Method of fabrication for mercury-based quaternary alloys of infrared sensitive materials
First Claim
1. A method for fabricating a variable bandgap infrared absorbing semiconductor material structure, comprising the steps of:
- forming a cadmium zinc telluride buffer layer on a substrate,forming on said buffer-layer, by epitaxial growth, alternating layers of mercury telluride, having the same lattice constant, and layers of cadmium zinc telluride wherein said buffer layer and said cadmium zinc telluride layers have a zinc mole fraction to produce a lattice constant substantially similar to the lattice constant of said mercury telluride layers, andannealing said structure to interdiffuse said mercury telluride layers and said cadmium zinc telluride layers to produce a homogeneous mercury cadmium zinc telluride alloy.
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Abstract
A variable bandgap infrared absorbing material, Hg1-x Cdx Te, is manufactured by use of the process termed MOCVD-IMP (Metalorganic Chemical Vapor Deposition-Interdifffused Multilayer Process). A substantial reduction in the dislocation defect density can be achieved through this method by use of CdZnTe layers which have a zinc mole fraction selected to produce a lattice constant which is substantially similar to the lattice constant of HgTe. After the multilayer pairs of HgTe and Cd0.944 Zn0.056 Te are produced by epitaxial growth, the structure is annealed to interdiffuse the alternating layers to produce a homogeneous alloy of mercury cadmium zinc telluride. The mole fraction x in Hg1-x (Cd0.944 Zn0.056)x Te can be varied to produce a structure responsive to multiple wavelength bands of infrared radiation, but without changing the lattice constant. The alloy composition is varied by changing the relative thicknesses of HgTe and Cd0.944 Zn0.056 Te. A similar structure can also be fabricated using HgTe and lattice matched CdTe1-y Sey. Thus, a multi-band infrared absorbing material structure can be fabricated which has reduced dislocation defects, and thereby produce detectors with improved performance.
49 Citations
31 Claims
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1. A method for fabricating a variable bandgap infrared absorbing semiconductor material structure, comprising the steps of:
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forming a cadmium zinc telluride buffer layer on a substrate, forming on said buffer-layer, by epitaxial growth, alternating layers of mercury telluride, having the same lattice constant, and layers of cadmium zinc telluride wherein said buffer layer and said cadmium zinc telluride layers have a zinc mole fraction to produce a lattice constant substantially similar to the lattice constant of said mercury telluride layers, and annealing said structure to interdiffuse said mercury telluride layers and said cadmium zinc telluride layers to produce a homogeneous mercury cadmium zinc telluride alloy. - View Dependent Claims (2, 3, 4)
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5. A method for fabricating a variable bandgap infrared absorbing semiconductor material structure, comprising the steps of:
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forming a cadmium telluride selenide buffer layer on a substrate, forming on said buffer layer, by epitaxial growth, alternating layers of mercury telluride, having the same lattice constant, and layers of cadmium telluride selenide wherein said buffer layer and said cadmium telluride selenide layers have a selenium mole fraction to produce a lattice constant substantially similar to the lattice constant of said mercury telluride layers, and annealing said structure to interdiffuse said mercury telluride layers and said cadmium telluride selenide layers to produce a homogeneous mercury cadmium telluride selenide alloy. - View Dependent Claims (6, 7, 8)
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9. A method for fabricating a variable bandgap infrared absorbing-semiconductor structure comprising:
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providing a substrate; and forming on the substrate from layers of cadmium zinc telluride and mercury telluride a homogenous alloy of the formula Hg1-x (Cd1-y Zny)x Te wherein y represents the mole fraction of zinc, and x represents the mole fraction of the cadmium and zinc, and wherein the variance in lattice constant is less than 0.1 percent between said layers of cadmium zinc telluride and the mercury telluride for the formation of the alloy. - View Dependent Claims (10, 11)
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12. A method of fabricating a variable bandgap infrared absorbing semiconductor material structure, comprising:
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(a) forming a layer of Cd1-y Zny Te on a substrate, wherein y represents the mole fraction of Zn such that the lattice constant of the cadmium zinc telluride is substantially similar to the lattice constant of the mercury telluride; (b) forming a layer of HgTe on the previously deposited layer of Cd1-y Zny Te; (c) repeating at least once, step (a); (d) repeating step (b) after each repetition of step (c) to create a number of alternating layers of Cd1-y Zny Te and HgTe; (e) annealing said layers to form a homogeneous alloy structure. - View Dependent Claims (13)
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14. A method of fabricating a variable bandgap infrared absorbing semiconductor material structure responsive to infrared radiation, comprising:
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(a) forming a buffer layer of Cd1-y Zny Te on a substrate, wherein y represents the mole fraction of Zn such that the lattice constant of the cadmium zinc telluride is substantially similar to the lattice constant of the mercury telluride; (b) forming a thin layer of HgTe on the previously deposited buffer layer; (c) forming a thin layer of Cd1-y Zny Te; (d) repeating steps (b) and (c) a number of times to create alternating layers of Cd1-y Zny Te and HgTe; (e) annealing the layers to form a homogeneous alloy structure.
