Tetra-lateral position sensing detector
The present invention is directed to a position sensing detector made of a photodiode having a semi insulating substrate layer; a buffered layer that is formed directly atop the semi-insulating substrate layer, an absorption layer that is formed directly atop the buffered layer substrate layer, a cap layer that is formed directly atop the absorption layer, a plurality of cathode electrodes electrically coupled to the buffered layer or directly to the cap layer, and at least one anode electrode electrically coupled to a p-type region in the cap layer. The position sensing detector has a photo-response non-uniformity of less than 2% and a position detection error of less than 10 μm across the active area.
1. A position sensing detector comprising a photodiode having an active area and having a first corner, a second corner, a third corner, and a fourth corner, said photodiode comprising
a. A semi insulating substrate layer;
b. A buffered layer, wherein said buffered layer is formed directly atop the semi-insulating substrate layer;
c. An absorption layer, wherein said absorption layer is formed directly atop the buffered layer;
d. A cap layer, wherein said cap layer is formed directly atop the absorption layer;
e. Four cathode electrodes electrically coupled to said buffered layer, wherein a first of said four cathode electrodes is positioned in the first corner, a second of said four cathode electrodes is positioned in the second corner, a third of said four cathode electrodes is positioned in the third corner, and a fourth of said four cathode electrodes is positioned in the fourth corner; and
f. At least one anode electrode electrically coupled to a p-type region in said cap layer, wherein said detector is capable of detecting eye-safe wavelengths and wherein said p-type region is doped with an effective amount of metal such that a position detection error, in both the X and Y direction is on the order of 100 μm across the active area.
2. The position sensing detector of claim 1 wherein said buffered layer comprises InP and wherein said eye-safe wavelengths are from 1.3-1.55 μm.
3. The position sensing detector of claim 1 wherein said absorption layer comprises InGaAs.
4. The position sensing detector of claim 1 wherein said cap layer comprises InP.
5. The position sensing detector of claim 1 wherein a photo response non-uniformity is less than 1 micron across said active area.
6. The position sensing detector of claim 1 wherein the photodiode further comprises an anti-reflective layer positioned atop the cap layer.
7. The position sensing detector of claim 1 wherein said p-type region in said cap layer is formed by diffusing a region of said cap layer with a suitable dopant to create said p-type region.
8. The position sensing detector of claim 7 wherein said dopant is zinc.
9. A position sensing detector comprising a photodiode having an active area, said photodiode being defined by a first corner, a second corner, a third corner, and a fourth corner and comprising
a. A semi insulating substrate layer;
b. A buffered layer, wherein said buffered layer is formed directly atop the semi-insulating substrate layer;
c. An absorption layer, wherein said absorption layer is formed directly atop the buffered layer;
d. A cap layer with a p-type region, wherein said cap layer is formed directly atop the absorption layer, wherein a p-n junction is formed between said cap layer and said absorption layer;
e. Four cathode electrodes electrically coupled to said buffered layer, wherein a first of said four cathode electrodes is positioned in the first corner, a second of said four cathode electrodes is positioned in the second corner, a third of said four cathode electrodes is positioned in the third corner, and a fourth of said four cathode electrodes is positioned in the fourth corner; and
f. At least one anode electrode electrically coupled to said cap layer, wherein said p-type region is doped with an effective amount of metal such that a position detection error, in both the X and Y direction is on the order of 100 μm across the active area.
10. The position sensing detector of claim 9 wherein said buffered layer comprises at least one of InGaAs or InP.
11. The position sensing detector of claim 9 wherein said absorption layer comprises at least one of InGaAs or InP.
12. The position sensing detector of claim 9 wherein said cap layer comprises at least one of InGaAs or InP.
13. The position sensing detector of claim 9 wherein said p-n junction is formed by diffusing a region of said cap layer with a suitable dopant.
14. The position sensing detector of claim 9 wherein said p-n junction is formed by diffusing a region of said absorption layer with a suitable dopant.