Silicon-based visible and near-infrared optoelectric devices
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.
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.