Photosensitive pixel structure with increased light absorption and photosensitive implant
The present invention refers to a photosensitive pixel structure comprising a substrate with a front surface and a back surface, wherein at least one photosensitive diode is provided on one of the surfaces of the substrate. A first material layer is provided at least partially on the back surface of the substrate, wherein the material layer comprises a reflective layer, in order to increase a reflectivity at the back surface of the substrate. Further, the present invention refers to an array and an implant comprising such a photosensitive pixel structure, as well as to a method to produce the pixel structure.
1. Photosensitive pixel structure comprising:
a substrate with a front surface and a back surface and at least one photosensitive diode provided on one of the front surface or the back surface of the substrate;
a first material layer provided at least partially on the back surface of the substrate, wherein the first material layer comprises a reflective layer; and
a second material layer provided on at least a part of a back surface of the first material layer and configured to hermetically cover and hermetically seal at least the first material layer and/or the back surface of the substrate and form an outer layer of the photosensitive pixel structure, the second material layer comprising titanium and/or ceramic.
2. Photosensitive pixel structure according to claim 1 , wherein the substrate comprises a material which is adapted to absorb light of a predetermined wavelength or wavelength range.
3. Photosensitive pixel structure according to either one of claim 1 or 2 , characterized in that the first material layer on the back surface of the substrate comprises a layer of buried oxide or the first material layer comprises a layer of metal.
4. Photosensitive pixel structure according to claim 3 , characterized in that the first material layer is formed as an integral part of the substrate.
5. Photosensitive pixel structure according to claim 3 , characterized in that the first and/or the second material layer comprises titanium and the titanium layer has a thickness selected from not less than 100 nm.
6. Photosensitive pixel structure according to claim 5 , wherein, in a case that a stack of titanium and buried oxide layer is used as a first material layer, the thickness of the buried oxide layer is in a range of about 65 nm and 210 nm, or, in a case that a stack of aluminium and buried oxide layer is used as a first material layer, the thickness of the buried oxide layer is in the range selected from 90 nm to 170 nm plus any multiple of 300 nm.
7. Photosensitive pixel structure according to claim 1 , characterized in that the first material layer comprises a layer of buried oxide, and a layer of aluminium, wherein the layer of buried oxide is sandwiched between the substrate and the layer of aluminium.
8. Photosensitive pixel structure according to claim 1 , characterized in that the second material layer consists of titanium and/or a ceramic layer.
9. Photosensitive pixel array comprising a plurality of pixel structures according to claim 1 , wherein the plurality of pixel structures is arranged in an array.
10. Implant with a photosensitive pixel array according to claim 9 , wherein the implant further comprises at least one electrode, which is adapted to provide an electrical stimulation pulse generated by photoelectric generation in the pixel structure or pixel array.
11. Photosensitive pixel array comprising a plurality of pixel structures according to claim 1 , wherein the second material layer is provided adjacent to the first material layer.
12. Implant with a photosensitive pixel structure according to claim 1 , wherein the implant further comprises at least one electrode, which is adapted to provide an electrical stimulation pulse generated by photoelectric generation in the pixel structure.
13. Implant according to claim 12 , wherein the implant is a retinal implant or a subretinal implant.
14. Method for providing a pixel structure according to claim 1 , characterized in that the method comprises the steps of:
providing the substrate adapted to absorb light of at least one predetermined wavelength,
providing on the front surface of the substrate the photosensitive diode,
providing on the back surface of the substrate the first material layer which comprises at least a reflective material layer, which is adapted to reflect light transmitted through the substrate to the first material layer back toward the substrate.
15. Method according to claim 14 , characterized in that the first material layer is provided by ion-implantation and/or the first material layer is thermally grown from the substrate.
16. Method according to of claim 15 , characterized in that the second material layer is provided at least on a surface of the first material layer facing away from the substrate.
17. Method according to claim 14 , characterized in that the second material layer is provided at least on a surface of the first material layer facing away from the substrate.
18. Implant with a photosensitive pixel structure according to claim 1 , wherein the second material layer comprises ceramic.