Radial Gradient Coaxial Detectors

Germanium crystals with radial impurity gradients have been prepared by diffusing Li into p-type material and then extracting most of it at the surface to produce n-core crystals. The diffusion is designed to produce coaxial detectors which reach full depletion at the inner and outer radii simultaneously, thereby minimizing the leakage which is caused by electrical stress at the electrodes. The depletion voltage and leakage current of these crystals are measured by methods which do not require that they be sectioned to expose the junction. Preliminary measurements of detectors made from radial gradient crystals are also reported.