JP2011146627A - GaAs HALL ELEMENT - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a GaAs hall element having a small variation of offset voltage. <P>SOLUTION: A magnetism sensing section 22 consisting of n-GaAs layer is placed in between a first and a second insulating layer 23a, 23b consisting of AlGaAs which has greater band gap than the n-GaAs layer 22, and the carrier concentration of the n-GaAs layer 22 is kept at not less than 5×10<SP>16</SP>/cm<SP>3</SP>and not more than 1×10<SP>18</SP>/cm<SP>3</SP>. The movement of electrons from the lower part of the n-GaAs layer 22 to the side surface, and the effect of electron trap on the side surface are then controlled. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a GaAs Hall element, and more particularly, to a GaAs Hall element in which fluctuations in offset voltage due to a manufacturing process, temperature, external stress, and the like are small.

  A Hall element made of a compound semiconductor has high magnetic sensitivity due to its high electron mobility, and is therefore widely used as a magnetic sensor for detecting rotation of a motor. Further, in recent years, application to a non-contact current sensor that can detect a weak magnetic field generated by a current flowing through a conductor in a non-contact manner using a Hall element has been promoted. However, since the magnetic field generated by this current is weak, the output voltage of the Hall element is small, which causes a large error.

  In general, the output voltage of a Hall element is expressed by the sum of magnetic sensitivity and offset voltage, but in order to detect current with high accuracy, an offset that causes an error with respect to magnetic sensitivity proportional to the current (magnetic field). It is necessary to reduce the voltage ratio. In general, the offset voltage is corrected by an external signal processing circuit in the configuration of the current sensor, and therefore, with respect to the Hall element, technical development has been conducted with a focus on increasing the electron mobility in the magnetosensitive portion. By increasing the magnetic sensitivity, the influence of the offset voltage was relatively suppressed.

  However, the offset voltage of the Hall element varies depending on the element due to the influence of operating temperature, external stress, etc., so the fluctuation of the offset voltage after performing the above correction becomes a measurement error, and it is highly accurate. It was a problem in current detection. Therefore, it is very important to suppress the offset voltage of the Hall element and its fluctuation itself.

  As a conventional GaAs Hall element, for example, Patent Document 1 proposes a GaAs Hall element having a structure in which characteristics are hardly deteriorated during the manufacturing process and the offset voltage is small. The Hall element described in Patent Document 1 includes a magnetosensitive part made of n-GaAs provided on an insulating substrate, a surface layer provided on the magnetosensitive part, and an ohmic electrode. is there.

FIGS. 1A to 1C are configuration diagrams for explaining a conventional GaAs Hall element, which is a configuration diagram of the GaAs Hall element disclosed in Patent Document 1 described above. GaAs has a wide band gap of about 1.4 eV at room temperature and depends on temperature. Usually, in order to protect the mesa of the Hall element from the external environment, an insulating film such as SiO ₂ or Si ₃ N ₄ is formed using sputtering or plasma CVD in the manufacturing process. When this insulating film is formed, defect levels are generated on the GaAs surface exposed to the outside due to plasma damage, etc., so fluctuations in electrical characteristics such as resistance, sensitivity, offset voltage, etc. by trapping nearby conduction electrons Will occur. Further, the ratio of electrons trapped in the defect changes due to the change in external temperature or the stress at the time of packaging, resulting in fluctuations in their electrical characteristics.

  Since the structure shown in FIG. 1A is a structure in which the n-GaAs layer 2 that is a magnetic sensitive part is exposed to the outside, it is directly affected by the defect level. The structure shown in FIG. 1B is a structure in which an undoped GaAs layer or an AlGaAs layer 3 is formed to protect the n-GaAs layer 2, and it is possible to suppress the influence of defect levels in the upper part of the mesa. Therefore, as the surface protective layer, it is preferable to use an AlGaAs layer having a wider band gap than the GaAs layer which is a magnetic sensitive portion. This is because the AlGaAs layer having a wide band gap serves as a potential barrier against the movement of electrons from the n-GaAs layer 2 to the surface defect level and functions as a barrier layer. In Patent Document 1, an insulating substrate is defined as a substrate on which a Hall element is formed, and a GaAs substrate 1 is used as an example.

