Methods for depositing group IIIA metal nitride films

Abstract

The present invention relates to a method for depositing a Group IIIA metal nitride layer having a preferred (002) orientation, comprising: a. Providing a substrate; b, depositing a seed crystal layer containing ZnO on the substrate through magnetron sputtering; and c, directly depositing a first group IIIA metal nitride layer on the seed crystal layer through magnetron sputtering. The invention further relates to a coated substrate comprising, in order from the surface of the substrate, a seed layer comprising ZnO and a first Group IIIA metal nitride layer, the first Group IIIA metal nitride layer having a preferred crystal orientation (002), and to the use of a seed layer comprising ZnO for increasing the crystallinity of a first Group IIIA metal nitride layer deposited directly on said seed layer.

Description

Technical Field

[0001] The present invention relates to a method for depositing a Group IIIA metal nitride film exhibiting a preferred crystalline orientation by magnetron sputtering.

[0002] Group IIIA metal nitride films, particularly those having a wide bandgap, can be used in a variety of applications, especially for the development and manufacture of various semiconductor devices. Background Art

[0003] Compound semiconductors of gallium nitride (GaN), aluminum nitride (AlN), and indium nitride (InN) are excellent materials for bandgap engineering because they form a series of continuous solid solutions and superlattices having direct room-temperature bandgaps ranging from 0.65 eV for InN to 3.4 eV for GaN to 6.2 eV for AlN. Recently, there has been a great deal of interest in InGaN, especially due to the global demand for high-brightness blue and green light-emitting diodes (LEDs) and laser diodes (LDs).

[0004] Group IIIA metal nitride films can be produced via various methods including: metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), metalorganic vapor phase epitaxy (MOVPE), electron cyclotron resonance dual ion beam sputtering, and pulsed laser ablation. However, these methods are expensive and / or slow and typically require high processing temperatures. Moreover, phase separation is typically observed for In X Al 1-X N (x>0.32), and chemical reactions need to occur, making it difficult to form non-equilibrium compositions.

[0005] Sputtering has been used to deposit Group IIIA metal nitride films on various substrates; however, a high degree of preferred (002) orientation is typically only obtained when using a crystalline substrate. Such substrates are expensive and only available in limited sizes. Summary of the Invention

[0006] The inventors of the present invention have made efforts to overcome the above-mentioned drawbacks and have developed an economical method for preparing Group IIIA metal nitride films, particularly at temperatures that reduce or avoid atomic diffusion (e.g., between different layers) and possible degradation of interface quality, and have found that Group IIIA metal nitride films exhibiting a preferred crystalline orientation can be prepared by magnetron sputtering on a zinc oxide seed layer deposited by magnetron sputtering.

[0007] In an embodiment, the present invention relates to a method for depositing a Group IIIA metal nitride film having a preferred (002) orientation, comprising: a. providing a substrate; b. Deposit a seed layer containing ZnO on the substrate by magnetron sputtering; c. Deposit a first group IIIA metal nitride film by magnetron sputtering.

[0008] The inventors of the present invention have found that, regardless of whether the substrate is crystalline, the resulting first group IIIA metal nitride film or layer exhibits excellent (002) crystallographic orientation. In particular, a high (002) crystallographic orientation is even obtained on substrates such as glass, plastic, or metal, on which a directly deposited first group IIIA metal nitride layer by magnetron sputtering exhibits almost no (002) crystallographic orientation.

[0009] Magnetron sputtering is particularly suitable for high deposition rates and large substrate surfaces and does not require substrate heating. In magnetron sputtering, the substrate can be static during deposition, but can advantageously be moved during deposition. The substrate can even be a continuous strip, such as a metal, with a width greater than 3 m. The substrate can also be a single substrate sheet, such as 3.21 m × 6.00 m or larger. In addition, compared to, for example, chemical vapor deposition, the layer produced by magnetron sputtering provides a smoother surface and can be deposited at room temperature, while chemical vapor deposition requires a high temperature of up to 800 °C. When using magnetron sputtering, the risk of unwanted contamination in the coating is also smaller because CVD methods, in particular, use carbon-containing precursors and may result in the presence of carbon in the coating and disrupt the crystalline structure of the coating. Atomic layer deposition is slow and generally requires high temperatures to obtain good crystal orientation, which may have many disadvantages during the coating process. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 and Figure 2 show XRD patterns of different aluminum nitride (AlN)-coated substrates according to embodiments of the present invention. DETAILED DESCRIPTION

