JPH0897484A - Gainas hetero-junction hall device - Google Patents

Abstract

PURPOSE: To relieve a displacement force which is introduced into a GaInAs magneto-sensitive layer by a thermal process, etc., and avoid the decline of the electron mobility of the base material by a method wherein the GaInAs layer is provided between two compound semiconductor layers which have a specific difference between their thicknesses, are made of the same material and are formed on a semiconductor substrate. CONSTITUTION: A buffer layer 102 which is made of undoped n-type InP epitaxial crystal and has a thickness about 100nm is formed on a substrate 101 by a normal pressure MOVPE method. An n-type Gax In1-x As layer (wherein (x) is 0<=x<=1) which is a magneto-sensitive layer 103 is formed on the buffer layer 102 by an atmospheric pressure MOVPE method. An n-type InP layer which is made of the same compound semiconductor as the layer 102 is formed on the magneto-sensitive layer 103 as a contact layer 104. With this constitution, an InP/GaInAs/InP double-hetero-junction can be formed. The difference between the thickness of the contact layer 104 and the thickness of the buffer layer 102 is less than 65%, for instance 120nm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor Hall element, and more particularly to high sensitivity of a double (double) heterojunction Hall element containing Ga _x In _1-x As.

[0002]

2. Description of the Related Art A Hall element is a magnetoelectric conversion element that generates a voltage according to a magnetic flux density. The Hall element is a kind of magnetic sensor and is already used in industry as a rotation detection sensor, a current sensor, and the like.

Hall elements have conventionally been composed of compound semiconductors such as GaAs and InSb in addition to elemental semiconductors such as Si. Recently, in response to the demand for high-performance Hall elements, a new high-sensitivity Hall element composed of a heterojunction of GaInAs and InP has been reported (Okuyama Shinobu et al., 19
1992 Autumn 53rd Annual Meeting of the Japan Society of Applied Physics Proceedings N
o. 3 (Published by Japan Society of Applied Physics), Lecture No. 16a-SZC
-16, 1078). Since this GaInAs heterojunction system can obtain room temperature electron mobility as high as about 12,000 cm ² / V · s (Kenjiro Onuma et al., Proc. Of the 53rd Annual Meeting of the Society of Applied Physics, 18a-ZE-3), Hall. This is advantageous for increasing the sensitivity of the device.

A conventional GaInAs Hall element is a layer of InP deposited on a high-resistance semi-insulating InP single crystal substrate.
And a single layer of GaInAs (single) heterojunction (Okuyama Shinobu et al., Autumn 1992 53rd Annual Meeting of the Society of Applied Physics, Proceedings No. 3 (published by the Society of Applied Physics), Lecture No. 16a-SZC-16, 1
078). Typically, this single heterojunction system first provides a buffer layer, such as InP, on the substrate and then deposits GaInAs with a small bandgap. The buffer layer is provided to reduce the penetration of impurities and the like from the substrate crystal into the magnetic sensing layer. GaInAs having a small band gap is used as the outermost layer in order to easily obtain an ohmic electrode.

Further, it is not a single heterojunction but GaIn.
GaI with a double (double) heterojunction with the As layer
An nAs double heterojunction Hall element is also known (Y. Sugiyama, Technical Dig).
est of the 11th Sensor Sym
podium (1992), p. 79). This Hall element includes a GaInAs / AlInAs double heterojunction in which a GaInAs layer is sandwiched by Al _0.48 In _0.52 As layers. That is, the same A on both upper and lower sides of the GaInAs layer
l _0.48 In _0.52 As layers are heterojunctions. However, G
Al _0.48 forming a double heterojunction with the aInAs layer
The thickness of the In _0.52 As layer is significantly different. GaIn
Al _0.48 In _0.52 A heterojunction directly under the As layer
The film thickness of the s layer is 400 nm. On the other hand, the film thickness of the Al _0.48 In _0.52 As layer heterojunction on the upper surface side of the GaInAs layer is 5 nm. Therefore, the thickness is 1.25% of the thickness of the Al _0.48 In _0.52 As layer on the lower surface side of the GaInAs layer. Up to the present, there is no known example in which the film thickness of the compound semiconductor layer to be heterojunctioned above and below the GaInAs magnetosensitive layer for the heterojunction Hall element is defined.

