Magnetic field sensor

• US 20030094943A1
• Filed: 10/29/2002
• Published: 05/22/2003
• Est. Priority Date: 05/19/2000
• Status: Active Grant

• Current Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Original Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Inventors: Ashley, Timothy, Phillips, Timothy J, Elliott, Charles T
• Granted Patent: US 6,809,514 B2
• Time in Patent Office: Days
• US Class Current: 324/251
• CPC Class Codes: G01R 33/07 Hall effect devices
• CPC Class Codes: Y10T 428/1107 Magnetoresistive
• CPC Class Codes: Y10T 428/1186 with head pole component

Abstract

The invention provides a Hall effect magnetic field sensor (10, 50) including carrier excluding or extracting means (36, 66) for reducing an intrinsic contribution to carrier concentration in the active region (14e, 53c) to provide for the sensor to be operative in an extrinsic saturated regime. This provides an advantage that magnetic field measurement sensitivity of the sensor (10, 50) can be made substantially insensitive to sensor temperature thereby improving measurement accuracy.

Claims

1. A magnetic field sensor incorporating a semiconducting sensor element (10, 50) with an active region (14e, 53e) in which a signal responsive to magnetic field is developed during operation, characterised in that the sensor element (10, 50):

a) is in an at least partially intrinsic conduction regime when unbiased and at a normal operating temperature;

b) includes a junction (36, 110) which is biasable to reduce intrinsic conduction in the active region (14e, 53e) and confine charge carriers predominantly to one type only corresponding to an extrinsic saturated regime, and

c) includes means for detecting a signal developed in the active region (14e, 53e) in response to applied magnetic field.

2. A sensor according to claim 1 characterised in that the junction is an excluding contact (36) for exclusion of minority carriers from the active region (14e).

3. A sensor according to claim 2 characterised in that the excluding contact (36) is a homojunction between indium antimonide materials of different doping concentration.

4. A sensor according to claim 2 characterised in that the excluding contact (36) is a heterojunction between indium antimonide (12) and a material (40, 41) having a wider band gap than indium antimonide.

5. A sensor according to claim 1 characterised in that it is a cruciform Hall effect sensor with a central active region (14e) from which four limbs (14a to 14d) extend, at least one limb (eg 14a) is connected to an excluding contact (eg 16a) for depleting the active region'"'"'s minority carrier concentration when biased, a first pair of limbs (14a, 14c) is connectable to a current supply and a second pair of limbs (14b, 14d) is connectable to Hall voltage measuring apparatus.

6. A sensor according to claim 5 characterised in that each of the second pair of limbs (53b, 53d) has a tapering portion adjacent the central active region (53e).

7. A sensor according to claim 5 characterised in that each limb (eg 14a) is connected to a respective excluding contact (eg 16a).

8. A sensor according to claim 1 characterised in that the junction is an extracting junction (110) for extraction of minority carriers from the active region (53e).

9. A sensor according to claim 8 characterised in that the extracting junction (110) is a junction between two sensor regions of materials having different majority carrier type and different band gap.

10. A sensor according to claim 8 characterised in that the extracting junction (110) is:

a) sufficiently thick to prevent electron tunnelling through it; and

b) sufficiently thin to avoid relaxing strain in materials associated with it.

11. A sensor according to claim 9 characterised in that the extracting junction (110) is a heterojunction of n-type indium antimonide (53) and In_1-xAl_xSb (54) where x is in the range 0.10 to 0.5.

12. A sensor according to claim 10 characterised in that x is in the range 0.15 to 0.2.

13. A sensor according to claim 11 characterised in that x substantially 0.15.

14. A sensor according to claim 8 characterised in it is cruciform with a central active region (53e) from which four limbs (53a to 53d) extend, the limbs have four successively disposed layers (64, 66, 53, 54) of which two adjacent layers are of one majority carrier type and two other adjacent layers are of the other majority carrier type, the extracting junction (110) is a heterojunction between an active region layer (53) and another layer (66) of different band gap and majority carrier type, a first pair of limbs (14a, 14c) is connectable to a current supply, a second pair of limbs (14b, 14d) is connectable to Hall voltage measuring apparatus, and the extracting junction (110) is reverse-biasable by means of a sensor substrate connection.

15. A sensor according to claim 14 characterised in that the four successively disposed layers (64, 66, 53, 54) are an n⁺npp⁺ structure.

16. A sensor according to claim 14 characterised in that each limb (53b, 53d) of the second pair of limbs has a tapering portion adjacent the central region (53e).

17. A sensor according to claim 14 characterised in that each limb (53b, 53d) of the second pair of limbs has a contact region adjoining onto the central active region (53e) which less than 10% of the limb width of each limb of the first pair of limbs (53a, 53c).

18. A sensor according to claim 8 characterised in that it is arranged for extraction current flow in a direction substantially orthogonal to charge carrier deflection by a magnetic field in normal operation.

19. A sensor according to claim 1 characterised in that the junction (514/520) is extracting and the active region is p-type.

20. A sensor according to claim 1 characterised in that the active region is a quantum well structure (510/512/514).

21. A sensor according to claim 20 characterised in that it includes a δ

-doping layer arranged to be a dominant source of charge carriers for the quantum well structure (510/512/514).

22. A sensor according to claim 20 or 21 characterised in that it is a n⁺-p³¹ -quantum well-p³¹ -p⁺ diode structure.

23. A sensor according to claim 1 characterised in that it includes a δ

-doping layer arranged to be a dominant source of charge carriers for the active region.

24. A sensor according to claim 23 characterised in that it is an n⁺-p-p⁺-p⁺ diode structure.

25. A method of detecting a magnetic field characterised in that it includes the steps of:

a) providing a magnetic field sensor incorporating a semiconducting sensor-element (10, 50) with an active region (14e, 53e) in which a signal responsive to magnetic field is developed during operation, the sensor element (10, 50) being in an at least partially intrinsic conduction regime at a normal operating temperature when unbiased, and including a junction (36, 110) which is biasable to reduce an intrinsic contribution to conduction in the active region (14e, 53e) and confine charge carriers predominantly to one type only corresponding to an extrinsic saturated regime;

b) biasing the sensor active region and the junction (36, 110) to provide for charge carrier flow in the active region and sensor operation to correspond to an extrinsic saturated regime and applying a magnetic field to the active region (14e, 53e); and

c) detecting a signal developed by the active region (14e, 53e) at least partially in response to the magnetic field.

26. A method of detecting a magnetic field according to claim 25 characterised in that the step of biasing the sensor active region is carried out at constant voltage and the step of detecting a signal involves detecting a voltage signal.

27. A method of detecting a magnetic field according to claim 25 characterised in that the sensor is a Hall effect sensor, the step of biasing the sensor active region involves applying a constant current thereto and the step of detecting a signal involves detecting a current signal.