Patent ID: 7087971

Claim:
A magnetic sensor comprising: a first ferromagnetic layer and a second ferromagnetic layer; a semiconductor layer formed between the first and second ferromagnetic layers; a first δ-doped layer formed between the first ferromagnetic layer and the semiconductor layer; and a second 6-doped layer formed between the second ferromagnetic layer and the semiconductor layer, wherein a conductivity between the first ferromagnetic layer and the second ferromagnetic layer provides a measure of an external magnetic field that the magnetic sensor senses, wherein: the first and second δ-doped layers and the semiconductor layer are negatively doped; and the first δ-doped layer satisfies a condition N d1 ⁢ l + 1 2 ≈ 2 ⁢ ɛ 0 ⁢ ɛ ⁡ ( Δ - Δ 0 ) q 2 and the second δ-doped layer satisfies a condition N d2 ⁢ l + 1 2 ≈ 2 ⁢ ɛ 0 ⁢ ɛ ⁡ ( Δ - Δ 0 ) q 2 , wherein N d1 and l +1 represent a donor concentration and a thickness of the first δ-doped layer, N d2 and 1 +2 represent a donor concentration and a thickness of the second δ-doped layer; q represents a positive elementary charge; εrepresents a relative permittivity of the semiconductor layer, ε 0 a represents a permittivity of vacuum; Δ represents a potential barrier height on interfaces between the fist ferromagnetic layer and the first δ-doped layer and between the second ferromagnetic layer and the second δ-doped layer; and Δ 0 represents a height of a potential barrier formed in the semiconductor layer.