Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
1994-01-10
2001-02-20
Monin, Jr., Donald L. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C257S028000
Reexamination Certificate
active
06191465
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the detection of the presence and extent of radiated atomic particles that are in rays of the Gamma, Alpha and X ray type and in particular to a radiation detector made of solid state materials and capable of operation in the 300 degree Kevin or room temperature range.
BACKGROUND AND RELATION TO THE PRIOR ART
In the detection, or sensing of the presence and extent of atomic particles, it has been the practice in the art to use solid state semiconductor structures that can produce a signal resulting from hole-electron pairs that result, when the atomic particles in passing through the semiconductor, engage in primary or secondary collisions. The hole-electron pairs are sensed by sweeping them into external contacts before they can recombine or be trapped.
There are several characteristics of radiation detection that result in special structural features in these devices. The propelling energy of the particles may be so great that relatively long distances may be required for absorbtion. The electron-hole pairs produced by an atomic particle collision must be distinguishable from any other carriers present due to any crystal imperfection or thermal carrier generation. Fields employed in sweeping the collision generated carriers into external contacts must be high due to the long absorbtion distances. The resulting charge is converted into a pulse, with the narrower the pulse, the better the time resolution and therefore a higher counting rate can be achieved. The total amount of charge in the pulse should be proportional to the energy of the exciting radiation. Thus, events that prevent extracting all of the charge within the pulse will degrade energy resolution.
In efforts to accommodate the needed features, the semiconductor structure generally has a large region, of intrinsic or semiinsulating conductivity, that is as depleted of carriers from any source other than an atomic particle collision, as the state of the technology will provide. In some cases several technological compromises are made.
In the case of the monoatomic semiconductors such as germanium and silicon since each has a relatively small band gap which produces more thermally generated carriers and limits the magnitude of any field applied across the absorbtion region for sweeping the collision produced carriers into the contacts, low, usually 77 degrees kelvin, liquid nitrogen temperatures are used to reduce thermally generated carriers. A requirement for such a low temperature in operation has a limiting effect on the places the device can be used. Recent efforts in the art have been in the use of the wider bandgap semiconductor material gallium arsenide in an effort to produce a radiation detector structure that can be operated in the 300 degree Kelvin or room temperature range. A serious limitation has been difficulty in producing thick enough and more perfectly crystalline absorbtion regions.
In an article by Alexiev et al. published in Nuclear Instruments & Methods in Physics Research A 317 (1992) Pages 111-115 there is reported the construction of room temperature radiation detectors of gallium arsenide wherein, using liquid phase epitaxial growth, 200 micro meter thick absorbtion regions are formed. The radiation enters the absorbtion region through a surface barrier rectifying contact.
Further efforts using the material GaAs are reported by Mc Gregor et al. published in Nuclear Instruments & Methods in Physics Research A 317 (1992) Pages 487-492, wherein detectors, using a Schottky barrier contact, and having absorbtion regions of increasing thicknesses of up to 250 micrometers, that were cut from pulled crystals, were found to exhibit decreasing resolution, as the thickness increased.
A need is developing in the radiation detector art for the ability to provide detector structures that operate at 300 degrees Kelvin and which have substantially greater thickness absorbtion regions without degrading energy resolution.
SUMMARY OF THE INVENTION
The invention provides a structural and processing principle in radiation detection in which, the long absorbtion distance required for atomic particle detection in rays such as X rays, Alpha rays and Gamma rays, is divided into a plurality of semiconductor absorbtion members with a sweeping field or bias impressed across the thickness of each. The absorption members are of high band gap and high density semiconductor material and are compatible with high quality growth capabilities. The principle of the invention is structurally implemented for high energy rays by providing, a stack of intrinsic or semiinsulating conductivity absorbtion layers that are relatively wide, about 100 micrometers or greater, each of high density, high band gap, semiconductor material. Each absorbtion member having on each side, a relatively thin, about 0.1 to 20 micrometers, thick conducting layer with external contacts.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a perspective illustration of the detection portion of the solid state radiation detector of the invention.
FIG. 2
is a perspective view of a portion of the absorbtion and contacting layers illustrating crystal growth and contact features.
FIG. 3
is an electrical schematic drawing of the biasing, the connections and the energy resolution conversion of the invention.
FIG. 4
is a depiction of the type of signal observed by the detector of the invention when detecting a gamma ray collision event.
FIG. 5
is a perspective view of an embodiment of the invention employed as a position sensitive detector.
REFERENCES:
patent: 4486765 (1984-12-01), Capasso
patent: 4751201 (1988-06-01), Nottenburg et al.
patent: 4785186 (1988-11-01), Street et al.
patent: 4839714 (1989-06-01), Doehler et al.
patent: 4891521 (1990-01-01), Danos
patent: 4917474 (1990-04-01), Yamazaki et al.
patent: 4947223 (1990-08-01), Biefeld et al.
Alexiev et al, “High Purity Liquid Phase Epitaxial Gallium Arsenide Nuclear Radiation Detector,” Nuclear Instruments and Methods in Physics Research, A317(1992), pp. 111-115.
McGregor et al, “Bulk GaAs Room Temperature Radiation Detectors”, Nuclear Instruments and Methods in Physics Research, A322, (1992), pp. 487-492.
Ploog et al, “Simultaneous Modulation of Electron and Hole Conductivity in a New Periodic GaAs Doping Multilayer Structure”, App. Phys. Lett. 38(11) Jun. 1, 1981 pp. 870-873.
Grüter et al., “Deposition of High Quality GaAs Films at Fast Rates in the LP-CVD System,” Journal of Crystal Growth, 94(1989) pp. 607-612.
Ploog et al, “The Use of Si and Be Impurities for Novel Periodic Doping Structures in GaAs Grown by Molecular Beam Epitaxy”, Journal of the Electro Chemical Society, vol. 128, No. 2 pp. 400-410.
Döhler et al, “Tunable Absorbtion Coefficient in GaAs Doping Superlattices”, Physical Review B, vol. 25 No. 4, Feb. 15, 1982, pp. 2616-2626.
Wang et al, “Evaluation of HgI2Detectors for Lead Detection in Paint”, IEEE Transactions on Nuclear Science, vol. 40 No. 4, Aug. 1993 pp. 846-850.
Conti et al, “Use of the EGS4 Monte Carlo Code to Evaluate the Response of HgI2and CoTe Detectors for Photons in the Diagnostic Energy Range”, Nuclear Instruments and Methods in Physics Research, A322 (1992), pp. 591-595.
McGregor et al, “Development of Bulk GAAS Room Temperature Radiation Detectors”, IEEE Transactions on Nuclear Science, vol. 39 No. 5, Oct. 1992 pp. 1226-1236.
Hazlett et al, “Large, High Resolution CdTe Gamma Ray Sensors”, IEEE Transactions on Nuclear Science, vol. 33 No. 1 Feb. 1986 pp. 332-335.
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