JP5030909B2 - Growth method of zinc oxide single crystal layer - Google Patents

Description

  The present invention relates to a method for growing a zinc oxide single crystal layer, and more particularly to a method for growing a single crystal layer of zinc oxide on a substrate such as sapphire by MOCVD.

  Zinc oxide (ZnO) is a direct transition type semiconductor having a band gap energy of 3.37 eV at room temperature, and is expected as a material for optical elements in the blue or ultraviolet region. In particular, the exciton binding energy is 60 meV and the refractive index n = 2.0, which is very suitable for a semiconductor light emitting device. Further, the present invention can be widely applied not only to light emitting elements and light receiving elements but also to surface acoustic wave (SAW) devices, piezoelectric elements, and the like. In addition, the raw material is inexpensive and harmless to the environment and the human body. In general, MOCVD (Metal Organic Chemical Vapor Deposition) method, MBE (Molecular Beam Epitaxy) method, and the like are used as crystal growth methods for zinc oxide compound semiconductors. The MBE method is a crystal growth method under an ultra-high vacuum, and has problems such as expensive equipment and low productivity. On the other hand, the MOCVD method has the advantages that the apparatus is relatively inexpensive, allows large area growth and simultaneous growth of a large number of sheets, has high throughput, and is excellent in mass productivity and cost. .

  As a crystal growth method of zinc oxide using the MBE method, for example, a low-temperature ZnO layer having a single crystal characteristic is grown on a sapphire substrate, and then flattened by heat treatment at a high temperature, and then a high-temperature ZnO layer is grown. A method for obtaining a ZnO layer with good crystallinity is disclosed (Patent Document 1). More specifically, it discloses a “low temperature growth ZnO single crystal layer” formed using a growth temperature lower than the crystal growth temperature for growing a ZnO single crystal. However, the method disclosed in this document is a growth condition / method effective only for the MBE method, and such a method cannot be applied to the MOCVD method. That is, as is well known (for example, Patent Document 2), the growth conditions of the MBE method capable of crystal growth under non-stoichiometric (non-stoichiometric composition) conditions cannot be directly applied to the MOCVD method. Therefore, a method for growing a single crystal layer of a zinc oxide based semiconductor using MOCVD has been actively studied.

Various methods for crystal growth of zinc oxide (ZnO) or zinc oxide-based semiconductors on a substrate such as sapphire (Al ₂ O ₃ ) by MOCVD have been disclosed (for example, Patent Documents 2 and 3). For example, in Patent Document 2, MgZnO microcrystals are formed on an A-plane sapphire substrate or C-plane silicon carbide substrate using O ₂ as an oxygen source as a reserve buffer layer, and the microcrystal serves as a seed crystal to serve as a buffer layer body. It is disclosed that an MgZnO crystal is formed on the entire surface of a substrate. Patent Document 3 discloses that a polycrystalline or amorphous laminate formed at a low temperature is annealed at a high temperature to form a buffer layer. However, in such a method, a defect remains between adjacent crystal grain boundaries when the polycrystal is converted into a single crystal by heat treatment. In addition, defects remain in the grain boundary coalescence at the stage where the buffer layer main body grows crystallites. Therefore, it is difficult to greatly reduce crystal defects. Thus, conventionally, attempts have been made to improve the crystallinity by forming a buffer layer made of polycrystal, microcrystal, or amorphous. However, the method for improving the crystallinity by MOCVD is complicated, and it is difficult to remove the crystal on the substrate. It was difficult to grow high quality ZnO-based crystals.

  As described above, although the MBE method has proposed a method for growing a good ZnO single crystal on a sapphire substrate or the like, a high quality ZnO single crystal is grown on a sapphire substrate or the like by an MOCVD method. There was a problem with the method.

