Radiant energy – Invisible radiant energy responsive electric signalling – Semiconductor system
Patent
1997-06-17
1999-04-06
Hannaher, Constantine
Radiant energy
Invisible radiant energy responsive electric signalling
Semiconductor system
25037013, H01L 21477
Patent
active
058922270
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a radiation detection system containing a continuous film of a wide band gap semiconductor, radiation-detecting, polycrystalline material and processes for the preparation of said continuous film for use therein, as well as to an image receptor for an imaging system, comprising a thin, continuous film of a wide band gap, semiconductor radiation-detecting material.
Mercuric iodide (HgI.sub.2), cadmium telluride (CdTe), cadmium zinc telluride (CdZnTe), and lead iodide (PbI.sub.2) single crystals are well-known, wide band gap semiconductor X-ray and gamma radiation detectors which operate at room temperature. The problem is that the production of high quality, single crystals is very expensive; wherever it is necessary to cover large areas with relatively small area crystals, it is necessary to arrange them in the form of mosaics, which in turn increases the cost of the detection system. The cost of crystal growth of both high melting point crystals, such as CdTe and CdZnTe (see Table 1 hereinbelow), and of low melting point crystals such as PbI.sub.2 is high. Therefore, only crystals of a very small size (.apprxeq.10 mm.sup.2) and thickness (.apprxeq.100 .mu.m) have been produced, which decreases the possibility of using them in mosaics for very large-area detection systems.
The state of the art of PbI.sub.2 single crystal technology in 1995 is such that until the present time, these very small crystals have been fabricated only into low energy detectors.
The semiconductor having the lowest melting point, HgI.sub.2, has an additional problem: HgI.sub.2 single crystals are produced from the vapor phase, and growth of large crystals, from which 5.times.5 cm.sup.2 detector plates can be sliced, may require a duration of approximately 3 months for the growth process. In addition, the sawing and polishing operation involves a 60% loss of material.
All of the above-mentioned factors contribute to the high cost of these crystals and the detectors fabricated therefrom.
The present invention provides for the production of large, textured plates of any desired size and thickness, produced from different polycrystalline semiconductors, as will be described and exemplified further below.
The present invention also enables the fabrication of polycrystalline, continuous films for radiation detection systems. The term "continuous films" as used herein is intended to denote that no short circuits between upper and lower electrodes are possible.
More particularly, the present invention provides a radiation detection system, comprising a continuous film of a wide band gap semiconductor, radiation-detecting, polycrystalline material formed from a multiplicity of crystalline grains, wherein said grains are sintered together to form a single, coherent, continuous film.
In preferred embodiments of the present invention, said continuous film is selected from the group consisting of mercuric iodide, cadmium telluride, cadmium zinc telluride, and lead iodide films.
Thus, according to the present invention, there are provided large-area, coherent, continuous semiconductor films, preferably having an area of between 10.sup.2 cm.sup.2 and 10.sup.4 cm.sup.2, and a thickness of between about 1-500 .mu.m, which can be partially or fully textured (50-100%), with grain size from 1 .mu.m to 5 mm.
The present invention also provides processes for the preparation of these films. More specifically, the present invention provides a process for the preparation of a continuous film of a wide gap semiconductor, radiation-detecting, polycrystalline material, comprising (a) preparing grains of polycrystalline powder material having a purity of at least 99.9999 (6N) %; (b) depositing said granular material on a conductive substrate; and (c) sintering said grains of polycrystalline material together, to form a single, coherent, continuous film.
In preferred embodiments of said process, said purified grains of polycrystalline powder material are prepared by evaporation in a vacuum medium at a temperature of about 100.deg
REFERENCES:
patent: 3754965 (1973-08-01), Mooney
patent: 3812361 (1974-05-01), Prag et al.
patent: 4048502 (1977-09-01), Guddent et al.
patent: 4243885 (1981-01-01), Agouridis et al.
patent: 4331873 (1982-05-01), Miller et al.
patent: 4894542 (1990-01-01), Schneider
patent: 5047645 (1991-09-01), Gundjian et al.
patent: 5072122 (1991-12-01), Jiang et al.
patent: 5079426 (1992-01-01), Antonuk et al.
patent: 5245191 (1993-09-01), Barber et al.
James et al., "Defects in Silver-Doped Merwric Iodide Crystals . . . " in B. James et al., ed. Semiconductors For Room-Temperature Radiation Detector Applications, Materials Research Society Symposium Proceedings, vol. 302, pp. 103-114 (Apr. 1993).
Gerrish, "Electronic Characterization of Mercuric Iodide Gamma Ray Spectrometers" in R.B. James et al. ed., Semiconductors For Room-Temperature Radiation Detector Applications, Materials Research Society Symposium Proceedings, vol. 302, pp. 129-140 (Apr. 1993).
Schieber et al. "Physical-Chemical Consideration for Semiconductor Room-Temperature Radiation Detectors" in R.B. James et al. ed., Semiconductors For Room-Temperature Radiation Detector Applications, Materials Research Society Symposium Proceedings, vol. 302, pp. 347-355 (Apr. 1993).
Harel Ze'ev
Nissenbaum Jacob Baruch
Schieber Michael Misho
Hannaher Constantine
Target Technologies Israel, Ltd.
Yissum Research Development Company of the Hebrew University of
LandOfFree
Radiation detection system and processes for preparing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Radiation detection system and processes for preparing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radiation detection system and processes for preparing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1373601