[0011] In a preferred embodiment of the present invention, the first group IIIA metal nitride layer is directly deposited on the seed layer, which means that no layer is deposited after the seed layer deposition and before the first group IIIA metal nitride layer deposition.

[0012] In an embodiment of the present invention, the seed layer contains optionally doped ZnO or consists essentially of it.

[0013] In an embodiment of the present invention, the seed layer has a thickness of at least 0.3 nm, 0.5 nm, 1 nm, or 2 nm.

[0014] In embodiments of the present invention, the seed layer has a thickness of up to 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 75 nm, 100 nm, 150 nm, 200 nm or 250 nm.

[0015] When the seed layer is too thin, it has little effect on the crystallinity of the subsequently deposited first IIIA group metal nitride layer. When the seed layer thickness is below 10 nm, a significant effect on the crystallinity of the subsequently deposited first IIIA group metal nitride layer has been observed. As the seed layer increases, this effect may increase; however, the surface roughness of the seed layer also increases, which may be disadvantageous for some applications.

[0016] Unless otherwise specified, all thicknesses mentioned herein are geometric or physical thicknesses.

[0017] In embodiments of the present invention, the seed layer comprises ZnO and a dopant selected from Al, Ga, B, In up to 10 at%. In alternative embodiments, the ZnO seed layer may be free of dopants. Dopants can be added, for example, to provide conductivity to the seed layer.

[0018] In embodiments of the present invention, the seed layer is deposited by magnetron sputtering from a sputtering target selected from: a. Optionally doped Zn metal target, for example in an atmosphere comprising Ar and O 2 in an atmosphere, for example 40% to 80% O in Ar 2 and b. Optionally doped ceramic target comprising ZnO, for example in a 100% Ar atmosphere.

[0019] Optional target dopants can be selected from Al, Ga, B and In.

[0020] Herein, the percentages in the gas composition are mole percentages.

[0021] According to an embodiment, the present invention further includes, after depositing the first IIIA group metal nitride film, directly depositing a second IIIA group metal nitride film on the first IIIA group metal nitride layer by magnetron sputtering, the second IIIA group metal nitride film being different from the first IIIA group metal nitride film.

[0022] According to an advantageous embodiment of the invention, before or during the deposition of the seed layer and / or the first IIIA group metal nitride layer and / or the second IIIA group metal nitride layer, the deposition of the seed layer and / or the first IIIA group metal nitride layer and / or the second IIIA group metal nitride film is carried out without additional heating of the substrate. This means that the substrate is not intentionally heated, but is introduced into the coating process at room temperature. Generally, during the deposition of the seed layer and / or the first IIIA group metal nitride layer, the temperature of the substrate can be maintained at a temperature between 20 °C and 150 °C. During the deposition of these layers, it is preferred to maintain the substrate temperature below 150 °C, below 100 °C, or even below 50 °C. The lower the temperature, the lower the diffusion of the substrate and / or layer components, and thus the fewer defects in the final product.

[0023] According to an embodiment of the invention, the first and second IIIA group metal nitrides are selected from indium nitride, aluminum nitride, gallium nitride, boron nitride, or a mixed nitride of two or more of indium nitride, aluminum nitride, gallium nitride, and boron nitride.

[0024] In an advantageous embodiment of the invention, the first IIIA group metal nitride comprises a mixed nitride of indium and aluminum, and the second IIIA group metal nitride comprises gallium nitride. It has been found that for the resulting gallium nitride layer, particularly good crystallinity can be obtained by fine-tuning the mixed nitride of indium and aluminum.

