KR20020026341A - ferromagnetic - semiconductor single crystal and their manufacturing method - Google Patents

Abstract

PURPOSE: A ferromagnetic semiconductor single crystal is provided which shows ferromagnetism around an ordinary temperature by growing the materials into a crystal by adding flux and transition metal to gallium, and a manufacturing method of the ferromagnetic semiconductor single crystal is provided. CONSTITUTION: The ferromagnetic semiconductor single crystal is formed by cooling the heated raw material reagent to an ordinary temperature in stages after preparing a raw material reagent by adding a flux selected from NaN3, Li3N, Ca3N2 and Mg3N2 to gallium and adding a transition metal to the flux added gallium, putting the prepared raw material reagent into a growing crucible, and sealing and heating the growing crucible. The manufacturing method of the ferromagnetic semiconductor single crystal comprises a mixing process of forming a mixture by mixing the weighed materials after weighing an initial reaction material of gallium(Ga), a flux selected from NaN3, Li3N, Ca3N2 and Mg3N2 and a transition metal to a certain mixing ratio; a sealing process of sealing the crucible from the outside after putting the mixture into a growing crucible; a heating process of heating the crucible so that a temperature gradient of 20 to 50 deg.C is formed after vertically positioning the sealed growing crucible at the central part of a vertical heat treatment furnace each zones of which are heated; a cooling process of cooling the growing crucible to an ordinary temperature by turning off a power supply of the vertical heat treatment furnace after the heating process; and a post-treatment process of washing and drying the cooled resulting material by opening the growing crucible passing through the cooling process.

Description

Ferromagnetic-semiconductor single crystal and their manufacturing method

The present invention relates to a ferromagnetic semiconductor single crystal, and more particularly, to a room temperature ferromagnetic semiconductor single crystal exhibiting a ferromagnetic phenomenon near room temperature by adding a flux and a transition metal to gallium to grow into a crystal, and a method of manufacturing the same. will be.

In recent years, research on ferromagnetic semiconductors has been conducted. In particular, attempts have been made to manufacture ferromagnetic semiconductors by adding manganese, which is made of gallium and arsenic, to form light emitting diodes by bonding them with nonmagnetic semiconductors, but the results are insignificant. .

While phenomena such as Giant Magneto-Resistance (GMR) and Magnetic Tunnel Junctions (MTJ) have led to a state-of-the-art magnetic recording industry, advances in materials manufacturing have been driven by the growth of Molecular Beam Epitaxy (MBE) growth equipment, the production equipment for ferromagnetic semiconductors. The revolution of Novel manufacturing equipment and various physical phenomena have been proposed to utilize the spindles of semiconductor carriers and have been proven by many researchers.

Recent proof of spin injection in semiconductors has been demonstrated by observing polarized light emission from spin-LEDs using ZnMnSe. Magnetic semiconductors (semiconductors with ferromagnetic alignment) play an important role in the realization of spintronics devices. In the past, after the transistor revolution, all aspects of semiconductor electrical devices were based on the development of electronic charges. However, many research efforts are currently focused on how to develop the properties of electron spin. Spintronic devices that utilize the quantum nature of the wave function of electron spins are based on quantum-based logic for electro-optic switches, ultra-sensitive magnetic field sensors, especially high-speed calculators. Major advances have been made in the development of logic and memory.

However, alloys made of spin materials (ferromagnetic metals) and electrical materials (semiconductors) are known to cause unnecessary interfacial problems in applications in terms of the crystal structure, bonding, and physical and chemical properties of materials. The solution is to use a dilute magnetic semiconductor (DMS) material. DMS is composed of a semiconductor doped with magnetic ions partially substituted with one element of the semiconductor. In addition, DMS materials can now directly integrate the devices associated with most semiconductors.

