JPH10150231A - Hall element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hall element, which responds also to a change in an external magnetic field at high speed and can obtain a high hall voltage, by a method wherein two-dimensional electron gas layers are respectively formed on both of an electron feeding layer containing N-type impurities. SOLUTION: A heterojunction structure 30 of a hall element is constituted into a structure, wherein a semi-insulative GaAs layer 2 is formed on a substrate, an AlGaAs layer 3 not containing impurities is junctioned in heterostructure with the layer 2 to form on the layer 2 as a first spacer layer, an AlGaAs layer 4, which is used as an electron supply layer, is formed on the layer 3, an AlGaAs layer 5, which is used as a second spacer layer, is formed on the layer 4 and moreover, a GaAs layer 6 is formed on the layer 5 to form a two-dimensional electron gas layer 7 in the vicinity of the interface between the layers 2 and 3 and to form a two-dimensional electron gas layer 8 in the vicinity of the interface between the layers 5 and 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Hall element having a high sensitivity, a high response speed, and a large driving current.

[0002]

2. Description of the Related Art Generally, a Hall element made of GaAs is manufactured by one of the following two methods (a) and (b).

(A) A semi-insulating substrate such as GaAs
An active layer serving as a magnetically sensitive portion for sensing a magnetic field is formed by selectively implanting Si ⁺ ions on a substrate by an ion implantation method and performing heat treatment. Next, AuGe is formed on this active layer.
After forming an ohmic electrode for current supply for driving the Hall element and an ohmic electrode for signal output using a metal composed of a system, a protective film made of SiNx or SiO ₂ film is formed by plasma CVD (Chemical Vapor Deposition, chemical vapor deposition). (A vapor phase epitaxy) method. Next, the thickness of the GaAs substrate is reduced to about 100 μm by back lapping, and then a chip is formed by dicing. This chipped substrate is die-bonded to a lead frame using Ag epoxy resin, and wire bonding is performed using a gold wire. The lead frame is resin-molded, and then subjected to a solder coating of the lead frame, a cutting of the lead frame, and a step of forming terminals, thereby producing a Hall element.

(B) A heterojunction Hall element is an MO-
By a VPE (Metal Organic Vapor Phase Epitaxy) method or a MBE (Molecular Beam Epitaxy) method, GaAs containing no impurities, AlGaAs containing no impurities, and AlG containing n-type impurities are formed on a semi-insulating GaAs substrate.
The GaAs layer containing no impurity and the impurity-free GaAs layer are formed by sequentially growing aAs to form a magneto-sensitive portion.
Electrons are supplied from an AlGaAs layer containing an n-type impurity in the vicinity of the heterointerface with the lGaAs layer, and a two-dimensional electron gas layer with high mobility is formed. Using the two-dimensional electron gas layer as an active layer, an ohmic electrode is formed in the same manner as in the method (a) described above. The steps after the formation of the ohmic electrode are as follows:
This is the same as the method (a).

[0005]

By the way, what is required for the performance of the Hall element is generally high sensitivity, small temperature dependency, good output linearity, and the like.

[0006] However, a hall element using GaAs as a material has the advantage that the temperature dependence of the output is small due to its large forbidden band width, but the electron mobility is lower than that of semiconductor materials other than GaAs. It has the disadvantage of being small.

In a Hall element based on the Lorentz force, the larger the electron mobility is, the stronger the influence of the magnetic field is. Therefore, the Hall voltage is proportional to the electron mobility. Therefore, a semiconductor element that outputs a voltage generated by the Hall effect, such as a Hall element, has low sensitivity if the mobility of electrons is small.

For this reason, when the ion implantation and heat treatment techniques are used for manufacturing the Hall element as in the method (a), the electron mobility is 5,000 cm ² · V ⁻¹ due to impurity scattering by the ion-implanted Si ions.・ Because it is as low as s ^-1 , it is not possible to manufacture a Hall element that generates a high Hall voltage. In addition, this Hall element has a low mobility and detects the position of a magnet as a rotor of a motor that rotates at high speed. There is a problem that cannot follow.