[0025] The thickness of the first IIIA group metal nitride film can be adjusted according to the application in which they are used. Thicknesses in the range of 10 nm to 100 nm, or 20 nm to 90 nm can be used, for example, in LED applications. Thicknesses in the range of 1 μm to 3 μm can be used, for example, in photovoltaic applications. When subsequently depositing the second IIIA group metal nitride layer, for example, thicknesses in the range of 10 nm to 3 μm can be useful.

[0026] According to an embodiment of the invention, the first IIIA group metal nitride layer has a thickness of at least 10 nm, or at least 20 nm, or at least 30 nm.

[0027] According to an embodiment of the invention, the first IIIA group metal nitride layer has a thickness of up to 1 μm, or up to 2 μm, or up to 3 μm.

[0028] In the mixed first IIIA group metal nitride layer, the ratio of the components is adjusted, for example, to achieve a certain bandgap. The atomic metal percentages can be adjusted within a very wide range, particularly any one of B, In, Al, and Ga from 1% to 99%.

[0029] The first IIIA group metal nitride layer of the invention can have a bandgap ranging from 0.65 eV to 6.2 eV.

[0030] Preferably, the first and / or second group IIIA metal nitride layer is stoichiometric, with a metal-to-nitrogen ratio of 1. However, the atomic ratio of metal to nitrogen can vary, for example, from 0.8 to 1.2, alternatively from 0.9 to 1.1.

[0031] The thickness of the second group IIIA metal nitride film can be adjusted according to the application in which they are used. Thicknesses in the range of 10 nm to 100 nm, or 20 nm to 90 nm can be used, for example, in LED applications. Thicknesses in the range of 1 μm to 3 μm can be used, for example, in photovoltaic applications.

[0032] According to an embodiment of the present invention, the second group IIIA metal nitride layer has a thickness of at least 10 nm, or at least 20 nm, or at least 30 nm.

[0033] According to an embodiment of the present invention, the second group IIIA metal nitride layer has a thickness of up to 1 μm, or up to 2 μm, or up to 3 μm.

[0034] In a mixed second group IIIA metal nitride layer, the ratio of the components is adjusted, for example, to achieve a certain bandgap. The atomic metal percentage can be adjusted over a very wide range, in particular any one of B, In, Al, and Ga from 1% to 99%.

[0035] The second group IIIA metal nitride layer of the present invention can have a bandgap ranging from 0.65 eV to 6.2 eV.

[0036] Preferably, the second group IIIA metal nitride layer is stoichiometric, with a metal-to-nitrogen ratio of 1. However, the atomic ratio of metal to nitrogen can vary, for example, from 0.8 to 1.2, alternatively from 0.9 to 1.1.

[0037] According to an embodiment of the present invention, the first and second group IIIA metal nitride layers are deposited by magnetron sputtering from one or more metal sputtering targets that contain indium, aluminum, gallium, and / or boron. One or more pure metal and / or metal alloy targets can be used to achieve the desired metal nitride composition. Sputtering with two or more targets having different compositions is generally referred to as co-sputtering.

[0038] As is well known, sputtering is carried out under vacuum. Typically, the pressure during deposition is maintained at a value in the range of from 0.1 to 99 mTorr (10 -3 Torr) (i.e., 0.13 mbar to 132 mbar), preferably 0.5 to 15 mTorr (i.e., 6.66 mbar to 20.0 mbar).

[0039] According to an embodiment, the sputter deposition of the first and / or second Group IIIA metal nitride layer is performed on a N 2 or N between 10% and 100% included 2 Ar and N 2 Preferably, the N 2 The amount of N contained in the mixture is preferably between 10% and 50%, preferably between 20% and 40%, in order to obtain a stoichiometric first and / or second Group IIIA metal nitride at the best possible deposition rate. 2 Ar and N 2 Alternatively, pure N may be used, for example to promote good stoichiometry. 2 , or N included between 50% and 100% 2 , preferably between 70% and 100% N 2 , even more preferably between 80% and 100% N 2 , most preferably between 90% and 100% N 2 Ar and N 2 mixture.

