High resolution amorphous silicon radiation detectors
First Claim
1. Detector elements in an array of such elements for high energy particles or photons that move through the detector, with each detector element comprising:
- first and second electrodes lying in approximately parallel planes and being spaced apart from each other;
an amorphous film including a mixture of at least 60 percent Si;
H and at most 40 percent Ge;
H, deposited approximately in a plane positioned between and adjacent to the first and second electrodes, the film having at least three contiguous regions, a first region of first electrical conductivity type adjacent to the first electrode, a second region of second electrical conductivity type opposite to the first conductivity type adjacent to the second electrode, and an intrinsic region positioned between the first and second regions where the first and second regions have smaller thickness than the thickness of the intrinsic region;
bias means, electrically connected to the first and second electrodes, for impressing an electrical field between the first and second electrodes; and
readout means, positioned adjacent to the first and second electrodes and electrically connected thereto, for selectively reading the voltage or current developed across the amorphous film.
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Abstract
A radiation detector employing amorphous Si:H cells in an array with each detector cell having at least three contiguous layers (n type, intrinsic, p type), positioned between two electrodes to which a bias voltage is applied. An energy conversion layer atop the silicon cells intercepts incident radiation and converts radiation energy to light energy of a wavelength to which the silicon cells are responsive. A read-out device, positioned proximate to each detector element in an array allows each such element to be interrogated independently to determine whether radiation has been detected in that cell. The energy conversion material may be a layer of luminescent material having a columnar structure. In one embodiment a column of luminescent material detects the passage therethrough of radiation to be detected and directs a light beam signal to an adjacent a-Si:H film so that detection may be confined to one or more such cells in the array. One or both electrodes may have a comb structure, and the teeth of each electrode comb may be interdigitated for capacitance reduction. The amorphous Si:H film may be replaced by an amorphous Si:Ge:H film in which up to 40 percent of the amorphous material is Ge. Two dimensional arrays may be used in X-ray imaging, CT scanning, crystallography, high energy physics beam tracking, nuclear medicine cameras and autoradiography.
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Citations
15 Claims
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1. Detector elements in an array of such elements for high energy particles or photons that move through the detector, with each detector element comprising:
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first and second electrodes lying in approximately parallel planes and being spaced apart from each other; an amorphous film including a mixture of at least 60 percent Si;
H and at most 40 percent Ge;
H, deposited approximately in a plane positioned between and adjacent to the first and second electrodes, the film having at least three contiguous regions, a first region of first electrical conductivity type adjacent to the first electrode, a second region of second electrical conductivity type opposite to the first conductivity type adjacent to the second electrode, and an intrinsic region positioned between the first and second regions where the first and second regions have smaller thickness than the thickness of the intrinsic region;bias means, electrically connected to the first and second electrodes, for impressing an electrical field between the first and second electrodes; and readout means, positioned adjacent to the first and second electrodes and electrically connected thereto, for selectively reading the voltage or current developed across the amorphous film. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. Particle detector elements in an array of such elements, for detecting the presence of high energy particles that move through the detector element array, with each detector element comprising:
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first and second electrodes lying in approximately parallel planes spaced apart from each other; an amorphous Si;
H film deposited adjacent to each of the first and second electrodes, the film having at least seven contiguous regions, a first highly doped region of first conductivity type positioned adjacent to the first electrode, a second highly doped region of second conductivity type opposite to the first conductivity type and positioned adjacent to the second electrode, a third region of first conductivity type positioned between and spaced apart from the first and second regions, a fourth region of second conductivity type positioned between and spaced apart from the second and third regions, a fifth intrinsic conductivity region positioned between the first and third regions, a sixth intrinsic conductivity region positioned between the second and fourth regions, and a seventh intrinsic conductivity region positioned between the third and fourth regions, where the intrinsic regions have a low charged particle trap density and the first, second, third and fourth regions have smaller thicknesses than the thicknesses of the intrinsic regions;bias means, electrically connected to the first and second electrodes, for impressing an electrical field between these two electrodes; a layer of luminescent material, positioned adjacent to the Si;
H film, the luminescent material having a characteristic wavelength of light emission from an excited state that is no more than 0.8 μ
m, and the luminescent material layer having a plurality of columns with longitudinal axes of the columns being oriented approximately perpendicular to an adjacent surface of the Si;
H film; andreadout means, positioned adjacent to the first and second electrodes and electrically connected to these two electrodes, for selectively reading the voltage or current developed across the Si;
H film in response to passage of high energy particles through the detector elements. - View Dependent Claims (11, 12, 13, 14, 15)
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Specification