  Further, as a Hall effect magnetic sensor, for example, the one of Patent Document 2 has been proposed. The one described in Patent Document 2 relates to a Hall effect magnetic sensor using a two-dimensional electron gas, and is an ultra-thin hole having a thickness of several tens of nm or less so that it can be incorporated into a thin film magnetic head that performs ultra-high density recording. The purpose is to provide an effective magnetic sensor, and in the barrier layer sandwiching the quantum well layer in which the two-dimensional electron gas is formed, a delta doped layer containing impurities at a high surface density is formed, and the quantum well layer is surface-depleted. Shield from layers.

  In addition, as a Hall element other than a GaAs Hall element, for example, in Patent Document 3, a sensor thin film layer having a high electron mobility with no disorder of the crystal lattice is manufactured, and there is no change in characteristics due to the process, and the temperature characteristics are excellent. InAs Hall elements have been proposed. The Hall element described in Patent Document 3 includes a high-resistance first compound semiconductor layer, an InAs thin film layer formed on the first compound semiconductor layer, and an electrode formed on the InAs thin film layer. Thus, the first compound semiconductor has the same or close lattice constant as InAs and has a larger band gap energy than InAs.

  FIG. 2 is a configuration diagram for explaining a conventional InAs Hall element, and is a configuration diagram of the Hall element disclosed in Patent Document 3 described above. An InAs layer 12 having high electron mobility is provided on the GaAs substrate 11 as a magnetic sensitive part, AlGaAsSb mixed crystal layers 13a and 13b are provided so as to sandwich the magnetic sensitive part, and a GaAsSb layer 14 is provided thereon. Furthermore, high electron mobility is achieved by lattice-matching the AlGaAsSb mixed crystal layer 13a serving as the buffer layer and the InAs layer 12 serving as the magnetosensitive portion.

Japanese Patent Laid-Open No. 03-240281 Japanese Patent Application Laid-Open No. 08-088425 Japanese Patent Laid-Open No. 06-077556

  In the GaAs Hall element described in Patent Document 1 described above, movement of electrons through the GaAs substrate 11 to the side surface occurs on the side surface of the mesa, and an imbalance in electron concentration occurs, resulting in fluctuations in offset voltage.

  FIG. 1C is a schematic view of a situation where defect levels are generated on the surface in the manufacturing process of the GaAs Hall element shown in Patent Document 2 described above. As described above, it is possible to suppress the movement of carriers from the n-GaAs layer 2 to the surface by forming the insulating layer made of the AlGaAs layer 3 on the surface. However, on the side surface of the mesa, n− The GaAs layer 2 is exposed as it is, and there is a problem that the movement of electrons through the GaAs substrate 1 to the side surface cannot be suppressed.

  In addition, the device described in Patent Document 2 described above is such that delta doping is performed on the undoped GaAs magnetic sensing portion (quantum well) from the barrier layer sandwiching the magnetic sensing portion. -It differs in that it is made of GaAs.

  Further, in the InAs Hall element described in Patent Document 3, it is difficult to completely remove threading dislocations due to lattice mismatch at the interface between the GaAs substrate 11 and the AlGaAsSb mixed crystal layer 12, and for the purpose of suppressing the fluctuation of the offset voltage. It is not preferable.

  The present invention has been made in view of such a situation, and the object of the present invention is process damage in the process of manufacturing a Hall element and characteristic variation caused by external stress such as thermal stress or resin package due to external temperature, In particular, it is an object to provide a GaAs Hall element having a small variation in offset voltage.