[0040] It should be noted that, although not intentionally added, the resulting metal nitride layer may contain trace amounts of other elements, originating, for example, from impurities in the sputtering target.

[0041] Furthermore, although not intentionally added, up to 10 at% oxygen may be seen in the first and / or second Group IIIA metal nitride layers, originating, for example, from water desorbed from the walls of the coating line. Preferably, the oxygen content of these nitride films is less than 5 at%, even less than 2 at%.

[0042] According to an embodiment of the present invention, the substrate may be provided as a substrate sheet or a substrate wafer.

[0043] The substrate material may be crystalline or non-crystalline, i.e. amorphous. A particular advantage of the present invention is that a crystalline substrate is not required to obtain a high degree of preferred crystalline orientation in the first Group IIIA metal nitride layer. In particular, the substrate may be selected from crystalline Ge, crystalline Si, sapphire, glass, metals (e.g. aluminum, copper, steel) and polymers.

[0044] The glass substrate material according to the present invention is made of glass, the matrix composition of which is not particularly limited and can therefore belong to different glass categories. The glass can be soda-lime silicate glass, aluminosilicate glass, alkali-free glass, borosilicate glass, etc. In the following glass composition, all component percentages are weight percentages.

[0045] According to an embodiment of the present invention, the glass substrate material has the following composition, which comprises the following items, the contents of which are expressed as a percentage of the total weight of the glass:

[0046] In a preferred manner, the glass substrate material has the following composition, which comprises the following items, the contents of which are expressed as a percentage of the total weight of the glass:

[0047] In a more preferred manner, the glass substrate material has the following composition, which comprises the following items, the contents of which are expressed as a percentage of the total weight of the glass:

[0048] This soda-lime type base glass composition has the advantage of being inexpensive, even though it is mechanically less resistant by itself.

[0049] Ideally, according to this last embodiment, the glass composition does not contain B 2 O 3 (meaning that it is not intentionally added, but may be present as a very low amount of an unwanted impurity).

[0050] In an alternative manner, the glass substrate material has the following composition, which comprises the following items, the contents of which are expressed as a percentage of the total weight of the glass:

[0051] Such aluminosilicate type base glass composition has the advantage of being more mechanically resistant, but it is more expensive than soda-lime glass.

[0052] Ideally, according to this last embodiment, the glass composition does not contain B 2 O 3 (meaning that it is not intentionally added, but may be present as a very low amount of an unwanted impurity).

[0053] According to an advantageous embodiment of the present invention, which can be combined with the previous embodiments regarding the base glass composition, the glass substrate material has a composition comprising a total iron content in the range of from 0.002% to 0.06% (expressed in the form of Fe 2 O 3 ). The total iron (expressed in the form of Fe 2 O 3in the form of) content such that a glass substrate material can be obtained that has little visible coloring and allows a high degree of flexibility in aesthetic design (e.g., no deformation when performing white screen printing on some glass elements of a smartphone). This minimum value allows for no excessive damage to the cost of the glass, since such low iron values typically require expensive, very pure starting materials and also the purification of these materials. Preferably, the composition includes a total iron content ranging from 0.002% to 0.04% (expressed in the form of Fe 2 O 3 in the form of). More preferably, the composition includes a total iron content ranging from 0.002% to 0.02% (expressed in the form of Fe 2 O 3 in the form of). In the most preferred embodiment, the composition includes a total iron content ranging from 0.002% to 0.015% (expressed in the form of Fe 2 O 3 in the form of).

[0054] According to another embodiment of the invention, in combination with the previous embodiments regarding the Fe 2 O 3 content, the glass has a composition including chromium such as: 0.0001% ≤ Cr 2 O 3 ≤ 0.06% expressed as a percentage of the total weight of the glass. Preferably, the glass has a composition including chromium such as: 0.002% ≤ Cr 2 O 3 ≤ 0.06% expressed as a percentage of the total weight of the glass. This chromium content allows for a glass with a higher IR transmittance to be obtained.

