Super-Flexible Transparent Semiconductor Film and Preparation Method Thereof

Abstract

The present invention discloses a super-flexible transparent semiconductor film and a preparation method thereof, the method includes: providing an epitaxial substrate; growing a sacrificial layer on the epitaxial substrate; stacking and growing at least one layer of Al.sub.1-nGa.sub.nN epitaxial layer on the sacrificial layer, wherein 0<n≤1; growing a nanopillar array containing GaN materials on the Al.sub.1-nGa.sub.nN epitaxial layer; etching the sacrificial layer so as to peel off an epitaxial structure on the sacrificial layer as a whole; and transferring the epitaxial structure after peeling onto a surface of the flexible transparent substrate. Compared to traditional planar films, the present invention can not only improve the crystal quality by releasing stress, but also improve flexibility and transparency through characteristics of the nanopillar materials. In addition, a total thickness of the buffer layer and the sacrificial layer required by the epitaxial structure can be small, and there is no need for additional catalyst during an epitaxial growth process, which is beneficial for reducing epitaxial costs and process difficulty. The present invention is practical in use, and can provide technical support for invisible semiconductor devices and super-flexible devices.

Claims

1. A preparation method of a super-flexible transparent semiconductor film, comprising: providing an epitaxial substrate; growing a sacrificial layer on the epitaxial substrate; stacking and growing at least one layer of Al.sub.1-nGa.sub.nN epitaxial layer on the sacrificial layer, wherein 0<n≤1; growing a nanopillar array containing GaN materials on the Al.sub.1-nGa.sub.nN epitaxial layer; etching the sacrificial layer so as to peel off an epitaxial structure on the sacrificial layer as a whole; and transferring the epitaxial structure after peeling onto a surface of a flexible transparent substrate.

2. The preparation method of a super-flexible transparent semiconductor film according to claim 1, wherein a plurality of Al.sub.1-nGa.sub.nN epitaxial layers are stacked and grown on the sacrificial layer, n values corresponding to adjacent two layers of Al.sub.1-nGa.sub.nN epitaxial layers are different, and the nanopillar array is formed on an outermost Al.sub.1-nGa.sub.nN epitaxial layer.

3. The preparation method of a super-flexible transparent semiconductor film according to claim 1, wherein etching the sacrificial layer includes the steps of: preparing electrodes conducting the sacrificial layer on the Al.sub.1-nGa.sub.nN epitaxial layer, and then etching the sacrificial layer in an electrochemical manner; and etching a pattern on the Al.sub.1-nGa.sub.nN epitaxial layer in a photolithographic manner prior to etching the sacrificial layer in an electrochemical manner, and separating nanopillars of the nanopillar array in patterns of different regions.

4. The preparation method of a super-flexible transparent semiconductor film according to claim 2, wherein the n values corresponding to the plurality of Al.sub.1-nGa.sub.nN epitaxial layers on the sacrificial layer gradually decreases or gradually increases in an epitaxial growth direction.

5. The preparation method of a super-flexible transparent semiconductor film according to claim 1, wherein a buffer layer is also grown on the epitaxial substrate before the step of growing the sacrificial layer on the epitaxial substrate; the sacrificial layer and/or the buffer layer uses one or more layers of Al.sub.1-bGa.sub.bN materials, wherein 0≤b<1, and b values corresponding to adjacent two layers of Al.sub.1-nGa.sub.nN materials are different.

6. The preparation method of a super-flexible transparent semiconductor film according to claim 5, wherein the b values corresponding to each layer of Al.sub.1-bGa.sub.bN materials on the epitaxial substrate gradually increases in an epitaxial growth direction.

7. The preparation method of a super-flexible transparent semiconductor film according to claim 1, wherein the nanopillar array includes a first Al.sub.1-mGa.sub.mN nanopillar, a second Al.sub.1-xGa.sub.xN nanopillar or an In.sub.1-xGa.sub.xN nanopillar, and a third Al.sub.1-zGa.sub.zN nanopillar that are stacked and grown sequentially on the Al.sub.1-nGa.sub.nN epitaxial layer from bottom to top, wherein 0<m≤1, 0≤x≤1, and 0<z≤1.