The present invention has been made in order to achieve such an object. The invention according to claim 1 is an n-type film having a thickness of 0.010 μm or more and 0.350 μm or less separated by a mesa on a GaAs substrate. In a GaAs Hall element having a magnetic sensitive part made of GaAs, the first insulating layer made of AlGaAs provided between the GaAs substrate and the magnetic sensitive part, and made of AlGaAs provided on the magnetic sensitive part. A second insulating layer is provided, and an electron concentration at room temperature of the magnetosensitive portion is 5 × 10 ¹⁶ / cm ³ or more and 1 × 10 ¹⁸ / cm ³ or less.

  According to a second aspect of the present invention, in the first aspect of the present invention, the first modulation doped layer made of AlGaAs doped with an N-type dopant between the first insulating layer and the magnetic sensing portion. And a second modulation doped layer made of AlGaAs doped with an N-type dopant between the second insulating layer and the magnetic sensitive part.

  According to a third aspect of the present invention, in the second aspect of the present invention, the band gap between the first insulating layer and the second insulating layer is the first modulation doped layer and the second modulation layer. It is characterized by being larger than the band gap of the modulation doped layer.

  According to a fourth aspect of the present invention, there is provided a GaAs Hall element having a magnetosensitive part made of n-GaAs separated by a mesa on a GaAs substrate so as to cover the GaAs substrate and the magnetosensitive part. Alternatively, a third insulating layer made of AlGaAs is provided.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, a fourth insulating layer made of AlGaAs provided between the GaAs substrate and the magnetic sensitive portion, and the magnetic sensitive portion on the magnetic sensitive portion. A first insulating layer having a thickness of 0.010 μm or more and 0.350 μm or less, and the electron concentration at room temperature of the magnetosensitive portion is 5 ×. It is 10 ¹⁶ / cm ³ or more and 1 × 10 ¹⁸ / cm ³ or less.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the third modulation doped layer made of AlGaAs doped with an N-type dopant between the fourth insulating layer and the magnetic sensing portion. And a fourth modulation doped layer made of AlGaAs doped with an N-type dopant between the fifth insulating layer and the magnetic sensitive part.

  The invention according to claim 7 is the invention according to claim 6, wherein the band gaps of the fourth insulating layer and the fifth insulating layer are the third modulation doped layer and the fourth modulation layer. It is characterized by being larger than the band gap of the modulation doped layer.

  According to the present invention, by forming an insulating layer on the upper, lower or side surfaces of the magnetic sensitive part, it is possible to protect the magnetic sensitive part from defects generated in the manufacturing process and increase the electron concentration in the magnetic sensitive part. It becomes. The offset voltage originates from the deviation of the balance of the resistance values inside and on the side of the magnetosensitive surface. In the GaAs Hall element, the fluctuation of the electron concentration due to the trap at the defect level is the main factor of the resistance fluctuation. As described above, it is possible to relatively suppress the influence of fluctuations in the electron concentration by protecting the magnetically sensitive portion having a high electron concentration with the insulating layer.

  Therefore, it is possible to manufacture a GaAs Hall element having a small variation in offset voltage caused by process damage in the Hall element manufacturing process, thermal stress due to external temperature, and external stress such as a resin package.

(A) thru | or (c) are the block diagrams for demonstrating the other conventional GaAs Hall element. It is a block diagram for demonstrating the conventional GaAs Hall element. It is a block diagram for demonstrating Example 1 of the GaAs Hall element based on this invention. It is a block diagram for demonstrating Example 2 of the GaAs Hall element based on this invention. It is a block diagram for demonstrating Example 3 of the GaAs Hall element based on this invention. It is a block diagram for demonstrating Example 4 of the GaAs Hall element based on this invention. It is a block diagram for demonstrating Example 5 of the GaAs Hall element based on this invention.

Embodiments of the present invention will be described below with reference to the drawings. In each of the following examples, the Al composition ratio in Al _x Ga _1-x As is set to 0 <x ≦ 1, so that the insulating layer and the modulation doped layer have a wider band gap than GaAs.

  FIG. 3 is a configuration diagram for explaining the first embodiment of the GaAs Hall element according to the present invention, and shows a vertical film structure of the GaAs Hall element separated by the mesa. In the figure, reference numeral 21 denotes a GaAs substrate, 22 denotes a magnetic sensitive part made of an n-GaAs layer, 23a denotes a first insulating layer made of AlGaAs, and 23b denotes a second insulating layer made of AlGaAs.

