KR100392783B1 - Zinc magnesium oxide thin films and method for preparing same by metal-organic chemical vapor deposition - Google Patents

Abstract

The present invention relates to a method for preparing a zinc oxide-magnesium thin film by an organometallic chemical vapor deposition method, in which zinc-containing organometallic and magnesium-containing organometallics, and oxygen-containing gas or organics are injected into a reactor through separate lines. , Under a reactor condition with a pressure of 10 ⁻³ to 760 mmHg and an internal temperature of 200 to 800 ° C., the magnesium was adjusted by adjusting the flow rate of the reactants in the range of 0.1 to 10 sccm, 5 to 50 sccm and 20 to 100 sccm, respectively. Including the growth of the thin film on the substrate by controlling the mole fraction of, according to the organometallic chemical vapor deposition method according to the present invention, it is possible to produce a zinc oxide-magnesium thin film capable of mass production and excellent crystallinity.

Description

ZnC MAGNESIUM OXIDE THIN FILMS AND METHOD FOR PREPARING SAME BY METAL-ORGANIC CHEMICAL VAPOR DEPOSITION}

The present invention relates to a method for producing a Zn _1-x Mg _x O thin film by metal-organic chemical vapor deposition (MOCVD), specifically, zinc, magnesium, and oxygen-containing gas or organic material as a reactant The present invention relates to a Zn _1-x Mg _x O (0 <x <1) thin film prepared by injecting a into a reactor through a separate line and growing the film by organometallic chemical vapor deposition while controlling the reaction conditions, and a method of manufacturing the same.

Since the bandgap increases when Zn ^{+ 2} is added with magnesium having a similar ion radius to Zn ^{+ 2} , the photodetection and the light emitting device can be manufactured by controlling the mole fraction of magnesium to be added. In addition, quantum structures such as quantum walls and quantum dots composed of ZnO / ZnMgO heterostructures increase luminous efficiency by changing the density of states through electron confinement. . Therefore, the high-quality ZnMgO film containing a large amount of magnesium has added importance with ZnO.

ZnMgO, which is present in a thermodynamically stable state, typically cannot contain more than 4% magnesium, but may be pulsed laser deposition (PLD) or molecular beam epitaxy by A. Ohtomo et al. It has been reported to grow metastable ZnMgO containing more than 33% of magnesium and increase the band gap to 4.0 eV by physical vapor deposition such as MBE) ( Appl. Phys. Lett. , 72 , 2466 ( 1998)).

However, the physical vapor deposition methods have a disadvantage in that it is difficult to deposit a thin film in a large area, it is expensive and disadvantageous in mass production, and it is not easy to control the mole fraction of magnesium.

In order to solve the above problems, the present inventors can deposit a large area, and by using a gaseous precursor, it is easier to control the mole fraction of magnesium, and the organic metal chemical vapor deposition (MOCVD) method enables low temperature deposition. It is early to develop a method for producing a Zn _1-x Mg _x O thin film.

An object of the present invention is to provide a zinc-containing organometallic, magnesium-containing organometallic, and oxygen-containing gas or organic material at a temperature of 200 to 800 ℃, 10 ^-3 to 760 while adjusting the flow rate through a separate line in the reactor To provide a method for producing a large amount of Zn _1-x Mg _x O thin film by chemical vapor deposition at a pressure of mmHg.

1 is a schematic diagram of an organometallic chemical vapor deposition apparatus used in the present invention,

2A and 2B show X-ray diffraction (XRD) θ-2θ scan results, and XRD rocking curves of ZnMgO films prepared from Examples according to the present invention and ZnO films as comparative examples, respectively,

3 shows c-axis lattice constants determined using extrapolation based on X-ray diffraction (XRD) θ-2θ scan results of ZnMgO films prepared from Examples according to the present invention and ZnO films as Comparative Examples,

4A and 4B are photoluminescence spectra at −258 ° C. and 25 ° C., respectively, of ZnMgO films prepared from examples according to the present invention and ZnO films as comparative examples.

In order to achieve the above object, the present invention introduces an organometallic chemical vapor deposition method, which is particularly advantageous for high-purity thin film growth, among chemical vapor deposition methods that are advantageous for mass production, and includes zinc-containing organometallic, magnesium-containing organometallic, and oxygen as reaction precursors A zinc oxide-magnesium thin film, which is injected into the reactor via a separate line in order to suppress their prereaction, and reacted at a pressure of 10 ^-3 to 760 mmHg and an internal temperature of 200 to 800 ° C. It provides a method of manufacturing. At this time, the zinc-magnesium oxide thin film may be deposited while varying the mole fraction of magnesium by controlling the flow rate of the transport gas carrying the zinc-containing organometallic and magnesium-containing organometallic to the reactor and the temperature of the thermostat. .

