Charge-carrier hall-effect sensor

A method of manufacturing a charge-carrier Hall-effect sensor comprising:

• selectively controlling magnetization of second regions of a ferromagnetic layer to provide, as magnetic islands, first regions of the ferromagnetic layer each magnetized in a first direction perpendicular to a plane occupied by the ferromagnetic layer;
• providing an electrically insulating layer over the ferromagnetic layer;
• providing a semiconductor or semimetal layer over the electrically insulating layer;
• and
• patterning the semiconductor or semimetal layer to form a Hall-effect sensor overlying the first regions of the ferromagnetic layer, wherein the Hall-effect sensor comprises a pair of electric current contacts in contact with the semiconductor or semimetal layer and separated in a first longitudinal direction along a first electric current channel and a pair of voltage contacts in electrical contact with the semiconductor or semimetal layer and separated in a second transverse direction, orthogonal to the first longitudinal direction and positioned on either side of the electric current channel.

A method of detecting a single addition or subtraction to a population of charge-carriers in a charge-carrier Hall-effect sensor comprising:

• a semiconductor or a semimetal layer;
• a pair of electric current contacts in electrical contact with the semiconductor or semimetal layer and separated in a first longitudinal direction along a first electric current channel;
• at least a pair of voltage contacts in electrical contact with the semiconductor or semimetal layer and separated in a second transverse direction, orthogonal to the first direction, and positioned on either side of the electric current channel;
• an electrically insulating layer underlying the semiconductor or the semimetal layer;
• and
• a ferromagnetic layer underlying the electrically insulating layer comprising at least one region having a magnetic moment with a component perpendicular to a plane comprising the pair of electric current contacts and the pair of voltage contacts, the method comprising:
• providing a constant electric current between the pair of electric current contacts while measuring variations in the voltage between the pair of voltage contacts.