The GaAs Hall element according to the first embodiment is a GaAs Hall element having a magnetic sensitive part 22 made of an n-GaAs layer on a GaAs substrate 21. The GaAs Hall element includes a first insulating layer 23a made of AlGaAs provided between the GaAs substrate 21 and the magnetic sensing part 22, and a second insulating layer 23b made of AlGaAs provided on the magnetic sensing part 22. And. Moreover, the electron concentration at room temperature of the magnetic sensitive part 22 is 5 × 10 ¹⁶ / cm ³ or more and 1 × 10 ¹⁸ / cm ³ or less. The above structure is formed by MBE or MOCVD.

  The magnetic sensitive part 22 is composed of an n-GaAs layer having a thickness of 0.010 μm or more and 0.350 μm or less separated by a mesa.

That is, the magnetosensitive part 22 made of an n-GaAs layer is sandwiched between the first and second insulating layers 23a and 23b made of AlGaAs having a band gap larger than that of the n-GaAs layer 22, and the n-GaAs layer 22 By making the carrier concentration of 5 × 10 ¹⁶ / cm ³ or more and 1 × 10 ¹⁸ / cm ³ or less, the movement of electrons from the bottom to the side surface of the n-GaAs layer 22 and the influence of electron traps on the side surface Can be suppressed. Here, the difference in lattice constant between the AlGaAs layer and the GaAs layer is small, and lattice matching can be achieved without the occurrence of dislocation, so that it is suitable as a barrier layer for confining electrons.

  FIG. 4 is a block diagram for explaining a second embodiment of the GaAs Hall element according to the present invention, showing the vertical film structure of the GaAs Hall element separated by the mesa, and formed by MBE or MOCVD. . In the figure, reference numeral 24a is the first modulation doped layer, 24b is the second modulation doped layer, and other components having the same functions as those in FIG.

  In the GaAs Hall element according to the second embodiment, a first modulation doped layer 24a made of AlGaAs doped with an N-type dopant is provided on the first insulating layer 23a, and an N-type dopant is provided below the second insulating layer 23b. The second modulation doped layer 24b made of AlGaAs doped with is provided.

  Further, the band gaps of the first and second insulating layers 23a and 23b are widened by increasing the Al composition in AlGaAs as compared with the first and second modulation doped layers 24a and 24b.

  That is, by providing modulation doped layers 24a and 24b made of AlGaAs doped with an N-type dopant above and below the magnetic sensitive part 22 made of an n-GaAs layer, modulation doping is performed and the electron concentration of the magnetic sensitive part 22 is increased. Can do. As a result, the influence of the imbalance of the electron concentration on the side surface due to the trap to the defect level exposed on the mesa side surface can be mitigated, and the fluctuation of the offset voltage can be suppressed.

  FIG. 5 is a block diagram for explaining Example 3 of the GaAs Hall element according to the present invention, and shows a vertical film structure of the GaAs Hall element separated by a mesa. In the figure, reference numeral 31 denotes a GaAs substrate, 32 denotes a magnetic sensitive part made of an n-GaAs layer, and 33 denotes a third insulating layer made of GaAs or AlGaAs.

  The GaAs Hall element according to the third embodiment is a GaAs Hall element having a magnetic sensitive part 32 made of an n-GaAs layer separated by a mesa on a GaAs substrate 31. This GaAs Hall element is provided with a third insulating layer 33 made of GaAs or AlGaAs so as to cover the GaAs substrate 31 and the magnetic sensing part 32.

  That is, the magnetically sensitive part 32 made of an n-GaAs layer is made of GaAs or AlGaAs on the upper and side surfaces of the mesa having the magnetically sensitive part 32, compared to a GaAs Hall element having a conventional mesa exposed to the outside in the manufacturing process. A third insulating layer 33 is provided.

