Hydrogenated amorphous silicon detector
The invention refers to a detector based on 3D geometry made from a hydrogenated amorphous silicon substrate. This detector finds application in the detection of ionizing radiation.
1. A detector for ionizing radiation comprising:
a support element ( 6 ) made of a material comprising a p-type doped conductive material or a semiconductor material;
an intrinsic layer comprised of p hydrogenated amorphous silicon substrate ( 10 ) of given thickness, provided with two substantially parallel and opposite faces in which a first face is placed in contact with said support element ( 6 ) and a second face is opposite to the first one;
a plurality of p-type electrodes ( 11 ) extending from said second face of the hydrogenated amorphous silicon substrate ( 10 ) in the direction of the thickness of said intrinsic layer ( 10 ), connected to each other by a polarization element ( 8 , 13 );
a plurality of n-type electrodes ( 12 ) extending from said second face of the hydrogenated amorphous silicon substrate ( 10 ) in the direction of the thickness of said intrinsic layer, suitable for collecting the charge signal generated at the passage of ionizing radiation in the detector;
a passivation layer ( 7 ) placed at least partially in contact with the second face of the intrinsic layer ( 10 ) and never being in contact with the support element ( 6 ); and
at least one electrode for reading the charge signal collected by one or more of said n-type electrodes ( 12 ) and connected to it by a signal reading contact ( 9 ).
2. The detector of claim 1 , wherein at least one of the p-type electrodes ( 11 ) is in contact with a polarization element ( 8 ) placed on the second face of said intrinsic layer ( 10 ).
3. The detector of claim 2 , wherein the polarization element is shaped like a grid ( 8 ).
4. The detector of claim 1 , wherein the p-type electrodes ( 11 ) extend over the whole thickness of the intrinsic layer ( 10 ) until touching the first face of said intrinsic layer ( 10 ) thus creating an electrical contact with the polarization element ( 13 ) through the support element ( 6 ).
5. The detector of claim 1 wherein the support element ( 6 ) is made of a material consisting of a semiconductor material.
6. The detector of claim 1 , wherein the support element ( 6 ) is made of a material comprising: a metal or metallic material; or, a semiconductor material comprising: silicon, or a silicon doped with chromium, molybdenum, aluminum, or platinum or a surface treated with chromium, molybdenum, aluminum, or platinum.
7. The detector of claim 6 , wherein the metallic material comprises: stainless steel, aluminum, chromed brass, or a Printed Circuit Board (PCB) on which a metallic copper is deposited.
8. The detector of claim 1 , wherein the passivation layer ( 7 ) is made of a material comprising: Silicon Oxide, Nitride, or Aluminum Oxide.
9. The detector of claim 1 , wherein the stoichiometric percentage of hydrogen in the hydrogenated amorphous silicon is between about 8 and about 15%.
10. The detector of claim 1 , wherein the n-type electrodes ( 12 ) are all in columnar form and the p-type electrodes ( 11 ) are selected from the group consisting of columnar and trench shapes.
11. The detector of claim 1 , wherein the n-type electrodes ( 12 ) and the p-type electrodes ( 11 ) are arranged alternately along the parallel lines drawn on the second face of the intrinsic layer ( 10 ).
12. The detector of claim 1 , wherein the thickness of the intrinsic layer ( 10 ) is greater than about 90 microns.
13. The detector of claim 1 , wherein which the n-type electrodes ( 12 ) and the p-type electrodes ( 11 ) are placed at mutual distances of between about 10 and 50 micrometers.
14. The detector of claim 1 , wherein the detector is a pixel detector.
15. A method for using the detector of claim 1 , comprising the following steps:
supplying the polarization electrode ( 8 ) so as to determine a polarization field internal to the intrinsic layer ( 10 );
exposing the detector to a flow of ionizing radiation for a fixed period of time; and
measuring the charge signal collected by the n-type electrodes ( 12 ) using the reading electrode.
16. The method of claim 15 , wherein the ionizing radiation comprises X-rays whose energy ranges between about 5 to about 100 keV.
17. An apparatus having contained therein a detector of claim 1 .
18. The apparatus of claim 17 , wherein the apparatus is selected from the group consisting of: dosimeters for medical use, X-ray detectors for structural analysis and medical diagnostics, particle trackers, and calorimeters.
19. The detector of claim 1 , wherein:
the n-type electrodes 12 are made by a method comprising deposition through Atomic Layer Deposition (ALD) of a metal oxide or by doping by ion implantation on at least part of a plurality of hole, wherein the holes extend starting from the second face of the intrinsic layer 10 along the thickness of the intrinsic layer itself; or
the p-type electrodes 11 are made by a method comprising deposition through ALD of a metal oxide.
20. The detector of claim 19 , wherein the metal oxide comprises: titanium oxide for n-type doping and tungsten oxide or molybdenum oxide for p-type doping.