# US 11,908,901 B1 · Graphene varactor including ferroelectric material > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,908,901 B1 - Document ID: US11908901B1 - Status: Granted - Kind: B1 - Application number: 16/818,494 - Filed: 2020-03-13 - Granted: 2024-02-20 - Earliest claimed: 2019-03-14 - Assignees: Regents of the University of Minnesota - Applicants: Regents of the University of Minnesota - Inventors: Steven J. Koester; Venkata Raghava Saran Kumar Chaganti - Web page: https://patentgrep.com/patent/US11908901B1 ## CPC - H10D 62/882: {Graphene} - H10D 1/045: {of capacitors having potential barriers, e.g. varactors} - H10D 1/64: Variable-capacitance diodes, e.g. varactors - H10D 1/66: Conductor-insulator-semiconductor capacitors, e.g. MOS capacitors - H10D 64/033: {comprising ferroelectric layers} - H10D 64/118: {Electrodes comprising insulating layers having particular dielectric or electrostatic properties, e.g. having static charges} - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES ## Abstract A varactor may include a gate electrode; a graphene layer; and a ferroelectric layer between the gate electrode and the graphene layer. ## Claims ### Claim 1 A varactor comprising: a gate electrode; a graphene layer; and a ferroelectric layer between the gate electrode and the graphene layer, wherein a capacitance tuning range of the varactor is based at least partially on a quantum capacitance effect of the graphene layer, and wherein a capacitance state of the varactor is non-volatile and based at least partially on the quantum capacitance effect. ### Claim 2 (depends on 1) The varactor of claim 1, further comprising a dielectric material between the ferroelectric layer and the graphene layer. ### Claim 3 (depends on 1) The varactor of claim 1, further comprising a dielectric material between the gate electrode and the ferroelectric layer. ### Claim 4 (depends on 1) The varactor of claim 1, further comprising an insulator layer, wherein the gate electrode is recessed in the insulator layer, and wherein the ferroelectric layer is over the gate electrode and the insulator layer. ### Claim 5 (depends on 4) The varactor of claim 4, further comprising a protective insulator on an exposed surface of the graphene layer opposite the ferroelectric layer. ### Claim 6 (depends on 1) The varactor of claim 1, further comprising an insulator layer, wherein the graphene layer is over the insulator layer, wherein the ferroelectric layer is over the graphene layer, and wherein the gate is over the ferroelectric layer. ### Claim 7 (depends on 1) The varactor of claim 1, wherein the ferroelectric layer comprises a hafnium-based ferroelectric. ### Claim 8 (depends on 1) The varactor of claim 1, wherein the ferroelectric layer comprises at least one of hafnium zirconate, hafnium lanthanate, or barium titanate. ### Claim 9 (depends on 1) The varactor of claim 1, wherein the graphene layer comprises a graphene monolayer. ### Claim 10 (depends on 1) The varactor of claim 1, further comprising at least two electrical contacts in electrical contact with the graphene layer. ### Claim 11 (depends on 1) The varactor of claim 1, wherein the varactor is part of an electrical device that includes an inductor electrically connected to the varactor, wherein the inductor and the varactor form an LC oscillator circuit having a resonant frequency responsive to a sense charge collected by the varactor. ### Claim 12 A varactor comprising: an insulator layer defining a plurality of fingers, wherein a first finger of the plurality of fingers extends in a first direction within the insulator layer, and wherein a second finger of the plurality of fingers extends in a second direction substantially opposite to the first direction; a gate electrode in the plurality of fingers; a first graphene layer positioned over the first finger; a second graphene layer positioned over the second finger; a ferroelectric layer between the gate electrode and the first graphene layer and between the gate electrode and the second graphene layer; and at least one contact electrode formed on the first and second graphene layers and making electrical contact with the first and second graphene layers, wherein a capacitance tuning range of the varactor is based at least partially on a quantum capacitance effect of the graphene layer, and wherein a capacitance state of the varactor is non-volatile and based at least partially on the quantum capacitance effect. ### Claim 13 (depends on 12) The varactor of claim 12, further comprising a dielectric material between the ferroelectric layer and the graphene layer. ### Claim 14 (depends on 12) The varactor of claim 12, further comprising a dielectric material between the gate electrode and the ferroelectric layer. ### Claim 15 (depends on 12) The varactor of claim 12, further comprising a protective insulator on an exposed surface of the graphene layer opposite the ferroelectric layer. ### Claim 16 (depends on 12) The varactor of claim 12, wherein the ferroelectric layer comprises a hafnium-based ferroelectric. ### Claim 17 (depends on 12) The varactor of claim 12, wherein the ferroelectric layer comprises at least one of hafnium zirconate, hafnium lanthanate, or barium titanate. ### Claim 18 (depends on 12) The varactor of claim 12, wherein the graphene layer comprises a graphene monolayer. ### Claim 19 (depends on 12) The varactor of claim 12, wherein the varactor is part of an electrical device that includes an inductor electrically connected to the varactor, wherein the inductor and the varactor form an LC oscillator circuit having a resonant frequency responsive to a sense charge collected by the varactor. ### Claim 20 A varactor comprising: a gate electrode; a graphene layer consisting essentially of graphene; and a ferroelectric layer between the gate electrode and the graphene layer, wherein a capacitance tuning range of the varactor is based at least partially on a quantum capacitance effect of the graphene layer, and wherein a capacitance state of the varactor is non-volatile and based at least partially on the quantum capacitance effect.