An apparatus and method for generating electrical power from the decay process of a radioactive material is disclosed, wherein a volume of radioactive material and a junction region are enclosed in a cell. The junction region is formed by appropriate construction of a number of p-type and n-type dopant sites. At least a portion of one of the junction regions is disposed within a porous region having an aspect ratio of greater than about 20:1, and disposed at an angle of greater than about 55 measured relative to the surface area in which it is formed. The dimensions and shapes of the macroporous regions and the improved junction region surface area available for collecting charged particles emitted during a radioactive decay series permit an improved current to be derived from the apparatus than would otherwise be expected given its external dimensions.