  By the way, when a ZnO-based crystal is grown on a sapphire substrate or the like by the MOCVD method, the grown crystal tends to be a needle-like crystal, hexagonal columnar crystal, network-like crystal, or hexagonal disk-like crystal. In addition, defects may be introduced into a semiconductor crystal layer to be subsequently laminated due to unevenness of the crystal growth interface. In such a polycrystal or imperfect single crystal that is strongly oriented in the crystal axis direction, the grain interface and transition cause leakage current and local current concentration of the semiconductor element, leading to deterioration of element characteristics and element life. In particular, in a semiconductor light emitting device, characteristics such as light emission efficiency and device life are deteriorated due to leakage current and current concentration. Furthermore, when the crystal surface is not flat, it leads to a decrease in process accuracy and a manufacturing yield in a semiconductor process such as lithography and etching. In addition, the production yield is reduced in cleavage and braking.

Thus, conventionally, it has been difficult to grow a flat ZnO-based semiconductor single crystal with few grain interfaces and transitions on a heterogeneous substrate such as a sapphire substrate by MOCVD. In order to achieve high performance and high reliability of a semiconductor device, particularly a semiconductor light emitting device having a large operating current density, it is extremely important to develop a crystal growth method with few crystal defects and close to a flat ideal crystal.
Japanese Patent No. 3424814 JP 2005-340370 A Japanese Patent No. 3859148

  The present invention has been made in view of the above-described points, and an object of the present invention is to provide a method for growing zinc oxide with few crystal defects and excellent single crystallinity and flatness on a substrate.

  The present invention is a method for crystal growth of a zinc oxide layer on a substrate by MOCVD using a metal organic chemical vapor deposition (MOCVD) apparatus, wherein the growth temperature is in the range of 250 ° C. to 450 ° C. The method includes a step of growing a single crystal layer of zinc oxide by blowing a material gas containing at least an organic zinc compound material not containing oxygen atoms and water vapor to a substrate at a pressure in a range of 1 kPa to 30 kPa. Yes.

  Moreover, the grown zinc oxide layer can be heat-treated within a temperature range of 700 ° C. to 1100 ° C. at a pressure within a range of 1 kPa to 30 kPa.

  Furthermore, the grown zinc oxide layer can be heat-treated in a water vapor atmosphere.

  The substrate may be an α-sapphire single crystal substrate, and the crystal growth plane may be a {11-20} plane.

  The low growth temperature may be a temperature within a range of 250 ° C to 450 ° C.

  FIG. 1 schematically shows the configuration of the MOCVD apparatus 5 used for crystal growth. The MOCVD apparatus 5 includes a gas supply unit 5A, a reaction vessel unit 5B, and an exhaust unit 5C. 5 A of gas supply parts are comprised from the part which vaporizes and supplies organometallic compound material, the part which supplies gaseous material gas, and the transport part provided with the function to convey these gas.

  In this example, a material containing no oxygen was used as the organometallic compound material (or organometallic material). That is, a material that does not contain oxygen atoms in its constituent molecules and a material that does not contain oxygen molecules were used.

Further, H ₂ O (water vapor) was used as a liquid material as an oxygen source. H ₂ O is suitable for low-temperature growth of ZnO crystals because it has high reactivity with an organometallic material that does not contain oxygen in the molecule even at room temperature. In addition, the H ₂ O molecule has two lone electron pairs, has a large polarization in the molecule, and has an excellent adsorption ability to the crystal surface and the like.

That is, DMZn (dimethylzinc) was used as the zinc (Zn) source, Cp2Mg (biscyclopentadienylmagnesium) was used as the magnesium (Mg) source, and TEGa (triethylgallium) was used as the gallium (Ga) source. In addition to the above materials, DEZn (diethyl zinc), TMGa (trimethyl gallium), or the like can be used. An organometallic material that does not contain oxygen is easily pyrolyzed at a low temperature, and reacts with O ₂ (oxygen) or H ₂ O (water vapor) even at room temperature, which is suitable for crystal growth at a low temperature.

  Nitrogen is used as a transport (carrier) gas, and liquid or solid material vapor and gaseous material (hereinafter referred to as material gas) are fed into the reaction vessel 5B by the carrier gas and supplied to the substrate.

