JP3044835B2 - Magnetoelectric conversion element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoelectric device using a compound semiconductor material.

[0002]

2. Description of the Related Art A Hall element is known as an element for measuring a magnetic field or detecting a change in a magnetic field and converting the signal into an electric signal.
The Hall element detects a so-called Hall voltage _VH which is generated in a direction perpendicular to the current I when a magnetic field B is applied to the semiconductor and a current I flows through the semiconductor, and is often used for a magnetic sensor for detecting a rotation angle. Have been.

The semiconductor used for the Hall element is S
i, InP, InSb, InAs, GaAs and the like are known. A characteristic required for a semiconductor for a Hall element is to have a large Hall output voltage so that a minute change in a magnetic field can be detected with high sensitivity. That is, it is first required that the Hall coefficient is large. The Hall coefficient is determined by the electron mobility (Electron Mobility). As the electron mobility is higher, a larger Hall voltage is generated, and a highly sensitive Hall element can be obtained. InSb and InAs are known as semiconductors having a high electron mobility, and the electron mobilities at room temperature are 30,000 and 28,000 cm ² / V ·, respectively.
s.

On the other hand, a Hall element with stabilized performance is required to have a small temperature dependency of a Hall voltage.
In order to reduce the temperature dependence of the Hall voltage, a material having a large band gap energy may be used, and the band gap of each of InSb and InAs is set to 0.1.
172 eV and 0.36 eV (at 300 K), whereas InP and GaAs have 1.35 eV and 1.
42 eV (at 300 K). However, the electron mobility is 43
^{00cm 2 / V · s, 6000cm} 2 / V · s and low.

A high-sensitivity Hall element utilizing the above-described properties of a semiconductor is, for example, InSb or InAs.
(Japanese Patent Application Laid-Open No. 59-13385) has been proposed. A device using GaAs is known as a Hall device having low temperature dependency and high reliability (see Japanese Patent Application Laid-Open No. 53-20782). InAsSb, InGa with high electron mobility and high band gap energy
It has also been proposed to apply a ternary mixed crystal III-V compound semiconductor such as Sb, InGaAs, etc.
20378). These semiconductors have an electron mobility of 8000 to 20,000 cm ² / V · by adjusting the mixed crystal ratio.
s, a band gap of 0.2 to 2.0 eV is obtained, and it is expected that a device having high sensitivity and high reliability can be obtained when used as a magnetic sensing portion of a Hall element.

[0006]

In recent years, as seen in advanced electrical equipment such as automobiles, the necessity of precise rotation control in an environment where temperature changes sharply has increased, and high output and high reliability have been provided. There has been a demand for the development of Hall elements. InSb and InAs exhibiting a large Hall voltage for high-sensitivity magnetoelectric transducers have a small band gap energy and a large temperature dependency, and therefore have a disadvantage that they have poor reliability in an environment where the temperature is high such as in an engine room of an automobile. there were. Heretofore, a GaAs semiconductor has been used for a highly reliable Hall element that has a problem of temperature dependency. However, GaAs semiconductors have a drawback that they cannot be used for controlling instrument and audio brushless micromotors because of their low electron mobility and low Hall voltage.

Normally, a semiconductor for a Hall element is used which is epitaxially grown on a semiconductor single crystal substrate.
GaP, GaAs, InP and the like can be used as the substrate. These are mass-produced with high quality single crystal substrates.
However, most of the mixed crystal III-V ternary compound semiconductors have a different lattice constant from the substrate single crystal, and the lattice constant changes depending on the mixed crystal ratio. Therefore, it is difficult to obtain an epitaxially grown crystal having good crystallinity. Was accompanied by

For example, Japanese Patent Application Laid-Open No. 61-20378 proposes epitaxial growth of a ternary mixed crystal compound on a GaAs substrate. However, while the lattice constant of the GaAs substrate is 5.653 °, the lattice constant increases as the group III Ga is replaced with In, and the lattice constant of InAs is increased.
It approaches 058 °. Difference in lattice constant (lattice mismatch)
The crystal grown epitaxially became incomplete as the value became larger, and high electron mobility was not obtained.

