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 processing a semiconductor substrate, comprising
depositing a solid charge-donating substance on a surface of a semiconductor substrate,
subsequently, irradiating said surface with a plurality of laser pulses having a pulse width in a range of about 50 femtoseconds to about 50 picoseconds incorporating at least a portion of said solid charge-donating substance into a surface layer of said semiconductor substrate at a concentration in a range of about 0.5 to about 5 atom percent,
wherein a diode junction is formed with an underlying portion of the substrate.
2. The method of claim 1 , wherein the solid charge-donating substance is a solid electron-donating substance.
3. The method of claim 2 , wherein said solid electron-donating substance comprises any of selenium and tellurium.
4. The method of claim 1 , wherein said pulse width is in a range of about 50 femtoseconds to about 500 femtoseconds.
5. The method of claim 1 , wherein said semiconductor substrate has an electrical resistivity in a range of about 0.001 ohm-m to about 10 ohm-m prior to said step of irradiating.
6. The method of claim 1 , wherein said pulses have fluence in a range of about 1 kJ/m 2 to about 12 kJ/m 2 .
7. The method of claim 1 , wherein said pulses have a central wavelength in range of about 200 nm to about 1200 nm.
8. The method of claim 1 , wherein said semiconductor substrate is a silicon substrate.
9. The method of claim 1 , wherein said pulses are applied to the semiconductor substrate at a repetition rate in a range of about 1 kHz to about 1 MHz.