8. The preparation method of a super-flexible transparent semiconductor film according to claim 7, wherein a height of the first Al.sub.1-mGa.sub.mN nanopillar is 100 nm to 1500 nm, a height of the second Al.sub.1-xGa.sub.xN nanopillar or the In.sub.1-xGa.sub.xN nanopillar is 20 nm to 500 nm, a height of the third Al.sub.1-zGa.sub.zN nanopillar is 20 nm to 600 nm; and/or a diameter of a single nanopillar in the nanopillar array is no more than 400 nm.

9. The preparation method of a super-flexible transparent semiconductor film according to claim 7, wherein the first Al.sub.1-mGa.sub.mN nanopillar includes a plurality of layers, m values corresponding to adjacent two layers of the first Al.sub.1-mGa.sub.mN nanopillar are different; and/or, the second Al.sub.1-xGa.sub.xN nanopillar or the In.sub.1-xGa.sub.xN nanopillar includes a plurality of layers, and x values corresponding to the adjacent two layers of the second Al.sub.1-xGa.sub.xN nanopillar or the adjacent two layers of the In.sub.1-xGa.sub.xN nanopillar are different; and/or, the third Al.sub.1-zGa.sub.zN nanopillar includes a plurality of layers, and z values corresponding to the adjacent two layers of the third Al.sub.1-zGa.sub.zN nanopillar are different.

10. The preparation method of a super-flexible transparent semiconductor film according to claim 9, wherein the m values gradually decrease in a growth direction of the first Al.sub.1-mGa.sub.mN nanopillar.

11. A super-flexible transparent semiconductor film produced using a preparation method of the super-flexible transparent semiconductor film, the preparation method of the super-flexible transparent semiconductor film including: providing an epitaxial substrate; growing a sacrificial layer on the epitaxial substrate; stacking and growing at least one layer of Al.sub.1-nGa.sub.nN epitaxial layer on the sacrificial layer, wherein 0<n≤1; growing a nanopillar array containing GaN materials on the Al.sub.1-nGa.sub.nN epitaxial layer; etching the sacrificial layer so as to peel off an epitaxial structure on the sacrificial layer as a whole; and transferring the epitaxial structure after peeling onto a surface of a flexible transparent substrate; wherein the super-flexible transparent semiconductor film includes a flexible transparent substrate and an epitaxial structure provided on a surface of the flexible transparent substrate, wherein the epitaxial structure includes at least one layer of Al.sub.1-nGa.sub.nN epitaxial layer provided on the surface of the flexible transparent substrate, and a nanopillar array containing GaN materials and provided on the Al.sub.1-nGa.sub.nN epitaxial layer, wherein 0<n≤1.

12. The super-flexible transparent semiconductor film according to claim 11, wherein a total thickness H.sub.1 of all Al.sub.1-nGa.sub.nN epitaxial layers provided on the surface of the flexible transparent substrate satisfies: 1 nm≤H.sub.1<800 nm.

13. The super-flexible transparent semiconductor film according to claim 11, wherein a plurality of Al.sub.1-nGa.sub.nN epitaxial layers are stacked and grown on the sacrificial layer, n values corresponding to adjacent two layers of Al.sub.1-nGa.sub.nN epitaxial layers are different, and the nanopillar array is formed on an outermost Al.sub.1-nGa.sub.nN epitaxial layer.

14. The super-flexible transparent semiconductor film according to claim 11, wherein etching the sacrificial layer includes the steps of: preparing electrodes conducting the sacrificial layer on the Al.sub.1-nGa.sub.nN epitaxial layer, and then etching the sacrificial layer in an electrochemical manner; and etching a pattern on the Al.sub.1-nGa.sub.nN epitaxial layer in a photolithographic manner prior to etching the sacrificial layer in an electrochemical manner, and separating nanopillars of the nanopillar array in patterns of different regions.

15. The super-flexible transparent semiconductor film according to claim 13, wherein the n values corresponding to the plurality of Al.sub.1-nGa.sub.nN epitaxial layers on the sacrificial layer gradually decreases or gradually increases in an epitaxial growth direction.

16. The super-flexible transparent semiconductor film according to claim 11, wherein a buffer layer is also grown on the epitaxial substrate before the step of growing the sacrificial layer on the epitaxial substrate; the sacrificial layer and/or the buffer layer uses one or more layers of Al.sub.1-bGa.sub.bN materials, wherein 0≤b<1, and b values corresponding to adjacent two layers of Al.sub.1-nGa.sub.nN materials are different; the b values corresponding to each layer of Al.sub.1-bGa.sub.bN materials on the epitaxial substrate gradually increases in an epitaxial growth direction.