[0009]

The inventor of the present invention has developed a Ga _x In crystal having good crystallinity epitaxially grown on an InP substrate.
_An object of the present invention is to provide a highly sensitive and highly reliable Hall element by using _(1-x) As as a magnetically sensitive part. In the present invention in order that constitutes a heterojunction between the InP epitaxial layer and _{Ga x In (1-x)} As epitaxial layer, InP epitaxial layer and Ga _x
The inventors have found that the object can be achieved by limiting the thickness of the In _(1-x) As epitaxial growth layer and the carrier concentration to specific ranges, and have reached the invention.

It is needless to say that the InP single crystal used for the substrate preferably has as few crystal defects as possible. For example, EPD (Etch Pit Density) is 5 × 10 ⁴
cm ^-2 is preferred. Further, it is preferable that the insulating property is high, and it is Fe-doped or undoped and has a specific resistance of 10 ⁴ Ω.
・ Thing more than cm can be used. Usually, an ingot obtained by the LEC method is sliced and the surface thereof is polished. The plane orientation is not particularly limited, and is usually (10
0) Use a plane or a direction inclined within 10 ° from this plane.

A heterojunction is formed on an InP substrate by using an InP epitaxial growth layer and a Ga _x In _(1-x) As epitaxial growth layer. By providing this hetero junction structure, for example, an effect of suppressing the diffusion of impurities from the substrate into the epitaxial growth layer region can be obtained. In addition, since the effect of suppressing the propagation of lattice defects existing in the substrate to the epitaxial growth layer and the like is produced, the electron mobility is improved. Usually, the input resistance is increased by increasing the sensitivity of the Hall element, but by providing a plurality of such heterojunctions, the high electron mobility is maintained and the input resistance is reduced to a practical range of the Hall element. There is an advantage that high sensitivity can be obtained while maintaining the sensitivity.

InP epitaxial growth layer and Ga _x In
There is no particular limitation on the order of _(1-x) As epitaxial layer, in order to obtain the _{Ga x In (1-x)} As epitaxial layer of high quality, loading the InP epitaxial layer as a buffer layer on a normal InP substrate I do. The InP buffer layer is usually undoped and has a thickness (d ₁ ) of 0.1 μm or more. If the thickness is less than 0.1 μm, the influence of lattice defects or the like on the substrate cannot be eliminated, and good Ga _x In _(1-x) A
An s epitaxial growth layer cannot be expected. The carrier concentration (n ₁ ) of the InP epitaxial growth layer is 1 × 10 ^15-
1 × 10 ¹⁷ cm ⁻³ is appropriate.

A target Ga _x In _(1-x) As epitaxial growth layer is mounted on the InP epitaxial layer,
Form a heterojunction. The thickness (d ₂ ) of the Ga _x In _(1-x) As epitaxially grown layer is set at 0.1 to obtain several hundred Ω to several kΩ which is a practical range of the input resistance of the Hall element.
1.0 μm is appropriate, and the relationship between the thicknesses d ₁ and d ₂ of the InP epitaxial layer needs to be d ₁ ≦ d ₂ . Since the electron mobility of InP is lower than the electron mobility of Ga _x In _(1-x) As, it is not advisable to increase d ₁ . d ₁ is kept smaller than d _2, d ₂ is 0.1
1.0 μm is appropriate.

In order to make the input resistance of the Hall element a practical range, the carrier concentration (n ₂ ) of the Ga _x In _(1-x) As epitaxial growth layer is 5 × 10 ¹⁵ to 1 × 10 ¹⁷ cm.
^-3 is appropriate. When the carrier concentration is 1 × 10 ¹⁷ cm ⁻³ or more, the electron mobility is rather reduced. Ga _x
Carrier concentration n of In _(1-x) As epitaxially grown layer
₂ needs to be higher than the carrier concentration n ₁ of the InP epitaxial layer, or at least the same.

