Photodetectors exploiting electrostatic trapping and percolation transport

Patent metadata

Field	Value
Publication number	US-10177271-B2
Application number	US-201615359882-A
Country	US
Kind code	B2
Filing date	Nov 23, 2016
Priority date	Nov 25, 2015
Publication date	Jan 8, 2019
Grant date	Jan 8, 2019

Abstract

This disclosure provides systems, methods, and apparatus related to photodetectors. In one aspect, a photodetector device comprises a substrate, a polycrystalline layer disposed on the substrate, and a first electrode and a second electrode disposed on the polycrystalline layer. The polycrystalline layer comprises nanograins with grain boundaries between the nanograins. The nanograins comprise a semiconductor material. A doping element comprising a halogen is segregated at the grain boundaries. A length of the polycrystalline layer is between and separating the first electrode and the second electrode.

First claim

What is claimed is:

1. A method comprising:
(a) fabricating a plurality nanocrystals, the plurality of nanocrystals comprising a semiconductor material, and each nanocrystal of the plurality of nanocrystals having ligands disposed on a surface of the nanocrystal;
(b) exchanging at least some of the ligands on each nanocrystal of the plurality of nanocrystals with a doping element comprising a halogen;
(c) after operations (a) and (b), depositing the plurality of nanocrystals on a substrate;
(d) thermally annealing the plurality of nanocrystals to form a polycrystalline layer comprising nanograins; and
(e) depositing a first electrode and a second electrode on the polycrystalline layer, a length of the polycrystalline layer being between and separating the first electrode and the second electrode.

2. The method of claim 1 , wherein the doping element segregates to grain boundaries in the polycrystalline layer during operation (d).

3. The method of claim 1 , wherein the plurality of nanocrystals comprise a semiconductor material selected from a group consisting of a III-V semiconductor material and a II-VI semiconductor material.

4. The method of claim 1 , wherein the doping element comprises chlorine.

5. The method of claim 1 , wherein operation (d) is performed at about 150° C. to 800° C.

6. The method of claim 1 , wherein operation (d) is performed for about 1 second to 30 minutes.

7. The method of claim 1 , wherein operation (d) is performed in an inert atmosphere.

8. The method of claim 1 , wherein each of the nanograins has a largest dimension of about 10 nanometers to 200 nanometers.

9. The method of claim 1 , wherein the polycrystalline layer has a thickness of about 10 nanometers to 5 microns.

10. The method of claim 1 , wherein the length of the polycrystalline layer between the first electrode and the second electrode is about 50 nanometers to 1 millimeter.

11. A method comprising:
(a) fabricating a plurality nanocrystals, the plurality of nanocrystals comprising cadmium telluride (CdTe), and each nanocrystal of the plurality of nanocrystals having cadmium oleate ligands disposed on a surface of the nanocrystal;
(b) exchanging at least some of the cadmium oleate ligands on each nanocrystal of the plurality of nanocrystals with a doping element comprising chlorine;
(c) after operation (b), depositing the plurality of nanocrystals on a substrate;
(d) thermally annealing the plurality of nanocrystals to form a polycrystalline layer comprising nanograins, the chlorine segregating to grain boundaries in the polycrystalline layer during the thermal annealing; and
(e) depositing a first electrode and a second electrode on the polycrystalline layer, a length of the polycrystalline layer being between and separating the first electrode and the second electrode.

12. The method of claim 11 , wherein operation (b) comprises:
dispersing the plurality of nanocrystals in toluene;
adding tributylphosphine (TBP) to the plurality of nanocrystals dispersed in toluene; and
after adding the tributylphosphine, adding trimethylsilychloride (TMSCl) to the plurality of nanocrystals dispersed in toluene.

13. The method of claim 11 , further comprising:
after operation (d), removing the polycrystalline layer from the substrate; and
depositing the polycrystalline layer on a substrate of a photodetector device.

14. The method of claim 11 , further comprising:
after operation (a), purifying the plurality of nanocrystals by suspending the plurality of nanocrystals in a liquid and separating the plurality of nanocrystals from the liquid.

15. The method of claim 11 , wherein operation (d) is performed at about 350° C.

16. The method of claim 11 , wherein operation (d) is performed for about 30 seconds to 5 minutes.

17. The method of claim 11 , wherein operation (d) is performed in an argon atmosphere.

18. The method of claim 11 , wherein each of the nanograins has a largest dimension of about 50 nanometers to 75 nanometers.

19. The method of claim 11 , wherein the polycrystalline layer has a thickness of about 10 nanometers to 5 microns.

20. The method of claim 11 , wherein the length of the polycrystalline layer between the first electrode and the second electrode is about 50 nanometers to 1 millimeter.

Assignees

• Alivisatos A Paul
• Salmeron Miquel
• Zhang Yingjie
• Hellebusch Daniel J
• Univ California

Inventors

• Alivisatos A Paul
• Salmeron Miquel
• Zhang Yingjie
• Hellebusch Daniel J

Classifications

• H01L31/0368

  Electricity · mapped topic

• Y02E10/50

  Photovoltaic [PV] energy · CPC title

• H01L31/1836

  Electricity · mapped topic

• H01L31/09

  Electricity · mapped topic

• H01L31/02963

  Electricity · mapped topic