Graphene on semiconductor detector
Ultraviolet or Extreme Ultraviolet and/or visible detector apparatus and fabrication processes are presented, in which the detector includes a thin graphene electrode structure disposed over a semiconductor surface to provide establish a potential in the semiconductor material surface and to collect photogenerated carriers, with a first contact providing a top side or bottom side connection for the semiconductor structure and a second contact for connection to the graphene layer.
1. A detector apparatus, comprising:
A semiconductor structure with a first surface;
a graphene layer disposed over at least a portion of the first surface of the semiconductor structure and having an upper surface with a first portion configured to collect photogenerated carriers and to establish a potential on the first surface of the semiconductor structure;
a first contact structure electrically connected to the semiconductor structure; and
a second contact structure electrically connected to a second portion of the upper surface of the graphene layer;
wherein the first contact structure is formed on a bottom side of the semiconductor structure, and the second contact structure is formed on a top side of the apparatus.
2. The apparatus of claim 1 , wherein the graphene layer has a thickness of about 0.3 nm or more.
3. The apparatus of claim 1 , wherein the graphene layer is a single atomic layer of carbon atoms forming a substantially two-dimensional honeycomb crystal lattice over the first surface of the semiconductor structure.
4. The apparatus of claim 1 , wherein the semiconductor structure is of a first conductivity type and comprises an implanted or epitaxially grown region having a dopant concentration of the first conductivity type greater than a dopant concentration of the remainder of the semiconductor structure, wherein the first contact structure is an ohmic metal contact formed over at least a portion of an upper surface of the implanted or epitaxially grown region of the semiconductor structure.
5. The apparatus of claim 1 , wherein the first contact structure is a Schottky metal contact formed over a portion of the first surface of the semiconductor structure, wherein the first contact structure is laterally spaced from the graphene layer.
6. The apparatus of claim 1 , comprising:
a plurality of detector cells spaced from one another on the top side of the apparatus, with individual detector cells including:
a graphene layer disposed over the first surface of the semiconductor structure, the graphene layer having and a thickness of about 3.0 nm or less and an upper surface with a first portion configured to collect photogenerated carriers and to establish a potential on the first surface of the semiconductor structure,
a first contact structure electrically connected to the semiconductor structure, and
a second contact structure formed on a second portion of the upper surface of the graphene layer; and
at least one isolation structure separating first and second detector cells from one another.
7. The apparatus of claim 1 , comprising a support substrate disposed along at least a portion of a bottom side of the semiconductor structure.
8. The apparatus of claim 7 , comprising a semiconductor epitaxial nucleation layer formed on a top side of the support substrate, wherein the semiconductor structure comprises an epitaxially grown semiconductor material formed over the nucleation layer.
9. The apparatus of claim 1 , comprising:
a plurality of detector cells laterally spaced from one another, with individual detector cells including:
a semiconductor structure of a first conductivity type, including an implanted lower region having a dopant concentration of the first conductivity type greater than a dopant concentration of the remainder of the semiconductor structure,
a graphene layer disposed over an upper surface of the semiconductor structure, the graphene layer having and a thickness of about 3.0 nm or less and an upper surface with a first portion configured to collect photogenerated carriers and to establish a potential on the first surface of the semiconductor structure,
a first contact structure electrically connected to the semiconductor structure, wherein the first contact structure is an ohmic metal contact formed over at least a portion of a lower surface of the implanted region of the semiconductor structure,
an indium structure disposed along at least a portion of a bottom surface of the first contact structure, and
a second contact structure formed on a second portion of the upper surface of the graphene layer; and
at least one isolation structure separating lateral sides of the semiconductor structures of first and second detector cells from one another.
10. The apparatus of claim 9 , wherein the at least one isolation structure comprises a deep level trap region of the semiconductor structure implanted with protons or oxygen.
11. The apparatus of claim 9 , wherein the at least one isolation structure comprises an implanted region of a second conductivity type in the semiconductor structure.