[0055] According to a preferred embodiment, the glass substrate material of the invention is a float glass sheet. The term "float glass sheet" should be understood to mean a glass sheet formed by a float process that includes pouring molten glass onto a bath of molten tin under reducing conditions. A float glass sheet includes in a known manner a "tin side", i.e., a side of the glass body that is rich in tin close to the surface of the sheet. The term "rich in tin" should be understood to mean an increase in the concentration of tin relative to the composition of the glass at the core, which may or may not be substantially zero (no tin). Thus, a float glass sheet can be easily distinguished from sheets obtained by other glass manufacturing processes, in particular by the tin oxide content, which can be measured, for example, by electron microprobe to a depth of about 10 μm.

[0056] According to another preferred embodiment, the glass substrate material of the present invention is a glass sheet formed by a slitting process or by a melting process, in particular the overflow down-draw melting process. These processes, in particular the melting process, produce glass sheets whose surfaces can achieve the excellent flatness and smoothness required in some applications, but they are also more expensive compared to the float process used for large-scale glass production.

[0057] The glass substrate according to the present invention can have a thickness of 0.5 to 25 mm. Depending on the intended application, the glass substrate can have a thickness of 1 to 6 mm, or 2 to 4 mm.

[0058] According to an embodiment of the present invention, the method includes depositing one or more layers before depositing the seed layer. The seed layer does not necessarily have to be deposited directly on the substrate. The one or more layers can be deposited by any known deposition method, such as by magnetron sputtering, plasma-enhanced chemical vapor deposition, chemical vapor deposition, atomic layer deposition, molecular vapor epitaxy deposition. The one or more layers can have different functions, such as providing a clean and smooth surface for depositing the seed layer, conducting electricity, and blocking the migration of any component of the substrate or any layer.

[0059] According to an embodiment of the present invention, a preferably amorphous bottom layer is deposited on the substrate before depositing the seed layer. Thereby, any possible crystallinity of the substrate is prevented from affecting the growth of subsequent layers. In particular, the bottom layer can be in direct contact with the substrate. In particular, the seed layer can be deposited directly on the amorphous layer. Example amorphous layers are Zn 2 SnO 4 、Si 3 N 4 、SiO 2 、 titanium oxide, nitrides of zirconium and silicon, oxides of titanium and zirconium.

[0060] According to an embodiment of the present invention, the method includes a heating step after depositing the first and / or second IIIA group metal nitride layer, the heating step including heating the substrate, for example, under vacuum or in an atmosphere containing nitrogen, in particular in order to further increase the preferred crystal orientation of the first and / or second IIIA group metal nitride layer. The temperature is preferably at least 100 °C. The temperature can reach up to the softening point of the substrate. The temperature can be included between 100 °C and 950 °C.

[0061] According to an advantageous embodiment of the present invention, the method does not include a heating step after depositing the first and / or second IIIA group metal nitride layer. The crystallinity of the first and / or second IIIA group metal nitride can be sufficient for the subsequent use of the first and / or second IIIA group metal nitride layer.

[0062] Referring to deposition rates in relation to molecular beam epitaxy, the inventors of the present invention have found that the first group IIIA metal nitride layer, in particular an aluminum nitride layer, can be deposited at a static deposition rate of up to at least 40 nm / min, while the MOCVD static deposition rate does not appear to exceed 20 nm / min.

[0063] The present invention further relates to a coated substrate comprising, in sequence starting from the substrate surface, a seed layer comprising ZnO and a first group IIIA metal nitride layer, wherein the first group IIIA metal nitride layer has a preferred crystalline orientation (002). Advantageously, the first group IIIA metal nitride layer is in direct contact with the seed layer.

