Materials, systems and methods for optoelectronic devices
A photodetector is described along with corresponding materials, systems, and methods. The photodetector comprises an integrated circuit and at least two optically sensitive layers. A first optically sensitive layer is over at least a portion of the integrated circuit, and a second optically sensitive layer is over the first optically sensitive layer. Each optically sensitive layer is interposed between two electrodes. The two electrodes include a respective first electrode and a respective second electrode. The integrated circuit selectively applies a bias to the electrodes and reads signals from the optically sensitive layers. The signal is related to the number of photons received by the respective optically sensitive layer.
1. A light-detecting pixel, comprising:
a substrate;
a first electrode;
an active layer comprising a photoconductive material;
a second electrode; and
an overlying layer including at least one material chosen from a list of materials consisting of a passivation layer, an encapsulation layer, a transparent dielectric, an optical filter, an additional active layer, and a contact, at least one of the first electrode and the second electrode being configured to form a rectifying junction with the active layer, and wherein an electrical bias is to be applied between the first electrode and the second electrode.
2. The light-detecting pixel of claim 1 , wherein the substrate is a silicon CMOS integrated circuit.
3. The light-detecting pixel of claim 1 , wherein the second electrode is an electron-withdrawing contact.
4. The light-detecting pixel of claim 1 , wherein the second electrode is a hole-withdrawing contact.
5. The light-detecting pixel of claim 1 , wherein an electrical bias is to be applied between the first electrode and the second electrode.
6. The light-detecting pixel of claim 1 , wherein the active layer of photoconductive material comprises mutually-touching semiconductor nanoparticles, wherein non-touching surfaces of the connected particles may be coated by one or more of a list of coatings consisting of an inorganic material, including at least one of an oxide and sulfate, and an organic material including an organic ligand.
7. The light-detecting pixel of claim 6 , wherein the mutually-touching semiconductor nanoparticles are chosen from the list consisting of PbS, PbSe, or PbTe; CdS, CdSe, or CdTe; Si, Ge, or C; In 2 Se 3 , In 2 S 3 , including either the alpha-phase or the beta-phase; InP; and Bi 2 S 3 .
8. The light-detecting pixel of claim 6 , wherein the organic ligand material coating the non-touching surfaces of the connected nanoparticles is chosen from a list of coatings consisting of Thiols including ethanethiol, ethanedithiol, benzenethiol, benzenedithiol; Amines including pyridine, butylamine, and octylamine; Hydrazine; and Carboxylates including oleic acid.
9. The light-detecting pixel of claim 1 , wherein at least one of the electrodes is a metal.
10. The light-detecting pixel of claim 1 , wherein at least one of the electrodes is a degenerately-doped semiconductor, or a combination of such materials.
11. The light-detecting pixel of claim 1 , wherein at least one material of at least one of the electrodes is chosen from a list of materials consisting of Au, Pt, Pd, Cu, Ni, NiS, TiN, TaN, p-type polysilicon, and p-type amorphous silicon.
12. The light-detecting pixel of claim 1 , wherein at least one material of at least one of the electrodes is chosen from a list of materials consisting of Al, Ag, In, Mg, Ca, Li, Cu, Ni, NiS, TiN, TaN, n-type polysilicon, and n-type amorphous silicon.
13. The light-detecting pixel of claim 1 , wherein at least one material of at least one of the electrodes is chosen from a list of materials consisting of combinations of a metal, a degenerately-doped semiconductor, and a combination of such materials; and a semiconductor, and an insulating material having a bandgap.
14. The light-detecting pixel of claim 13 , wherein the semiconductor or insulator is in direct physical contact with the active layer.
15. The light-detecting pixel of claim 14 , wherein the semiconductor or insulator is an amorphous material.
16. The light-detecting pixel of claim 14 , wherein the semiconductor or insulator has a thickness in the range of about 2 nm to about 20 nm.
17. The light-detecting pixel of claim 1 , wherein at least one of the biased junctions is to produce a region within the active layer that is substantially depleted of free charges.
18. The light-detecting pixel of claim 1 , wherein at least one of the biased junctions is to produce an active layer that is substantially depleted of free charges throughout its thickness.
19. The light-detecting pixel of claim 1 , wherein a frequency of response of the light-detecting pixel to modulation of an incoming light signal exceeds about one thousand cycles per second.
20. The light-detecting pixel of claim 1 , wherein a frequency of response of the light-detecting pixel to modulation of an incoming light signal exceeds about one million cycles per second.
21. The light-detecting pixel of claim 1 , wherein a dark current density of the light-detecting pixel is less than about 0.1 nA/cm 2 .
22. The light-detecting pixel of claim 1 , wherein a dark current density of the light-detecting pixel is less than about 10 pA/cm 2 .
23. The light-detecting pixel of claim 1 , wherein a dark current density of the light-detecting pixel is less than about 1 pA/cm 2 .
24. The light-detecting pixel of claim 1 , wherein a dark current density of the light-detecting pixel is less than about 0.1 pA/cm 2 .
25. The light-detecting pixel of claim 1 , wherein, following a turn-off of incident illumination, the device returns to a dark current value within about 10 milliseconds.
26. The light-detecting pixel of claim 1 , wherein, following a turn-off of incident illumination, the device returns to a dark current value within about 1 millisecond.
27. The light-detecting pixel of claim 1 , wherein, following a turn-off of incident illumination, the device returns to a dark current value within about 0.1 milliseconds.
28. The light-detecting pixel of claim 1 , wherein, following a turn-off of incident illumination, the device returns to a dark current value within about 10 microseconds.
29. The light-detecting pixel of claim 1 , wherein, following a turn-off of incident illumination, the device returns to a dark current value within about 1 microsecond.
30. The light-detecting pixel of claim 1 , wherein the first electrode possesses a deep work function electrode.
31. The light-detecting pixel of claim 1 , wherein the first electrode has a work function deeper than about −4.5 eV.
32. The light-detecting pixel of claim 1 , wherein the first electrode comprises at least one deep work function material selected from a list of materials including Au, Pt, Pd, Ni, Cu, Au-rich ITO, Pt-rich ITO, Pd-rich ITO, and a deep-work-function ITO.
33. The light-detecting pixel of claim 1 , wherein the second electrode possesses a shallow work function.
34. The light-detecting pixel of claim 1 , wherein the second electrode possesses a work function shallower than about −4.5 eV.
35. The light-detecting pixel of claim 1 , wherein the second electrode comprises at least one shallow work function material selected from a list of materials including Al, Mg, Ca, and shallow-work-function ITO.