KR100852184B1 - Hybrid semiconductor-ferromagnet device with a junction of positive and negative magnetic-field regions - Google Patents

Abstract

The semiconductor-magnetic material fusion device of the present invention is a device having a junction structure of a negative and positive magnetic field region using a stray field from which micro-magnets (Co) are deposited on two-dimensional semiconductor (InAs) electrons. The magnetoresistance measured in the semiconductor-magnetic material fusion device has an asymmetric Hall resistance shape, and the magnetoresistance change is very large. The measured data are in good agreement with the results calculated by the diffusive and ballistic models.

Description

HYBRID SEMICONDUCTOR-FERROMAGNET DEVICE WITH A JUNCTION OF POSITIVE AND NEGATIVE MAGNETIC-FIELD REGIONS}

The present invention relates to a semiconductor-magnetic material fusion device having a junction structure between a region in which a magnetic field is negative and a region in a semiconductor.

Semiconductor-magnetic material fusion device is attracting attention as a device that can be applied to the recently attracted field, such as magnetic field sensor, nonvolatile memory device, spintronics. In particular, the sensor based on the magnetoresistance of the semiconductor-magnetic material fusion device is a next generation technology that can be the core of the high-density information storage and position / speed measurement device technology. In these devices, the movement of electrons in the semiconductor is controlled by a nonuniform local magnetic field.

Recently, magnetic field sensors that are attracting attention include GMR and TMR devices. However, these devices have disadvantages in some applications, and especially in the field of biomolecule sensors using magnetic beads, which have been in the spotlight recently, the device proposed in the present invention exhibits superior performance than the GMR and TMR devices.

On the other hand, as an recently introduced magnetic field sensor, there is an extraordinary magnetoresistance (EMR) device reported by Solin et al. The EMR device has a very high magnetoresistance value, but the contact resistance between the metal and the semiconductor must be very low, and the manufacturing process is difficult.

The semiconductor-magnetic material fusion device known to date has a positive local magnetic field region and a negative local magnetic field region separated from each other even if local magnetic fields are uniform in one direction or local magnetic fields in opposite directions are formed in a single element. The voltage measurement terminal, which senses the magnitude of the signal, was located regardless of the direction of the local magnetic field.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a semiconductor-magnetic material fusion device having a structure in which two magnetic field regions are bonded because local magnetic field regions in opposite directions are very close to each other.

It is also an object of the present invention to propose a novel type of semiconductor-magnetic material fusion device in which a voltage measuring terminal is located in a positive and negative magnetic field region.

The device manufactured according to the present invention exhibits superior performance than existing devices, and may be applied to MRAM, spintronics, biomolecule sensors, etc. as well as magnetic field sensors.

The semiconductor-magnetic material fusion device according to an aspect of the present invention for achieving this object,

Two micro-magnets having a predetermined spacing on the same plane are positioned on a semiconductor 2-Dimensional Electron Gas (DEG) having a current-flowing channel, and a semiconductor under a portion where the two micro-magnets face each other as an external magnetic field is applied. It is characterized in that two magnetic barriers having different signs are formed in a junction structure between a region having a negative magnetic field and a region having a positive magnetic field.

At this time, one side of the channel may further include a positive and positive voltage terminal respectively connected to the negative and positive regions of the magnetic field, the negative and positive voltage terminals respectively correspond to the minimum and maximum height of the magnetic barrier It is preferable to be formed in the position to make.

In addition, the semiconductor 2DEG preferably includes InAs or HgCdTe, and in this case, the junction surface between the negative and positive regions of the magnetic field may be an up-down junction surface of electron spin.

On the other hand, the semiconductor-magnetic material fusion device according to another aspect of the present invention for achieving the above object,

A micromagnet intersecting the channel is located on the semiconductor 2DEG having a channel through which current flows. As an external magnetic field is applied, two magnetic barriers having different signs are formed in the semiconductor under the micromagnet, so that the magnetic field is positive and negative. It is characterized by having a junction structure between regions.