Regardless of the single or double heterojunction system, there is a difference in the coefficient of thermal expansion between the GaInAs layer serving as the magnetic sensing layer and the conventional compound semiconductor layer used for forming the heterojunction with the GaInAs layer. For example, the linear expansion coefficient of InP is 4.6 × 10 ⁻⁶ / ° C. (Hario Nagai et al., “III.
-Group V semiconductor mixed crystals "(October 25, 1988, published by Corona Publishing Co.), p. 52). In addition, Al _0.48 In _0.52 As
That of the layer is calculated to be approximately 5.2 × 10 ⁻⁶ / ° C. On the other hand, that of Ga _0.47 In _0.53 As is 5.8 × 10 ⁻⁶ /
Calculated as ° C. Due to this difference in the coefficient of linear expansion, GaInAs is generated during the temperature rising / falling process necessary for growing the compound semiconductor layer.
Strain is introduced into the magnetosensitive layer. Especially, as in the past, GaInA
In the single heterostructure of s and InP, GaI
Since one surface of the nAs magnetosensitive layer is bonded to InP having a different linear expansion coefficient and the other surface is open, there is a drawback that the GaInAs magnetosensitive layer is easily displaced.

When strain is introduced into the magnetosensitive layer, electron mobility is lowered. When the electron mobility decreases, the product sensitivity, which is an important characteristic of the Hall element, decreases. Further, particularly in a single heterojunction, the GaInAs magnetosensitive layer whose one surface is open is displaced and distorted, causing "warpage" in the base material. If this "warp" is large, the degree of adhesion between the exposure mask for photolithography and the object to be patterned, that is, the base material becomes non-uniform. As a result, it becomes difficult to perform uniform and precise patterning of the magnetosensitive layer, and the unbalanced voltage due to the asymmetry of the shape of the magnetosensitive layer also deteriorates. Unbalanced voltage refers to the Hall voltage generated under zero magnetic field (Kataoka Teruei, "Magnetic-electric conversion element").
(Published by Nikkan Kogyo Shimbun, February 1972), p. 61).

[0008]

The amount of displacement that the GaInAs magnetosensitive layer undergoes can be quantitatively measured as a warp. The warp is, for example, G as shown in FIG.
aInAs magnetic sensitive layer (103) and InP buffer layer (10
When the single heterostructure consisting of 2) has a “warp”, it is the amount of displacement defined by the height difference (112) between the lowest point (110) and the highest point (111) of the “warp”. The warp of the InP or GaAs crystal used as the substrate is about 10 ^-3 c
It is less than m. However, as a result of earnest studies by the present inventors, for example, InP formed on an InP single crystal substrate
The warp of the / GaInAs single heterojunction material could reach 2-5 times that of the substrate crystal itself. When the warp becomes large like this, as described above, GaInAs
This causes deterioration of the characteristics of the heterojunction Hall element. Therefore, in the present invention, in order to obtain a high-performance GaInAs heterojunction Hall element having excellent sensitivity characteristics and suppressing unbalance voltage to a low level, it is possible to reduce the displacement of the GaInAs magnetosensitive layer in the conventional heterojunction structure material. Find a simple laminated structure.

[0009]

That is, the present invention provides Ga _x I
n _1-x As (x represents a composition ratio, and 0 <x <1.)
In a GaInAs heterojunction Hall element comprising a heterojunction including a double bond, the Ga _x In _1-x As is inserted in the middle of the same compound semiconductor layer having a thickness difference of ± 65% or less. A Hall element is made of a heterojunction material. As the same compound semiconductor layer, InP,
Either AlInAs, GaInP or AlInP can be used.

