Low noise graphene hall sensors, systems and methods of making and using same

Patent metadata

Field	Value
Publication number	US-10069065-B2
Application number	US-201514676233-A
Country	US
Kind code	B2
Filing date	Apr 1, 2015
Priority date	Apr 1, 2015
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

Graphene Hall sensors, magnetic sensor systems and methods for sensing a magnetic field using an adjustable gate voltage to adapt the Hall sensor magnetic field sensitivity according to a control input for environmental or process compensation and/or real-time adaptation for balancing power consumption and minimum detectable field performance. The graphene Hall sensor gate voltage can be modulated and the sensor output signal can be demodulated to combat flicker or other low frequency noise. Also, graphene Hall sensors can be provided with capacitive coupled contacts for reliable low impedance AC coupling to instrumentation amplifiers or other circuits using integral capacitance.

First claim

What is claimed is:

1. A magnetic sensor system, comprising:
a graphene Hall sensor for sensing a magnetic field, including:
a graphene layer formed on a substrate;
a dielectric structure formed over a channel portion of the graphene layer;
a conductive gate structure formed over at least a portion of the dielectric structure above the channel portion of the graphene layer for applying a gate voltage to control a carrier concentration of the channel portion of the graphene layer;
first and second conductive excitation contact structures coupled with corresponding first and second excitation portions of the graphene layer for applying at least one of the following to the channel portion of the graphene layer: a bias voltage; and a bias current; and
first and second conductive sense contact structures coupled with corresponding first and second sense portions of the graphene layer for sensing a Hall voltage of the channel portion of the graphene layer;

a sensor interface circuit for providing at least one of an excitation current and voltage to the graphene layer via the first and second conductive excitation contact structures, and for receiving an output signal from at least one of the first and second conductive sense contact structures representing the magnetic field; and
a control circuit that includes an AC modulator to apply an alternating square wave voltage signal to the conductive gate structure at a modulating frequency to alternately increase a magnetic field sensitivity of the Hall sensor in opposite polarity directions as the alternating square wave voltage signal alternately increases in opposite polarity directions;
the sensor interface circuit including a demodulator to demodulate the output signal at the modulating frequency to provide a demodulated output signal representing the magnetic field.

2. The magnetic sensor system of claim 1 , wherein at least one of the conductive excitation and sense contact structures is capacitively coupled with its corresponding portion of the graphene layer.

3. The magnetic sensor system of claim 2 , wherein the dielectric structure is formed at least partially between the first conductive sense contact structure and the first sense portion of the graphene layer to form a first capacitive contact.

4. The magnetic sensor system of claim 1 , wherein the modulating frequency is greater than 10 kHz.

5. The magnetic sensor system of claim 4 , wherein the modulating frequency is greater than 1 MHz.

6. The magnetic sensor system of claim 1 , wherein the control circuit is coupled to provide the alternating square wave voltage signal to the conductive gate structure, at least partially according to a temperature compensation control input signal for temperature compensating the magnetic field sensitivity of the Hall sensor.

7. The magnetic sensor system of claim 1 , wherein the control circuit is coupled to provide the alternating square wave voltage signal to the conductive gate structure, at least partially according to a sensitivity control input signal from an external system for adaptive control of the magnetic field sensitivity of the Hall sensor.

8. A method of sensing a magnetic field, the method comprising:
applying at least one of the following to a channel portion of a Hall sensor graphene layer: a bias voltage; and a bias current;
applying an alternating square wave voltage signal to a gate contact of the Hall sensor at a modulating frequency to alternately increase a magnetic field sensitivity of the Hall sensor in opposite polarity directions as the alternating square wave voltage signal alternately increases in opposite polarity directions;
receiving an output signal from a sense contact of the Hall sensor; and
demodulating the output signal at the modulating frequency to provide a demodulated output signal representing a sensed magnetic field.

9. The method of claim 8 , wherein the modulating frequency is greater than 10 kHz.

10. The method of claim 9 , wherein the modulating frequency is greater than 1 MHz.

11. A graphene device for sensing a magnetic field, the graphene device comprising:
a graphene layer formed on a substrate;
a dielectric structure formed over a channel portion of the graphene layer;
a conductive gate structure formed over at least a portion of the dielectric structure above the channel portion of the graphene layer for applying a gate voltage to control a carrier concentration of the channel portion of the graphene layer;
first and second conductive source/drain contact structures coupled with corresponding first and second source/drain portions of the graphene layer for applying at least one of the following to the channel portion of the graphene layer: a bias voltage; and a bias current;
first and second conductive sense contact structures coupled with corresponding first and second sense portions of the graphene layer for sensing a Hall voltage of the channel portion of the graphene layer, in which: the dielectric structure is positioned between the first conductive sense contact structure and the first sense portion of the graphene layer to form a first capacitive contact for capacitively coupling between them through the dielectric structure; and the dielectric structure is positioned between the second conductive sense contact structure and the second sense portion of the graphene layer to form a second capacitive contact for capacitively coupling between them through the dielectric structure;
a sensor interface circuit for providing at least one of an excitation current and voltage to the graphene layer via the first and second conductive source/drain contact structures, and for receiving an output signal from at least one of the first and second conductive sense contact structures representing the magnetic field; and
a control circuit that includes an AC modulator to apply an alternating square wave voltage signal to the conductive gate structure at a modulating frequency to alternately increase a magnetic field sensitivity of the graphene device in opposite polarity directions as the alternating square wave voltage signal alternately increases in opposite polarity directions;
wherein the sensor interface circuit including a demodulator to demodulate the output signal at the modulating frequency to provide a demodulated output signal representing the magnetic field.

12. The graphene device of claim 11 , wherein the modulating frequency is greater than 10 kHz.

13. The graphene device of claim 12 , wherein the modulating frequency is greater than 1 MHz.

Assignees

• Texas Instruments Inc

Inventors

• Polley Arup
• Venugopal Archana
• Doering Robert Reid
• Colombo Luigi

Classifications

• G01R33/07

  Hall effect devices · CPC title

• H01L43/065

  Electricity · mapped topic

• H01L43/10 Primary

  Electricity · mapped topic

• H10N50/85 Primary

  Materials of the active region · CPC title

• H10N52/101

  Semiconductor Hall-effect devices · CPC title