Silicon-based visible and near-infrared optoelectric devices

• US 7,504,702 B2
• Filed: 06/02/2006
• Issued: 03/17/2009
• Est. Priority Date: 05/25/2001
• Status: Expired due to Term

• Current Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation)
• Inventors: Carey, James Edward III, Mazur, Eric
• Primary Examiner(s): NGO, NGAN V
• Application Number:
  US11/445,900
• Publication Number:
  US 20060231914A1
• Time in Patent Office: 1,019 Days
• Field of Search: 257/461, 257/463, 257/464, 257/E31.092, 257/E31.093
• US Class Current: 257/463
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02686 Pulsed laser beam
• CPC Class Codes: H01L 21/268 using electromagnetic radiation, e.g. laser radiation
• CPC Class Codes: H01L 31/0236 Special surface textures
• CPC Class Codes: H01L 31/02363 of the semiconductor body itself, e.g. textured active layers
• CPC Class Codes: H01L 31/028 including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/0288 characterised by the doping material
• CPC Class Codes: H01L 31/036 characterised by their crystalline structure or particular orientation of the crystalline planes
• CPC Class Codes: H01L 31/068 the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/1864 Annealing
• CPC Class Codes: H01L 31/1872 Recrystallisation
• CPC Class Codes: Y02E 10/52 PV systems with concentrators
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10S 438/94 Laser ablative material removal

Abstract

In one aspect, the present invention provides a silicon photodetector having a surface layer that is doped with sulfur inclusions with an average concentration in a range of about 0.5 atom percent to about 1.5 atom percent. The surface layer forms a diode junction with an underlying portion of the substrate. A plurality of electrical contacts allow application of a reverse bias voltage to the junction in order to facilitate generation of an electrical signal, e.g., a photocurrent, in response to irradiation of the surface layer. The photodetector exhibits a responsivity greater than about 1 A/W for incident wavelengths in a range of about 250 nm to about 1050 nm, and a responsivity greater than about 0.1 A/W for longer wavelengths, e.g., up to about 3.5 microns.

Claims

1. A photodetector, comprising:

a silicon substrate having a surface layer doped with electron-donating inclusions so as to exhibit a diodic current-voltage characteristic, said surface layer being configured for exposure to external radiation,

one or more electrical contacts disposed on the substrate for applying a selected reverse bias voltage to said surface layer to facilitate generation of an electrical signal in response to exposure of the surface layer to radiation,

wherein said surface layer is configured such that generation of said electrical signal in response to said radiation at a reverse bias voltage less than about 15 volts exhibits a responsivity greater than about 1 ampere/watt (A/W) for at least one wavelength in a range of about 250 nm to about 1050 nm.

2. The photodetector of claim 1, wherein said electron-donating inclusions comprise sulfur inclusions.

3. The photodetector of claim 2, wherein said sulfur inclusions have an average concentration in a range of about 0.5 to about 5 atom percent.

4. The photodetector of claim 1, wherein said photodetector exhibits a responsivity greater than about 0.1 amperes/watt for at least one wavelength in range of about 1050 nm to about 3500 nm.

5. The photodetector of claim 1, wherein said photodetector exhibits an average responsivity greater than about 1 A/W for wavelengths in a range of about 250 nm to about 1050 nm.

6. The photodetector of claim 1, wherein said photodetector exhibits a responsivity in a range of about 1 A/W to about 200 A/W for wavelengths in a range of about 250 nm to about 1050 nm.

7. The photodetector of claim 1, wherein said photodetector exhibits a responsivity in a range of about 1 A/W to about 100 A/W for at least one wavelength in a range of about 250 nm to about 1050 nm.

8. The photodetector of claim 1, wherein said photodetector exhibits a responsivity in a range of about 100 A/W to about 200 A/W for at least one wavelength in a range of about 250 nm to about 1050 nm.

9. The photodetector of claim 2, wherein said photodetector exhibits an average responsivity greater than about 0.1 A/W for wavelengths in a range of about 1050 nm to about 2000 nm.

10. The photodetector of claim 2, wherein said photodetector exhibits an average responsivity greater than about 0.1 A/W for wavelengths in a range of about 1050 nm to about 3500 nm.

11. The photodetector of claim 1, wherein said doped surface layer has a thickness in a range of about 10 nm to about 1 micron.

12. The photodetector of claim 1, wherein said electrical signal comprises any of a current or a voltage.

13. The photodetector of claim 1, wherein said reverse bias voltage lies in a range of about 0.1 volt to about 15 volts.

14. The photodetector of claim 1, wherein said photodetector exhibits a responsivity in a range of about 1 A/W to about 200 A/W for radiation wavelengths in a range of about 250 nm to about 1100 nm at reverse bias voltages in a range of about 0.1 volts to about 15 volts.

15. The photodetector of claim 1, wherein said surface layer comprises silicon nanocrystals having diameters in a range of about 10 to about 50 nanometers.

16. The photodetector of claim 1, wherein said silicon substrate is p-doped.

17. A photodetector for use in the visible and the infrared regions of the electromagnetic spectrum, comprising:

a silicon substrate having a doped layer containing an electron-donating dopant, said doped layer exhibiting a diodic current-voltage curve and being configured to receive an external radiation,

one or more electrical contacts disposed on said substrate for applying a reverse bias voltage to said doped layer to facilitate generation of an electrical signal in response to irradiation of at least a portion of said doped layer,

wherein said photodetector exhibits a responsivity greater that about 1 amperes/watt for at least one radiation wavelength in a range of about 250 nm to about 1050 nm and a responsivity greater than about 0.1 amperes/watt for at least one radiation wavelength in a range of about 1050 nm to about 3500 nm.

