Charge coupled devices employing nonuniform concentrations of immobile charge along the information channel

Claim 1

In a charge coupled device for storage and serial transfer in a predetermined direction of information represented by varying amounts of mobile charge carriers coupled to localized potential wells and wherein the device includes a semiconductive storage medium whose bulk is of a first conductivity type and which has a major surface, an insulating layer disposed over and contiguous with said surface, and a plurality of spaced, localized field plate electrodes disposed successively over said layer so as to form a path along said predetermined direction, the improvement being that along said path and beneath each said electrode there is disposed a localized surface zone of about 2000 Angstroms depth of the same conductivity type but higher impurity concentration than the bulk, and limited in lateral extent so as to lie essentially entirely under a limited portion of said electrode and disposed asymmetrically toward the input end with respect to the lateral geometric center of said electrode, the difference in impurity concentrations being sufficient that in response to successive application of operating voltages to the electrodes there are produced under the electrodes localized potential wells having a lower depth in the portions underlying the localized zones, whereby there is favored the transfer of mobile charge carriers in the predetermined direction along said path.