An organometallic compound material that is liquid (or solid) at room temperature is vaporized and supplied as vapor. First, the supply of DMZn will be described. As shown in FIG. 1, the nitrogen gas is set to a predetermined flow rate by a flow rate adjusting device (mass flow controller) 21S and sent to the DMZn storage container 21C through the gas supply valve 21M to saturate the DMZn vapor in the nitrogen gas. Then, the DMZn saturated nitrogen gas is taken out through the take-out valve 21E and the pressure adjusting device 21P and supplied to the VENT1 pipe 28V during growth standby and to the RUN1 pipe 28R during growth. At this time, the internal pressure of the storage container is adjusted to be constant by the pressure adjusting device 21P. Further, the DMZn storage container is kept at a constant temperature in the thermostatic chamber 21T. The same applies to other organometallic compound materials Cp2Mg and TEGa. That is, nitrogen gas having a predetermined flow rate is supplied to the storage containers 22C (Cp2Mg) and 23C (TEGa) for storing these materials, respectively, through the flow rate adjusting devices 22S and 23S, and the take-out valves 22E and 23E and the pressure adjusting device 22P are supplied. , 23P, these material gases are supplied to the VENT1 pipe 28V during growth standby and to the RUN1 pipe 28R during growth. In addition, H ₂ O (water vapor), which is a liquid material as an oxygen source, is supplied with a predetermined flow rate of nitrogen gas through the flow rate adjusting device 24S to the storage container 24C, and waits for growth through the take-off valve 24E and the pressure adjusting device 24P. Sometimes it is supplied to the VENT2 pipe 29V and at the time of growth is supplied to the RUN2 pipe 29R.

As the p-type impurity source, NH ₃ (ammonia) gas, which is a gaseous material, was used. The NH ₃ gas is supplied at a predetermined flow rate by the flow rate adjusting device 25S. It is supplied to the VENT2 pipe 29V during standby and to the RUN2 pipe 29R during growth. Note that the gas may be diluted with an inert gas such as nitrogen or Ar (argon).

  The above-described material gas is supplied to the shower head 30 of the reaction vessel section 5B through the RUN1 pipe 28R and the RUN2 pipe 29R. The RUN1 pipe 28R and the RUN2 pipe 29R are also provided with flow control devices 20C and 20B, respectively, and the material gas is sent to the shower head 30 attached to the upper part of the reaction vessel 39 by a carrier gas (nitrogen gas). .

  In the reaction vessel 39, a shower head 30 for blowing a material gas onto the substrate, a substrate 10, a susceptor 19 for holding the substrate 10, and a heater 49 for heating the susceptor 19 are installed. The heater 49 can heat the substrate from room temperature to about 1100 ° C.

  The reaction vessel 39 is provided with a rotation mechanism for rotating the susceptor 19. More specifically, the susceptor 19 is supported by a susceptor support cylinder 48, and the susceptor support cylinder 48 is rotatably supported on the stage 42. Then, the rotation motor 43 rotates the susceptor support cylinder 48 to rotate the susceptor 19 (that is, the substrate 10). The heater 49 described above is installed in the susceptor support tube 48.

  The exhaust part 5C includes a container internal pressure adjusting device 51 and an exhaust pump 52, and the internal pressure adjusting device 51 can adjust the pressure in the reaction container 39 to about 0.01 kPa to 120 kPa. .

  FIG. 2 is a sectional view showing a zinc oxide crystal layer (hereinafter referred to as a ZnO crystal layer) 11 grown on the substrate 10 according to the present invention. More specifically, the ZnO crystal layer 11 was grown on the sapphire substrate using MOCVD.

As the substrate 10, an α-sapphire single crystal sapphire (Al ₂ O ₃ ) substrate having a corundum structure was used. In this example, the ZnO crystal layer 11 was grown on the sapphire A plane using the sapphire A plane ({11-20} plane) as the crystal growth plane. Hereinafter, a substrate having a sapphire A plane ({11-20} plane) as a principal plane (crystal growth plane) is also referred to as an A-plane sapphire substrate. Here, the Miller index {} indicates a representative value of an equivalent surface.