  The mesa having the conventional structure can be formed by using wet etching, dry etching, or the like on the magnetically sensitive portion having the conventional structure formed by ion implantation, MBE, MOCVD, or the like.

  Thereafter, the third insulating layer 33 made of undoped GaAs or AlGaAs is further formed by MBE or MOCVD, whereby the GaAs Hall element according to the third embodiment is formed. Since the difference in lattice constant between the third insulating layer 33 and the magnetic sensing portion 32 is small and lattice matching can be achieved without the occurrence of dislocation, it is suitable as an insulating layer for protecting the magnetic sensing portion 32.

  By confining the conduction electrons existing in the magnetic sensitive part 32 by the upper and lower and side insulating layers 33 by the GaAs Hall element according to the third embodiment, the flow of electrons to the defects generated on the mesa surface is prevented, and the offset voltage is thereby increased. It is possible to suppress fluctuations in

  FIG. 6 is a block diagram for explaining a GaAs Hall element according to a fourth embodiment of the present invention, showing a vertical film structure of the GaAs Hall element separated by a mesa, which is formed by MBE or MOCVD. . In the figure, reference numeral 34a is a fourth insulating layer made of AlGaAs, 34b is a fifth insulating layer made of AlGaAs, and other components having the same functions as those in FIG. 5 are given the same reference numerals.

The GaAs Hall element according to the fourth embodiment has the same configuration as that of the first embodiment in which the third insulating layer 33 is provided. This is a GaAs Hall element having a magnetosensitive part 32 made of an n-GaAs layer on a GaAs substrate 31. The GaAs Hall element includes a fourth insulating layer 34a made of AlGaAs provided between the GaAs substrate 31 and the magnetic sensing part 32, and a fifth insulating layer 34b made of AlGaAs provided on the magnetic sensing part 32. And a third insulating layer 33 made of GaAs or AlGaAs is provided on the top and side surfaces of the mesa so as to cover the GaAs substrate 31 and the magnetic sensing portion 32. In addition, the electron concentration at room temperature of the magnetic sensitive part 32 is 5 × 10 ¹⁶ / cm ³ or more and 1 × 10 ¹⁸ / cm ³ or less.

  In addition, the magnetic sensitive part 32 is composed of an n-GaAs layer having a thickness of 0.010 μm or more and 0.350 μm or less separated by a mesa.

That is, the magnetosensitive portion 32 made of the n-GaAs layer is sandwiched between the insulating layers 34a and 34b made of AlGaAs having a larger band gap than the n-GaAs layer, and the carrier concentration of the n-GaAs layer 32 is 5 × 10 5. By setting it to ¹⁶ / cm ³ or more and 1 × 10 ¹⁸ / cm ³ or less, it is possible to suppress the influence of the electron movement from the lower part of the magnetic sensing portion 32 to the side surface and the trapping of electrons on the side surface. Here, the difference in lattice constant between the AlGaAs layer and the GaAs layer is small, and lattice matching can be achieved without the occurrence of dislocation, so that it is suitable as a barrier layer for confining electrons. Further, it is preferable because the magnetic sensitive part is protected from defects and a higher electron concentration can be obtained.

  FIG. 7 is a block diagram for explaining Example 5 of the GaAs Hall element according to the present invention, and shows a vertical film structure of the GaAs Hall element separated by a mesa. In the figure, reference numeral 35a denotes a third modulation doped layer, 35b denotes a fourth modulation doped layer, and other components having the same functions as those in FIG.

  The GaAs Hall element according to the fifth embodiment has a configuration in which the third insulating layer 33 is provided in the second embodiment described above, and after forming a mesa having a magnetosensitive portion as in the second embodiment, the MBE or The third insulating layer 33 made of undoped GaAs or AlGaAs is formed by MOCVD. A third modulation doped layer 35a made of AlGaAs doped with an N-type dopant between the fourth insulating layer 34a and the magnetic sensitive part 32, and an N type between the fifth insulating layer 34b and the magnetic sensitive part 32. And a fourth modulation doped layer 35b made of AlGaAs doped with a dopant. Further, a third insulating layer 33 made of GaAs or AlGaAs is provided so as to cover the GaAs substrate 31 and the magnetic sensing part 32, that is, on the top and side surfaces of the mesa.

