# US 2019/0378919 A1 · Cascade Field Effect Transistors

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2019/0378919 A1
- Document ID: US20190378919A1
- Status: Published application
- Kind: A1
- Application number: 16/435,457
- Filed: 2019-06-07
- Published: 2019-12-12
- Earliest claimed: 2018-06-08
- Assignees: Purdue Research Foundation
- Applicants: Purdue Research Foundation
- Inventors: Tillmann C. Kubis; James Charles
- Web page: https://patentgrep.com/patent/US20190378919A1

## CPC

- H10D 48/383: {Quantum effect devices, e.g. of devices using quantum reflection, diffraction or interference effects}
- H10D 62/121: {oriented parallel to substrates}
- B82Y 10/00: Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
- H10D 12/211: {Gated diodes}
- H10D 62/117: {Shapes of semiconductor bodies}
- H10D 62/8162: {having quantum effects only in the vertical direction, i.e. layered structures having quantum effects solely resulting from vertical potential variation}
- H10D 62/8164: {comprising only semiconductor materials (potential variation in long-range structurally-disordered materials H10D62/8163)}
- H10D 62/822: comprising only Group IV materials heterojunctions, e.g. Si/Ge heterojunctions
- H10D 62/824: comprising only Group III-V materials heterojunctions, e.g. GaN/AlGaN heterojunctions
- H10D 62/882: {Graphene}
- H10D 64/27: Electrodes not carrying the current to be rectified, amplified, oscillated or switched, e.g. gates
- H10D 30/43: having one-dimensional [1D] charge carrier gas channels, e.g. quantum wire FETs or transistors having 1D quantum-confined channels
- H10D 64/518: {characterised by their lengths or sectional shapes}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES

## Abstract

A field-effect transistor (FET) includes a fin, an insulator region, and at least one gate. The fin has a doped first region, a doped second region, and an interior region between the first region and the second region. The interior region is undoped or more lightly doped than the first and second regions. The interior region of the fin is formed as a superlattice of layers of first and second materials alternating vertically. The insulator layer extends around the interior region. The gate is formed on at least a portion of the insulator region. The insulator layer and the gate are configured to generate an inhomogeneous electrostatic potential within the interior region, the inhomogeneous electrostatic potential cooperating with physical properties of the superlattice to cause scattering of charge carriers sufficient to change a quantum property of such charge carriers to change the ability of the charge carriers to move between the first and second materials.

## Claims

### Claim 1

A field-effect transistor (FET) comprising:
a fin have a doped first region, a doped second region, and an interior region between the first region and the second region, the interior region being undoped or more lightly doped than the first region and the second region, at least the interior region of the fin formed as a superlattice of layers of first and second materials alternating vertically;
an insulator layer formed around the interior region;
at least one gate formed on at least a portion of the insulator region; and
wherein the insulator layer and the at least one gate are configured to generate an inhomogeneous electrostatic potential within the interior region, the inhomogeneous electrostatic potential cooperating with physical properties of the superlattice to cause scattering of charge carriers sufficient to change a quantum property of such charge carriers to change the ability of the charge carriers to move between the first and second materials.

### Claim 2 (depends on 1)

The FET of claim 1, wherein the quantum property of the charge carriers in the first material differs from the quantum property of the charge carriers in the second material.

### Claim 3 (depends on 2)

The FET of claim 2, wherein the quantum property is a momentum of the charge carriers.

### Claim 4 (depends on 2)

The FET of claim 2, wherein the quantum property is the band valley in which the charge carriers reside.

### Claim 5 (depends on 2)

The FET of claim 2, wherein the quantum property is a spin direction of the charge carriers.

### Claim 6 (depends on 2)

The FET of claim 2, wherein the inhomogeneous electrostatic potential cooperates with physical properties of the superlattice to change the overlap of the wave functions of the first and second materials in comparison to the absence of the inhomogeneous electrostatic potential, sufficient to change the conductance between the doped first region and the doped second region.

### Claim 7 (depends on 6)

The FET of claim 6, wherein the inhomogeneous electrostatic potential cooperates with the physical properties of the superlattice to cause scattering of the charge carriers on phonons.

### Claim 8 (depends on 6)

The FET of claim 6, wherein the inhomogeneous electrostatic potential cooperates with the physical properties of the superlattice to cause scattering of the charge carriers, wherein said physical properties of the superlattice includes roughness at boundaries between the layers of first and second materials, said roughness contributing to the scattering of the charge carriers.

### Claim 9 (depends on 6)

The FET of claim 6, wherein the inhomogeneous electrostatic potential cooperates with the physical properties of the superlattice to cause scattering of the charge carriers, wherein said physical properties of the superlattice includes roughness at boundaries between the layers of first and second materials, said roughness contributing to the scattering of the charge carriers.

### Claim 10 (depends on 6)

The FET of claim 6, wherein the inhomogeneous electrostatic potential cooperates with the physical properties of the superlattice to cause scattering of the charge carriers, wherein said physical properties of the superlattice includes impurities in at least one of the first and second materials in the superlattice.

### Claim 11 (depends on 1)

The FET of claim 1, wherein the interior region is undoped.

### Claim 12 (depends on 1)

The FET of claim 1, wherein the at least one gate comprises a metal or a heavily doped semiconductor.

### Claim 13 (depends on 1)

The FET of claim 1, wherein the at least one gate comprises a first gate and a separate second gate, a top portion of the first gate extending over a top of the interior region, and a bottom portion of the second gate extending under the bottom of the interior region, wherein the top portion and the second portion have different thicknesses.

### Claim 14 (depends on 1)

The FET of claim 1, wherein the doped first region is formed from the first material, and the doped second region is formed from the second material.

### Claim 15 (depends on 14)

The FET of claim 14, wherein the first region is p-doped, and the second region is n-doped.

### Claim 16 (depends on 1)

The FET of claim 1, wherein the first material and second material have different chemical components.

### Claim 17

A field-effect transistor (FET) comprising:
a fin have a doped first region, a doped second region, and an interior region between the first region and the second region, the interior region being undoped or more lightly doped than the first region and the second region, at least the interior region of the fin formed as a superlattice of layers of first and second materials alternating vertically;
an insulator layer formed around the interior region;
at least one gate formed on at least a portion of the insulator region; and
wherein the fin extends in a current direction from the first region to the second region and through the interior region, wherein the insulator layer and the at least one gate are configured to apply an electric field perpendicular to the current direction when voltage is applied to the at least one gate;
and wherein the insulator layer and the at least one gate are configured to generate an inhomogeneous electrostatic potential to cause scattering of charge carriers sufficient to change a quantum property of such charge carriers to change the ability of the charge carriers to move between the first and second materials.

### Claim 18 (depends on 17)

The FET of claim 17, wherein the at least one gate comprises a first gate and a separate second gate, a top portion of the first gate extending over a top of the interior region, and a bottom portion of the second gate extending under the bottom of the interior region, wherein the top portion and the second portion have different thicknesses.