Quantum tunneling devices and circuits with lattice-mismatched semiconductor structures
Structures include a tunneling device disposed over first and second lattice-mismatched semiconductor materials. Process embodiments include forming tunneling devices over lattice-mismatched materials.
1. A device comprising:
an analog-to-digital converter comprising:
a first voltage divider, an input node of the first voltage divider being electrically coupled to a circuit analog input node,
a first multi-state resonant tunneling bipolar transistor having a first base, a first collector, and a first emitter, a voltage-divided node of the first voltage divider being electrically coupled to the first base, the first collector being a first output and being electrically coupled to a first node of a first impedance element, a second node of the first impedance element being electrically coupled to a first power node, the first emitter being electrically coupled to a second power node,
a second voltage divider, an input node of the second voltage divider being electrically coupled to the circuit analog input node, and
a second multi-state resonant tunneling bipolar transistor having a second base, a second collector, and a second emitter, a voltage-divided node of the second voltage divider being electrically coupled to the second base, the second collector being a second output and being electrically coupled to a first node of a second impedance element, a second node of the second impedance element being electrically coupled to the first power node, the second emitter being electrically coupled to the second power node; wherein:
the first multi-state resonant tunneling bipolar transistor is on a first crystalline material, the first crystalline material being on a substrate crystalline material of a substrate, the first crystalline material being lattice-mismatched to the substrate crystalline material, a majority of defects in the first crystalline material arising from the first crystalline material being lattice-mismatched to the substrate crystalline material terminating at sidewalls of the first crystalline material, and
the second multi-state resonant tunneling bipolar transistor is on a second crystalline material, the second crystalline material being on the substrate crystalline material, the second crystalline material being lattice-mismatched to the substrate crystalline material, a majority of defects in the second crystalline material arising from the second crystalline material being the lattice-mismatched to the substrate crystalline material terminating at sidewalls of the second crystalline material.
2. The device of claim 1 , wherein the first power node is a power supply node, and the second power node is a ground node.
3. The device of claim 1 , wherein:
the first voltage divider comprises a first resistor and a second resistor, a first node of the first resistor being the input node of the first voltage divider, a second node of the first resistor being the voltage-divided node of the first voltage divider and being electrically coupled to a first node of the second resistor, a second node of the second resistor being electrically coupled to the second power node, and
the second voltage divider comprises a third resistor and a fourth resistor, a first node of the third resistor being the input node of the second voltage divider, a second node of the third resistor being the voltage-divided node of the second voltage divider and being electrically coupled to a first node of the fourth resistor, a second node of the fourth resistor being electrically coupled to the second power node, the first resistor and the third resistor having a same resistance value, the second resistor and the fourth resistor having a different resistance value.
4. The device of claim 1 , wherein the sidewalls of the first crystalline material are defined by first sidewalls of a dielectric material, and the sidewalls of the second crystalline material are defined by second sidewalls of the dielectric material.
5. The device of claim 1 , wherein each of the first multi-state resonant tunneling bipolar transistor and the second multi-state resonant tunneling bipolar transistor comprises a stack of dual tunnel structures.
6. The device of claim 1 , wherein each of the first multi-state resonant tunneling bipolar transistor and the second multi-state resonant tunneling bipolar transistor comprises:
a first n+ doped layer over the first crystalline material or the second crystalline material, respectively, an contact being on the first n+ doped layer,
a first n doped layer over the first n+ doped layer,
a p+ doped layer over the first n doped layer, a base contact being on the p+ doped layer,
a second n doped layer over the p+ doped layer,
a first tunnel structure over the second n doped layer,
a second n+ doped layer over the first tunnel structure,
a second tunnel structure over the second n+ doped layer, and
a third n+ doped layer over the second tunnel structure, an emitter contact being on the third n+ doped layer.
7. The device of claim 6 , wherein:
the first tunnel structure comprises:
a first layer of a first undoped material over the second n doped layer,
a second layer of a second undoped material over the first layer, and
a third layer of the first undoped material over the second layer, and
the second tunnel structure comprises:
a fourth layer of a third undoped material over the second n+ doped layer,
a fifth layer of a fourth undoped material over the fourth layer, and
a sixth layer of the third undoped material over the fifth layer.