12. The apparatus of claim 1 , comprising:
a plurality of detector cells laterally spaced from one another, with individual detector cells including:
a semiconductor structure of a first conductivity type,
a graphene layer disposed over an upper surface of the semiconductor structure, the graphene layer having and a thickness of about 3.0 nm or less and an upper surface with a first portion configured to collect photogenerated carriers and to establish a potential on the first surface of the semiconductor structure,
a first contact structure electrically connected to the semiconductor structure, wherein the first contact structure is a Schottky metal contact formed over at least a portion of a lower surface of the semiconductor structure,
an indium structure disposed along at least a portion of a bottom surface of the first contact structure, and
a second contact structure formed on a second portion of the upper surface of the graphene layer; and
at least one isolation structure separating lateral sides of the semiconductor structures of first and second detector cells from one another.
13. The apparatus of claim 12 , wherein the at least one isolation structure comprises a deep level trap region of the semiconductor structure implanted with protons or oxygen.
14. The apparatus of claim 12 , wherein the at least one isolation structure comprises an implanted region of a second conductivity type in the semiconductor structure.
15. The apparatus of claim 1 , comprising at least one of an upper support substrate disposed over a portion of the upper surface of the graphene layer, and a lower support substrate disposed along the lower side of the apparatus.
16. The apparatus of claim 1 , wherein the semiconductor structure comprises silicon carbide.
17. The apparatus of claim 1 , wherein the semiconductor structure comprises aluminum gallium nitride.
18. The apparatus of claim 1 , wherein the semiconductor structure has a bandgap more than 2.5 electron volts.
19. The apparatus of claim 1 , wherein the graphene layer has a thickness of about 3.0 nm or less.
20. The apparatus of claim 1 , wherein the second contact structure and the first contact structure have the about the same voltage.
21. The apparatus of claim 1 , wherein the first contact structure is electrically connected to the semiconductor structure via a CMOS transfer transistor.
22. A method of making a detector, the method comprising:
forming a graphene layer over a first surface of a semiconductor structure to a thickness of about 3.0 nm or less, the graphene layer comprising first and second portions;
forming a first contact structure on a bottom side of the semiconductor structure, the first contact structure being electrically connected to the semiconductor structure; and
forming a second contact structure on a top side of the second portion of the upper surface of the graphene layer.
23. An active pixel sensor apparatus, comprising:
a semiconductor structure with a first surface;
at least one pixel detector, comprising a graphene layer disposed over at least a portion of the first surface of the semiconductor structure, the graphene layer including a sensing surface configured to collect photogenerated carriers and adapted to establish a potential at the first surface of the semiconductor structure;
a transfer transistor including:
a source formed in the semiconductor structure,
a control gate, and
a drain electrically coupled with a readout circuit operative to read data from the at least one pixel detector using the control gate; and
a reset transistor formed in the semiconductor structure and operative to selectively remove charge from the at least one pixel detector.
24. The active pixel sensor apparatus of claim 23 , comprising a coating layer formed over at least a portion of the sensing surface of the graphene layer.
25. The active pixel sensor apparatus of claim 24 , wherein the coating layer is at least one of a protective layer, an anti-reflectance material, a filter, a neutron conversion layer, and a micro lens.
26. The active pixel sensor apparatus of claim 23 , wherein the at least one pixel detector is operative to detect ultraviolet light.
27. The active pixel sensor apparatus of claim 23 , wherein the at least one pixel detector is operative to detect visible light.
28. A charge coupled device (CCD), comprising:
a semiconductor structure with a first surface;
at least one pixel detector, comprising a graphene layer disposed over at least a portion of the first surface of the semiconductor structure, the graphene layer including a sensing surface facing a backside of the CCD;
a transfer transistor including a source formed in the semiconductor structure, and a drain electrically coupled with a readout circuit operative to read data from the at least one pixel detector.
29. The CCD of claim 28 , wherein the at least one pixel detector is operative to detect visible light.