Previous Seed Grant Winners

Where are they now?

In 2006, Serge Kuryi of the Department of Electrical and Computer Engineering was awarded a seed grant for his proposal Semiconductor Scintillator: Detector of High-Energy Radiation.

The seed grant helped establish the collaboration with BNL which was essential for the success of the proposal to the Department of Homeland Security, awarded $4 million for a period of 5 years beginning in 2007.

The team is developing a detector of nuclear radiation against the terrorist threat. An essential issue is to be able to tell the bad isotopes from irrelevant ones, otherwise the detection effort would be doomed by false alarms. The team's detector provides a unique approach to isotope discrimination and furthermore enables the determination of the direction to source of radiation. This goes to the heart of the homeland security needs.

This research program is concerned with a feasibility study, demonstration and assessment of advantages of a recently proposed new scintillation-type multilayer radiation detector. In this detector high-energy radiation produces electron-hole pairs in a direct-gap semiconductor material that subsequently recombine producing infrared light to be registered by integrated photo-detectors located on the surface of each semiconductor layer. The key issue is how to make the semiconductor material essentially transparent to its own infrared light, so that photons generated deep inside the semiconductor layer reach its surface with little attenuation. The proposed novel way to accomplish this is based on doping the semiconductor with shallow donors to produce the Burstein shift between emission and absorption spectra in heavily doped direct-gap semiconductors.

From the standpoint of DNDO applications, the most innovative feature of the proposed detector is that it enables three-dimensional (3D) integration of standard semiconductor wafers, each provided with a pixellated epitaxial photosensitive layer on its surface as well as amplifying and analog-to-digital electronic circuits. The detector stack can accommodate virtually any absorption length of high-energy radiation, without any loss in scintillator yield and speed of response. The information about each ionizing radiation event, comprising simultaneous response from several 3D pixels, is converted to digital form, suitable for rapid analysis. The 3D pixellation of the scintillator response enables a novel scheme for high-resolution angular discrimination. The angular information resides in the directionality of Compton scattering cross-section. It is only owing to the 3D pixellation that this information can be extracted.
Simultaneous signal registration by several pixels in the stack allows a direct measurement of the incident particle energy complementary to the conventional statistical spectroscopy and free from complications associated with Compton escape processes. This goes to the heart of the homeland security needs, where accurate spectral characterization is of the essence to avoid "false alarms". The integrated device, functionally a 3D scintillator array of linear dimensions limited only by the size of a semiconductor wafer, will have the energy resolution similar to best semiconductor diodes.


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