  FIG. 3 shows a crystal growth sequence used for crystal growth by the MOCVD method. First, the A-plane sapphire substrate 10 was set on the susceptor in the MOCVD apparatus, and the reaction vessel pressure was adjusted to 10 kPa (kilopascal) (time T = T1). The substrate 10 was rotated at a rotation speed of 10 rpm by a rotation mechanism.

Next, supply of H ₂ O (water vapor) as an oxygen source from the shower head to the substrate 10 at a flow rate of 640 μmol / min was started (T = T2). Further, the substrate 10 was heated to 900 ° C. with a heater, and the substrate 10 was heat-treated for 10 minutes (T = T3 to T4). Thereafter, H ₂ O (water vapor) was kept flowing at the same flow rate until the growth was completed.

  After the heat treatment, the substrate temperature was lowered to 400 ° C., and DMZn (dimethylzinc) as a zinc raw material was supplied to the substrate 10 at a flow rate of 1 μmol / min for about 15 minutes (T = T5 to T6). That is, a ZnO crystal layer 11 having a growth temperature (Tg) of 400 ° C., a growth rate of 1.7 nm / min, and a layer thickness of 25 nm was grown under reduced pressure growth conditions (growth pressure Pg = 10 kPa).

  After the growth of the ZnO crystal layer 11, the substrate temperature was raised to 900 ° C. and heat treatment (annealing) was performed for 10 minutes (T = T7 to T8). As will be described later, this heat treatment further improves the crystallinity and flatness of the ZnO crystal layer 11.

  After the heat treatment was completed, cooling was performed while flowing water vapor. After the substrate temperature became 300 ° C. or lower, the supply of water vapor was stopped.

  As described above, a substrate with a crystal growth layer (hereinafter, simply referred to as a substrate with a growth layer) 15 in which the growth of the ZnO crystal layer 11 has been completed was manufactured.

  The ZnO crystal layer 11 obtained in the above-described growth step (T = T5 to T6) is a single crystal layer that is c-axis oriented on an A plane ({11-20} plane) sapphire substrate. That is, the {0001} plane of zinc oxide was laminated on the substrate having the {11-20} plane of the α-sapphire single crystal as the main surface. The single crystallinity and flatness of the ZnO crystal layer 11 were examined by RHEED (reflection high-energy electron diffraction) and AFM (atomic force microscope) measurements.

FIG. 4 is a diagram showing an RHEED diffraction image of the grown ZnO crystal layer 11 when heat treatment (annealing) is not performed after the growth step (T = T5 to T6) is completed. As shown in FIG. 4, streak-like RHEED diffraction images arranged at equal intervals were obtained. This shows that the surface crystal arrangement is single and smooth. Further, it was found by RFM (atomic force microscope) measurement that Rms (root mean square roughness) of 1 μm ² area was 0.62 nm (nanometer). Since the c-axis length (lattice constant) of the ZnO crystal was c = 5.207 Å, the surface roughness was equivalent to the c-axis length of the ZnO crystal, and it was found that the crystal layer surface was flat. From these results, it was confirmed that the ZnO crystal layer 11 was a single crystal layer with good flatness.

5A, 5B, and 5C show RHEED diffraction images when the ZnO crystal layer 11 is grown and subjected to heat treatment at 800 ° C., 900 ° C., and 1000 ° C. for 10 minutes, respectively. Show. In this example, the pressure Pa during the heat treatment was set to a low pressure (the same as in crystal growth, Pa = Pg = 10 kPa). Further, as described above, heat treatment was performed while supplying H ₂ O (water vapor) to the substrate 10, that is, in a water vapor atmosphere.

  As shown in FIG. 5, it was confirmed that by performing the heat treatment, the RHEED diffraction image has a more streak shape as compared with the case where the heat treatment was not performed (FIG. 4). In addition, in AFM measurement, it was found that Rms (root mean square roughness) was 0.5 nm or less, which was less than the c-axis length of the ZnO crystal. Therefore, it was confirmed that the single crystallinity and flatness were improved by the heat treatment.

