Photo-sensitive device including layers of different conductivity types

Claim 1

A PHOTO-SENSITIVE DEVICE SELECTIVELY RESPONSIVE TO RADIATION HAVING A WAVE-LENGTH LONGER THAN AT LEAST PART OF THE VISIBLE RANGE COMPRISING A SUPPORT, A PHOTO-SENSITIVE LAYER ON SAID SUPPORT, SAID LAYER HAVING IN THE DIRECTION OF THICKNESS ZONES HAVING DIFFERENT ELECTRICAL CONDUCTIVITIES SUPERPOSED OVER ONE ANOTHER, AND MEANS TO SUPPLY AN ELECTRICAL CURRENT ON ONE SIDE OF SAID LAYER, SAID LAYER HAVING A FIRST ZONE OF A THICKNESS OF THE ORDER OF MICRONS AND OF AN INTRINSIC CONDUCTIVITY TYPE, AND A SECOND ADJACENT ZONE OF THE SAME MATERIAL AS THAT OF SAID FIRST ZONE BUT OF P-TYPE CONDUCTIVITY TYPE AND HAVING A CONDUCTIVITY SUBSTANTIALLY GREATER THAN THAT OF SAID FIRST ZONE WHEREBY SAID SECOND ZONE SERVES AS AN ELECTRODE FOR SAID FIRST ZONE, SAID SECOND ZONE HAVING A THICKNESS AT WHICH WAVE-LENGTHS SHORTER THAN AT LEAST PART OF THE VISIBLE RANGE ARE ABSORBED WHEREBY SAID LATTER ZONE SERVES AS AN OPTICAL FILTER WHEN SAID FIRST ZONE IS IRRADIATED THROUGH SAID SECOND ZONE.