  The band gaps of the fourth and fifth insulating layers 34a and 34b are larger than the band gaps of the third and fourth modulation doped layers 35a and 35b.

  That is, by providing modulation doped layers 35a and 35b made of AlGaAs doped with an N-type dopant above and below the magnetic sensitive part 32 made of an n-GaAs layer, modulation doping is performed and the electron concentration of the magnetic sensitive part 32 is increased. Can do. As a result, the influence of the imbalance of the electron concentration on the side surface due to the trap to the defect level exposed on the mesa side surface can be mitigated, and the fluctuation of the offset voltage can be suppressed. Further, it is preferable because the magnetic sensitive part is protected from defects and a higher electron concentration can be obtained.

DESCRIPTION OF SYMBOLS 1 GaAs substrate 2 n-GaAs layer 3 GaAs layer or AlGaAs layer 11 GaAs substrate 12 InAs layer 13a, 13b AlGaAsSb mixed crystal layer 14 GaAsSb layer 21 GaAs substrate 22 Magnetosensitive part 23a made of n-GaAs layer First made of AlGaAs Insulating layer 23b Second insulating layer 24a made of AlGaAs First modulation doped layer 24b made of AlGaAs Second modulation doped layer 31 made of AlGaAs GaAs substrate 32 Magnetosensitive part 33 made of n-GaAs layer Made of GaAs or AlGaAs Third insulating layer 34a Fourth insulating layer 34b made of AlGaAs Fifth insulating layer 35a made of AlGaAs Third modulated doped layer 35b made of AlGaAs Fourth modulated doped layer made of AlGaAs

Claims (7)

In a GaAs Hall element having a magnetic sensitive part made of n-GaAs having a thickness of 0.010 μm or more and 0.350 μm or less separated by a mesa on a GaAs substrate,
A first insulating layer made of AlGaAs provided between the GaAs substrate and the magnetic sensitive part; and a second insulating layer made of AlGaAs provided on the magnetic sensitive part, and the magnetic sensitive part The electron concentration at room temperature is 5 × 10 ¹⁶ / cm ³ or more and 1 × 10 ¹⁸ / cm ³ or less.   A first modulation doped layer made of AlGaAs doped with an N-type dopant between the first insulating layer and the magnetic sensitive part; and an N-type dopant between the second insulating layer and the magnetic sensitive part. A GaAs Hall element according to claim 1, further comprising a second modulation doped layer made of AlGaAs doped with.   The band gap between the first insulating layer and the second insulating layer is larger than the band gap between the first modulation doped layer and the second modulation doped layer. GaAs Hall element. In a GaAs Hall element having a magnetosensitive part made of n-GaAs separated by a mesa on a GaAs substrate,
3. A GaAs Hall element comprising a third insulating layer made of GaAs or AlGaAs so as to cover the GaAs substrate and the magnetic sensitive part. A fourth insulating layer made of AlGaAs provided between the GaAs substrate and the magnetic sensitive part, and a fifth insulating layer made of AlGaAs provided on the magnetic sensitive part; Has a thickness of 0.010 μm or more and 0.350 μm or less, and the electron density at room temperature of the magnetically sensitive portion is 5 × 10 ¹⁶ / cm ³ or more and 1 × 10 ¹⁸ / cm ³ or less. The GaAs Hall element according to claim 4.   A third modulation-doped layer made of AlGaAs doped with an N-type dopant between the fourth insulating layer and the magnetic sensitive part; and an N-type dopant between the fifth insulating layer and the magnetic sensitive part. 6. A GaAs Hall element according to claim 5, further comprising a fourth modulation doped layer made of AlGaAs doped with.   The band gap between the fourth insulating layer and the fifth insulating layer is larger than the band gap between the third modulation doped layer and the fourth modulation doped layer. GaAs Hall element.

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