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US 5,491,461 AGranted
Magnetic field sensor on elemental semiconductor substrate with electric field reduction means
AssigneeGeneral Motors Corporation
InventorsDale L. Partin, Joseph P. Heremans, Louis Green
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Abstract
A magnetic field sensor apparatus that comprises an active layer of indium antimonide or indium arsenide supported on an elemental semiconductor substrate. Magnetoresistor sensors of indium antimonide and indium arsenide active layers on silicon and germanium substrate wafers are described. Means are described for providing reduced electric fields and parasitic conduction in the elemental semiconductor substrate. The means includes unique device geometries and buffer layers between the active layers and the substrate wafers.
Claims20
An electronic apparatus that includes a magnetic field sensor of indium antimonide for applications having thermal cycling with wide temperature variation, said apparatus comprising:
- a monocrystalline substrate of at least one substantially intrinsic elemental semiconductor selected from the class consisting of silicon and germanium, said semiconductor having a given energy band gap and said substrate having a substantially planar monocrystalline surface portion;
- an epitaxial active layer about 1 to 5 .mu.m thick of a compound semiconductor selected from the group consisting of indium antimonide and indium arsenide on the substrate surface portion, said compound semiconductor epitaxial layer being configured as an elongated mesa on said substrate surface portion and having an electron mobility of greater than about 15,000 cm.sup.2 /V s;
- said layer being doped n-type such that it contains an excess density of electrons in said compound semiconductor epitaxial layer, said excess density relatively stabilizing majority carrier density from about -40.degree. C. to about 200.degree. C. without degrading said electron mobility to less than about 15,000 cm.sup.2 /V s;
- at least two electrical conductors respectively contacting spaced portions of said elongated compound semiconductor epitaxial mesa layer for applying a voltage difference between said spaced portions, which voltage difference would form an associated electric field in said elemental semiconductor substrate;
- and
- field reduction means for limiting the maximum associated electrical field formed in said elemental semiconductor by said voltage difference to a value that does not exceed the dielectric strength of the elemental semiconductor,
- effective to provide a compound semiconductor magnetic field sensor on a lower cost substrate in said apparatus, which compound semiconductor magnetic field sensor substantially retains its original electron mobility after extensive thermal cycling, and thereby substantially retains its original magnetic sensitivity after such cycling.
4 more elements
An indium antimonide magnetic field sensor that retains its high electron mobility, and attendant high magnetic sensitivity, after thermal cycling with wide temperature variation and that includes voltage protection, said magnetic field sensor comprising:
- a monocrystalline substrate of at least one substantially intrinsic elemental semiconductor selected from the class consisting of silicon and germanium, said semiconductor having a given energy band gap and attendant intrinsic resistivity, and said substrate having a substantially planar monocrystalline surface portion;
- a monocrystalline layer about 0.01 to 2.0 .mu.m thick of a substantially intrinsic compound semiconductor on the elemental semiconductor substrate surface portion, said compound semiconductor having an energy band gap and attendant resistivity that is higher than that of silicon, and also having a crystal lattice constant between that of silicon and indium antimonide;
- a monocrystalline layer about 1 to 3 .mu.m thick of indium antimonide on the monocrystalline compound semiconductor layer, said monocrystalline indium antimonide layer being configured as an elongated mesa and having an electron mobility of greater than about 15,000 cm.sup.2 /V s;
- an n-type doping of said indium antimonide layer generally stabilizing majority carrier density from about -40.degree. C. to about 200.degree. C. without significantly degrading said electron mobility and attendant sensitivity to applied magnetic fields;
- terminal contacts on spaced portions of said elongated indium antimonide epitaxial layer for applying a voltage difference to said spaced portions, which voltage difference would form an associated electric field extending through said higher resistivity compound semiconductor layer into said elemental semiconductor substrate;
- effective to provide an indium antimonide magnetic field sensing layer that retains high magnetic sensitivity even after extensive thermal cycling on a low cost substrate, with electric field absorbing means therebetween.
3 more elements
A high sensitivity indium antimonide magnetoresistor sensor for applications having thermal cycling and wide temperature variation and having a relatively stable high electron mobility after extensive thermal cycling, said indium antimonide magnetoresistor comprising:
- a monocrystalline substrate of at least one intrinsic elemental semiconductor selected from the class consisting of silicon and germanium, said substrate having a substantially planar and monocrystalline surface portion;
- an epitaxial layer about 1 to 3 .mu.m thick of indium antimonide directly on said substrate surface portion, said indium antimonide epitaxial layer having an elongated mesa conformation on said substrate surface portion and having an areal electron mobility of greater than about 15,000 cm.sup.2 /V s;
- an n-type doping of said indium antimonide epitaxial layer, said doping being at a concentration of about 0.3.times.10.sup.17 cm.sup.-3 to 3.times.10.sup.17 cm.sup.-3, and sufficient to relatively stabilize majority carrier density from about -40.degree. C. to about 200.degree. C. without degrading said electron mobility to less than about 15,000 cm.sup.2 /V s;
- at least two electrical conductors respectively contacting spaced portions of said elongated indium antimonide epitaxial mesa layer for applying a voltage difference between said spaced portions, which voltage difference would form an associated electric field in said elemental semiconductor substrate;
- and
- field reduction means for limiting the maximum electrical field formed in said elemental semiconductor by said voltage difference to a value that does not exceed the dielectric strength of the elemental semiconductor, wherein the field reduction means includes a mesa geometry parallel to said substrate surface portion that provides significant spacing between mesa portions of significant voltage difference;
- effective to provide an indium antimonide magnetic field sensor on a lower cost substrate, which indium antimonide magnetic field sensor substantially retains magnetic sensitivity after extensive thermal cycling and includes integral electric field protection.
4 more elements
Dependencies are inferred from the claim text.