For example, when Ga _x In _1-x As of the magnetic sensitive layer is inserted in the middle of the n-type InP layer, Ga _x In _1-x As is formed.
A double heterojunction between InP and InP can be obtained. Similarly, n-type GaIn is formed on both upper and lower sides of the Ga _x In _1-x As layer.
If P is provided, Ga _{x is formed in} the middle of the same compound semiconductor stack.
A double heterojunction structure in which In _1-x As is arranged can be formed. When the compound semiconductor layer immediately below the Ga _x In _1-x As layer is Ga _0.51 In _0.49 P, Ga _x I
The compound semiconductor layer to be heterojunction above the n _1-x As layer is also Ga _0.51 In _0.49 P. GaInP and AlInA
When Ga _x In _1-x As is sandwiched by ternary compound semiconductor layers such as s, it is preferable that the composition ratios of Ga and Al are also the same. Similarly, if an AlInAs layer or an AlInP layer is arranged on both sides of the Ga _x In _1-x As magneto _- sensitive layer, AlI
nAs / Ga _x In _1-x As / AlInAs, AlIn
A double heterojunction structure composed of P / Ga _x In _1-x As / AlInP can be formed.

As described above, the same compound semiconductor layer is provided above and below the Ga _x In _1-x As layer. That is, Ga _x In
_{The 1-x} As layer is sandwiched between the same compound semiconductor layers. By arranging the same compound semiconductor layer on both sides of the Ga _x In _1-x As layer, can reduce the distortion stress expansion coefficients is applied to the Ga _x In _1-x As feeling free layer if Hasamikome the same material. The carrier concentration does not necessarily have to be the same on both sides of the magnetosensitive layer.

InP and AlInP provided to form a double heterojunction both above and below the Ga _x In _1-x As layer.
The difference in film thickness between the two is accommodated within the difference within 65%. Here, the difference in film thickness is expressed by the following formula (1) based on the film thickness of the compound semiconductor layer which is hetero-junctioned on the substrate side below the Ga _x In _1-x As layer. Define. Film thickness difference (%) = | (t _u −t ₁ ) / t ₁ | × 100 (1) where t _u is provided on the upper side of the Ga _x In _{1 -x} As magnetosensitive layer. It is the film thickness of the compound semiconductor layer. t ₁ is the standard Ga
_x In _1-x As is the film thickness of the compound semiconductor layer provided below the magnetosensitive layer. Therefore, the difference in film thickness is obtained based on the absolute value of the difference between t _u and t ₁ . For example, InP / Ga _x In
_{In the 1-x} As / InP hetero system, the film thickness of the InP buffer layer immediately below the Ga _x In _1-x As magnetosensitive layer is 100 nm, and the film thickness immediately above the magnetosensitive layer is 35 nm or more and 165 nm or less.
The provision of the nP layer can satisfy the requirements of the present invention. When the film thickness of the compound semiconductor layers provided above and below the magnetosensitive layer exceeds the regulation of the present invention, the amount of strain introduced into the Ga _x In _1-x As layer due to the difference in linear expansion coefficient increases remarkably. Ga _x In _1-x As
If the compound semiconductor layers provided on both sides of the layer have extremely different film thicknesses, “warp” occurs in the Ga _x In _1-x As layer, which is not preferable.

Of the above double heterojunctions, InP / G
a _x In _1-x As / InP and AlInAs / Ga _x In
_{The 1-x} As / AlInAs junction system preferably utilizes InP as the substrate. This is because not only InP but also Ga _0.47 In _0.53 As having a Ga composition ratio of 0.47 and an Al _0.48 In _0.52 As layer having an Al composition ratio of 0.48 are lattice-matched with InP. The lattice-matched system has an advantage that the hetero-structure layer can be easily grown. On the other hand, since GaInP and AlInP have a lattice matching composition with GaAs, GaAs should be used as the substrate. For example, Ga _0.51 In _0.49 P having a Ga composition ratio of 0.51 lattice-matches with GaAs.

When a double heterojunction is formed by a compound semiconductor layer that lattice-matches InP, Ga _x In _1-x A
The mixed crystal ratio (x) of s is preferably 0.37 ≦ x ≦ 0.57. Because Ga _x lattice-matched to InP
This is because as the composition ratio of In _1-x As (x) = 0.47 deviates, the degree of lattice mismatch becomes noticeable and a large amount of crystal defects are induced, resulting in deterioration of crystallinity. Also, the electrical characteristics such as electron mobility are deteriorated, and the characteristics of the Hall element greatly hinder the improvement of product sensitivity.