On the other hand, the semiconductor-magnetic material fusion device according to another aspect of the present invention for achieving the above object,

And a semiconductor 2DEG having a channel through which a current flows and a plurality of voltage terminals vertically connected to one side of the channel, and micro-magnets alternately positioned on channel portions between two neighboring voltage terminals.

In this case, the two neighboring voltage terminals are preferably formed at positions corresponding to minimum and maximum heights of two magnetic barriers having different signs formed in the channel as an external magnetic field is applied.

According to the present invention, a semiconductor-magnetic material fusion device having a junction structure between a region in which a magnetic field is negative and a region in which a magnetic field is negative can be manufactured, and such a device can be applied not only to unipolar spin elements but also to highly integrated magnetic field sensors and memory elements.

Hereinafter, embodiments of a semiconductor-magnetic material fusion device according to the present invention will be described in detail with reference to the accompanying drawings.

Devices aimed at in the present invention are spin diodes and transistors based on spin up / down junctions. Unipolar spin transistors are based on the concept of "spin junctions" rather than "spin implants." Unipolar spin transistors are homogeneous rather than heterojunction structures, and are distinguished from other spin devices in that they do not require spin injection.

In order to fabricate such unipolar spin diodes and transistors, it is necessary to achieve spin up / down junctions. In the case of ferromagnetic magnetic semiconductors, spin up / down junctions can be implemented as junctions of domains with opposite spin directions. Ruster et al. Fabricated a magnetic semiconductor device that forms a kind of spin up / down junction structure using nanoconstrictions of GaMnAs wire and observes the giant magnetoresistance. However, these magnetic semiconductors are so large that the concentration of the carrier cannot be an effective diode. In other words, because the Fermi level is a degenerate semiconductor located below the valance band, it is closer to the metal than the semiconductor, so it cannot act as a spin diode or transistor.

When the magnetic semiconductor is used for the spin up / down junction, as described above, since the Fermi level is a degenerate semiconductor located below the valance band, it is closer to the metal than the semiconductor and thus cannot act as a spin diode or a transistor. Accordingly, for the unipolar spin transistor, a non-degenerate semiconductor having a relatively low carrier concentration, that is, a semiconductor having a Fermi level located between the band gaps, is required. All are degenerate semiconductors. Therefore, in order to form an effective unipolar spin diode, it is preferable to use a semiconductor having a large spin separation by an external magnetic field, that is, a semiconductor having a large paramagnetism. In the present invention, a semiconductor having a large paramagnetic property due to the Zeeman effect, ie, g A large semiconductor factor was used.

On the other hand, some dilute magnetic semiconductors (DMS) have a very large g-factor due to the exchange interaction between magnetic ions and electrons present in the material, but the spin relaxation time is very small when magnetic ions are present. Difficult to use as an effective spin junction device. Therefore, a preferred material for unipolar spin diodes or transistors is a semiconductor with a large g-factor and no magnetic ions.

In order to achieve the spin up / down junction by the Zeeman effect, first, a junction structure of a negative region and a positive region is required. In other words, first, when a positive-negative junction of a magnetic field is formed in a semiconductor having a large g-factor, spin separation occurs in each junction region due to a large Zeeman effect, and a junction of two regions in which a majority carrier is spin up and down is performed. . Such a spin junction is a spin diode corresponding to a conventional pn junction diode, and a negative, positive and negative junction structure formed by repeating regions of negative and positive magnetic fields becomes a unipolar spin transistor corresponding to a pnp junction transistor.

Negative and negative magnetic fields should form a local magnetic field, which is appropriately positioned with a micromagnet on the sample, using the stray field from it. That is, a semiconductor-magnetic material fusion device in which a magnetic material having a suitable shape and size is deposited on the semiconductor is fabricated.

The present invention relates to the formation and control of the yin-yang junction structure of the magnetic field region, which can be said to be the core of such a spin junction structure. In order to investigate such a structure, a method of measuring magnetoresistance was mainly used. In the Yin-Yang junction structure of the magnetic field region, the charge of the carrier is subjected to oriental motion under the force of the magnetic field, which appears as a very unique form of magnetoresistance.

