Low capacitance x-ray radiation detector

Abstract

A low capacitance radiation detector comprises a monocrystalline silicon substrate heavily doped to N type conductivity with a more lightly doped N type conductivity epitaxial layer formed on the substrate. A plurality of heavily doped N type upper surface layer segments are formed in the epitaxial layer. A patterned region of the epitaxial layer, heavily doped to P type conductivity and in the shape of parallel stripes joined at each end by a respective stripe perpendicular to the parallel stripes, is formed in the epitaxial layer and situated between adjacent ones of the upper surface layer segments, with each stripe extending into the epitaxial layer deeper than, and separated from, the upper surface layer segments so as to form a minority charge carrier-collecting PN junction with the epitaxial layer. The parallel stripes are spaced apart from each other by a distance smaller than or comparable to the minority charge carrier recombination diffusion length for the epitaxial layer, and the epitaxial layer thickness is smaller than or comparable to the minority charge carrier recombination diffusion length. In a second embodiment, the epitaxial layer has beveled edges and the heavily doped N type upper surface layer segments formed in the epitaxial layer extend over the beveled edges.