Nanowire photodetector and image sensor with internal gain
A 1D nanowire photodetector device includes a nanowire that is individually contacted by electrodes for applying a longitudinal electric field which drives the photocurrent. An intrinsic radial electric field to inhibits photo-carrier recombination, thus enhancing the photocurrent response. Circuits of 1D nanowire photodetectors include groups of photodetectors addressed by their individual 1D nanowire electrode contacts. Placement of 1D nanostructures is accomplished with registration onto a substrate. A substrate is patterned with a material, e.g., photoresist, and trenches are formed in the patterning material at predetermined locations for the placement of 1D nanostructures. The 1D nanostructures are aligned in a liquid suspension, and then transferred into the trenches from the liquid suspension. Removal of the patterning material places the 1D nanostructures in predetermined, registered positions on the substrate.
1. A method for placement of 1D nanostructures with registration onto a substrate, the method comprising steps of:
coating a substrate with a patterning material, and patterning trenches dimensioned to align individual 1D nanostructures in the patterning material at a plurality of predetermined locations for the placement of individual 1D nanostructures in predetermined registered positions with respect to other individual 1D nanostructures;
aligning the 1D nanostructures in a liquid suspension;
transferring 1D nanostructures into the trenches from the liquid suspension; and
removing the patterning material from the substrate.
2. The method of claim 1 , wherein:
the 1D nanostructures comprise 1D nanowires; and
said steps of aligning and transferring are accomplished with the Langmuir-Blodgett or Langmuir-Schaeffer technique.
3. The method of claim 2 , further comprising a preliminary step of treating the substrate to adhere 1D nanowires.
4. The method of claim 1 , further comprising:
incorporating the placed nanostructures to serve as at least one of a photodetector, a field effect transistor, a memory, a logic gate, a metallic interconnect, a light emitting diode, a laser diode, an optical intrachip interconnect, a waveguide, a gas sensor matrix, a chemical sensor, a biosensor, a mechanical sensor, a MEMS device, an actuator, a photovoltaic device, a piezoelectrical device, etc. in a CMOS circuit, or a Si photonic circuit.
5. The method of claim 1 , wherein the 1D nanostructures comprise 1D nanowires and the trenches are dimensioned to approximately correspond to diameters of the 1D nanostructures.
6. The method of claim 1 , wherein the 1D nanostructures comprise 1D nanowires and the trenches are dimensioned to accommodate a predetermined angular misalignment of said step of aligning.
7. The method of claim 6 , wherein said step of aligning comprises the Langmuir-Blodgett or Langmuir-Schaeffer technique and the predetermined angular misalignment comprises 10%.
8. The method of claim 6 , wherein said step of aligning comprises fluidic, magnetophoretic or electrophoretic alignment.
9. The method of claim 8 , wherein the 1D nanostructures comprise 1D nanowires and said step of aligning comprises fluidic aligning, the fluidic aligning comprising:
dispersing the nanostructures into solution;
aligning flexible microchannels with the trenches;
circulating the solution in the flexible microchannels, and wherein said transferring comprises the nanostructures falling into the trenches from the microchannels.
10. The method of claim 8 , wherein the 1D nanostructures comprise 1D nanowires and said step of aligning comprises magnetophoretic or electrophoretic alignment, the magnetophoretic or electrophoretic alignment comprising:
dispersing the nanostructures into solution; and
immersing the substrate in the solution; and wherein said transferring comprises applying an electric or magnetic field to promote the nanostructures falling into the trenches.
11. The method of claim 1 , further comprising a preliminary step of treating the substrate to create hydrophobic or hydrophilic areas.
12. The method of claim 1 , further comprising forming patterned contacts to individual ones of the individual 1D nanostructures.