SBIR Phase I: New Thin N+ Contacts for Germanium Detectors

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This Small Business Innovation Research Phase I project will perform an in-depth investigation of the phosphorus implantation and the pulsed excimer laser annealing steps in order to make this approach a commercially viable process for producing thin n+ contacts on large HPGe detectors. High purity germanium (HPGe) detectors are the most widely used devices for high resolution X-ray and y-ray spectroscopy, and these detectors are currently used in diverse applications such as nuclear physics, environmental monitoring, high energy physics experimentation, materials science studies, geophysical exploration, and y-ray astronomy. One of the long standing problems in the germanium technology is the lack of a thin n+-type contact, which prevents fabrication of detectors with high detection efficiency for low energy X-rays from p-type germanium crystals. It is important to solve this problem because p-type material is generally cheaper than n-type material and is more readily available in larger volumes. Also, p-type detectors have better charge collection properties in close end coaxial structures than n-type detectors. Recently, this firm has successfully produced thin n+-type contact on HPGe detectors by implanting phosphorus in germanium, and then using pulsed laser annealing to remove implantation damage. Successful fabrication of the proposed contacts would increase the energy range over which p-type germanium detectors can be used and would also allow fabrication of complex detector designs such as monolithic arrays. Thus the HPGe detectors with our new n+ contacts can be used in nuclear physics, astronomy, environmental monitoring, synchrotron studies, nuclear safeguards and verification, and geophysical exploration.