Ultra-sensitive photo-transistor device comprising wafer having high resistivity center region with opposite conductivity, diffused, low-resistivity, and translucent outer layers

Claim 1

A PHOTO-TRANSISTOR DEVICE, COMPRISING: A THIN WAFER OF SINGLE-CRYSTALLINE SILICON HAVING THE RESISTIVITY OF ABOUT 1000 TO 2000 OHM-CENTIMETERS AND HAVING A GIVEN CONDUCTIVITY TYPE; A PAIR OF LOW-RESISTIVITY DIFFUSED LAYERS IN OPPOSITE SURFACES OF SAID WAFER OF A CONDUCTIVITY TYPE OPPOSITE TO SAID GIVEN CONDUCTIVITY TYPE, SAID LAYERS BEING SUFFICIENTLY THIN TO LEAVE BETWEEN THEM A CENTRAL REGION OF SAID WAFER OF SAID GIVEN CONDUCTIVITY TYPE AND TO FORM A PAIR OF OPPOSED RECTIFYING BARRIERS AT THE TWO INTERFACES BETWEEN SAID CENTRAL REGION AND SAID PAIR OF LAYERS, AT LEAST ONE OF SAID LAYERS BEING OPEN TO ILLUMINATION FROM THE EXTERIOR OF SAID DEVICE AND TRANSMISSIVE OF SAID ILLUMINATION, THE SEMICONDUCTIVE MATERIAL OF SAID CENTRAL REGION HAVING A DIFFUSION LENGTH FOR MINORITY CARRIERS WHICH IS AT LEAST AS GREAT AS THE THICKNESS OF SAID CENTRAL REGION; AND A CONDUCTIVE CONTACT TO EACH OF SAID LAYERS.