GALLIUM NITRIDE SINGLE CRYSTAL BASED ON A SCALMGO4 SUBSTRATE AND PREPARATION METHOD THEREOF

Abstract

The present invention provides a preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate, comprising following steps: (1) providing a ScAlMgO.sub.4 substrate; (2) growing a buffer layer on a surface of the ScAlMgO.sub.4 substrate; (3) annealing the buffer layer; (4) growing a GaN crystal on the buffer layer; (5) performing cooling, so that the GaN crystal is automatically peeled off from the ScAlMgO.sub.4 substrate. The present invention does not need to use a complex MOCVD process for GaN deposition and preprocessing to make a mask or a separation layer, which effectively reduces production costs; compared with traditional substrates such as sapphire, it has higher quality and a larger radius of curvature, and will not cause a problem of OFFCUT non-uniformity for growing GaN over 4 inches; finally, the present invention can realize continuous growth into a crystal bar with a thickness of more than 5 mm, which further reduces the costs.

Claims

1. A preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate, comprising following steps: (1) providing a ScAlMgO.sub.4 substrate; (2) growing a buffer layer on a surface of the ScAlMgO.sub.4 substrate; (3) annealing the buffer layer; (4) growing a GaN crystal on the buffer layer; (5) performing cooling, so that the GaN crystal is automatically peeled off from the ScAlMgO.sub.4 substrate.

2. The preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate of claim 1, wherein the ScAlMgO.sub.4 substrate is a circle or a regular hexagon.

3. The preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate of claim 2, wherein the surface of the ScAlMgO.sub.4 substrate is polished, and have an atomic layer surface, a surface roughness of no more than 0.5 nm, and a c-plane OFFCUT of 0 to 1.5 degrees.

4. The preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate of claim 1, wherein the growing a buffer layer in step (2) adopts a low-temperature AlN sputtering method, with a temperature set to 300-800° C., and an AlN thickness of 10-300 nm, and in step (3), high-temperature annealing is performed on the buffer layer in an H.sub.2/N.sub.2 environment.

5. The preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate of claim 1, wherein the growing a buffer layer in step (2) is growing an AlN thin film template with a thickness of 1-10 urn by adopting an MOCVD method.

6. The preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate of claim 1, wherein the growing a buffer layer in step (2) adopts a high-temperature AlN HVPE method, with a temperature set to 1000-1600° C., and a thickness of 50-3000 nm, and in step (3), reducing at a high temperature of 1600-1700° C. or annealing in an inert environment is performed.

7. The preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate of claim 1, wherein the growing a buffer layer in step (2) adopts a low-temperature GaN HYPE method, with a temperature set to 300-800° C., and a thickness of about 20-500 nm, and in step (3), annealing at 950-1100° C. is performed.

8. The preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate of claim 1, wherein performing low-temperature AN sputtering deposition on bottom and side surfaces of the ScAlMgO.sub.4 substrate is further comprised between step (3) and step (4), with a temperature set to 300-800° C., and a thickness of no more than 50 nm.

9. The preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate of claim 1, wherein step (4) adopts an HVPE method, and farther comprises a method of maintaining continuous growth and morphology of a GaN single crystal thick film: (1) continuously increasing a temperature, and an increase range of the temperature is 1-10° C. for every 1 mm increase in the GaN single crystal thick film; (2) continuously increasing NH.sub.3; an increase range of NH.sub.3 (or corresponding VIII) is 5%-50% for every 1 mm increase in the GaN single crystal thick film.

10. A gallium nitride single crystal based on a ScAlMgO.sub.4 substrate, wherein the gallium nitride single crystal based on a ScAlMgO.sub.4 substrate is prepared by the preparation method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a production process flow chart of the present invention.

DESCRIPTION OF THE EMBODIMENTS

[0026] Through specific examples of the present invention below, technicians of the field can easily understand other advantages and efficacies of the present invention revealed by the specification. The present invention can also be implemented or applied through other different ways, and the details of the specification can also be modified or changed based on different views and applications without deviating from the spirit of the present invention.

[0027] It should be noted that the illustrations provided in these embodiments are only to illustrate the basic concept of the present invention in a schematic way, although the illustrations only show the components related to the present invention instead of being drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the component layout pattern may also be more complicated.

Embodiment 1

[0028] Please refer to FIG. 1, the present invention provides a preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate, including following steps: [0029] (1) providing a ScAlMgO.sub.4 substrate; [0030] (2) growing a buffer layer on a surface of the ScAlMgO.sub.4 substrate; [0031] (3) annealing the buffer layer; [0032] (4) growing a GaN crystal on the buffer layer; [0033] (5) performing cooling, so that the GaN crystal is peeled off from the ScAlMgO.sub.4 substrate.

[0034] Referring to FIG. 1 and step (1), a ScAlMgO.sub.4 substrate 100 is provided.

[0035] As a preferred setting of this embodiment, the ScAlMgO.sub.4 substrate is a circle or a regular polygon; more preferably, the ScAlMgO.sub.4 substrate is a circle or a regular hexagon.