[0064] The present invention further relates to a coated substrate comprising, in sequence starting from the substrate surface, a seed layer comprising ZnO, a first group IIIA metal nitride layer and a second group IIIA metal nitride layer, wherein the composition of the second group IIIA metal nitride layer is different from that of the first group IIIA metal nitride layer, and wherein the first group IIIA metal nitride layer has a preferred crystalline orientation (002), and the second group IIIA metal nitride layer also has a preferred crystalline orientation (002). Advantageously, the first group IIIA metal nitride layer is in direct contact with the seed layer and the second group IIIA metal nitride layer.

[0065] According to an embodiment of the present invention, the coated substrate can be deposited using the method of the present invention.

[0066] In the coated substrate of the present invention, the substrate can be selected from the substrates mentioned above for the method of the present invention.

[0067] In the coated substrate of the present invention, the seed layer composition can be selected from the seed layer compositions mentioned above for the method of the present invention.

[0068] In the coated substrate of the present invention, the first and second group IIIA metal nitrides can be selected from the group IIIA metal nitrides mentioned above for the method of the present invention.

[0069] The present invention further relates to the use of a seed layer comprising ZnO, which is deposited in particular by magnetron sputtering, in particular by magnetron sputtering to increase the crystallinity of a first group IIIA metal nitride layer deposited directly on the seed layer in particular by magnetron sputtering.

[0070] The present invention further relates to the use of a seed layer comprising ZnO, which is deposited by magnetron sputtering in particular to increase the crystallinity, in particular the crystal orientation (002), of a first IIIA group metal nitride layer deposited directly on the seed layer by magnetron sputtering, and to increase the crystallinity, in particular the crystal orientation (002), of a second IIIA group metal nitride layer deposited directly on the first IIIA group metal nitride layer by magnetron sputtering, wherein the composition of the second IIIA group metal nitride layer is different from that of the first IIIA group metal nitride layer.

[0071] A first example according to the present invention is prepared in a magnetron sputtering coating production line, in which the substrate is continuously conveyed through different coating stations without interruption during the deposition of these layers. For all deposition steps, the pressure is maintained at a value in the range from 0.1 to 99 mTorr.

[0072] On a 4 mm thick soda-lime glass substrate of 40 cm × 40 cm, a 27 nm thick amorphous Zn 2 (80% of O 2 ) film is deposited by magnetron sputtering from a mixed zinc-tin metal target in an atmosphere of Ar and O 2 SnO 4 .

[0073] Then, an undoped ZnO seed layer is deposited by magnetron sputtering using a Zn target in an atmosphere of Ar and O 2 (80% of O 2 ). The seed layer has a thickness of 7 nm.

[0074] Next, an aluminum nitride layer is deposited directly on the seed layer by magnetron sputtering an aluminum target in an atmosphere of Ar and N 2 (30% N 2 ). The aluminum nitride layer has a thickness of 30 nm. To achieve this thickness, the substrate is moved through the same coating station 6 times.

[0075] A second comparative example is prepared by directly depositing the same aluminum nitride layer as in the first example on a soda-lime glass substrate without any seed layer.

[0076] After or during the deposition step, no heating is performed on any of the examples.

[0077] X-ray diffraction (XRD) measurements are performed on the prepared examples in a non-grazing angle mode. The obtained XRD patterns can be found in Figure 1 (Example 1) and Figure 2It can be seen in (Example 2). Generally, for the AlN film, based on the PDF card (No.: 01-080-6097), different diffraction peaks at 2θ values of 33.2°, 35.8°, 37.7°, 51.7°, 59.3°, 65.0° and 71.0° are respectively assigned to the (100), (002), (101), (102), (110), (103) and (112) planes of hexagonal AlN. Arrow (2) indicates the 2θ value of AlN(002). Arrow (1) indicates the 2θ value of ZnO(002).

[0078] Comparing Figure 1 and Figure 2 , we can see that, compared with the direct deposition on the substrate in Example 2, depositing the aluminum nitride layer on the seed layer in Example 1 very significantly increases the preferred (002) crystallization orientation.

[0079] When the AlN film is deposited on a soda-lime glass substrate provided with a 27-nm-thick amorphous Zn 2 SnO 4 film, results similar to those in Example 2 are obtained.