8. A device comprising:
a comparator comprising:
a first resonant tunneling diode (RTD) having a first anode and a first cathode, the first anode being electrically coupled to a first power node, the first cathode being electrically coupled to an output node,
a first high electron mobility transistor (HEMT) having a first gate, a first source/drain, and a second source/drain, the first gate being electrically coupled to an input node, the first source/drain being electrically coupled to the output node,
a second RTD having a second anode and a second cathode, the second anode being electrically coupled to the second source/drain, the second cathode being electrically coupled to a second power node, and
a second HEMT having a second gate, a third source/drain, and a fourth source/drain, the second gate being electrically coupled to a clock node, the third source/drain being electrically coupled to the first power node, the fourth source/drain being electrically coupled to the output node; wherein:
the first RTD is on a first crystalline material, the first crystalline material being on a substrate crystalline material of a substrate, the first crystalline material being lattice-mismatched to the substrate crystalline material, a majority of defects in the first crystalline material arising from the first crystalline material being lattice-mismatched to the substrate crystalline material terminating at sidewalls of the first crystalline material, and
the second RTD is on a second crystalline material, the second crystalline material being on the substrate crystalline material, the second crystalline material being lattice-mismatched to the substrate crystalline material, a majority of defects in the second crystalline material arising from the second crystalline material being lattice-mismatched to the substrate crystalline material terminating at sidewalls of the second crystalline material.
9. The device of claim 8 further comprising a dielectric layer over the substrate, the dielectric layer having a first opening and a second opening, the first crystalline material being in the first opening, sidewalls of the first opening defining the sidewalls of the first crystalline material, the second crystalline material being in the second opening, sidewalls of the second opening defining the sidewalls of the second crystalline material.
10. The device of claim 8 , wherein a distal portion of the first crystalline material distal from the substrate has a dislocation defect density of less than 10 6 cm −2 , and a distal portion of the second crystalline material distal from the substrate has a dislocation defect density of less than 10 6 cm −2 .
11. The device of claim 8 , wherein a distal portion of the first crystalline material distal from the substrate has a dislocation defect density of less than 10 6 cm −2 , and a distal portion of the second crystalline than 10 3 cm −2 .
12. The device of claim 8 , wherein each of the first RTD and the second RTD comprises:
a first doped layer of a first material over the first crystalline material or the second crystalline material, respectively,
a first undoped layer of the first material over the first doped layer,
a first barrier layer over the first undoped layer,
a second undoped layer of the first material over the first barrier layer,
a second barrier layer over the second undoped layer,
a third undoped layer of the first material, and
a second doped layer of the first material over the third undoped layer.
13. The device of claim 8 further comprising:
a first contact on a top portion of the first RTD;
a second contact on the first crystalline material;
a third contact on a top portion of the second RTD; and
a fourth contact on the second crystalline material.
14. A device comprising:
a clock-generator comprising:
a first resonant tunneling diode (RTD) having a first anode and a first cathode, the first anode being electrically coupled to an output node, the first cathode being electrically coupled to a first power node,
a second RTD having a second anode and a second cathode, the second anode being electrically coupled to the output node, the second cathode being electrically coupled to a second power node,
a third RTD having a third anode and a third cathode, the third anode being electrically coupled to the first power node, the third cathode being electrically coupled to a complementary output node, and
a fourth RTD having a fourth anode and a fourth cathode, the fourth anode being electrically coupled to the second power node, the fourth cathode being electrically coupled to the complementary output node;
wherein each of the first RTD, the second RTD, the third RTD, and the fourth RTD is on a respective first crystalline material, the first crystalline material being on a substrate crystalline material of a substrate, the first crystalline material being lattice-mismatched to the substrate crystalline material, a majority of defects in the first crystalline material arising from the lattice-mismatch to the substrate crystalline material terminating at sidewalls of the first crystalline material.
15. The device of claim 14 further comprising a dielectric layer over the substrate, the dielectric layer having respective openings, the first crystalline material being in the respective openings, sidewalls of the respective openings defining the sidewalls of the first crystalline material.
16. The device of claim 14 , wherein respective distal portions of the first crystalline material distal from the substrate has a dislocation defect density of less than 106 cm-2.
17. The device of claim 14 , wherein each of the first RTD, the second RTD, the third RTD, and the fourth RTD comprises: a first doped layer of a first material over the respective first crystalline material, a first undoped layer of the first material over the first doped layer, a first barrier layer over the first undoped layer, a second undoped layer of the first material over the first barrier layer, a second barrier layer over the second undoped layer, a third undoped layer of the first material, and a second doped layer of the first material over the third undoped layer.