  Thus, the ZnO crystal layer 11 already has good flatness and a single crystal layer at the stage where crystal growth is completed, and further, the single crystallinity is improved by heat treatment, and the c-axis length of the ZnO crystal. It was confirmed to have the following flatness.

  The substrate with a growth layer 15 obtained by the above process can be used for the manufacture of semiconductor elements in the MOCVD apparatus without cooling. Alternatively, after cooling, a semiconductor element can be manufactured using an MOCVD apparatus or another crystal growth apparatus.

  That is, if the substrate 15 with a growth layer is used, a single crystal is grown directly on the single crystal layer (ZnO crystal layer 11) having excellent single crystallinity and flatness by using an MOCVD apparatus or another crystal growth apparatus. It is also possible to do this. Therefore, a high-quality ZnO-based crystal layer with few crystal defects and excellent single crystallinity and flatness can be formed.

Further, the crystal that can be grown on the substrate with growth layer 15 is not limited to zinc oxide (ZnO). It may be a zinc oxide based crystal. For example, Mg _x Zn _(1-x) O containing magnesium (Mg), ZnO-based crystals (zinc oxide crystals) containing calcium (Ca), and the like may be used. Alternatively, a ZnO-based crystal containing selenium (Se), sulfur (S), tellurium (Te), or the like may be used.

  Further, using the substrate 15 with a growth layer, optical semiconductor elements, various electronic devices, and the like are formed by various methods other than MOCVD, such as MBE, plasma CVD, PLD (Pulsed Laser Deposition), and hydride VPE. It is also possible.

  As described above, according to the present invention, a growth in which a high-quality single crystal layer with few crystal defects, excellent single crystal properties and flatness, which can be applied to manufacture of optical semiconductor elements and various electronic devices is formed. A layered substrate can be provided.

As described above, according to the present invention, an organometallic compound material that does not contain oxygen and H ₂ O (water vapor) that is highly reactive with the organometallic compound material are used on the substrate, even if it is a heterogeneous substrate. The ZnO crystal layer 11, which is a single crystal layer with good flatness, can be grown by performing crystal growth at a low growth temperature and a low growth pressure. Moreover, the single crystallinity and flatness of the ZnO crystal layer 11 can be improved by performing the heat treatment at a low pressure (reduced pressure). Note that the heat treatment is preferably performed in a steam atmosphere.

In the above embodiment, the substrate 10 is an A-plane sapphire substrate which is the {11-20} plane of α sapphire (α-Al ₂ O ₃ ), DMZ is used as the organometallic compound material not containing oxygen, and the growth temperature is set. The growth pressure was set to 400 kPa and 10 kPa. Further, the case where the growth rate is 1.7 nm / min and the growth layer thickness is 25 nm has been described as an example.

However, the conditions such as the substrate, the material gas, the growth temperature, the growth pressure, the growth rate, the growth layer thickness and the like shown in the above embodiments are merely examples, and are not limited thereto. The growth conditions including the heat treatment conditions were changed, the ZnO crystal layer 11 was grown, and the conditions for growing a single crystal layer with high flatness were studied. Hereinafter, such conditions will be described in detail.
<Board>
An A-plane sapphire substrate is optimal. This is because the lattice mismatch between the A plane of the sapphire crystal and the C plane of the ZnO crystal is small. That is, the lattice mismatch between the sapphire <0001> direction (oxygen atom) and the ZnO <11-20> direction (zinc atom) is 0.07%, and the sapphire <10-10> direction (oxygen atom) and ZnO <10- The lattice mismatch in the 10> direction (zinc atom) is 2.46%. Here, since the ZnO <11-20> direction is locked to the sapphire <0001> direction, the ZnO crystal can grow a single crystal without forming a 30 ° rotation domain during growth.

