Preparation of silicon avalanche photodiodes by a planar method in epitaxial PP+ silicon slices limited charge collection to carriers generated in or close to the depletion region. Reducing the effective size of the zero-field absorption region surrounding the depletion region by this method, resulted in the output signal current of the device reproducing the input light pulse shape, within 15 ns. When illuminated with monochromatic radiation, the shot noise of a detector prepared in epitaxial material was less than that observed with a device fabricated in homogeneous material, due to the reduced signal current.