Low-offset Graphene Hall sensor

Patent metadata

Field	Value
Publication number	US-10001529-B2
Application number	US-201514936631-A
Country	US
Kind code	B2
Filing date	Nov 9, 2015
Priority date	Sep 3, 2015
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

A Graphene Hall sensor (GHS) is provided with a modulated gate bias signal in which the modulated gate bias signal alternates at a modulation frequency between a first voltage that produces a first conductivity state in the GHS and a second voltage that produces approximately a same second conductivity state in the GHS. A bias current is provided through a first axis of the GHS. A resultant output voltage signal is provided across a second axis of the Hall sensor that includes a modulated Hall voltage and an offset voltage, in which the Hall voltage is modulated at the modulation frequency. An amplitude of the Hall voltage that does not include the offset voltage is extracted from the resultant output voltage signal.

First claim

What is claimed is:

1. A method of operating a graphene Hall sensor, the method comprising:
providing a modulated gate signal to a first gate of the graphene Hall sensor (GHS), in which the modulated gate signal alternates at a modulation frequency between a first voltage that produces a first conductivity state in the GHS and a second voltage that produces a second conductivity state in the GHS, the second conductivity state having a same conductivity as the first conductivity state;
providing a bias current through a first axis of the GHS;
obtaining a resultant output voltage signal across a second axis of the Hall sensor that includes a modulated Hall voltage and an offset voltage, in which the Hall voltage is modulated at the modulation frequency; and
extracting an amplitude of the Hall voltage that does not include the offset voltage.

2. The method of claim 1 , in which extracting the amplitude of the Hall voltage is performed by synchronous demodulation of the output voltage signal.

3. The method of claim 1 , in which extracting the amplitude of the Hall voltage is performed by bandpass filtering the output voltage signal.

4. The method of claim 1 , in which extracting the amplitude of the Hall voltage is performed using a Fast Fourier Transform.

5. The method of claim 1 , in which the modulated gate signal is modulated at a frequency in a range of 10-100 MHz.

6. The method of claim 1 , in which the first gate is a top gate and the GHS has a back gate, in which the modulated gate signal is provided to the top gate and an adaptively controlled voltage is applied to the back gate.

7. The method of claim 1 , in which the first gate is a back gate, in which the modulated gate signal is provided to the back gate.

8. The method of claim 1 , in which the modulated gate signal is modulated between a negative voltage amplitude VG 1 and a positive voltage amplitude VG 2 to cause the GHS to switch between two equal conductivity states that result in equal offset voltages at each state.

9. A Hall effect sensor system comprising:
a graphene Hall sensor (GHS) having a graphene layer with a first pair of contacts configured to provide a bias current through a first axis of the graphene layer and a second pair of contacts configured to measure a Hall effect voltage across a second axis of the graphene layer and a conductive first gate spaced apart from the graphene layer by a dielectric, in which the Hall effect voltage includes an offset voltage;
an oscillator coupled to the gate configured to provide a modulated gate signal that alternates at a modulation frequency between a first voltage that produces a first conductivity state in the GHS and a second voltage that produces a second conductivity state in the GHS, the second conductivity state having a same conductivity as the first conductivity state; and
a demodulator coupled to receive the Hall effect voltage configured to extract an amplitude of the Hall effect voltage that does not include the offset voltage.

10. The system of claim 9 , in which the first gate is a top gate that covers only a channel portion of the GHS and does not cover the first pair of contacts and the second pair of contacts.

11. The system of claim 9 , in which the demodulator includes a local oscillator coupled to a mixer, and in which the second pair of contacts are coupled to the mixer via a low noise amplifier.

12. The system of claim 9 , in which the demodulator includes a bandpass filter.

13. The system of claim 9 , in which the demodulator includes an analog to digital converter and a processor configured to perform a Fast Fourier Transform of the Hall Effect voltage.

14. The system of claim 9 , in which the oscillator is configured to provide the modulated gate signal with a modulation frequency in a range of 10-100 MHz.

15. The system of claim 9 , in which the first gate is a top gate and the GHS has a back gate, in which the modulated gate signal from the oscillator is applied to the top gate and an adaptively controlled voltage source is applied to the back gate.

16. The system of claim 9 , in which the first gate is a back gate, in which the modulated gate signal from the oscillator is applied to the back gate.

17. The system of claim 9 , further including a fuel tank, in which the GHS is coupled to the fuel tank.

18. The system of claim 9 , in which the GHS is coupled to flux core that surrounds a conductive wire.

19. A method of operating a Hall effect sensor, the method comprising:
applying an oscillating gate voltage at a modulation frequency to a first gate of the Hall effect sensor, wherein the gate voltage oscillates between a first voltage that produces a first conductivity state in the Hall effect sensor and a second voltage that produces a second conductivity state in the Hall effect sensor, the second conductivity state having a same conductivity as the first conductivity state;
conducting a bias current through a first axis of the Hall effect sensor;
producing an output voltage signal across a second axis of the Hall effect sensor that includes a Hall voltage modulated at the modulation frequency and an offset voltage; and
extracting an amplitude of the Hall voltage that does not include the offset voltage.

20. The method of claim 19 , comprising:
mixing an oscillator voltage at the modulation frequency with the modulated Hall voltage to produce a demodulated output signal; and
filtering the demodulated output signal.

Assignees

• Texas Instruments Inc

Inventors

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

Classifications

• G01R33/075

  Hall devices configured for spinning current measurements · CPC title

• G01R33/0029

  Treating the measured signals, e.g. removing offset or noise · CPC title

• G01R33/07 Primary

  Hall effect devices · CPC title

• G01R33/0041

  using feed-back or modulation techniques · CPC title

• G01R33/1284

  Spin resolved measurements; Influencing spins during measurements, e.g. in spintronics devices · CPC title