Sample Preparation and Measurement

In the present invention, a new type of semiconductor-magnetic material fusion device was fabricated to form a yin-yang junction structure in the magnetic field region. In the conventional semiconductor-magnetic material fusion device, there was only one magnetic barrier, but in the present invention, a magnetic barrier having two different directions is formed, and a voltage probe (hereinafter, referred to as a "voltage terminal") is formed. And used in combination with and to create the position corresponding to the maximum and minimum height of the magnetic barrier to implement the positive and negative junction structure of the magnetic field region.

Referring to FIG. 2, in the semiconductor-magnetic material fusion device according to an embodiment of the present invention, a micro-magnet is placed on an InAs 2-Dimensional Electron Gas (hereinafter, referred to as “2DEG”).

InAs 2DEG is Hall-bar type, and voltage measuring terminals ([A], [B], [C], [D]) are about 76 ^{o for} channels with two current terminals ([I +], [I-]). Made in a slanted form. Adjacent voltage measurement terminals are shaped like a "V" to match the "average distance" between them to the position where the magnetic barrier corresponds to the maximum and minimum. Computational simulation based on the diffusive model of the sample produced is assumed to be separated by the "average distance" of adjacent voltage measurement terminals as shown in FIG. 3, and the "average distance" idea is considered to be in good agreement with the computational results. Is considered to be a good application. Alternatively, the voltage terminals may be formed so as to be perpendicular to the channel without forming the "V" shape. In the present embodiment, the channel and the voltage terminal are integrally formed, but the contents of the present invention are not limited thereto and may be formed separately and connected.

As the semiconductor 2DEG used in the present invention, a general semiconductor 2DEG such as HgCdTe, Si, GaAs, InGaAs, etc. may be used in addition to InAs. Among them, semiconductors with large g-factors and small electron concentrations, such as InAs and HgCdTe, become the spin-up / down junction structure of the magnetic field. It is preferable to use InAs having a smaller electron concentration than that. InAs-based devices show excellent MR characteristics even at room temperature, and their spin sensitivity to magnetic fields can be applied to spin isolation or spin junction devices. In addition, HgCdTe having a much higher spin sensitivity (g-factor) to magnetic fields than other semiconductors may also be used. HgCdTe has a spin field polarization of 57 meV at 1 Tesla and a very long spin life (356 ps at 150K).

In addition, a cobalt (Co) micromagnet having a thickness of 300 nm and a length of 20 μm was formed on the surface of the InAs mesa by a sputtering method. CoPt, CoFe, FeNi, CoFeB, CoZrB, FePt and the like may be used for the micro magnets used in the present invention. Two kinds of samples were produced.

As shown in FIG. 2, two cobalt micromagnets each having a width of 1.0 μm and 0.5 μm and a width of 0.66 μm were used, respectively, as shown in FIG. 2. At this time, the width of the micro-magnet is preferably larger than the width of the channel, so that the magnetic barrier is formed uniformly on the vertical cross section of the channel. Moreover, it is preferable that the distance between two micro magnets is 0.1-1.0 micrometer. In this device, the strength of the magnetic field should be changed rapidly at the Yin-Yang junction. If the distance between two micro-magnets is larger than 1.0 µm, a junction with moderate magnetic field change can be formed, resulting in deterioration of device performance. This is because if it is small, the magnetic field from the micro-magnetism may cause a canceling effect and the performance of the device may be degraded.

4 is a SEM photograph of the S2 sample, wherein a rectangular cobalt micromagnet having a width of 1.85 μm and a voltage of 0.84 μm and a width of 0.93 μm is formed between adjacent voltage measuring terminals.

InAs 2DEG is located 35.5nm below the surface with micromagnets. An insulating layer is interposed between the InAs 2DEG and the micro magnet. It is preferable that the thickness of the insulating layer is smaller than that of the micromagnet. In consideration of the fact that the thickness of the micromagnet used in this embodiment is 300 nm, if the thickness of the insulating layer is greater than 300 nm, the sensitivity of the device is very low. The smaller the thickness of the insulating layer, the higher the sensitivity of the device. Therefore, when the micro magnet is an insulator, a separate insulating layer is unnecessary and the InAs 2DEG may contact the micro magnet.

