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 photovoltaic device, comprising:
a silicon substrate having a thickness in a range of about 2 microns to about 260 microns,
said silicon substrate having a textured surface layer formed by exposure of a surface of the substrate to a plurality of short radiation pulses,
wherein the photovoltaic device exhibits 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.
2. The photovoltaic device of claim 1 , wherein said device exhibits said responsivity at a zero applied bias.
3. The photovoltaic device of claim 1 , wherein said textured layer has a thickness in a range of about 10 nm to about 1 micron.
4. The photovoltaic device of claim 1 , wherein said short radiation pulses comprise laser pulses having a pulsewidth in a range of about 100 fs to about 30 ns.
5. The photovoltaic device of claim 1 , wherein said short radiation pulses comprise laser pulses having a pulsewidth in a range of about 50 fs to about 50 picoseconds.
6. The photovoltaic device of claim 1 , wherein said short radiation pulses comprise laser pulses having a pulsewidth in a range of about 50 fs to about 500 fs.
7. The photovoltaic device of claim 1 , wherein said silicon substrate has an electrical resistivity in a range of about 0.001 ohm-m to about 10 ohm-m.
8. The photovoltaic device of claim 1 , wherein said textured surface layer exhibits a plurality of microstructures.
9. The photovoltaic device of claim 8 , wherein said microstructures are roughly conical.
10. The photovoltaic device of claim 9 , wherein said conical microstructures exhibit a height in a range of about 8 microns to about 20 microns.
11. The photovoltaic device of claim 9 , wherein said conical microstructures are separated by a distance in a range of about 4 microns to about 20 microns.
12. The photovoltaic device of claim 1 , wherein said silicon substrate comprises any of a p-doped and n-doped substrate.
13. The photovoltaic device of claim 12 , wherein said silicon substrate exhibits a doping level in a range of about 10 11 to about 10 18 .
14. The photovoltaic device of claim 12 , wherein said silicon substrate includes boron as dopant.
15. The photovoltaic device of claim 12 , wherein said silicon substrate includes phosphorous as dopant.
16. The photovoltaic device of claim 12 , wherein said silicon substrate includes nitrogen as dopant.
17. The photovoltaic device of claim 1 , wherein said silicon substrate comprises a crystalline silicon portion.
18. The photovoltaic device of claim 1 , wherein said silicon substrate includes a diode junction.