Light-driven ultrafast electric gating
View Patent ↗A source and drain electrode are spaced apart by an optically exposed gate region above a surface photovoltage effect (SPV) bulk. A two-dimensional material is deposited upon the gate region. The gate region is activated by exposure to an ultrafast light pulse, which may be infrared or near-infrared, and may be a focused collimated laser pulse with a sub-picosecond width. The pulse causes electron-hole pair generation resulting in band bending in the SPV material, which generates an electric field within the 2D material, thereby modifying the electronic properties between source and drain via a field-effect. After passage of the pulse, conduction continues in the device until the conductive electron-hole pairs recombine during the SPV decay time. The two-dimensional material may comprise a crystalline atomic monolayer. The activation is repeatable with subsequent pulses, resulting in the device cycling on and off within timescales less than 200 picoseconds.
1 . A device comprising:
a semiconductor, the semiconductor capable of exhibiting a surface photovoltage effect;
an insulating buffer layer disposed on the surface of the semiconductor;
a two-dimensional material disposed on the surface of the insulating buffer layer;
a drain electrode disposed on the two-dimensional material and a source electrode disposed on the two-dimensional material; and
an area between the drain electrode and the source electrode configured to be illuminated by sub-picosecond infrared pulses from an infrared light source,
wherein a current flowing from the source electrode to the drain electrode is modified by a gate dependent property of the two-dimensional material when the area is illuminated by the sub-picosecond infrared pulse and subsequent surface photovoltage decay time afterward.
2 . The device of claim 1 , wherein the two-dimensional material comprises a crystalline solid selected from a group consisting of: a single layer of atoms, a single molecular layer, one or more layers of atoms ranging from approximately 1 Å to approximately 10 nm thickness, one or more single molecular layers totaling approximately 1 Å to approximately 10 nm thickness, one or more molecular layers totaling approximately 1 Å to approximately 10 nm thickness, and a thin multilayered material of approximately 1 to approximately 5 monolayers thickness.
3 . The device of claim 1 , wherein the gate dependent property is selected from a group of properties consisting of magnitude and spin polarization.
4 . The device of claim 1 , wherein the modification by the gate dependent property of the two-dimensional material is reversibly restored after the area is illuminated by the sub-picosecond infrared pulse and the surface photovoltage has substantially decayed.
5 . The device of claim 1 , wherein switching of the modification of the gate dependent property and back occurs at timescales of less than about 200 picoseconds.
6 . The device of claim 1 , wherein the semiconductor is a semiconductor selected from a group consisting of: bismuth selenide (Bi 2 Se 3 ), gallium arsenide (GaAs), and silicon.
7 . The device of claim 1 , wherein the two-dimensional material is a two-dimensional material selected from a group consisting of: graphene, and a transition metal dichalcogenide (TMD).
8 . The device of claim 1 , wherein the insulating buffer layer is a material selected from group consisting of: hexagonal boron nitride (hBN), a thin-film high-k dielectric, and a thin film strontium titanate (SrTiO 3 ) dielectric.
9 . The device of claim 1 , further comprising an infrared light source capable of producing sub-picosecond coherent infrared pulses.
10 . The device of claim 9 , wherein the infrared light source is an infrared laser.
11 . The device of claim 10 , wherein the infrared laser is a focused sub-picosecond near-infrared pulsed laser having a full width at half maximum (FWHM) pulse of less than one picosecond.
12 . An apparatus comprising:
a focused sub-picosecond near-infrared pulsed laser having a full width at half maximum (FWHM) pulse of less than one picosecond capable of producing sub-picosecond infrared pulses;
a bulk semiconductor, the semiconductor exhibiting a surface photovoltage effect, a two-dimensional electronic system being formed at a surface of the bulk material;
a drain electrode disposed on the surface of the semiconductor and a source electrode disposed on the surface of the semiconductor; and
an area between the drain electrode and the source electrode configured to be illuminated by sub-picosecond infrared pulses from the infrared laser, producing picosecond time-varying electric fields at the bulk material's surface, thereby reversibly modulating a quantum well spectrum and a Rashba effect.
13 . The apparatus of claim 12 , where the two-dimensional electronic system formed at the surface of the bulk material is that of a two-dimensional electron gas.
14 . The apparatus of claim 12 , wherein when the device is in operation, current flowing from the source electrode to the drain electrode is modified by a gate dependent property of the two-dimensional electronic system when the area is illuminated by a sub-picosecond infrared pulse and subsequent surface photovoltage decay time afterward.
15 . The apparatus of claim 14 , wherein the gate dependent property of the two-dimensional electronic system is selected from a group consisting of magnitude and spin-polarization.
16 . The apparatus of claim 15 , wherein the semiconductor is a semiconductor from the group of bismuth selenide (Bi 2 Se 3 ), gallium arsenide (GaAs), and silicon.
17 . The apparatus of claim 14 , wherein when the device is in operation, the modification by the gate dependent property of the two-dimensional electronic system is reversibly restored after the area is illuminated by the sub-picosecond infrared pulse and the surface photovoltage has decayed.
18 . The apparatus of claim 14 , wherein switching of the modification of the gate-dependent property and back occurs at timescales of less than about 200 picoseconds.