In the measurement, the resistance according to the external magnetic field was measured by 1Lock-in technology using AC 1㎂ of 98Hz, while the current flowed from the [I +] terminal to the [I-] terminal, the voltage measuring terminals ([A], [B] ], [C], [D]) and the resistance was measured by the 4-terminal method. The mobility and carrier concentrations of S1 and S2 are 7.86m ² / Vsec and 2.0x10 ¹⁶ m ^-2 at 2K, respectively, and 2.0m ² / Vsec and 2.1x10 ¹⁶ m ^-2 at 300K, respectively. Considering that the carrier's mean free path, obtained from mobility and carrier concentration at 2K, is 1.85 μm and that this size is smaller than the size of the S1 sample, the conduction of the S1 sample at 2K is considered to be ballistic motion. It can be seen.

As shown in Fig. 5, when an external magnetic field B _ext is applied in parallel to the sample plane, the micromagnet is magnetized by this external magnetic field, and the vertical component B _z of the stray field coming from both sides is Make two magnetic barriers opposite. Due to the characteristics of the two-dimensional electrons, the magnetic field component horizontal to the element surface does not contribute to the magnetic resistance. Therefore, only vertical magnetic field components can affect the sample, so the carriers contributing to the conduction are only affected by the magnetic barrier due to the magnetization of the micromagnet.

Computer simulation of magnetoresistance

In order to investigate the conduction phenomenon of the measured results and to obtain the fabrication conditions of the sample to obtain the maximum magnetoresistance effect, computer simulation of the magnetoresistance was performed. The carrier of the sample used in the experiment is electron, but for the convenience of calculation, the positively charged particle (positron) should be considered in the computer simulation, but the magnetic field whose sign is opposite to the actual magnetic field is used. It was. The conduction phenomena can be distinguished by diffusive or ballistic model according to the average free path of the carrier and the relative size of the sample. In other words, if the mean free path was larger than the sample size, the simulation was performed using the ballistic model, otherwise the diffusive model was used.

Diffusive models calculate the potential ( φ ) and current density (J) distributions using the finite difference method. Under the steady-state condition in steady state, the divergence of current density

▽ J (x, y) = 0 (1)

to be. In addition, when E is an electric field, it is J = σ * E by Ohm's law. When there is a magnetic field perpendicular to the plane, the conductivity σ can be expressed as a function of the magnetic field as a two-dimensional tensor as follows.

Where μ is the mobility, B _z is the magnetic field perpendicular to the sample plane, and σ ₀ is the conductivity when there is no magnetic field. When considering a local magnetic field such as a magnetic barrier, the conductivity tensor should also be treated as a function of position. In steady state, E =-▽ · φ, so (1) becomes the following two-dimensional elliptic partial differential equation:

▽ ((σ (x)) ▽ φ (x, y)) = 0 (3)

The extended form of this expression is

to be. The potential distribution φ (x, y) in the solution of equation (4) is obtained by the finite difference method using the boundary condition that the voltage difference between the two current terminals is constant and there is no current component perpendicular to the boundary at the other boundary. One of the important physical quantities is the Hall angle ( Φ _H ), which is defined as the angle between the current density and the electric field. The Hall angle represented by Φ _H = tan ⁻¹ μB _z can be derived from equation (2).

The magnetoresistance by the ballistic model was calculated using the Landauer-Buttiker (LB) formula, and the shape and size of the specimen including the voltage measurement terminals as well as the spatial distribution of the magnetic field are used as the calculation parameters. The resistance is obtained by finding the orbits of each incident particle. In this calculation, a system consisting of classical positrons subjected to Lorentz forces is considered. Particles incident at various positions and angles through the current and voltage terminals move at Fermi velocity and are orbited by the effects of magnetic barriers and reflections at the sample boundary, returning to their original terminals or exiting to other terminals. At this time, the number of particles arriving at each terminal is calculated to obtain a transmission probability, thereby obtaining conductance. When the particle enters the terminal q and exits the terminal p, the conductance (G _pq ) is obtained by the following equation.