In addition, as a usable substrate, in the case of a ZnO crystal with c-axis orientation on the substrate surface, the substrate surface has lattice matching points at rotationally symmetric positions of 60 °, 120 °, and 180 °. Any crystal substrate may be used. Further, in the case of an a-axis or m-axis oriented ZnO crystal, any crystal substrate in which a lattice matching point exists at a rotationally symmetric position of 180 ° may be used. For example, an R-plane sapphire substrate, an M-plane sapphire substrate, a SiC (silicon carbide) substrate, a GaN (gallium nitride) substrate, a Ga ₂ O ₃ (gallium oxide) substrate, a Si (silicon) substrate, or the like can be used.
<Growth pressure>
For single crystal growth, the migration length of reactive chemical species (DMZn, H ₂ O, intermediate products, Zn atoms before crystallization, O atoms before crystallization, etc.) on the substrate surface should be large. . Therefore, the reduced pressure growth is suitable, and specifically, the growth pressure is preferably 1 kPa to 30 kPa, more preferably 5 kPa to 20 kPa. When the growth pressure is 1 kPa or less, the growth rate is remarkably slowed.
<Growth temperature>
It is appropriate that the growth temperature is generally lower than a crystal growth temperature (referred to as “high growth temperature”) for growing a ZnO single crystal (referred to as “low growth temperature”). This is because at the high growth temperature, island-like growth is easy and layered single crystals are hardly formed.

  Specifically, the growth temperature is suitably in the range of 250 ° C to 450 ° C. Furthermore, it is preferable that it exists in the temperature range of 300 to 400 degreeC. At 250 ° C. or lower, the migration length becomes short, so that it becomes easy to be amorphous or polycrystallized. Further, as described above, when the temperature is higher than 450 ° C., island-like growth is likely to occur and flatness is lowered (Rms value is increased).

FIG. 6 is a diagram showing an example of an RHEED diffraction image when the ZnO crystal layer 11 is grown at different growth temperatures. The growth was performed under the same growth conditions as in the above-described example except that the growth temperature (Tg) was 300 ° C. The layer thickness of the ZnO crystal layer 11 is also 25 nm as in the above example. The ZnO crystal layer 11 is a crystal layer that has not been subjected to heat treatment after growth. A streak-like RHEED diffraction image was obtained, and it was confirmed that the ZnO crystal layer 11 was a single crystal layer with good flatness.
<Material gas>
In order to form a ZnO single crystal layer under a low growth pressure and a low growth temperature, it is necessary to select a material having high mutual reactivity. This is because if the mutual reactivity is low, the crystal does not grow, or becomes amorphous or polycrystallized. As the Zn source, an organometallic compound that does not contain oxygen in the constituent molecules and has high reactivity with the oxygen source material is suitable. In addition to the DMZn described above, for example, there is DEZn (diethyl zinc). As the oxygen source, H ₂ O (water vapor) having a large intramolecular polarization and high reactivity with the organometallic compound material is suitable.
<Growth rate>
The growth rate is preferably in the range of 0.4 nm / min to 9 nm / min. Furthermore, it is more preferable to be within the range of 0.8 to 4 nm / min. When the growth rate is 9 nm / min or more, the surface irregularities become large, and sufficient flatness may not be obtained.
<Growth layer thickness>
The growth layer thickness is preferably in the range of 5 nm to 60 nm, and preferably in the range of 10 nm to 40 nm. Furthermore, it is more preferably 15 nm to 30 nm. That is, when the layer thickness is less than 5 nm, the crystal layer may not sufficiently cover the substrate surface. On the other hand, when the thickness is 60 nm or more, the unevenness of the surface becomes large and sufficient flatness may not be obtained.
<VI / II ratio (F _H2O / F _MO ratio)>
The water vapor flow rate and the organometallic (DMZn) flow rate ratio (F _H2O / F _DMZn ratio) may be about 2 or more. Specifically, about 2000 is sufficient. The water vapor flow rate is preferably about 70% of the saturated water vapor amount in which water vapor does not aggregate in the shower head.
<Heat treatment conditions>
As described above, the ZnO crystal layer 11 already has good flatness and single crystal layer at the stage where crystal growth is completed. However, the single crystallinity and flatness can be further improved by performing heat treatment. Can do. Further, it is preferable to perform the heat treatment under a low pressure where the migration length becomes long. Note that the pressure range suitable for the heat treatment is the same as the growth pressure range of the ZnO crystal layer 11.

