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Abstract

A photodiode structure for the detection of radiation comprises a semiconductor base layer of p-type conductivity with a high doping density, an epitaxial layer of p-type conductivity with a relatively low doping density, areas of n-type conductivity and oxide layers covering the areas of n-type conductivity. The oxide layers comprise doping impurities of the same conductivity type as the areas below them. The doping density in the areas of n-type conductivity decrease towards the junction with the epitaxial layer. Due to this decrease in doping density, an electric field gradient is produced which guides the charge carriers to the junction. The generation of a field gradient and the creation of a surface charge result in an improved quantum efficiency. The invention is preferably used in photodiode arrays. Due to the gradient in doping density in the epitaxial layer, charge carriers are reflected at the interface between the layers and so that cross talk between adjacent diodes in a photodiode array is reduced. According to a preferred method for manufacturing a photodiode structure of the invention, the doping of the photodiode structures is performed by ion implantation.

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First Claim