Where W is the width of the incident terminal, λ _F is the Fermi wavelength, and T _{p ← q} is the transmission probability passing from the q terminal to the p terminal.

Experiment Results and Analysis

In the device manufactured in the present invention, two resistance measurement methods are possible according to the selection of the voltage terminal. 2 and 4, the measurement of the potential difference between [A] [B] or [C] [D], which is a pair of voltage measuring terminals located on one side of the device, yields a typical resistance (R _AB or R _CD ) of the device. If you select [D] [B] or [C] [A], a pair of voltage measurement terminals located on two sides of the device, the Hall resistance (R _{H , DB} Or R _{H , CA} ), in which case the magnetic field becomes the respective Hall resistance for the negative and positive magnetic field regions.

In general, the magnetoresistance curve including hysteresis is an even function with respect to the external magnetic field. That is, when the resistance is placed on the y axis and the external magnetic field is on the x axis, the resistance is symmetrical with respect to the y axis. Hall resistance, on the other hand, is an odd fucntion and has a symmetrical characteristic with respect to the origin.

However, as shown in FIGS. 6A and 6B, although the resistance R _CD measured according to the external magnetic field is a normal resistance rather than a Hall resistance, the measured data is monotonically reduced even when the direction of the magnetic field is changed like the Hall resistance. It is a form similar to the hole function that tends to. In other words, the magnetic resistance rapidly changes linearly in the vicinity of the small external magnetic field. In particular, at 2K, the negative resistance was measured when the external magnetic field was in the positive direction. The asymmetric structure of the magnetoresistance is due to the structure in which the magnetic field region near the voltage measuring terminal is connected to the positive and the positive, which will be discussed in detail later. The total change of the magnetoresistance measured for the external magnetic field is very large, 104 and 148 at 300K and 2K, respectively, and the current sensitivity (d R / d B ) in the vicinity of zero external magnetic field is 315Ω / T at 300K and 2K, respectively. , 368Ω / T.

In order to calculate the magnetoresistance by computer simulation, it is necessary to know the vertical magnetic field component (B _z ) according to the magnetization (M) of the micromagnet. In the present invention, the B _z distribution is obtained for a given M using a simple formula used by Vencurar et al., And the relationship between M and the external magnetic field is assumed as shown in the inset of FIG. 6A. With this one assumption, all measured magnetoresistance characteristics for the S1 sample were successfully fitted. In 300K, the average free path of InAs 2DEG carrier is 0.46㎛, which is small compared to the size of the device, and the magnetoresistance was calculated using the diffusive model (solid line in FIG. 6A). Since it is larger than that, it was calculated using a ballistic model (solid line in FIG. 6b). It can be seen that the calculated magnetoresistances are almost in agreement with the experimental values.

In order to investigate the cause of the magnetoresistance of the device in detail, the magnetic and Hall resistance measurements and the computer simulation of the S2 device were systematically performed. The size of the S2 device at 2K is similar to the mean free path, so diffusive conduction is expected to be the main factor. The measured data and the calculation result agree relatively well as shown in Fig. 7A. The two Hall resistors (R _{H , DB} , R _{H , CA} ) represent positive and negative slopes, respectively, and have a symmetrical relationship with the resistance axis (y-axis). It can be seen that this is well separated. On the other hand, the two magnetoresistance (R _CD , R _AB ) measured from the two sides of the sample also has a similar shape to the Hall resistance, and also shows a symmetrical relationship with respect to the resistance axis. Therefore, the magnetoresistance R can be expressed as follows.