[0036] As a preferred setting of this embodiment, the ScAlMgO.sub.4 has high crystal quality, and its (001) XRDFWHM is usually less than 20 arcsec, preferably less than 10 aresec; the ScAlMgO.sub.4 substrate has an atomic layer surface prepared by using CMP (that is, a chemical mechanical polishing process), which will not be repeated here.

[0037] In step (2), growing a buffer layer based on a surface of the ScAlMgO.sub.4 substrate adopts a low-temperature AlN sputtering method. In this embodiment, the sputtering production process adopts a high-purity aluminum target (above 5N), and a mixed gas environment of N.sub.2 and Ar, pressure is set to 0.1-2 Pa, and preferably, a low temperature range is set to 300-800° C.; more preferably, a low temperature range is set to 400-650° C.; more preferably, a low temperature range is set to 500-600° C.

[0038] As a preferred setting of this embodiment, in step (3), annealing is performed on the AlN buffer layer in an H.sub.2/N.sub.2 environment at 1200-2000° C.; more preferably, annealing is performed on the buffer layer in an H.sub.2/N.sub.2 environment at 1350-18500° C.; more preferably, annealing is performed on the buffer layer in an H.sub.2/N.sub.2 environment at 1600-17000.

[0039] As a preferred setting of this embodiment, performing low-temperature AN sputtering deposition at 300-800° C., preferably 400° C., on bottom and side surfaces of the ScAlMgO.sub.4 substrate is farther included between step (3) and step (4), to form a protective layer with a thickness of no more than 50 nm on the bottom surface and side surfaces, so as to avoid decomposition and evolution of O.sub.2 from ScAlMgO.sub.4 during high-temperature growth, and improve purity of the grown GaN.

[0040] Step (4) adopts an HATE method, including HCl reacting with Ga at 700-900° C. to grow GaCl as a gallium source, NH.sub.3 gas directly providing a nitrogen source, a temperature range being set to 900-1100° C., a VIII ratio being 2-1000, a carrier gas being H.sub.2/N.sub.2 mixture, and other HVPE process means well known to those skilled in the art, and further including a method of maintaining continuous growth and morphology of a GaN single crystal thick film:

[0041] (1) continuously increasing a temperature, and an increase range of the temperature is 1-10° C. for every 1 mm increase in the GaN single crystal thick film;

[0042] (2) continuously increasing NH.sub.3; an increase range of NH.sub.3 (or corresponding V/III) is 5%-50% for every 1 mm increase in the GaN single crystal thick film.

[0043] The present invention also provides a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate, and the gallium nitride single crystal based on a ScAlMgO.sub.4 substrate is prepared based on the above preparation method.

Embodiment 2

[0044] The present invention also provides a preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate. The preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate described in this embodiment is substantially the same as the preparation method described in other embodiments, and the difference is: the growing a buffer layer in step (2) of Embodiment 2 is growing a thin film template with a thickness of 1-10 μm by adopting an MOCVD method, and its (102) XRDFWHM is less than 320 arcsec, preferably less than 240 aresec.

[0045] The MOCVD method is well known to those skilled in the art, and its principle is not repeated here.

[0046] In step (3), in-situ annealing is performed in an MOCVD furnace, that is, after low-temperature growth is completed, the temperature is raised to 1000° C. for annealing.

Embodiment 3

[0047] The present invention also provides a preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate. The preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate described in this embodiment is substantially the same as the preparation method described in other embodiments, the difference is that: the growing a buffer layer in step (2) of this embodiment adopts a high-temperature AlN HDPE method, Preferably, under the HYPE process conditions, a temperature is set to 1000-1600′C; more preferably, a temperature is set to 1200-1600° C.; more preferably, a temperature is set to 1500-1600° C., and a thickness is 50-3000 nm.

[0048] As a preferred setting of Embodiment 3 of the present invention, the buffer layer prepared by the AlN HVPE method can be allowed not to be annealed, and can also be annealed under a reducing environment at a high temperature of 1600-1700° C. in step (3).

Embodiment 4

[0049] The present invention also provides a preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate. The preparation method of a gallium nitride single crystal based on a ScAlMgO.sub.4 substrate described in this embodiment is substantially the same as the preparation method described in other embodiments, the difference is that the growing a buffer layer in step (2) adopts a low-temperature GaN HVPE method. Preferably, under the HVPE process conditions, a temperature is set to 300-800° C.; more preferably, a temperature is set to 400-700° C.; more preferably, a temperature is set to 500-600° C. A thickness is about 20-500 nm; more preferably, a temperature is set to 50-100 nm.

[0050] As a preferred setting of Embodiment 3 of the present invention, the buffer layer prepared by the low-temperature GaN HVPE method is annealed at 950-1100° C. in step (3).

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of technical features thereof; and these modifications or replacements do not snake the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

[0052] Furthermore, it will be understood by those skilled in the art that although some of the embodiments described herein include certain features included in other embodiments and not others, combinations of features of different embodiments are meant to be within the scope of the present invention and form different embodiments. For example, in the above claims, any one of the claimed embodiments may be used in any combination. The information disclosed in this background art section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgment or any form of a suggestion that this information forms the prior art already known to those skilled in the art.