[0080] It is found that the deposition of the AlN film in a 100% N 2 atmosphere produces results comparable to those in Examples 1 and 2.

[0081] For plastic and metal substrates, the deposition processes of Examples 1 and 2 are repeated. Also on these substrates, which are polycarbonate, Kapton and aluminum in this example, compared with the direct deposition on the substrate, when the aluminum nitride layer is deposited on the seed layer, the preferred (002) crystallization orientation is increased.

Claims

1. A method for depositing a Group IIIA metal nitride layer, which comprises: a. providing a substrate; b. depositing a seed layer containing ZnO on the substrate by magnetron sputtering; c. directly depositing a first Group IIIA metal nitride layer on the seed layer by magnetron sputtering.

2. The method according to claim 1, which further comprises: d. directly depositing a second Group IIIA metal nitride layer on the first Group IIIA metal nitride layer, the second Group IIIA metal nitride being different from the first Group IIIA metal nitride film.

3. The method according to any one of the preceding claims, wherein, the first and / or second Group IIIA metal nitride layers have a preferred (002) orientation.

4. The method according to any one of the preceding claims, wherein, the seed layer has a thickness of at least 0.3 nm and / or up to 250 nm.

5. The method according to any one of the preceding claims, wherein, the seed layer contains up to 10 at% of a dopant selected from Al, Ga, B, and In.

6. The method according to any one of the preceding claims, wherein, the seed layer is deposited by magnetron sputtering from a target selected from: a. a Zn metal target, optionally doped with Al, Ga, B, or In, and b. a ceramic ZnO target, optionally doped with Al, Ga, B, or In.

7. The method according to any one of the preceding claims, wherein, the first and / or second Group IIIA metal nitride is selected from indium nitride, aluminum nitride, gallium nitride, boron nitride, or a mixed nitride of two or more of indium nitride, aluminum nitride, gallium nitride, and boron nitride.

8. The method according to any one of the preceding claims, wherein, the first Group IIIA metal nitride comprises a mixed nitride of indium and aluminum, and the second Group IIIA metal nitride comprises gallium nitride.

9. The method according to any one of the preceding claims, wherein, the first and / or second Group IIIA metal nitride layer has a thickness of at least 10 nm.

10. The method according to any one of the preceding claims, wherein, the substrate is selected from crystalline Ge, crystalline Si, sapphire, metal, and glass.

11. The method according to any one of the preceding claims, wherein, the substrate is not heated before or during the deposition of the seed layer and / or the first Group IIIA metal nitride layer and / or the second Group IIIA metal nitride layer.

12. The method according to any one of the preceding claims, which further comprises heating the substrate to at least 100 °C after the deposition of the first and / or second Group IIIA metal nitride layer.

13. The method according to any one of the preceding claims, further comprising depositing an amorphous layer before the deposition of the seed layer, the amorphous layer comprising a material preferably selected from Zn 2 SnO 4 , Si 3 N 4 , SiO 2 , titanium oxide, zirconium, nitrides of silicon, oxides of titanium and zirconium.

14. A coated substrate comprising, starting from the substrate surface, a seed layer containing ZnO, a first IIIA group metal nitride layer, and optionally a second IIIA group metal nitride layer, wherein the composition of the second IIIA group metal nitride layer is different from that of the first IIIA group metal nitride layer, and wherein the first IIIA group metal nitride layer is in direct contact with the seed layer and has a preferred crystalline orientation (002), and wherein the second IIIA group metal nitride layer is in direct contact with the seed layer and has a preferred crystalline orientation (002).

15. Use of a seed layer containing ZnO for increasing the crystallinity of a first IIIA group metal nitride layer directly deposited on the seed layer.

16. Use of a seed layer containing ZnO for increasing the crystallinity of a first IIIA group metal nitride layer directly deposited on the seed layer and for increasing the crystallinity of a second IIIA group metal nitride layer directly deposited on the first IIIA group metal nitride layer, wherein the composition of the second IIIA group metal nitride layer is different from the composition of the first IIIA group metal nitride layer.

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