R = R ₀ + R _H (6)

Here, R ₀ is a resistance due to the average spacing of the voltage terminals and is a constant independent of the magnetic field, and R _H is a resistance in the form of a hole function similar to the Hall resistance. The cause of this R _H is well understood in the case of the diffusive model considering the current and potential distribution calculated in FIG. 7C in relation to the Hall angle. The Hall angle near the magnetic barrier (near x = −0.5 μm) is about ± 80 °, whose sign is the same as the sign of the magnetic field. Considering that the electric field is perpendicular to the equipotential lines, the Hall angle close to this means that the direction of the current is almost parallel to the equipotential lines. In other words, considering the two magnetic barriers as approximating regions of negative and positive magnetic fields, the direction of current is parallel to the equipotential lines in this region, and opposite directions in each of the regions of negative and positive. In the region where the magnetic field is negative (near x = -0.5 μm in FIG. 7C), current flows in the positive y direction, and positive charge is accumulated near the terminal [A], and the region in which the magnetic field is positive (x = 0.5 μm in FIG. 7C). Nearby), a current flows in the negative y direction, and a positive charge is accumulated in the vicinity of the terminal [D]. By this charge accumulation, the relative potential V between the terminals [A] and [D] becomes higher than other voltage terminals. Since the resistance measured is determined by a value divided by a constant current (I) applying a potential difference between voltage terminals, a magnetic field region having an opposite sign is formed as shown in FIG. 7B, so that R _AB (= (V _A -V _B ) / I ) Increases and R _CD (= (V _C -V _D ) / I) decreases. By this mechanism, one of the resistances measured at two sides of the device increases as the external magnetic field increases, and the other decreases. In addition, the result of charge accumulation on different sides in each magnetic field region is well supported by the Hall resistance measurement result of FIG. 7A.

The results calculated by the ballistic model are similar to the diffusive case. The main difference is that the measured resistance is negative when it is ballistic. 8A is the trajectory of the particles calculated for the S1 device. Since these trajectories are the most probable of the trajectories from the current terminal [I +] to [I-], they can be understood as representative paths through which current flows by ballistic motion. Particles starting from [I +] (or representative paths of current) exit through [A] and [D] to [I-]. In this case, charges are accumulated at terminals [A] and [D], and the charges accumulated at these terminals increase the potentials of [A] and [D]. Since it is ballistic, ignoring R ₀ in Equation (6), the potential of the [A] and [D] terminals increased by these accumulated charges contributes to the magnetoresistance in the same manner as it contributes to the Hall resistance. As shown in Fig., Hall resistance and magnetoresistance show very similar characteristics in size and shape.

The calculation results based on the diffusive and ballistic models described so far are in good agreement with the measured Hall and magnetoresistance. 8b to 8d briefly describe the operating mechanism of the device fabricated in the present invention based on the common core content of these two models.

First, the magnetic field distribution felt by the carrier in the actual device can be approximated simply to the positive magnetic field region and the negative magnetic field region as shown in FIG. 8B. Since the sides (or voltage terminals) of the device where charges are accumulated by Lorentz forces are determined by the direction of the magnetic field in a given region, the magnetic field regions in opposite directions are charged on the sides (or voltage terminals) of the devices on opposite sides. Will accumulate. As a result, charge accumulation occurs in the voltage terminals [A] and [D] as shown in FIG. 8C, and these terminals have a relative potential larger than that of other voltage terminals as shown in FIG. 8D. Particularly in the case of ballistic, the resistance due to the average spacing of the voltage terminals (R _{0 in} Equation 6) is ignored, so the potential V _D in [D] is greater than the potential V _C in [C]. The resistor (R _CD = (V _C -V _D ) / I) becomes negative. Therefore, the magnetoresistance characteristic of the device fabricated in the present invention is based on the Hall effect, and can be interpreted as a characteristic by the combination of two Hall effects in one device.

Application of Fabricated Devices

The positive and negative junction technology of the magnetic field region obtained in the present invention is a core technology that can be directly applied to a unipolar spin device based on spin up-down junction. In addition to the unipolar spin device, the device fabricated in the present invention may be applied to various fields.

If the spatial change is nonzero (ie ∂B / ∂x ≠ 0) because it is a local magnetic field, spin up and down are forced in opposite directions, respectively. By using this, the device fabricated in the present invention can be applied to a spin filter.

The magnetoresistance measured in this device shows hysteresis because it is due to the magnetization of the micromagnet, and when there is no external magnetic field, there are two resistance values according to the history of magnetization. The difference ΔR between the resistance values is 24 kV and 38 kV at 300K and 2K, respectively, as shown in Figs. 6A and 6B. This large ΔR indicates that the device can be applied to magnetic random access memory (MRAM). The MRAM device using a semiconductor-magnetic material fusion device has been proposed by Johnson et al., But it is difficult to apply to a high density device because it is a Hall resistance measurement device. However, since the device fabricated in the present invention uses a conventional resistor, the voltage measurement terminal is located on one side of the device, so that it is easy to apply to high density.