When a double heterojunction composed of a compound semiconductor layer lattice-matched to InP is formed, G is used as a magnetic sensitive layer.
The film thickness of the a _x In _1-x As layer is different from that of the lattice mismatched Ga _x In _1-x As of GaAs heterojunction system.
There are no special restrictions. However, if the thickness exceeds 10 ⁻³ cm, the difference in the mesa etching shape due to the difference in the crystal axis is promoted when the magnetosensitive layer is processed into the mesa type, and the unbalance ratio may be deteriorated. Therefore, Ga _x In used as the magnetic sensitive layer
The film thickness of the _1-x As layer is usually 1 to 2 × 10 ^-4 cm.

Ga _0.51 I lattice-matched on a GaAs substrate
n _0.49 P layer or Al _0.52 In _0.48 P layer and Ga _x In _1-x A
When forming a double heterojunction consisting of an s layer, Ga
The Ga composition ratio of _x In _1-x As is preferably about 0.2. Ga _x In _1-x As does not lattice match with GaAs regardless of the Ga composition ratio (x), and the degree of lattice mismatch increases as (x) increases. Therefore,
The reason why (x) is extremely increased is that it is disadvantageous to obtain high electron mobility.

The film thickness of Ga _x In _{1 -x} As having a double heterojunction (x) of about 0.2 grown on a GaAs substrate is preferably about 10 nm or less. When the film thickness becomes thick, strain due to lattice mismatch cannot be contained in the layer, and it becomes difficult to improve electrical characteristics such as electron mobility.

The Ga _x In _1-x As layer serving as the magnetic sensitive layer is generally n-type. This is because a higher electron mobility can be obtained as compared with the p-type, which is advantageous in increasing the sensitivity of the Hall element.
In addition, a p-type InP layer is provided directly above the n-type Ga _x In _1-x As magnetosensitive layer, and an n-type InP that is the opposite conductivity type is arranged immediately below the magnetosensitive layer. , Magnetic sensitive layer and p-type I
The nP heterojunction becomes a pn junction, which causes an increase in capacitance and deteriorates the high-speed response of the Hall element. Therefore, the conduction type of the compound semiconductor layers provided on the upper and lower sides of the Ga _x In _{1 -x} As magnetic sensitive layer is preferably the same n type as the magnetic sensitive layer from the viewpoint of obtaining high electron mobility. For example AlI
nAs / Ga _x In _1-x As / AlInAs double heterojunction system, AlInAs immediately below Ga _x In _1-x As
If the layer is n _-type , Al immediately above the Ga _x In _1-x As layer
The InAs layer is also n-type.

A Ga _x In _1-x As layer serving as a magnetically sensitive layer and InP, AlInAs, and GaInP heterojunction therewith.
And each layer of AlInP are liquid phase epitaxial growth (LP
E method), molecular beam epitaxial growth method (MBE method), metalorganic pyrolysis vapor phase growth method, so-called MOVPE (MOC)
It may also be called the VD method or the OMVPE method. ) And so on. Or MOVPE and MB
It can be grown by the MO / MBE method or the like in which both E are combined. There is no problem even if the growth method is different for each layer, and it is not necessary to provide each layer for forming the heterojunction according to the present invention by the only growth method. Further, in order to obtain a GaInAs heterojunction Hall element from the double heterostructure according to the present invention, it can be manufactured by using a known process technique.

[0020]

By specifying the film thickness of the clad layer of the double heterojunction, the Ga _x In _1-x As associated with the thermal process etc.
The displacement of the magnetic sensitive layer is reduced, and the generation of thermal strain is suppressed.

[0021]

EXAMPLES The present invention will be specifically described below based on examples. FIG. 1 shows InP / Ga _0.47 In _0.53 A according to the present invention.
It is a plane schematic diagram of an s / InP double heterojunction Hall element. 2 is a schematic cross-sectional view taken along the broken line AA ′ of FIG. In forming the heterojunction, a semi-insulating {10
0} InP single crystal was used. InP single crystal substrate (10
The resistivity of 1) is 1 × 10 ⁷ Ω · cm, and the thickness is about 3
It was 50 μm.