To date, the experimental phase transition temperature (Tc) of DMS materials for InMnAs, GaMnSb and GaMnAs is consistent with the theory, but is still below room temperature. Among the DMS materials that are still required for commercial applications, room temperature Tc can be regarded as far. Until recently, the ferromagnetic models induced by the interaction of charge carriers with locally existing spins showed theoretical calculations that DMS properties only exist in p-type semiconductors, and the Tc of one of these materials, GaMnN, exceeded room temperature. It was foretold. Recently, however, experimental results showing DMS characteristics regardless of p-type and n-type semiconductors have been reported. This brightens the prospect of semiconductor electronics. In other words, these DMS materials are semiconductor devices capable of making spintronics known as the integrated use of electron charge and spin.

However, up to now, no room temperature DMS material has been prepared in the form of crystals. In addition, the existing DMS material growth equipment is difficult to be mainly grown as MBE equipment, and due to the expensive manufacturing cost, another growth method should be presented.

Accordingly, the present invention has been made to solve the above problems, and provides a room temperature ferromagnetic semiconductor single crystal exhibiting a ferromagnetic phenomenon near room temperature by growing flux into a crystal by adding flux and transition metal to gallium, and a method of manufacturing the same. It aims to do it.

1-Schematic diagram of an internal growth crucible required for producing a DMS material according to the present invention.

Figure 2 shows an external crucible in which pressure is required to produce the material by the flux method.

3-The degree of binding of the growth crucible and the external crucible containing the reactants.

4 is a view showing a growth crucible installed in a vertical heat treatment furnace;

5 shows a washing process.

Fig. 6 shows a polarization microscope picture of a DMS single crystal of GaN: Cr grown by the flux method.

7 shows a change in magnetic moment with temperature.

8-M-H hysteresis result data.

<Description of Symbols for Major Parts of Drawings>

100: growth crucible 200: external crucible

300: vertical heat treatment 400: quartz tube

500: Beaker

The present invention for achieving the above object, by adding one of the flux selected from NaN ₃ , Li ₃ N, Ca ₃ N ₂ , Mg ₃ N ₂ to gallium, to prepare a raw material reagent added to the transition metal The technical subject is a room temperature ferromagnetic semiconductor single crystal formed by accommodating a growth crucible, sealing heating, and cooling stepwise to room temperature.

Here, the heating temperature is 750 ℃ to 800 ℃, the growth crucible is preferably a metal-plated stainless steel crucible or boron crucible.

In addition, the first reactant was mixed with gallium (Ga) and one selected from NaN ₃ , Li ₃ N, Ca ₃ N ₂ , and Mg ₃ N ₂ as a flux and a transition metal in a predetermined amount to form a mixture. Process; Sealing the growth crucible from the outside after accommodating the mixture inside the growth crucible; A heating process of placing the sealed growth crucible vertically at the center of the vertical heat treatment furnace heated by zones and then heating the sealed growth crucible; A cooling process of cooling the growth crucible to room temperature by turning off the power of the vertical heat treatment furnace after the heating process; In addition, the method of manufacturing a room temperature ferromagnetic semiconductor single crystal comprising a; and the post-treatment process of opening, washing and drying the growth crucible after the cooling process is also a technical subject.

Here, the post-treatment process, the first washing step of immersing the growth crucible in alcohol for 2 to 4 hours; A second washing process in which the growth crucible of which the first washing process is completed is immersed in distilled water for 2 hours or more; In addition, the drying process of drying the growth crucible after the secondary washing process is completed in an oven; the heating process is carried out for more than 24 hours, the final heating temperature is preferably 750 ℃ to 800 ℃.

Accordingly, there is an advantage that a four-ion ferromagnetic semiconductor having an electro-optical function and magnetic properties of the semiconductor is manufactured.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram of an internal growth crucible required for preparing a DMS material according to the present invention, FIG. 2 is a diagram illustrating an external crucible requiring pressure holding to prepare a material by flux method, and FIG. Fig. 4 is a diagram showing the growth crucible and the external crucible, and Fig. 4 shows the shape of the growth crucible installed in the vertical heat treatment furnace. Fig. 5 shows the washing process. Fig. 7 is a diagram showing a polarization micrograph of a single crystal, Fig. 7 is a diagram showing a change in magnetic moment with temperature, and Fig. 8 is a diagram showing MH hysteresis result data.