On the other hand, the device can also be applied as a magnetic sensor. The change in resistance to the external magnetic field is similar to the Hall resistance, so it can measure not only the direction of the magnetic field but also the intensity. As described above, it shows a great sensitivity (d R / d B ) in the small magnetic field. Is expected to be. In particular, the application to the biomolecule sensor using a magnetic bead, which is in the spotlight recently. The principle of the biomolecule sensor is well illustrated in FIG. 9 and can be understood as a small and sensitive magnetic field sensor. Considering that the size of the sensor portion of the device is about 1 μm, and that the size of the commercially available magnetic bead is 0.5 to 5 μm, the device may be used as a single magnetic bead sensing device.

Currently, representative devices attracting attention as solid-state biomolecule sensors include spin metal type devices based on magnetic metals and Hall sensors based on semiconductors. This device has several advantages over these devices, which are summarized as follows.

First, the superiority of the conventional spin valve type device will be described.

To detect a magnetic bead, it must first be magnetized by an external magnetic field. The magnetic field required for magnetization of commercially available magnetic beads is about 100 to 1000 Oe. However, GMR or TMR spin valve type devices are already saturated in such a magnetic field region, making it difficult to use them as magnetic bead sensors. In addition, the spin valve-type device has a nonlinear signal due to a magnetic field. That is, the device signal for detecting the intensity of the stray field from the magnetic bead is rapidly changed non-linearly, there is a difficulty in detecting the number or position of the magnetic bead. However, as shown in the measurement data, the device has a linear magneto-resistive element signal in the range of about ± 1500 Oe, thereby overcoming the above-mentioned disadvantages of the spin valve type device.

Next, we look at the advantages over conventional Hall sensors.

The hall sensor has a cross shape with voltage terminals located on both sides of a channel through which current flows. Due to this type of voltage terminal configuration, the size occupied by one device becomes relatively large, and when the integrated device forming an array structure is manufactured, the total area may be increased. 1 is a one-dimensional array structure of a biomolecule sensor using a recently released Hall device.

However, when the one-dimensional array having the same function as the device proposed in the present invention is constructed, the device shown in FIGS. 10A and 10B can be manufactured.

10A and 10B, the device proposed in this invention alternates over a semiconductor 2DEG having a channel through which a current flows and a plurality of voltage terminals vertically connected to one side of the channel, and a channel portion between two neighboring voltage terminals. It consists of a micro-magnet positioned as. Here, the two neighboring voltage terminals are preferably formed at positions corresponding to minimum and maximum heights of two magnetic barriers having different signs formed in the channel as an external magnetic field is applied.

In the case of measuring the voltage terminals V ₁ and V ₂ , there are micro-magnets between the voltage terminals, which is the same as the S2 sample produced in the present invention. That is, when the micro magnet is located on the channel portion between the two neighboring voltage terminals, as the external magnetic field is applied, a junction surface between the negative magnetic field and the positive region is formed at the channel portion between the two neighboring voltage terminals. .

In addition, when measuring the V ₂ and V ₃ are equal to the voltage terminal of the sample S1 and the configuration of the micro-magnets. That is, when the micro magnet is not located on the channel portion between the two neighboring voltage terminals, as the external magnetic field is applied, a junction surface between the negative and positive regions is formed at the channel portion between the two neighboring voltage terminals. do.

As such, the area between each voltage terminal of the current channel forms a unit device of a one-dimensional array as a magnetic field sensor. Compared with the conventional Hall sensor structure (Fig. 1), the structure has the number of voltage terminals reduced in half, and the arrangement of voltage terminals is also located on one side of the current channel, thereby reducing the overall size of the device. have.

