electrode being connectible to an auxiliary voltage having the same polarity as the emitter bias.