  Specifically, the heat treatment temperature of the grown ZnO crystal layer 11 is suitably 700 ° C. to 1100 ° C. The processing time is suitably in the range of 1 to 60 minutes. More preferably, the treatment temperature is 800 ° C. to 1000 ° C., and the treatment time is 3 minutes to 10 minutes. If the treatment temperature is less than 700 ° C., the effect is low, and if it is 1100 ° C. or more, the layer surface becomes rough. In addition, when the processing time is 60 minutes or more, film defects may occur due to film evaporation.

As described above in detail, according to the present invention, on a substrate such as an A-plane sapphire substrate, oxygen-free organometallic compound material and H ₂ O ( A single crystal layer of zinc oxide can be grown by performing crystal growth at a low growth temperature and low growth pressure using water vapor. Further, the single crystallinity and flatness of the growth layer can be further improved by performing the heat treatment under a low pressure (reduced pressure) and in a water vapor atmosphere. The single crystal layer is excellent in flatness and single crystallinity and has few crystal defects. Furthermore, since the MOCVD method is used, large area growth and large number growth are possible. Therefore, it is excellent in mass productivity and manufacturing cost.

It is a figure which shows typically the structure of a MOCVD apparatus. It is sectional drawing which shows the zinc oxide layer grown on the board | substrate by this invention. It is a figure which shows the crystal growth sequence used for the crystal growth by MOCVD method. It is a figure which shows the RHEED diffraction image of the ZnO crystal layer at the time of not heat-processing. It is a figure which shows the RHEED diffraction image at the time of performing the heat processing for 10 minutes at the temperature of 800 degreeC, 900 degreeC, and 1000 degreeC, respectively after the growth of a ZnO crystal layer. It is a figure which shows the RHEED diffraction image of the ZnO crystal layer whose growth temperature (Tg) is 300 degreeC.

Explanation of symbols

10 Substrate 11 Crystal Growth Layer 19 Susceptor 30 Shower Head

Claims (10)

A method of growing a zinc oxide layer on a substrate by MOCVD using a metal organic chemical vapor deposition (MOCVD) apparatus,
A material gas containing at least an organic zinc compound material that does not contain oxygen atoms and a water vapor within a range of growth temperature of 250 ° C. to 450 ° C. and a growth pressure of 1 kPa to 30 kPa is sprayed onto the substrate. And a step of growing a single crystal layer of zinc oxide.   2. The method according to claim 1, wherein after the step, the zinc oxide layer is subjected to a heat treatment in a temperature range of 700 ° C. to 1100 ° C. under a pressure of 1 kPa to 30 kPa.   The method according to claim 2, wherein the heat treatment is performed in an atmosphere of water vapor.   The method according to claim 1, wherein the substrate is an α-sapphire single crystal substrate, and a crystal growth surface is a {11-20} plane.   4. The method according to claim 1, wherein the substrate is a single crystal substrate having lattice matching points at rotationally symmetric positions of 60 °, 120 °, and 180 ° of the substrate surface. 5. The substrate is any one of an R-plane sapphire substrate, an M-plane sapphire substrate, a silicon carbide (SiC) substrate, a gallium nitride (GaN) substrate, a gallium oxide (Ga ₂ O ₃ ) substrate, and a silicon (Si) substrate. The method according to any one of claims 1 to 3 and 5, characterized in that:   The method according to any one of claims 1 to 6, wherein the growth rate of the zinc oxide layer is within a range of 0.4 nm / min to 9 nm / min.   The method according to any one of claims 1 to 7, wherein a growth layer thickness of the zinc oxide layer is in a range of 5 nm to 60 nm.   The method according to any one of claims 1 to 8, wherein the organic zinc compound material not containing an oxygen atom contains at least one of DMZn (dimethylzinc) and DEZn (diethylzinc). The method according to any one of claims 1 to 9, wherein a flow rate ratio (VI / II ratio) of the water vapor and the organozinc compound material is 2 or more and 2000 or less.