Proximity Charge Sensing Electrodes for Semiconductor Detectors

Semiconductor-based radiation detectors are routinely used for the detection, imaging, and spectroscopy of x-rays, gamma rays, and charged particles in nuclear and medical physics, astrophysics and Homeland Security applications. Imaging with HPGe, Si or CdZTe is an increasing segment of radiation detection. Position sensitive implementations needed for imaging or tracking of radiation are most often realized by segmenting the electrical contacts in one or two dimensions. In order to achieve sufficient position resolution, many segments have to be implemented which is associated with complex fabrication processes to obtain a reliable and high-resolution detector and a complex and costly readout scheme to process the signals from each segment. The yield in the fabrication as well the reliability of operation, and the performance of high-energy and position resolution and large-volume semiconductors suffer due to these complexities. We propose to develop and demonstrate an alternative approach to obtain a position-sensitive detection of radiation, which is significantly easier to realize and provides excellent position resolution, reliability, and superior flexibility in adjusting segmentation and readout schemes according to experiment-specific requirements. The proposed approach of employing close-proximity electrodes to obtain energies and positions of radiation interaction will enable a significantly simpler detector fabrication process and readout configuration. It will provide the ability to adjust the resolution according to experimental requirements without re-fabricating the detector. In addition, close proximity electrodes can be used to measure specific charge losses due to charge collection on non-contact surfaces. Such processes are observed in semiconductor detectors due to imperfect surfaces and passivation techniques. Employing proximity electrodes close to these non-contact surfaces will allow us to observe these events which deteriorate the performance of the detector. These events can then be further processed to improve the response of the detector. Another major benefit of the proximity sensor approach is that charge appears and is fully integrated on all electrodes, dispensing with the need for computationally expensive spectator signals. Commercial Applications and Other Benefits: If this concept can be successfully demonstrated for imaging as well as particle tracking applications, we envision developing a marketable product available for commercial applications, basic and applied research, and for several branches of the federal government. Estimates: Biomedical research field is large in instrumentation ( & gt$100M), nuclear security is medium ( & gt$10M), Research demands in imaging is medium ( & gt$10M)