Development of a Germanium Avalanche-Type Semiconductor Nuclear Particle Detector and Discussion of Avalanche Detector Arrays

Research on avalanche or high field types of semiconductor detectors has increased within the past two years, impelled, in part, by the great interest in the photo-detection field. We have concentrated on the surface contoured-deep junction diffusion approach while other investigators generally have pursued the use of a planar-oxide passivated-shallow diffused structures. Reported herein are results of studies of deep (25-50 microns) diffused N + P type germanium avalanche detector structures. A relatively simple closed "box" type process has been developed for diffusion of arsenic and antimony into germanium. Results of detector characteristics and multiplication measurements are presented. A concept for arrays of avalanche detectors (particularly to this time of silicon) is discussed. Results, in terms of uniformity of avalanche breakdown and gain, of a number of arrays fabricated are indicated together with the insight that this work has given to what appears to be the limitation of avalanche devices - resistivity inhomogeneities in the starting semiconductor crystal. These inhomogeneities take the form, at least in crystal produced by the floating zone technique, of micro-striations. Our example of a developed array is shown - a large area quadrature instrument that, it is hoped, will find use in detection of plutonium in wounds by detecting its 17keV X-ray emanation.