The flow rates of the reactants, ie zinc-containing organometallic, magnesium-containing organometallic and oxygen-containing gas or organic, are preferably in the range of 0.1 to 10 sccm, 5 to 50 sccm and 20 to 100 sccm, respectively.

Hereinafter, the present invention will be described in more detail.

1 is a schematic diagram of an organometallic chemical vapor deposition apparatus used in the present invention. According to the ZnMgO thin film manufacturing method of the present invention, reactants are reacted in advance using a separate reactant line or deposition is performed on a wall of a reactor. By preventing re-decomposition again, it is possible to significantly reduce the deterioration of the quality of the ZnMgO thin film.

In addition, the organometallic chemical vapor deposition method of the present invention used to prepare a zinc oxide-magnesium thin film is easy to control the flow rate of the reactants, it is possible to control the mole fraction of Mg in the ZnMgO thin film, it can be deposited to a desired concentration proportion Red deposition is possible.

Zinc-containing organometals used in the present invention include dimethylzinc (Zn (CH ₃ ) ₂ ), diethylzinc (Zn (C ₂ H ₅ ) ₂ ), zinc acetate (Zn (OOCCH ₃ ) ₂ .2H ₂ O ), Zinc acetate anhydride (Zn (OOCCH ₃ ) ₂ ), zinc acetylacetonate (Zn (C ₅ H ₇ O ₂ ) ₂ .H ₂ O), and the like. Magnesium-containing organometals used in the present invention include biscyclopentadienyl magnesium (bis-cyclopentadienyl-Mg; (C ₅ H ₅ ) ₂ Mg), bismethylcyclopentadienyl magnesium (bis-methylcyclopentadienyl-Mg; ( CH ₃ C ₅ H ₄ ) ₂ Mg), bisethylcyclopentadienylmagnesium (bis-cyclopentadienyl-Mg; (C ₂ H ₅ C ₅ H ₄ ) ₂ Mg), bispentamethylcyclopentadienylmagnesium (bis- pentamethylcyclopentadienyl-Mg; [(CH ₃ ) ₅ C ₅ ] ₂ Mg), magnesium acetate (Mg (OOCCH ₃ ) ₂ 2H ₂ O), magnesium acetate anhydride (Mg (OOCCH ₃ ) ₂ ) and magnesium acetylacetonate (Mg (C ₅ H ₇ O ₂ ) ₂ H ₂ O), and the like.

In addition, the oxygen-containing gas used in the present invention includes O ₂ , O ₃ , NO ₂ , water vapor and CO ₂ , and the like, and C ₄ H ₈ O as the oxygen-containing organic material.

The results of measurement of the change in crystal orientation and c-axis lattice constant of the ZnMgO thin film prepared by the present invention by X-ray diffraction (XRD) are shown in FIGS. 2 and 3, respectively. From this, it can be seen that the ZnMgO film has excellent crystallinity. In addition, according to the method of the present invention, a zinc magnesium oxide thin film can be produced in large quantities.

The invention can be better understood by the following examples, which are intended for the purpose of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.

Example

ZnMgO films were grown on a substrate of Al ₂ O ₃ (0001) using the organometallic chemical vapor deposition apparatus shown in FIG. Diethylzinc, biscyclopentadienylmagnesium and O ₂ were used as reactants, and argon was used as a carrier gas. In separate lines, argon containing diethyl zinc, argon containing biscyclopentadienyl magnesium, and O ₂ were each injected into the reactor. At this time, while maintaining a constant pressure and temperature in the reactor to 5 mmHg, 500 ℃, respectively, the flow rate of each reactant is 50 sccm of argon, 0.1 to 1 sccm of diethyl zinc, 10 to 50 sccm of biscyclopentadienyl magnesium and The film was grown by vapor deposition over about 1 hour while adjusting to a range of 20 sccm 0 ₂ .

After completion of the deposition reaction, the thickness of the formed zinc magnesium oxide film was 0.5 to 1 m as measured by surface profilometry and cross-sectional scanning electron microscopy. The crystal orientation and c-axis lattice constant of the thin film were determined by X-ray diffraction (XRD), and the magnesium content was measured using an energy dispersion type X-ray analyzer (EDAX). The change of the band gap was measured by the measuring method.

1) X-ray diffraction analysis

As a comparative example, a ZnO thin film containing no Mg, a ZnMgO thin film containing 11%, 47%, and 60% Mg, and a MgO thin film containing 100% Mg were formed on an Al ₂ O ₃ (0001) substrate, The XRD θ-2θ scan results for these films are shown in Fig. 2A, respectively.

These exhibited prominent ZnO (0002) peaks in addition to the substrate peak, indicating that the ZnMgO thin film was highly oriented along the c-axis direction perpendicular to the substrate surface.