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15. A method for forming a variable bandgap infrared absorbing semiconductor structure comprising:
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providing a substrate; and forming thereon a homogenous alloy of the formula (HgTe)1-x (CdTe1-z Sez)x wherein z represents the mole fraction of selenium and x represents the mole fraction of the cadmium telluride selenide. - View Dependent Claims (16, 17, 18)
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19. A method of forming two or more lattice matched quaternary alloys of infrared absorbing semiconductor comprising:
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(a) forming a first region of quaternary alloy by (i) forming a first layer of a composition of the formula Cd1-y Zny Te wherein y is the mole fraction of zinc having a first thickness and such that the lattice constant of the cadmium zinc telluride is substantially similar to the lattice constant of the mercury telluride; (ii) forming a second layer of a composition of the formula HgTe having a second thickness; (iii) forming one or more additional alternating layers of said first layer and said second layer; (b) forming a second quaternary region by (i) forming a third layer of a composition of the formula Cd1-y Zny Te wherein y is the mole fraction of zinc having a thickness and such that the lattice constant of the cadmium zinc telluride is substantially similar to the lattice constant of the mercury telluride; (ii) forming a fourth layer of a composition of the formula HgTe having a thickness; (iii) forming one or more additional alternating layers of said third and said fourth layers; and (c) annealing the layers to form homogeneous alloys of Hg1-x (Cd1-y Zny)x Te.
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20. A method of forming two or more lattice matched quaternary alloys of infrared absorbing semiconductor comprising:
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(a) forming a first region of quaternary alloy by (i) forming a first thin layer of a composition of the formula HgTe having a first thickness and such that the lattice constant of the cadmium zinc telluride is substantially similar to the lattice constant of the mercury telluride; (ii) forming a second layer of a composition of the formula Cd1-y Zny Te wherein y is the mole fraction of zinc having a second thickness; (iii) forming one or more additional alternating layers of said first layer and said second layer; (b) forming a second quaternary region by (i) forming a third layer of a composition of the formula HgTe having a first thickness and such that the lattice constant of the cadmium zinc telluride is substantially similar to the lattice constant of the mercury telluride; (ii) forming a fourth layer of a composition of the formula Cd1-y Zny Te wherein y is the mole fraction of zinc having a thickness; (iii) forming one or more additional alternating layers of said third and said fourth layers; and (c) annealing the layers to form homogeneous alloys of Hg1-x (Cd1-y Zny)x Te. - View Dependent Claims (21, 22, 23, 24)
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25. A method of fabricating a variable bandgap infrared absorbing semiconductor material structure responsive to infrared radiation, comprising:
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(a) forming a layer of CdTe1-z Sez on a substrate, wherein z represents the mole fraction of selenium such that the lattice constant of the cadmium selenium telluride is substantially similar to the lattice constant of the mercury telluride; (b) forming a layer of HgTe on the previously deposited layer of CdTe1-z Sez ; (c) repeating steps (a) and (b) one or more times to create alternating layers of CdTe1-z Sez and HgTe; (d) annealing the resulting layers to form a homogeneous alloy structure.
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26. A method of fabricating a variable bandgap infrared absorbing semiconductor material structure responsive to infrared radiation, comprising:
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(a) forming a layer of HgTe on a substrate; (b) forming a layer of CdTe1-z Sez wherein z represents the mole fraction of selenium on the previously deposited layer of CdTe1-z Sez such that the lattice constant of the cadmium selenium telluride is substantially similar to the lattice constant of the mercury telluride; (c) repeating steps (a) and (b) one or more times to create alternating layers of CdTe1-z Sez and HgTe; (d) annealing the layers to form a homogeneous alloy structure. - View Dependent Claims (27)
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28. A method of forming two or more lattice matched quaternary alloys of infrared absorbing materials comprising:
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(a) forming a first region by (i) forming a first layer having a predetermined thickness of a composition of the formula CdTe1-z Sez wherein z is the mole fraction of selenium such that the lattice constant of the cadmium selenium telluride is substantially similar to the lattice constant of the mercury telluride; (ii) forming a second layer having a thickness of a composition of the formula HgTe; (iii) forming one or more additional alternating layers of said first layer and said second layer; (b) forming a second region of quaternary alloy by (i) forming a third layer having a thickness of a composition of the formula CdTe1-z Sez wherein z is the mole fraction of selenium such that the lattice constant of the cadmium selenium telluride is substantially similar to the lattice constant of the mercury telluride; (ii) forming a fourth layer having a thickness of a composition of the formula HgTe having a predetermined thickness; (iii) forming one or more additional alternating layers of said third layer and said fourth layers and (c) annealing the layers to form homogeneous alloys of (HgTe)1-x (CdTe1-z Sez)x. - View Dependent Claims (29)
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30. A method of forming two or more lattice matched quaternary alloys of infrared absorbing materials comprising:
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(a) forming a first region by (i) forming a first layer having a thickness of a composition of the formula HgTe; (ii) forming a second layer having a thickness of a composition of the formula CdTe1-z Sez wherein z is the mole fraction of selenium such that the lattice constant of the cadmium selenium telluride is substantially similar to the lattice constant of the mercury telluride; (iii) forming one or more additional alternating layers of said first layer and said second layer; (b) forming a second region of quaternary alloy by (i) forming a third layer having a thickness of a composition of the formula HgTe; (ii) forming a fourth layer having a thickness of a composition of the formula CdTe1-z Sez wherein z is the mole fraction of selenium having a predetermined thickness and such that the lattice constant of the cadmium selenium telluride is substantially similar to the lattice constant of the mercury telluride; (iii) forming one or more additional alternating layers of said third layer and said fourth layers and (c) annealing the layers to form homogeneous alloys of (HgTe)1-x (CdTe1-z Sez)x. - View Dependent Claims (31)
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Specification