17. The super-flexible transparent semiconductor film according to claim 11, wherein the nanopillar array includes a first Al.sub.1-mGa.sub.mN nanopillar, a second Al.sub.1-xGa.sub.xN nanopillar or an In.sub.1-xGa.sub.xN nanopillar, and a third Al.sub.1-zGa.sub.zN nanopillar that are stacked and grown sequentially on the Al.sub.1-nGa.sub.nN epitaxial layer from bottom to top, wherein 0<m≤1, 0≤x≤1, and 0<z≤1.

18. The super-flexible transparent semiconductor film according to claim 17, wherein a height of the first Al.sub.1-mGa.sub.mN nanopillar is 100 nm to 1500 nm, a height of the second Al.sub.1-xGa.sub.xN nanopillar or the In.sub.1-xGa.sub.xN nanopillar is 20 nm to 500 nm, a height of the third Al.sub.1-zGa.sub.zN nanopillar is 20 nm to 600 nm; and/or a diameter of a single nanopillar in the nanopillar array is no more than 400 nm.

19. The super-flexible transparent semiconductor film according to claim 17, wherein the first Al.sub.1-mGa.sub.mN nanopillar includes a plurality of layers, m values corresponding to adjacent two layers of the first Al.sub.1-mGa.sub.mN nanopillar are different; and/or, the second Al.sub.1-xGa.sub.xN nanopillar or the In.sub.1-xGa.sub.xN nanopillar includes a plurality of layers, and x values corresponding to the adjacent two layers of the second Al.sub.1-xGa.sub.xN nanopillar or the adjacent two layers of the In.sub.1-xGa.sub.xN nanopillar are different; and/or the third Al.sub.1-zGa.sub.zN nanopillar includes a plurality of layers, and z values corresponding to the adjacent two layers of the third Al.sub.1-zGa.sub.zN nanopillar are different.

20. The super-flexible transparent semiconductor film according to claim 19, wherein the m values gradually decrease in a growth direction of the first Al.sub.1-mGa.sub.mN nanopillar.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 is a schematic flowchart of preparing an epitaxial structure of a super-flexible transparent semiconductor film according to the present invention;

[0032] FIG. 2 is a schematic structural view illustrating an epitaxial structure of a super-flexible transparent semiconductor film according to a first embodiment of the present invention;

[0033] FIG. 3 is a side view of a scanning electron microscope (SEM) of the semiconductor film according to the first embodiment of the present invention;

[0034] FIG. 4 is a schematic view of the epitaxial structure of the super-flexible transparent semiconductor film after peeling and transfer according to the first embodiment of the present invention;

[0035] FIG. 5 is a pictorial diagram of the super-flexible transparent semiconductor film according to the first embodiment of the present invention;

[0036] FIG. 6 is a test diagram of transmission spectrum of the super-flexible transparent semiconductor film according to the first embodiment of the present invention;

[0037] FIG. 7 is a pictorial diagram of the super-flexible transparent semiconductor film in a bending state according to the first embodiment of the present invention;

[0038] FIG. 8 is a schematic diagram of a photolithographic structure of a semiconductor film surface according to a sixth embodiment of the present invention; and

[0039] FIG. 9 is a schematic structural view of a semiconductor film after peeling and curling according to the sixth embodiment of the present invention.

REFERENCE NUMERALS ARE AS FOLLOWS

[0040] 1—epitaxial substrate; [0041] 100—flexible transparent substrate; [0042] 2—sacrificial layer; [0043] 11—Al.sub.1-nGa.sub.nN epitaxial layer; [0044] 111—lower Al.sub.1-nGa.sub.nN epitaxial layer; [0045] 112—upper Al.sub.1-nGa.sub.nN epitaxial layer; [0046] 12—nanopillar array; [0047] 121—first Al.sub.1-mGa.sub.mN nanopillar; [0048] 122—second Al.sub.1-xGa.sub.xN nanopillar or In.sub.1-xGa.sub.xN nanopillar; [0049] 123—third Al.sub.1-zGa.sub.zN nanopillar; and [0050] C—groove.

DETAILED DESCRIPTION

[0051] To provide a clearer understanding of the purpose, technical solutions and advantages of the present invention, the present invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustration of the present invention only and are not intended to limit the present invention.

[0052] In the drawings, shapes and sizes of elements may be enlarged for clarity, and the same reference numerals will be used throughout to represent the same or similar elements.