The mixed crystal ratio x of the Ga _x In _(1-x) As epitaxial layer is set to 0.37 ≦ x ≦ 0.57. x = 0.4
The lattice constant in the case of 7 is 5.869 °, which is preferable because it matches the lattice constant of the InP substrate and does not cause significant lattice mismatch. However, it is difficult to maintain the mixed crystal ratio at x = 0.47. As x deviates from 0.47, the lattice mismatch also increases, which tends to cause crystal defects and lower electron mobility. Electron mobility 6000cm
The allowable range of the lattice mismatch of ² / V · s is approximately ±
It is within 0.7%. When x = 0.37, the lattice constant is 5.9086 °, the lattice mismatch is + 0.68%, x =
In the case of 0.57, the lattice constant is 5.8275 ° and the lattice mismatch is -0.70%.

The relationship between the bandgap energy Eg (eV) and the mixed crystal ratio x is Eg = 0.36 + 1.0.
64x, and the bandgap energy increases as the mixed crystal ratio x increases. As a result, the temperature dependence of the Hall voltage decreases as the mixed crystal ratio x increases. When the mixed crystal ratio x is in the range of 0.37 ≦ x ≦ 0.57, the temperature coefficient of the Hall voltage is as very small as 0.03 to 0.08%.

The Ga _x In _(1-x) As epitaxial layer may be formed by a liquid phase growth method or a vapor phase growth method. In particular, a good Ga _x In _{(1-x )} As epitaxially grown film can be obtained by the atmospheric pressure MO-VPE method using cyclopentanedienyl indium (C ₅ H ₅ In) as the group III raw material compound.

Using the Ga _x In _(1-x) As epitaxially grown crystal on the InP substrate obtained as described above, a known photolithography method, a vacuum deposition method, a lift-off method, a mesa etching method and the like are used. To obtain a Hall element. To form a good ohmic electrode on Ga _x In _(1-x) As, an Au-12% Ge alloy is used. After forming a pattern for an ohmic electrode according to a normal photolithography process, about 120
Continuously deposit 0% Au-12% Ge alloy and about 400% Ni. Next, after an electrode pattern is formed by the lift-off method, the remaining portion is removed by mesa etching except for a portion corresponding to the active layer of the Hall element to form a pattern of a magnetically sensitive portion, and the photoresist is removed.
Furthermore, in order to alloy the _{Ga x In (1-x)} As and Au-12% Ge electrode material is subjected to a 1-2 minute heat treatment at about 420 ° C. in a nitrogen atmosphere.

[0019]

The material of the magnetic sensing portion that determines the basic characteristics of the magnetoelectric conversion element is made of a high-quality Ga _x In _(1-x) As crystal which is physically excellent, and forms a heterojunction with the InP epitaxial layer.
Ga _x In _(1-x) As
Greater than the thickness of the epitaxial layer and Ga _x
The carrier concentration of the In _(1-x) As epitaxial layer
By making the carrier concentration higher than the P epitaxial layer, high sensitivity and high reliability of the magnetoelectric conversion element are realized.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the magnetoelectric conversion element of the present invention will be described in detail with reference to embodiments. (Example 1) Semi-insulating Fe-doped InP having a specific resistance of 1 × 10 ⁷ Ω · cm
The single crystal mirror wafer is set in a normal atmospheric pressure MO-VPE apparatus, and after vacuum substitution, arsine (AsH ₃ ), phosphine (PH ₃ ) and hydrogen (H ₂ ) are each 50 c.
A gas mixed at a rate of c / min, 60 cc / min, 6 l / min was circulated and heated to 600 ° C. while preventing evaporation of the group V element. After heating, cyclopentanedienyl indium (CpIn: C) was used as a source gas for InP growth.
₅ H ₅ In), phosphine (PH ₃ ), and a mixed gas of hydrogen sulfide gas (H ₂ S) as a dopant gas at 100 cc / min, 500 cc / min, and 2 cc / min, respectively.
min at a rate of 6 l / mi of hydrogen gas as a carrier gas
In addition to n, the gas was instantly switched and introduced into the apparatus, and InP was epitaxially grown for 30 minutes. Then, CpI was used as a source gas for growing Ga _x In _(1-x) As.
n, trimethylgallium (TMG: (CH ₃ ) ₃ G
a), a mixed gas consisting of arsine (AsH ₃ ), hydrogen sulfide as a dopant gas, and hydrogen (H ₂ ) as a carrier gas was supplied at 100 cc / min, 5 cc / min,
The gas was instantaneously switched at a rate of 00 cc / min, 5 cc / min, and 6 l / min and introduced into the apparatus.
Ga _x In _(1-x) As was epitaxially grown for minutes.

