A light sensor having a light conversion element between first and second electrodes is disclosed. The light conversion element includes a body of semiconductor material having first and second surfaces. The body of semiconductor material is of a first conductivity type and has doping elements in a concentration gradient that creates a first electrostatic field having a magnitude that varies monotonically from the first surface to the second surface. A bias circuit applies a variable potential between the first and second electrodes to create a second electrostatic field having a direction opposite to that of the first electrostatic field and a magnitude determined by the potential. One of the electrodes is transparent to light in a predetermined band of wavelengths. The body of semiconductor material can include an epitaxial body having a monotonically increasing concentration of a doping element as a function of the distance from one the surfaces.