As shown, the room temperature ferromagnetic semiconductor single crystal manufacturing method according to the present invention is largely composed of mixing, sealing, heating, cooling, and post-treatment.

First, the mixing process is explained.

The mixing process is the first process to form a DMS material, the melting point is 29.7 ℃, the liquid metallic gallium (Ga) NaN ₃ , and the chemical properties decompose into N ₂ and Na near 300 ℃ in the vicinity of 300 ℃ Metal is the first reactant.

Li ₃ N, Ca ₃ N ₂ , Mg ₃ N _2, or the like may be used instead of NaN ₃ used as the flux. In addition, chromium (Cr) was used as the transition metal.

In order to produce the raw material as a DMS material, it is weighed in a suitable amount of mixing ratio.

In the present invention, 47% by weight of gallium (Ga) is mixed with 50% by weight of NaN ₃ and 3% by weight of chromium (Cr) which is a transition metal.

Since the characteristics of the DMS single crystal formed by the change in the molar ratio of the raw materials to be mixed appear differently, it is important to find a mole% ratio suitable for the semiconductor device.

For example, when the addition amount of chromium, which is a transition metal, is 10% by weight or more, problems such as deterioration of the quality of the DMS single crystal due to excessive defects occur.

After the raw material mixture is formed and the raw material mixture is accommodated in the growth crucible 100, a sealing process of sealing the growth crucible 100 from the outside is performed.

The growth crucible 100 may be a stainless steel or boron crucible plated with nickel (Ni), chromium (Cr), iron (Fe), or the like.

When the raw material is accommodated in the growth crucible 100, the growth crucible 100 must be sealed by blocking the outside from the outside, and the growth crucible 100 can be sealed inside the external crucible 100 using the external crucible 200. After accommodating, the growth crucible 100 is sealed from the outside by welding the external crucible 200.

Next, a heating process of growing a DMS single crystal is performed by heat-treating the external crucible 200 in which the growth crucible 100 is accommodated. The vertical heat treatment furnace 300 of FIG. ). Installation of the external crucible 200 should be suspended so as to be located at the center of the vertical heat treatment furnace (300).

Here, the external crucible 200 is installed in the vertical heat treatment furnace 300 in a state accommodated in the quartz tube 400.

Next, the vertical heat treatment furnace 300 should be heated, and the power of the vertical heat treatment furnace 300 is turned on to heat the temperature of the vertical heat treatment furnace 300 to be 750 ° C to 800 ° C.

The vertical heat treatment furnace 300 is heated to achieve a temperature gradient and the heating time should be more than 24 hours. And the temperature gradient width is adjusted by heating so that the temperature is 20 ~ 50 ℃.

When the heating time of the vertical heat treatment furnace 300 ends, the power of the vertical heat treatment furnace 300 is cut off and the cooling process is performed. The cooling process takes a natural cooling method.

The growth crucible 100 accommodated in the vertical heat treatment furnace 300 is cooled by natural cooling in a state accommodated in the vertical heat treatment furnace 300, and when the temperature of the external crucible 200 approaches a room temperature, the external The crucible 200 is pulled out of the vertical heat treatment furnace 300.

Then, the outer crucible 200 is cut at a predetermined height from the bottom of the outer crucible 200.

In the above state, the growth crucible 100 accommodated inside the external crucible 200 is exposed to the outside.

When the growth crucible 100 is exposed to the outside, a post-treatment process is performed on the single crystal accommodated therein.

The post-treatment process is largely carried out as a first and second washing process and a drying process.

The first washing process is performed using ethyl alcohol, soaking the growth crucible 100 after the cooling process in a beaker 500 containing the ethyl alcohol solution for a predetermined time (2 hours to 4 hours). Proceed by.

The primary washing process separates the sodium (Na) material used as the flux during the growth of the DMS single crystal from the DMS single crystal.

After the first washing process, the second washing process is performed. The second washing process is by immersing the growth crucible 100 containing the DMS single crystal in a beaker 500 containing distilled water for a predetermined time (more than 2 hours). Proceed. The secondary washing process removes impurities contained in the DMS single crystal.