The method (b) is a heterojunction Hall element using a two-dimensional electron gas layer that can obtain a relatively high mobility by preventing the influence of impurity scattering. The Hall element has a relatively high sensitivity and a high response speed when the current input is small, but when a large current is input, excess carriers are generated in the n-type AlGaAs layer and the two-dimensional electron gas layer The sensitivity is saturated because the carrier is excessively filled, and the extra carrier contributes to the electric conduction in parallel with the two-dimensional electron gas layer, so that the average mobility is lowered and the high output cannot be obtained. As a result, there is a problem that the linearity of the output deteriorates.

Accordingly, an object of the present invention is to use GaAs as a material which responds quickly to changes in an external magnetic field, provides a high Hall voltage, and does not saturate the output even under conditions of use with a large amount of current. It is to provide a Hall element.

[0011]

In order to solve the above-mentioned problems, a first aspect of the present invention provides a heterojunction in which a high mobility two-dimensional electron gas layer is formed at a junction between different kinds of semiconductors having different band gaps. In the heterojunction Hall element including
The two-dimensional electron gas layers are formed on both sides of an electron supply layer containing a type impurity.

According to a second aspect of the present invention, the heterojunction structure for forming two two-dimensional electron gas layers includes a G layer containing no impurities.
an aGaAs layer, an impurity-free AlGaAs layer hetero-joined on the GaAs layer, and an AlG layer containing an n-type impurity serving as an electron supply layer joined on the AlGaAs layer.
An aGaAs layer, an impurity-free AlGaAs layer bonded on the AlGaAs layer, and an impurity-free GaAs layer hetero-joined on the AlGaAs layer.

Consider the basic design principle of a Hall element.

[0014] input in the rectangle of the Hall element voltage V _in
And the Hall voltage (output voltage) V _H is expressed by the following equation.

V _H = (w / l) · μ _e · B · V _in where 1 and w are the length and width of the element, μ _e is the electron mobility, and B is the magnetic flux density.

In view of this relationship, a method of increasing the electron mobility μ _e is an effective technical means for increasing the output of the Hall voltage.

Accordingly, the present invention is to provide a GaAs semiconductor having a hetero-interface having a structure for generating a two-dimensional electron gas capable of obtaining a high mobility, thereby obtaining a Hall voltage to achieve a high-speed response. Further, a hetero interface is formed on both sides of the electron supply layer to double the channel through which electrons flow.

According to the above structure, AlGaAs having different forbidden band widths is grown on a semi-insulating GaAs substrate by GaAs.
By the method of generating a two-dimensional electron gas at the hetero interface between s and AlGaAs, the electron mobility of the Hall element has a maximum value as compared with the case where the active layer serving as the magnetically sensitive portion is formed by the conventional method (a). The ratio becomes about twice, and assuming Hall elements of the same shape, the Hall voltage also doubles.

Further, since there are two two-dimensional electron gas layers sandwiching the electron supply layer, when the input current is increased, excess carriers in the electron supply layer are supplied to both two-dimensional electron gas layers. As in the method (b), the allowable amount is twice as large as that in the case where the two-dimensional electron gas layer is one. Therefore, 2
The carriers in the two-dimensional electron gas layer are no longer saturated, and the mobility does not decrease due to an increase in the current input to the Hall element.

[0020]

Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 2 shows a schematic diagram of the present invention.

As shown in FIG. 2, the Hall element 40
A magnetic sensing portion 9 formed of a cross-shaped semiconductor wafer having two ends 9a, 9a, 9b, 9b for sensing an external magnetic field, and a pair of end portions 9a facing one of the magnetic sensing portions 9 ,
9a, input ohmic electrodes 10, 10 for inputting a control current in a predetermined direction to the magnetic sensing portion 9.
And a pair of end portions 9b, 9 facing the other of the magneto-sensitive portion 9.
b, and has a four-terminal bridge structure including output ohmic electrodes 11 and 11 for outputting a Hall voltage generated in a direction orthogonal to the control current flowing through the magnetic sensing portion 9. .