(102) is cyclopentadienyl indium (molecular formula: C ₅ H ₅ In) I formed on the substrate (101).
It is a buffer layer made of undoped n-type InP epitaxial crystal having a film thickness of about 100 nm, which is grown by MOVPE method of atmospheric pressure (atmospheric pressure) using n source. Buffer layer (10
2) was grown at a temperature of 610 ° C. Carrier concentration is 2
It was × 10 ¹⁵ cm ^-3 .

On the buffer layer (102), a Ga composition ratio of 0.
47, n-type Ga _0.47 In _0.53 A with a thickness of about 400 nm
The magnetic sensitive layer (103) of s was provided by the atmospheric pressure MOVPE growth method described above. The growth temperature of this magnetic sensitive layer (103) was also set to 610 ° C., like the InP buffer layer (102). Magnetic layer (10
The carrier concentration of 3) was 2 × 10 ¹⁶ cm ⁻³ . The carrier concentration of the magnetic sensing layer (103) was obtained by adjusting the amount of sulfur (S) added as an n-type dopant.

A buffer layer (10) is formed on the magnetic sensing layer (103).
The same InP layer as the compound semiconductor layer constituting 2) was deposited as the contact layer (104). This contact layer (104) was also n-type. As a result, InP / GaI
A double heterojunction of nAs / InP was formed. The thickness of the contact layer (104) was 120 nm. Therefore,
In the text, t _u was 120 nm, t ₁ was 100 nm, and the difference in film thickness defined by the above formula (1) was 20%. The contact layer (104) was an n-type layer doped with Si and had a carrier concentration of 1.2 × 10 ¹⁸ cm ⁻³ . The reason for increasing the carrier concentration in this way is to utilize this layer as an ohmic contact layer.

A GaInAs double heterojunction hole is formed by using the obtained double heterojunction material as a base material and using well-known photolithography technology to form electrodes (105), scribe lines (106), an insulating film (107), and the like. The device was formed. The electrode was made of AuGe alloy and was alloyed at a temperature of 420 ° C. for 3 minutes to form an ohmic electrode.

In the above double heterojunction material, 110
A product sensitivity of 750 V / A · T was obtained with an input resistance of 0Ω. The value of this product sensitivity was 5% lower on average from the theoretical product sensitivity calculated from the pattern shape of the device based on electron mobility, sheet resistance and the like. The imbalance rate was ± 6%. On the other hand, the average value of product sensitivity obtained from the conventional single hetero structure in which one surface of the GaInAs magnetosensitive layer is opened is 6
The value was 60 V / AT, which was about 16% lower than the theoretical product sensitivity value.
The unbalance rate was ± 12%. The electron mobility of the conventional single heterojunction structure is particularly lowered in the ohmic alloying process of the electrode which requires heating.

[0027]

EFFECTS OF THE INVENTION It is possible to suppress the deterioration of sensitivity and unbalance rate due to a thermal process or the like.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a GaInAs Hall element according to the present invention.

FIG. 2 is a schematic cross-sectional view taken along the broken line A-A ′ in FIG.

FIG. 3 is a diagram illustrating warping by taking a GaInAs / InP heterojunction material as an example.

[Explanation of symbols]

 (101) Crystal substrate (102) Buffer layer (103) Magnetosensitive layer (104) Contact layer (105) Electrode (106) Scribe line (107) Insulating film (110) Lowest point of "warp" (111) "Warp" Highest point (112) Height difference equivalent to warp amount

Claims (2)

[Claims] 1. A Ga _x In _1-x As layer (provided that a Ga _x In _{1 -x} As layer is provided between two compound semiconductor layers composed of the same element and having a thickness difference of 65% or less mounted on a semiconductor substrate). ,
x represents a composition ratio, and 0 <x <1) is included in the double heterojunction, which is characterized by including GaInAs.
Heterojunction Hall element. 2. The GaInAs heterojunction Hall element according to claim 1, wherein the compound semiconductor layer composed of the same element is InP, AlInAs, GaInP or AlInP.