US5510644A
Expired / Lapsed
US
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CDTE x-ray detector for use at room temperature
Assignee: Gula Consulting LLC
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Filing: 1994-09-23
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Granted: 1996-04-23
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Expires: 2014-09-23
Abstract
Abstract An improved x-ray detector in the form of a p-i-n CdTe homojunction device is disclosed. The intrinsic ("i") layer is of high resistivity CdTe, while the n- and p-doped CdTe layers are epitaxially grown in a photo-assisted process in a molecular beam epitaxial apparatus. The n-dopant is conveniently indium, with an indium metal contact. The "i" layer is optionally epitaxially grown in a photo-assisted process. The p-dopant is preferably arsenic. A PAMBE formed mercury telluride contact layer enhances the ohmic contact to the p-layer, and a gold contact is provided to the contact layer. The use of the PAMBE technique facilitates high quality crystal growth and activation of the dopants. The resulting CdTe p-i-n homojunction device has a wide band gap (1.45 eV) essential to room temperature operation.
Inventors
- 👤 Karl A. Harris
- 👤 II Thomas H. Myers
- 👤 Robert W. Yanka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 21:31
CPC Classifications
H; H10; H10F; H10F30/00; H10F30/20; H10F30/21; H10F30/22; H10F30/223; H10F30/29; H10F71/00; H10F71/125; Y; Y02; Y02E; Y02E10/00; Y02E10/50; Y02E10/543; Y02E10/548
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
118 words
A CdTe x-ray detector for use at room temperature comprising in combination A) a high resistivity, intrinsic CdTe layer dimensioned for x-ray absorption, having two parallel faces, B) a photo-assisted molecular beam epitaxially (PAMBE) grown CdTe layer using a group III element as an n type dopant to form an n type layer and forming on one of said faces an n-i interface, said n type layer having a first metal contact, and C) a PAMBE grown CdTe layer using arsenic as a p-type dopant to form a p type layer and forming on the other of said faces an i-p interface, said p type layer having a second metal contact, said combination forming a CdTe p-i-n homojunction.
Claim 2
Dependent Claim
118 words
A CdTe x-ray detector for use at room temperature comprising in combination A) a high resistivity, intrinsic CdTe layer dimensioned for x-ray absorption, having two parallel faces, B) a photo-assisted molecular beam epitaxially (PAMBE) grown CdTe layer using a group III element as an n type dopant to form an n type layer and forming on one of said faces an n-i interface, said n type layer having a first metal contact, and C) a PAMBE grown CdTe layer using arsenic as a p-type dopant to form a p type layer and forming on the other of said faces an i-p interface, said p type layer having a second metal contact, said combination forming a CdTe p-i-n homojunction.
Claim 3
Dependent Claim
29 words
A CdTe x-ray detector as set forth in claim 1, wherein the second metal contact is gold, consisting of an electroless gold layer, over which additional gold is evaporated.
Claim 4
Dependent Claim
136 words
A CdTe x-ray detector for use at room temperature comprising in combination A) a high resistivity, intrinsic CdTe layer dimensioned for x-ray absorption, having two parallel faces, B) a photo-assisted molecular beam epitaxially (PAMBE) grown CdTe layer using a group III element as an n type dopant to form an n type layer and forming on one of said faces an n-i interface, said n type layer having a first metal contact, C) a PAMBE grown CdTe layer using arsenic as a p-type dopant to form a p type layer and forming on the other of said faces an i-p interface,, said p type layer having a second metal contact, D) a PAMBE grown HgTe layer formed on said arsenic doped layer to enhance formation of an ohmic contact, said combination forming a CdTe p-i-n homojunction.
Claim 5
Dependent Claim
136 words
A CdTe x-ray detector for use at room temperature comprising in combination A) a high resistivity, intrinsic CdTe layer dimensioned for x-ray absorption, having two parallel faces, B) a photo-assisted molecular beam epitaxially (PAMBE) grown CdTe layer using a group III element as an n type dopant to form an n type layer and forming on one of said faces an n-i interface, said n type layer having a first metal contact, C) a PAMBE grown CdTe layer using arsenic as a p-type dopant to form a p type layer and forming on the other of said faces an i-p interface,, said p type layer having a second metal contact, D) a PAMBE grown HgTe layer formed on said arsenic doped layer to enhance formation of an ohmic contact, said combination forming a CdTe p-i-n homojunction.
Claim 6
Dependent Claim
29 words
A CdTe x-ray detector as set forth in claim 3, wherein the second metal contact is gold, consisting of an electroless gold layer, over which additional gold is evaporated.
Claim 7
Dependent Claim
24 words
A CdTe x-ray detector as set forth in claim 4, wherein said n type dopant is indium, and said first metal contact is indium.
Claim 8
Dependent Claim
20 words
A CdTe x-ray detector as set forth in claim 5, wherein said two parallel faces have a (100) crystallographic orientation.
Claim 9
Dependent Claim
46 words
A CdTe x-ray detector as set forth in claim 6, wherein said intrinsic CdTe layer has a resistivity in excess of 10 7 ohm centimeters, and a thickness of from 2 to 3 millimeters measured in a direction of x-ray propagation through said intrinsic CdTe layer.