The ends 9a and 9b of the magneto-sensitive portion 9 are formed with a predetermined width and depth, respectively, and the distance between the input ohmic electrodes 10 and 10 and the distance between the output ohmic electrodes 11 and 11, respectively. Is equal to

The materials of the ohmic electrodes 10 and 11 are as follows.
AuGe-based metal is used.

Next, FIG. 1 is a cross-sectional view of a wafer serving as the magnetic sensing unit 9 constituting the present invention.

As shown in FIG. 1, the wafer of the present invention mainly comprises a semi-insulating GaAs substrate 1 and a heterojunction structure 30.

The heterojunction structure 30 has a semi-insulating Ga
GaAs not containing impurities grown on the As substrate 1
an s layer (thickness: 50 nm) 2, an AlGaAs layer (thickness: 3 nm) 3 containing a heterojunction on the GaAs layer 2 and hetero-junction-grown and containing no impurity as a first spacer layer; An AlGaAs layer (thickness: 5) using Si atoms as an electron supply layer and having n-type impurities as n-type impurities.
0 nm) 4 and a layer is grown on the AlGaAs layer 4,
AlGa not containing impurities as a second spacer layer
An As layer (thickness: 3 nm) 5 and a GaAs layer (thickness: 50 nm) hetero-junction-grown on the AlGaAs layer 5
6 is comprised.

A two-dimensional electron gas layer 7 is generated near the interface of the heterojunction between the GaAs layer 2 and the AlGaAs layer 3, and also near the interface of the heterojunction between the AlGaAs layer 5 and the GaAs layer 6. An electron gas layer 8 is generated. These two-dimensional electron gas layers 7 and 8 become active layers.

The carrier density of the AlGaAs layer 4 containing an n-type impurity serving as an electron supply layer shown in FIG.
0 ¹⁸ cm ³ . The mixed crystal ratio between the AlGaAs layer 4 and the spacer-free AlGaAs layers 3 and 5, which is a spacer layer, is 0.2. This GaAs layer 4 and AlGaAs
The mixed crystal ratio with the s layers 3 and 5 is desirably 0.3 or less. When the mixed crystal ratio is 0.3 or more, the efficiency of activating electrons is deteriorated.

The AlGaAs layer 3 containing no impurities
And the thickness of the AlGaAs layer 5 must be the same.

In other words, when the present invention is shown in a circuit diagram, as shown in FIG. 4, two two-dimensional electron gas layers 7 and 8 are provided.
And an output electrode constitute an equivalent circuit. Therefore, when the thicknesses (potentials) of the AlGaAs layers 3 and 5 as the spacer layers are different, the Hall voltage is changed to the output electrode 1.
Since they are short-circuited in parallel with each other, they are averaged and output is not performed efficiently.

Next, the operation of the present invention will be described with reference to FIGS.

The input ohmic electrodes 10, 1 shown in FIG.
0, a carrier in the AlGaAs layer 4 containing the n-type impurity shown in FIG.
From the As layer 4 through the AlGaAs layers 3 and 5, the GaAs
Move to the two-dimensional electron gas layers 7 and 8 in the layers 2 and 6
The two-dimensional electron gas layers 7 and 8 are gradually filled. Along with this, the carriers in the two-dimensional electron gas layers 7 and 8 move at high speed toward the output ohmic electrode 11 shown in FIG.

In FIG. 1, the carrier is a two-dimensional electron gas layer 7,
8, AlGaAs containing an n-type impurity is used.
Since the two-dimensional electron gas layers 7 and 8 are formed on both sides of the s layer 4, excess carriers generated in the AlGaAs layer 4 are supplied to both the two-dimensional electron gas layers 7 and 8. For this reason,
The carriers in the two-dimensional electron gas layers 7 and 8 do not saturate. Therefore, even when a large amount of current is input, the carriers show high mobility and the Hall element shows high output. That is, excellent linearity of output can be obtained.