While the ZnO (0002) peak is shown at 34.78 degrees, the peak of the ZnMgO thin film containing 47% Mg appears on the right side, indicating that the lattice constant of the c-axis was changed by the addition of Mg. On the other hand, when the amount of Mg added is increased to about 60% or more, phase separation of MgO occurs, resulting in a separate MgO (111) peak. From FIG. 2A, phase separation did not occur in the ZnMgO thin film containing 47% Mg, which indicates that the ZnMgO thin film formed by the conventional physical vapor deposition method increased by 42% p compared with the maximum containing 33%.

In addition, the XRD rocking curves for the (0002) plane of the ZnO thin film and Zn _0.89 Mg _0.11 O thin film formed on the Al ₂ O ₃ (0001) substrate are shown in FIG. 2B. Vibration curves were each measured at the (0002) reflection of the films. As can be seen from FIG. 2B, the full width at half maximum (FWHM) in the vibration curves of the ZnO and ZnMgO films formed on Al ₂ O ₃ (0001) was 0.045 and 0.065 °, respectively. This value is much narrower than the previously reported 0.13 °, and is almost similar to 0.042 °, which is the FWHM value of the single crystal Al ₂ O ₃ plane, and shows excellent crystallinity of the ZnMgO thin film grown in this example. Indicates.

2) Change of c-axis lattice constant according to Mg content

As a comparative example, the ZnO thin film containing no Mg and the ZnMgO thin film containing 11%, 21%, and 47% Mg, respectively, were based on the X-ray diffraction (XRD) θ-2θ scan results, and an extrapolation method was used. The c-axis lattice constant was determined, and the results are shown in FIG. 3. As can be seen from FIG. 3, the c-axis lattice constant decreased by 1.2% as the Mg content increased by 47%, which is similar to the ZnMgO thin film grown using physical vapor deposition such as pulsed laser deposition or molecular beam epitaxy deposition. Results are shown.

3) photoluminescence spectrum at room temperature

The photoluminescence spectra of the ZnO thin film and the ZnMgO thin film containing 11%, 21%, and 47% Mg, respectively, were measured at −258 ° C. using a He-Cd laser (325 nm) as the excitation source, and are shown in FIG. 4A. 4B shows photoluminescence spectra of a ZnO thin film and a ZnMgO thin film containing 9% Mg at 25 ° C. From FIG. 4A, the photoluminescence spectrum of the ZnO film at a low temperature such as -258 ° C. shows sharp peaks at 3.364 eV, and the photoluminescence spectrum of the ZnMgO thin film containing 9%, 11%, 21%, and 47% Mg, respectively, is shown at the band edge. The energy values of the emission peaks were 3.462 eV, 3.522 eV, 3.798 eV and 3.932 eV, respectively, which were higher than those of Mg-free films, and the band gap was increased. In addition, in FIG. 4B, the photoluminescence spectrum of the ZnO film at 25 ° C. showed an emission peak at 3.282 eV, and the ZnMgO film containing 9% Mg had a higher photoluminescence spectrum of 3.399 eV and an increased band gap. Able to know.

ZnMgO thin film formed by the organometallic chemical vapor deposition method of the present invention, the band gap is increased without significant change with the addition of Mg, containing Mg at least 47% phase separation does not occur, by controlling the mole fraction of Mg of the desired wavelength band It can be used as a photodetector and a light emitting device, and furthermore, by using a quantum well structure having a heterojunction structure such as ZnO / ZnMgO, the electrons can be efficiently constrained to increase luminous efficiency.

Simple modifications and variations of the present invention can be easily made by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (9)

Zn _1-x Mg by organometallic chemical vapor deposition, characterized in that a film is grown on a substrate while injecting zinc-containing organometallic, magnesium-containing organometallic, and oxygen-containing gas or organics into the reactor via separate lines. _{x O (0 <x <1} ) method of manufacturing a thin film. delete delete The method of claim 1, Wherein the zinc-containing organometal is dimethylzinc, diethylzinc, zinc acetate, zinc acetate anhydride or zinc acetylacetonate. The method of claim 1, Magnesium-containing organometals with biscyclopentadienylmagnesium, bismethylcyclopentadienylmagnesium, bisethylcyclopentadienylmagnesium, bispentamethylcyclopentadienylmagnesium, magnesium acetate, magnesium acetate anhydride and magnesium acetylacetonate And selected from the group consisting of: The method of claim 1, And wherein the oxygen-containing gas is O ₂ , O ₃ , NO ₂ , water vapor or CO ₂ . The method of claim 1, The oxygen-containing organic is C ₄ H ₈ O. A Zn _1-x Mg _x O (0 <x <1) thin film prepared by the method of any one of claims 1 to 7. A device comprising the thin film of claim 8.