On the other hand, the device proposed in the present invention is similar to the conventional Hall sensor in that it is basically due to the Hall voltage, but because the micro-magnet located on the current channel acts to amplify the magnitude of the magnetic field to be detected, Sensitivity is greater than conventional Hall sensors. Therefore, the biomolecule sensor array proposed in the present invention has an advantage that the sensitivity is larger than that of the hall sensor, and the complexity and size of the device can be reduced by half compared to the hall sensor.

Although the present invention has been described with reference to the illustrated embodiments, it is merely exemplary, and the present invention may encompass various modifications and equivalent other embodiments that can be made by those skilled in the art. Will understand.

1 is a one-dimensional array structure of a conventional biomolecule sensor using a Hall element, the voltage terminal (V _H ) and the current channel for detecting a signal cross-shaped (cross), this cross-sectional area acts as a unit sensor.

2 is a SEM image of a semiconductor-magnetic material fusion device (S1 sample) according to an embodiment of the present invention.

3 is a calculation model based on diffusive movement for the S1 sample shown in FIG.

4 is an SEM image of a semiconductor-magnetic material fusion device (S2 sample) according to another embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of the S1 sample shown in FIG. 2 and a graph showing the magnitude of the vertical component of the micromagnet magnetized by an external magnetic field.

6A and 6B are graphs showing measured and calculated values of MR and Hall resistances at 300K and 2K, respectively. The solid lines in each figure are calculated using a diffusive model at 300K and a ballistic model at 2K, respectively.

Figure 7a is a graph showing the measurement and calculation of the MR and Hall resistance of the S2 sample at 2K. The solid line in the figure is calculated using the diffusive model.

7B is a graph showing the magnitude of the vertical component of the magnetic field when the magnetization of the micromagnet is 1T. Inset of FIG. 7B is a graph assuming a relationship between the magnetization of a micromagnet and an external magnetic field.

FIG. 7C shows the current distribution (small arrow) and equipotential line (solid line) by the magnetic field given in FIG. 7B.

8A shows the most probable ballistic trajectory of the trajectories of particles going from the current terminal [I +] to [I-] in the S1 sample. The thin solid line represents the magnitude of the magnetic field vertical component when the micromagnet is 1.8T magnetized.

FIG. 8B is a view showing a junction consisting of negative and positive magnetic field regions when the magnetization of the micromagnet is 1T, FIG. 8C is a schematic diagram showing the trajectory of charge in the negative and positive magnetic field regions, and FIG. 8D is a diagram of each voltage terminal. The graph shows the constant voltage measured in.

9 is a schematic diagram illustrating the principle of a biomolecule sensor.

10A and 10B are a plan view and a cross-sectional view, respectively, of a semiconductor-magnetic material fusion device according to another embodiment of the present invention.

Claims (6)

A semiconductor 2DEG having a channel through which a current flows and a plurality of voltage terminals vertically connected to one side of the channel; And a micro-magnet positioned alternately on a channel portion between two neighboring voltage terminals among the plurality of voltage terminals. The method of claim 1, Two adjacent voltage terminals of the plurality of voltage terminals are formed at positions corresponding to minimum and maximum heights of two magnetic barriers having different signs formed in the channel as an external magnetic field is applied. Magnetic material fusion device. The method of claim 1, When the micro-magnet is located on the channel portion between the two neighboring voltage terminals of the plurality of voltage terminals, as the external magnetic field is applied, the junction surface between the negative magnetic field and the positive region in the channel region between the two neighboring voltage terminals The semiconductor-magnetic material fusion device, characterized in that formed. The method of claim 1, When the micro magnet is not located on the channel portion between two neighboring voltage terminals among the plurality of voltage terminals, a junction between a region having a negative magnetic field and a region having a positive magnetic field is applied to a channel portion between the two neighboring voltage terminals as an external magnetic field is applied. A semiconductor-magnetic material fusion device, characterized in that the surface is formed. The method of claim 1, The semiconductor-magnetic material fusion device, characterized in that the insulating layer is interposed between the micro-magnet and the semiconductor 2DEG. The method of claim 1, The semiconductor 2DEG is a semiconductor-magnetic material fusion device, characterized in that consisting of InAs or HgCdTe.

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