FIG. 3 shows the drive current-Hall voltage characteristics of this Hall element together with the prior art. FIG. 3 shows the change of the Hall voltage with respect to the current in a constant magnetic field of the Hall element manufactured by the method (a) and the Hall element manufactured by the method (b) according to the present invention. In the figure, a line d connecting white circles indicates the characteristic of the present invention, a line s connecting white triangles indicates the characteristic of (b), and a line i connecting black circles indicates the characteristic of (a). .

It should be noted that the distance between the two input electrodes 10 and 10 shown in FIG.
The distance between the first and the first 11 is 300 μm, and the width of the ends 9 a and 9 b of the magnetic sensing part 9 is 100 μm.

As shown in FIG. 3, the Hall element of the present invention using the two-dimensional electron gas layer and the Hall element of (b) can obtain a higher output than the Hall element of (a).

Although the output of the Hall element (b) gradually decreases as the drive current increases, the present invention can maintain a high output and is excellent in the straightness of the output voltage.

As described above, according to the present invention, since the sensitivity is increased, the driving current can be reduced. Thereby, the present invention can be applied to a small D-type camera used for a portable video camera, for example.
By using it as a sensor for detecting the position of a magnet of a rotor such as a C brushless motor, power consumption can be reduced and long-term driving can be expected.

Further, according to the present invention, the response speed is high, so that the present invention can be applied to a high-speed motor, and a disk-type information recording medium such as a floppy disk drive or a CD-RO
Reading and writing of information such as M can be expected.

Further, according to the present invention, since it can be used by changing the magnitude of the amount of current, it can perform a wide range of measurement as a sensor for measuring a magnetic field.

Next, a modification of the present invention is shown in FIG.

The wafer shown in FIG. 5 is heteroepitaxially grown on the semi-insulating GaAs substrate 12 so that a plurality of two-dimensional electron gas layers 7 and 8 are formed.
Are provided on the semiconductor substrate 50. By forming a plurality of heterojunction structures 30 in this manner, a Hall element with low input resistance can be manufactured.

[0044]

In summary, according to the present invention, while maintaining the advantages of a GaAs Hall element having good temperature characteristics, it responds quickly to changes in an external magnetic field, and provides a high Hall voltage. The output does not saturate even under use conditions where the amount of current is large.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a wafer serving as a magnetic sensing unit constituting the present invention.

FIG. 2 is a schematic diagram of the present invention.

FIG. 3 is a diagram showing drive current-Hall voltage characteristics according to the present invention and the prior art.

FIG. 4 is a circuit diagram illustrating the present invention.

FIG. 5 is a sectional view showing a modification of the wafer of FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 semi-insulating GaAs substrate 2 GaAs layer containing no impurities 3 AlGaAs layer containing no impurities 4 AlGaAs layer containing n-type impurities 5 AlGaAs layer containing no impurities 6 GaAs layer containing no impurities 7 2-dimensional electron gas layer 8 2 Dimensional electron gas layer 30 heterojunction structure

Claims (2)

[Claims] In a heterojunction Hall element including a heterojunction in which a two-dimensional electron gas layer having a high mobility is formed at a junction of different semiconductors having different forbidden bandwidths, both sides of an electron supply layer containing an n-type impurity are included. Characterized in that the two-dimensional electron gas layer is formed on each of them. 2. The hetero-junction structure for forming two two-dimensional electron gas layers includes a GaAs layer containing no impurity and an Al-free heterojunction formed on the GaAs layer.
A GaAs layer, an AlGaAs layer containing an n-type impurity serving as an electron supply layer bonded on the AlGaAs layer, and an impurity-free AlG bonded on the AlGaAs layer.
an aAs layer and a heterojunction on the AlGaAs layer,
2. The Hall element according to claim 1, comprising a GaAs layer containing no impurities.