Silicon-based visible and near-infrared optoelectric devices

• US 8,080,467 B2
• Filed: 05/10/2010
• Issued: 12/20/2011
• 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: Mazur, Eric, Carey, III, James Edward
• Primary Examiner(s): NGO, NGAN V
• Application Number:
  US12/776,694
• Publication Number:
  US 20100240203A1
• Time in Patent Office: 589 Days
• Field of Search: 438/535, 438/663, 438/940, 257/E21.347, 257/E21.475
• US Class Current: 438/535
• 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 method of fabricating a semiconductor wafer, comprising:

irradiating one or more surface locations of a silicon substrate with a plurality of temporally short laser pulses while exposing said one or more locations to a substance so as to generate a plurality of surface inclusions containing at least a constituent of said substance in a surface layer of said substrate, and

annealing said substrate at an elevated temperature and for a duration selected to enhance a density of charge carriers in said surface layer.

2. The method of claim 1, wherein said charge carriers comprise electrons.

3. The method of claim 1, wherein said charge carriers comprise holes.

4. The method of claim 1, wherein said elevated temperature and duration are selected such that said annealed substrate exhibits a responsivity in a range of about 1 A/W to about 200 A/W in response to exposure of said surface layer to radiation having one or more wavelengths in a range of about 250 nm to about 1100 nm.

5. The method of claim 4, wherein said annealed substrate exhibits said responsivity when a reverse bias in a range of about 0.1 V to about 15 V is applied to said surface layer.

6. The method of claim 1, wherein said elevated temperature is selected to be in a range of about 500 K to about 1100 K.

7. The method of claim 6, wherein said duration is selected to be in a range of about a few seconds to about a few hours.

8. The method of claim 1, wherein said elevated temperature is selected to be in a range of about 700 K to about 900 K.

9. The method of claim 1, wherein said increase in the density of charge carriers is in a range of about 10 percent to about 200 percent.

10. The method of claim 1, wherein said annealing step enhances a responsivity of said substrate to radiation having one or more wavelengths in a range of about 250 nm to about 1100 nm by at least a factor about 10.

11. The method of claim 1, wherein said elevated temperature and duration are selected such that said annealed substrate exhibits a responsivity in a range of about 0.1 A/W to about 100 A/W in response to exposure of said surface layer to radiation having one or more wavelengths in a range of about 1050 nm to about 3500 nm.