second conductivity type opposite to the first conductivity type and a source for generating a majority carrier current in the semiconductor layer between the two control regions the majority current being associated with an electrical field the detection regions surround the control regions thereby forming at least two taps the device is configured for backside illumination and further comprises a well of the first conductivity type between the two detection regions for insulating the detection regions the well comprises pixel circuitry elements application_number US 201515321376 A description the invention will be explained with reference to p type epitaxial layer and substrate but the present invention includes within its scope a complementary device whereby p and n regions become n and p regions respectively a skilled person can make such modification without departing from the spirit of the invention it should also be understood that the terms n p n p p u2212 and p u2212 u2212 n well p well deep n well and deep p well are well known by the one skilled in the art the terms n p n p p u2212 and p u2212 u2212 refer to ranges of doping levels in semiconductor materials well known by the one skilled in the art the terms n and p refer to n doped and p doped regions usually arsenic and boron doped regions respectively n p refer to highly doped shallow contact regions for nwell and pwell respectively p u2212 refers to lowly doped p type region such as a pwell and p u2212 u2212 refers to very lowly.