Claim 10
Dependent Claim
56 words
A CdTe x-ray detector as set forth in claim 7, wherein said p and n type layers have doping levels on the order of 10 17 per cc and thicknesses on the order of 10 microns; said doping levels, p and n type layer thicknesses and applied bias providing a depletion region optimized for x-ray absorption.
Claim 11
Dependent Claim
18 words
A CdTe x-ray detector as set forth in claim 3, wherein said intrinsic CdTe layer is PAMBE grown.
Claim 12
Dependent Claim
146 words
A CdTe x-ray detector for use at room temperatures comprising in combination A) a substrate suitable for epitaxial growth of CdTe material, B) a photo-assisted molecular beam epitaxially (PAMBE) grown CdTe layer using an n-type dopant, for forming an n-type layer on said substrate, the n-type layer having a metallic contact layer on a first surface portion thereof, and C) a high resistivity PAMBE formed intrinsic CdTe layer dimensioned for x-ray absorption grown on a second surface portion of said n type layer and forming an n-i interface, D) a PAMBE grown CdTe layer using arsenic as a p-type dopant for forming a p-type layer on said intrinsic CdTe layer and forming a p-i interface, E) a PAMBE grown HgTe contact layer formed on said p-type layer, and F) a metallic contact being formed on said HgTe contact layer, said combination forming a CdTe p-i-n homojunction.
Claim 13
Dependent Claim
146 words
A CdTe x-ray detector for use at room temperatures comprising in combination A) a substrate suitable for epitaxial growth of CdTe material, B) a photo-assisted molecular beam epitaxially (PAMBE) grown CdTe layer using an n-type dopant, for forming an n-type layer on said substrate, the n-type layer having a metallic contact layer on a first surface portion thereof, and C) a high resistivity PAMBE formed intrinsic CdTe layer dimensioned for x-ray absorption grown on a second surface portion of said n type layer and forming an n-i interface, D) a PAMBE grown CdTe layer using arsenic as a p-type dopant for forming a p-type layer on said intrinsic CdTe layer and forming a p-i interface, E) a PAMBE grown HgTe contact layer formed on said p-type layer, and F) a metallic contact being formed on said HgTe contact layer, said combination forming a CdTe p-i-n homojunction.
Claim 14
Dependent Claim
36 words
A CdTe x-ray detector as set forth in claim 10, wherein said intrinsic layer has a resistivity in excess of 10 ohm centimeters, and a thickness suitable for x-ray absorption in a direction of x-ray propagation.
Claim 15
Dependent Claim
55 words
A CdTe x-ray detector as set forth in claim 11, wherein said p and n type layers have doping levels on the order of 10 17 per cc and thicknesses on the order of 10 microns, said doping levels, p and n type thicknesses and applied bias providing a depletion region optimized for x-ray absorption.
Claim 16
Dependent Claim
17 words
A CdTe x-ray detector as set forth in claim 10, wherein said n type dopant is indium.
Claim 17
Dependent Claim
125 words
A CdTe x-ray detector for use at room temperature, comprising: a first layer including intrinsic CdTe, the first layer having two parallel faces; a second layer including CdTe and a group III element as an n type dopant for the second layer, the second layer forming with the first layer an n-i interface on one of the faces; a third layer including CdTe and arsenic as a p type dopant for the third layer, the third layer forming with the first layer an i-p interface on the other of the faces; a fourth layer including HgTe formed on the third layer; a first metal contact for the fourth layer; and a second metal contact for the second layer, whereby a CdTe p-i-n homojunction is formed.
Claim 18
Dependent Claim
125 words
A CdTe x-ray detector for use at room temperature, comprising: a first layer including intrinsic CdTe, the first layer having two parallel faces; a second layer including CdTe and a group III element as an n type dopant for the second layer, the second layer forming with the first layer an n-i interface on one of the faces; a third layer including CdTe and arsenic as a p type dopant for the third layer, the third layer forming with the first layer an i-p interface on the other of the faces; a fourth layer including HgTe formed on the third layer; a first metal contact for the fourth layer; and a second metal contact for the second layer, whereby a CdTe p-i-n homojunction is formed.
Claim 19
Dependent Claim
13 words
The detector as in claim 14, wherein the second metal contact is gold.
Claim 20
Dependent Claim
20 words
The detector as in claim 14, wherein the n type dopant is indium and the first metal contact is indium.
Claim 21
Dependent Claim
14 words
The detector as in claim 14, wherein the faces have a (100) crystallographic structure.
Claim 22
Dependent Claim
41 words
The detector as in claim 14, wherein the first layer has a resistivity in excess of 10 7 ohm centimeters and a thickness of from 2 to 3 millimeters as measured in a direction of x-ray propagation through the first layer.
Claim 23
Dependent Claim
67 words
The detector as in claim 14, wherein the second and third layers each have doping levels on the order of 10 17 per cc and thicknesses on the order of 10 microns, wherein the doping levels, thickness of the second and third layers and an electrical bias applied between the first and second metal contact provide a depletion region of the first layer for optimizing x-ray absorption.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-04-23 | 1999-10-23 | 2000-04-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-04-23 | 2003-10-23 | 2004-04-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-04-23 | 2007-10-23 | 2008-04-23 | $7700.00 | Window Closed / Lapsed |