After the second washing process, a drying process is performed. The drying process is performed in air or in a dry oven, and water and alcohol buried in the DMS single crystal are evaporated during the drying process.

When the above process is completed, only the DMS single crystal, which is the final residual material, is present in the growth crucible 100.

The final residual material remaining in the growth crucible 100 is shown in FIG. 6 to show the crystal structure using a polarizing microscope. The magnetic moment according to the temperature in FIG. The change was shown.

That is, a superconducting quantum interference device quantum design (SQUID) experiment was conducted to measure the magnetic properties of the sample.

It was confirmed that the crystal form of the DMS single crystal produced in FIG. 6 was generated depending on the crystal structure.

The DMS material exhibits magnetic properties by interacting with the atomic magnetic moments of the carrier and the transition element addition material in the semiconductor. When a substance has a magnetic moment, it is called 'magnetization', and when it is self-magnetized without an external magnetic field, the magnetization of it is called spontaneous, and its intensity is the atomic magnetic moment per unit volume. Expressed as the grand total of the vector. Spontaneous magnetization takes maximum when the temperature is absolute. When the temperature rises and the thermal motion of the atom becomes active, the atomic magnets become difficult to align regularly. Because of this, spontaneous decay slowly decreases and disappears above a certain temperature. This temperature is called Curie temperature. As shown in FIGS. 7 and 8, the DMS material grown by the growing method of the present invention was confirmed to be a room temperature DMS single crystal material having a Curie temperature at room temperature (absolute temperature 300K).

According to the present invention, the transition metal is easily added to pure single crystal GaN, unlike the conventional thin film, thereby producing an room temperature ferromagnetic semiconductor single crystal.

In addition, there is an effect that the DMS single crystal in the form of plate structure can be obtained under low pressure.

Claims (7)

One flux selected from NaN ₃ , Li ₃ N, Ca ₃ N ₂ , and Mg ₃ N ₂ was added to gallium, a raw material reagent containing transition metal was added thereto, accommodated in a growth crucible (100), and sealed and heated. A room temperature ferromagnetic semiconductor single crystal formed by cooling stepwise to room temperature afterwards. The room temperature ferromagnetic semiconductor single crystal according to claim 1, wherein the heating temperature is 750 ° C to 800 ° C. The room temperature ferromagnetic semiconductor single crystal according to claim 1, wherein the growth crucible (100) is a metal-plated stainless steel crucible or a boron crucible. The room temperature ferromagnetic semiconductor single crystal according to claim 1, wherein the sealing is formed by accommodating the growth crucible (100) in the outer crucible (200) and welding the outer crucible (200). The first reaction material is gallium (Ga) and the mixing process to form a mixture by weighing a certain amount of the transition metal and a transition metal of NaN ₃ , Li ₃ N, Ca ₃ N ₂ , Mg ₃ N ₂ as a flux and ; Sealing the growth crucible 100 from the outside after accommodating the mixture in the growth crucible 100; A heating process of placing the sealed growth crucible 100 vertically at a central portion of the vertical heat treatment furnace 300 heated by zones and then heating it to give a temperature gradient (20 to 50 ° C.); A cooling process of cooling the growth crucible 100 to room temperature by turning off the power of the vertical heat treatment furnace 300 after the heating process; And, And a post-treatment process of opening, cleaning, and drying the growth crucible 100 after the cooling process. According to claim 5, The post-treatment process, A first washing step of immersing the growth crucible in alcohol for 2 to 4 hours; A second washing process in which the growth crucible of which the first washing process is completed is immersed in distilled water for 2 hours or more; And, Room temperature ferromagnetic semiconductor single crystal manufacturing method characterized in that consisting of; drying process of drying the growth crucible after the secondary washing process is completed in an oven. The method of manufacturing a ferromagnetic semiconductor single crystal according to claim 5 or 6, wherein the heating process is performed for 24 hours or more, and the final heating temperature is 750 ° C to 800 ° C.