The characteristics of the InP and Ga _x In _(1-x) As epitaxially grown layers were measured and the results were as follows. The InP epitaxial layer is n-type, has a thickness of 0.2 μm, has a carrier concentration of (1 ± 0.1) × 10 ¹⁶ cm ⁻³ by ordinary Hall effect measurement, and has an electron mobility of 3200 ± 200 cm ² / V · at 300K. s.
The Ga _x In _(1-x) As epitaxial growth layer is n-type, has a thickness of 0.4 μm, and has a carrier concentration of (2 ± 0.1) × 10.
¹⁶ cm ^-3 , mixed crystal ratio x is x = 0.47 ± 0.03, 300
The electron mobility at K is 11000 ± 500 cm ² / V
S, band gap energy Eg is Eg = 0.86
At eV, the temperature coefficient of the Hall voltage was 0.05% / ° C. Table 1 summarizes these results.

[0022]

[Table 1]

Next, the InP, Ga _x In _(1-x) As
Heterojunction composed of epitaxial growth layer,
An example in which the present invention is applied to a Hall element, which is one of the magnetoelectric conversion elements, will be described. First, a pattern for an ohmic electrode is formed by a normal photolithography process, and A
u-Ge (Ge: 12%) is 1200Å, Ni is 400
Continuously deposited to a thickness of Å. After depositing the electrode material, an electrode pattern was formed by a usual photolithography method.

Next, a pattern of a magnetically sensitive portion was formed by mesa etching except for a portion corresponding to the active layer of the Hall element, and the photoresist was removed. Further, in order to alloy the ohmic electrode material and Ga _x In _(1-x) As, N
Heat treatment was performed at 420 ° C. for 1 minute in _two atmospheres. A good ohmic electrode was formed by this heat treatment. The characteristics of the Ga _x In _(1-x) As Hall element produced by the above-described process are compared with those of the conventional InSb Hall element and the GaAs Hall element, and the results are shown in Table 2.

[0025]

[Table 2]

As is evident from Table 2, the Hall element of the present invention has a high sensitivity of 70 mV / mA · KG, exhibiting high sensitivity and excellent temperature characteristics not available in the conventional Hall element.

(Examples 2-3, Comparative Examples 1-2) InP,
Ga _x In _(1-x) As epitaxial growth layer thickness (d
₁ , d ₂ ) and the carrier concentration (n ₁ , n ₂ ) were changed in the same manner as in Example 1 except that the carrier element (n ₁ , n ₂ ) was changed, and the characteristics were measured. The thickness was controlled by adjusting the time for epitaxial growth. The carrier concentration was adjusted by adjusting the flow rate of hydrogen sulfide as a doping gas. These results are summarized in Table 3.