18. The photodetector of claim 17, wherein an average concentration of said dopent in the doped layer is in a range of about 0.5 to about 1.5 atom percent.

19. The photodetector of claim 17, wherein said photodetector exhibits said responsivities upon application of a reverse bias voltage in a range of about 0.1 V to about 15 V to said doped layer.

20. The photodetector of claim 17, wherein said silicon substrate comprises crystalline silicon.

21. The photodetector of claim 17, wherein said dopant comprises any of sulfur, chlorine, nitrogen, tellurium or selenium.

22. A photodetector, comprising:

a silicon substrate having a layer containing a plurality of electron-donating inclusions, said layer being adjacent to an underlying bulk portion of the substrate and forming a diode junction with said bulk portion,

a plurality of electrical contacts disposed on said substrate such that at least a portion of said layer remains exposed for receiving incident electromagnetic radiation,

wherein upon application of a selected reverse bias voltage to said diode junction via said electrical contacts, said substrate generates a photocurrent in response to exposure of said microstructured layer to incident radiation having a responsivity in a range of about 1 A/W to about 200 A/W for at least one radiation wavelength in a range of about 250 nm to about 1050 nm and a responsivity greater than about 0.1 A/W for at least one radiation wavelength in a range of about 1050 nm to about 3500 nm.

23. The photodetector of claim 22, wherein said diode junction comprises a p-n junction.

24. The photodetector of claim 22, wherein said silicon substrate generates a photocurrent in response to exposure of said layer to incident radiation having at least one wavelength in a range of about 1050 nm to about 2000 nm at a responsivity in a range of about 0.1 A/W to about 100 A/W.

25. The photodetector of claim 22, further comprising a voltage source for applying a bias voltage across said electrical contacts to said silicon substrate.

26. The photodetector of claim 25, wherein said voltage source applies a bias voltage in a range of about −

0.1 to about −

15 V to said substrate.

27. The photodetector of claim 22, wherein said electron-donating inclusions comprise sulfur inclusions.

28. The photodetector of claim 22, wherein said electron-donating inclusions comprise nitrogen inclusions.

29. The photodetector of claim 22, wherein said electron-donating inclusions comprise chlorine inclusions.

30. The photodetector of claim 22, wherein said electron-donating inclusions comprise selenium inclusions.

31. The photodetector of claim 22, wherein said electron-donating inclusions comprise tellurium inclusions.

32. The photodetector of claim 22, wherein a concentration of said electron-donating inclusions lies in a range of about 0.5 to about 5 atom percent.

33. The photodetector of claim 32, wherein the concentration of said electron-donating inclusions lies in a range of about 0.5 to about 1 atom percent.

34. A photodetector, comprising:

a silicon substrate having a surface layer including a dopant, said surface layer exhibiting a sheet charge density in a range of about 10¹² cm<sup>−

2</sup> to about 10¹⁴ cm<sup>−

2</sup>,

one or more electrical contacts disposed on the substrate for applying a reverse bias voltage to said surface layer,

wherein an exposure of at least a portion of the surface layer to radiation having at least one wavelength in a range of about 250 nm to about 1050 nm results in generation of an electrical signal at a responsivity greater than about 1 ampere/watt (A/W).

35. The photodetector of claim 34, wherein said responsivity is in a range of about 1 A/W to about 200 A/W.

36. The photodetector of claim 34, wherein an exposure of at least a portion of the surface layer to radiation having at least one wavelength in a range of about 1050 nm to about 3500 nm results in generation of an electrical signal at a responsivity greater than about 0.1 amperes/watt.

37. A photodetector, comprising:

a silicon substrate having a surface layer including electron-donating inclusions so as to form a diodic junction with an underlying portion of the substrate, said surface layer having an average thickness less than about 1 micron,

wherein upon application of a selected bias voltage to said junction, said substrate is capable of generating an electrical signal in response to radiation having at least one wavelength in a range of about 250 nm to about 1050 nm at a responsivity greater than about 1 ampere/watts (A/W).

38. The photodetector of claim 37, wherein said electron-donating inclusions comprise any of sulfur, selenium, or tellurium.

39. The photodetector of claim 37, wherein said photodetector exhibits a responsivity greater than about 0.1 amperes/watt for at least one wavelength in a range of about 1050 nm to about 3500 nm.

40. The photodetector of claim 37, wherein said surface layer has a thickness in a range of about 10 nm to about 1 micron.

41. A photodetector, comprising:

a silicon substrate having a doped layer adjacent a bulk silicon layer, said doped layer being configured for exposure to radiation over at least a portion thereof,

wherein said substrate is adapted to generate an electrical signal in response to exposure of said portion of the doped layer to radiation having one or more wavelengths in a range of about 250 nm to about 3500 nm, said electrical signal being characterized by a responsivity greater than about 1 amperes/watt for at least one wavelength in a range of about 250 nm to about 1050 nm and a responsivity greater than about 0.1 amperes/watt for at least one radiation wavelength in a range of about 1050 nm to about 3500 nm.

42. The photodetector of claim 41, further comprising one or more electrical contacts disposed on the substrate for applying an electrical bias to the substrate for facilitating generation of said electrical signal.

43. The photodetector of claim 42, wherein said electrical bias comprises a reverse bias voltage.

44. The photodetector of claim 43, wherein said bias voltage is less than about 15 volts.

45. The photodetector of claim 42, wherein said electrical bias comprises a forward bias voltage.

46. The photodetector of claim 41, wherein said substrate exhibits a diodic current-voltage characteristic.

47. The photodetector of claim 41, wherein said substrate exhibits a resistive current-voltage characteristic.

48. The photodetector of claim 41, wherein said doped layer comprises a plurality of charge-donating inclusions.

49. The photodetector of claim 48, wherein said charge-donating inclusions comprise sulfur inclusions.