[0053] It should be understood that, although terms “first”, “second”, etc. can be used herein to describe various structures, these structures should not be limited by these terms, which are merely used to distinguish one structure from another. Terms “upper” and “lower” are merely for convenience of describing relative positional relationships of various objects in the embodiments of the present invention, and are distinguished only by an orientation shown in corresponding drawings and do not refer to an absolute direction.

[0054] Referring to FIGS. 1 and 2, the present invention provides a preparation method of a super-flexible transparent semiconductor film, including:

[0055] S01, providing an epitaxial substrate 1.

[0056] Here, the epitaxial substrate 1 can be selected from a silicon wafer (Si), a sapphire substrate, a GaN self-supporting substrate, silicon carbide (SiC), a diamond substrate, a metal substrate, and a substrate covered with a two-dimensional material.

[0057] S02, growing a sacrificial layer 2 on the epitaxial substrate 1.

[0058] A buffer layer and the sacrificial layer 2 can be sequentially stacked and grown on the epitaxial substrate 1, or only the sacrificial layer 2 can be grown on the epitaxial substrate 1. That is, the buffer layer can also be grown on the epitaxial substrate 1 before the step of growing the sacrificial layer 2 on the epitaxial substrate 1. The sacrificial layer 2, the buffer layer can use single-layer or multi-layer Al.sub.1-bGa.sub.bN materials respectively, in which 0≤b<1. Preferably, b values corresponding to adjacent two layers of Al.sub.1-bGa.sub.bN materials on the epitaxial substrate 1 are different, that is, the b values corresponding to the interior adjacent two layers of Al.sub.1-bGa.sub.bN materials are different when the sacrificial layer 2 or the buffer layer is multi-layer Al.sub.1-bGa.sub.bN materials. Whether the sacrificial layer 2 and the buffer layer use single-layer or multi-layer Al.sub.1-bGa.sub.bN materials, the b values corresponding to the two layers of Al.sub.1-bGa.sub.bN materials in which the sacrificial layer 2 is in contact with the buffer layer are also different.

[0059] A total thickness of the buffer layer and the sacrificial layer 2 is H.sub.0, 1 nm≤H.sub.0<200 nm, the thickness of the sacrificial layer 2 is H.sub.0 when only the sacrificial layer 2 is grown on the epitaxial substrate 1 without the buffer layer; and the sum of the thicknesses of the buffer layer and the sacrificial layer 2 is H.sub.0 when the buffer layer and the sacrificial layer 2 are sequentially stacked and grown on the epitaxial substrate 1. Further, the b values corresponding to each layer of Al.sub.1-bGa.sub.bN materials on the epitaxial substrate 1 gradually increases in an epitaxial growth direction.

[0060] S03, stacking and growing single-layer or multi-layer Al.sub.1-nGa.sub.nN epitaxial layer 11 on the sacrificial layer 2, in which 0<n≤1.

[0061] When a plurality of Al.sub.1-nGa.sub.nN epitaxial layers 11 are stacked and grown on the sacrificial layer 2, n values corresponding to adjacent two layers of Al.sub.1-nGa.sub.nN epitaxial layers 11 are different, and a nanopillar array 12 is formed on the outermost Al.sub.1-nGa.sub.nN epitaxial layer 11. A total thickness H.sub.1 of all Al.sub.1-nGa.sub.nN epitaxial layers 11 provided on a surface of a flexible transparent substrate 100 satisfies: 1 nm≤H.sub.1<800 nm.

[0062] S04, growing the nanopillar array 12 containing GaN materials on the Al.sub.1-nGa.sub.nN epitaxial layer 11.

[0063] The Al.sub.1-nGa.sub.nN epitaxial layer 11 can serve as a connection layer between the nanopillars after peeling, and also facilitates further buffering and nucleation of the nanopillars. The film mainly includes a nanopillar array, which facilitates release of epitaxial stress and improves crystal quality as compared to traditional film structures; and the buffer layer and the sacrificial layer 2 that are grown at the bottom facilitate further relieving the stress due to crystal lattice and thermal mismatch and facilitate formation of a nanopillar nucleation layer.

[0064] When a plurality of Al.sub.1-nGa.sub.nN epitaxial layers 11 are provided, the n values corresponding to the plurality of Al.sub.1-nGa.sub.nN epitaxial layers on the sacrificial layer 2 gradually decreases or gradually increases in the epitaxial growth direction in a gradient trend, which facilitates preparing a curly film.

