Optically-sensitive semiconductor devices

Claim 1

A semiconductor device comprising a semiconductor body having first and second regions of a first conductivity type, electrode connection to said first and second region,and an optically-sensitive barrier region located between the first and second regions at a given depth in said body to control current flow along a current path between said electrode connections to the first and second regions, which barrier region contains a net impurity concentration of the second, opposite conductivity type and is at least substantially fully depleted of free charge carriers by depletion layers formed with the first and second regions at zero bias and in the absence of incident light, optically transmissive means for permitting incident light to generate charge carriers in the vicinity of the barrier region to reduce the barrier height of the barrier region, and closely-spaced field-relief regions, the barrier region being divided laterally into plural areas located between said closely-spaced field-relief regions, which field-relief regions protrude to a greater depth in the body than that of the barrier region, and, in the absence of incident light and with reverse bias of the barrier region, the device having a high voltage blocking characteristic due to the field-relief regions being spaced such that depletion layers extending in the second region from neighboring field-relief regions merge together under reverse-bias of the barrier region to reduce the electrostatic field below the barrier region, the device being switchable between the high voltage blocking state and a current conducting state by means of incident light.