[0028]

[Table 3]

According to Table 3, the electron mobility of the magnetosensitive part is 6000c.
The condition that the sensitivity is not less than m ² / V · s, the sensitivity is not less than 60 mV / mA · kG, and the temperature coefficient of the Hall voltage is not more than 0.08% / ° C. must satisfy the conditions described in the claims of the specification. You can see that. When this condition was not satisfied, the sensitivity of the Hall element was significantly reduced.

(Examples 4 and 5, Comparative Examples 3 and 4) Ga _x I
A Hall element was prepared in the same manner as in Example 1 except that the value of the Ga mixed crystal ratio x of the n _(1-x) As epitaxial growth layer was changed. The change of the mixed crystal ratio x was performed by changing the flow rates of TMG and CpIn in the Ga _x In _{(1- x)} As epitaxial growth step. Table 4 shows the results.

[0031]

[Table 4]

According to Table 4, the Ga mixed crystal ratio x is 0.37 ≦ x ≦
It was found that the electron mobility was increased in the range of 0.57. The temperature coefficient of the Hall voltage tends to decrease with an increase in the mixed crystal ratio x, and within the above range, 0.03 to 0.08% /
It turned out that it shows a favorable result with ° C.

(Embodiment 6) Ga _x I prepared in Embodiment 1
On top of the n _(1-x) As epitaxial growth layer,
A P epitaxial growth layer was formed under the same conditions as in Example 1. The carrier concentration of this InP epitaxial growth layer was 1.0 × 10 ¹⁶ cm ⁻³ . Using the epitaxial wafer having two hetero interfaces thus obtained, a Hall element was prepared in the same manner as in Example 1.
The sensitivity of this Hall element was 60 mV / mA · KG, the temperature coefficient of the Hall voltage was 0.045% / ° C., and the sensitivity was the same as that of a conventional Hall element. A high-performance Hall element was obtained.

[0034]

As described above, the magnetoelectric conversion element of the present invention makes it possible to detect a small change in the low magnetic flux density in an environment where the temperature change is large. As a result, for example, the use thereof is widened for rotation control in an automobile having a severe temperature environment or in an industrial machine having a high-output electric motor.

Continuation of the front page (72) Inventor Masahiko Usuda 1505 Shimokagemori, Chichibu City, Saitama Prefecture Showa Denko KK Chichibu Plant (56) References JP-A-60-198877 (JP, A) Revue Phys. Appl. 18 (1983) pp. 757-761 (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 43/00-43/14 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. An InP epitaxial growth layer formed on a semi-insulating indium phosphide (InP) single crystal substrate and gallium indium arsenide (Ga _x In _(1-x) As,
0.37 ≦ x ≦ 0.57) comprises a hetero-interface consisting of the epitaxial growth layer, the InP epitaxial growth thickness of the layer d ₁ (μm) and the _{Ga x In (1-x)} As epitaxial growth thickness of the layer d ₂ (Μm) satisfies 0.1 ≦ d ₁ ≦ d ₂ ≦ 1 (1), and the carrier concentration n ₁ (cm ⁻³ ) of the InP epitaxial growth layer and the Ga _x The relationship with the carrier concentration n ₂ (cm ⁻³ ) of the In _(1-x) As epitaxial growth layer is n ₁ ≦ n ₂ ... (2) 5 × 10 ¹⁵ ≦ n ₂ ≦ 1 × 10 ^17. ... A magnetoelectric conversion element comprising a semiconductor material satisfying (3) as a magnetically sensitive portion. 2. The magnetoelectric conversion element according to claim 1, wherein the element has at least two or more heterointerfaces. 3. The magnetoelectric conversion element according to claim 1, wherein the electron mobility of the Ga _x In _(1-x) As epitaxial growth layer of the magnetically sensitive portion is 6000 cm ² / V · s or more. . 4. The temperature coefficient of the Hall voltage is 0.03 to 0.03.
2. The magnetoelectric conversion element according to claim 1, wherein the rate is 0.08% / ° C.