[0065] In particular, the nanopillar array 12 includes a first Al.sub.1-mGa.sub.mN nanopillar 121, a second Al.sub.1-xGa.sub.xN nanopillar or an In.sub.1-xGa.sub.xN nanopillar 122, and a third Al.sub.1-zGa.sub.zN nanopillar 123 that are stacked and grown sequentially on the Al.sub.1-nGa.sub.nN epitaxial layer 11 from bottom to top, in which 0<m≤1, 0≤x≤1, and 0<z≤1.

[0066] The first Al.sub.1-mGa.sub.mN nanopillar 121 can have a single-layer structure or can include a multi-layer structure. When the first Al.sub.1-mGa.sub.mN nanopillar 121 includes a multi-layer structure, m values corresponding to adjacent two layers of the first Al.sub.1-mGa.sub.mN nanopillar 121 are different. Preferably, the m values gradually decrease in a growth direction of the first Al.sub.1-mGa.sub.mN nanopillar 121 in a gradient trend.

[0067] Similarly, the second Al.sub.1-xGa.sub.xN nanopillar or the In.sub.1-xGa.sub.xN nanopillar 122 can have a single-layer structure or can include a multi-layer structure. When the second Al.sub.1-xGa.sub.xN nanopillar or the In.sub.1-xGa.sub.xN nanopillar 122 includes a multi-layer structure, x values corresponding to the adjacent two layers of the second Al.sub.1-xGa.sub.xN nanopillar or the adjacent two layers of the In.sub.1-xGa.sub.xN nanopillar are different.

[0068] The third Al.sub.1-zGa.sub.zN nanopillar 123 can have a single-layer structure or can include a multi-layer structure. When the third Al.sub.1-zGa.sub.zN nanopillar 123 includes a multi-layer structure, z values corresponding to the adjacent two layers of the third Al.sub.1-zGa.sub.zN nanopillar 123 are different.

[0069] Furthermore, content of Al component within each of the first Al.sub.1-mGa.sub.mN nanopillar 121, the second Al.sub.1-xGa.sub.xN nanopillar 122, and the third Al.sub.1-zGa.sub.zN nanopillar 123 is uniformly distributed or distributed in a gradually changing manner (e.g., gradually increases or gradually decreases in the growth direction) respectively.

[0070] For example, a height of the first Al.sub.1-mGa.sub.mN nanopillar 121 can be 100 nm to 1500 nm, a height of the second Al.sub.1-xGa.sub.xN nanopillar or the In.sub.1-xGa.sub.xN nanopillar 122 can be 20 nm to 500 nm, a height of the third Al.sub.1-zGa.sub.zN nanopillar 123 can be 20 nm to 600 nm, and a diameter of a single nanopillar in the nanopillar array 12 is no more than 400 nm.

[0071] S05, etching the sacrificial layer 2 so as to peel off an epitaxial structure on the sacrificial layer 2 as a whole.

[0072] As one of the embodiments, the step of etching the sacrificial layer 2 can include: preparing electrodes conducting the sacrificial layer 2 on the Al.sub.1-nGa.sub.nN epitaxial layer 11, and then etching the sacrificial layer 2 in an electrochemical manner.

[0073] A pattern is etched on the Al.sub.1-nGa.sub.nN epitaxial layer 11 in a photolithographic manner prior to etching the sacrificial layer 2 in an electrochemical manner, and the nanopillars of the nanopillar array 12 are separated in patterns of different regions, so that the shape and curvature of the semiconductor film after peeling are conveniently regulated. A voltage U used in the etching in a photolithographic manner satisfies: 0.1 V≤U≤500 V. The photolithography process cannot damage a large area of the nanopillar array 12, a shape of an etching pattern can be triangular, rectangular, polygonal, circular, and a radial dimension is between 1 μm and 10000 μm. That is, multiple nanopillars of the nanopillar array 12 can be separated into several interspaced sub-regions by etching the etching pattern configured to be a closed shape on the Al.sub.1-nGa.sub.nN epitaxial layer 11, which helps to regulate internal stress of the Al.sub.1-nGa.sub.nN epitaxial layer 11, thereby regulating the shape and curvature of the film after peeling.

[0074] All the buffer layer, the sacrificial layer 2, the Al.sub.1-nGa.sub.nN epitaxial layer 11, and the nanopillar array 12 as described above can be formed using molecular beam epitaxy or vapor deposition.

[0075] S06, transferring the epitaxial structure after peeling onto a surface of the flexible transparent substrate 100.

[0076] The flexible transparent substrate 100 may include conductive film, epoxy, glass, transparent tape, and two-dimensional film materials.

[0077] Corresponding to the above preparation method, the present invention further provides a super-flexible transparent semiconductor film, including: a flexible transparent substrate 100; and an epitaxial structure provided on a surface of the flexible transparent substrate 100, in which the epitaxial structure includes at least one layer of Al.sub.1-nGa.sub.nN epitaxial layer 11 provided on the surface of the flexible transparent substrate 100, and a nanopillar array 12 containing GaN materials and provided on the Al.sub.1-nGa.sub.nN epitaxial layer 11, in which 0<n≤1.

[0078] The above preparation methods and corresponding structures of the present invention will be described by specific embodiments, but the following embodiments are only specific examples of the present invention and the invention is not limited to all these embodiments.

First Embodiment

[0079] As shown in FIG. 2, the present embodiment provides a preparation method of a super-flexible transparent semiconductor film.

[0080] First, taking a sheet of n-type Si substrate as the epitaxial substrate 1, and cleaning a surface of the Si substrate with HF acid, acetone, and ethanol solution respectively for 5 minutes.

[0081] Then, placing the Si substrate in a Molecular Beam Epitaxy (MBE) growth chamber for epitaxial growth and forming an epitaxial structure, specifically including the following steps:

[0082] Step 1, growing an AlN sacrificial layer 2 having a thickness of about 3 nm on the Si substrate, i.e., the sacrificial layer 2 is Al.sub.1-bGa.sub.bN materials and can also function as a buffer layer, in which b=0.

[0083] Step 2, growing a GaN epitaxial layer having a height of about 10 nm on the AlN sacrificial layer 2, i.e., the Al.sub.1-nGa.sub.nN epitaxial layer 11, in which n=1.

[0084] Step 3, growing a layer of GaN nanopillars having a height of about 400 nm on the GaN epitaxial layer as the first Al.sub.1-mGa.sub.mN nanopillar 121, in which m=1.

[0085] Step 4, growing a layer of In.sub.0.3Ga.sub.0.7N nanopillars having a thickness of 30 nm on the GaN nanopillar as the In.sub.1-xGa.sub.xN nanopillar 122, in which x=0.7; then growing a layer of GaN nanopillars having a thickness of 10 nm as the third Al.sub.1-zGa.sub.zN nanopillar 123, in which z=1, thereby obtaining a nanopillar array similar to that shown in FIG. 3.

[0086] Step 5, introducing electrodes to a rear side (bottom surface) of the Si substrate, performing an electrochemical etching in the NaOH solution using a voltage of about 5 V to etch the AlN sacrificial layer 2, etching the Si substrate to obtain an epitaxial film on the sacrificial layer 2, and transferring the epitaxial film to a surface of a transparent tape, in which the transparent tape can be taken as the flexible transparent substrate 100 as shown in FIG. 4.

[0087] As shown in FIG. 5, a sample of a super-flexible transparent semiconductor film can be obtained by the preparation process described above. A “SINANO” mark was written on a piece of paper, and was still visible through the sample, which fully shows that the sample had a higher transparency. As shown in FIG. 6, the sample was found to have a transmittance greater than 70% in a visible wave band (380 nm to 800 nm) after a transmittance test. As shown in FIG. 7, the film sample has excellent flexibility.

Second Embodiment

[0088] The present embodiment provides another preparation method of a super-flexible transparent semiconductor film.

[0089] First, taking a sheet of n-type Si substrate as the epitaxial substrate 1, and cleaning a surface of the Si substrate with HF acid, acetone, and ethanol solution respectively for 6 minutes.

[0090] Then, placing the Si substrate in an MBE growth chamber for epitaxial growth and forming an epitaxial structure, specifically including the following steps:

[0091] Step 1, growing an AlN sacrificial layer having a thickness of about 5 nm on the Si substrate, i.e., the sacrificial layer is Al.sub.1-bGa.sub.bN materials and can also function as a buffer layer, in which b=0.

[0092] Step 2, growing a layer of n-type Si-doped GaN epitaxial layer having a height of about 100 nm on the AlN sacrificial layer, i.e., the Al.sub.1-nGa.sub.nN epitaxial layer 11, in which n=1.

[0093] Step 3, growing a layer of n-type Si-doped GaN nanopillars having a height of about 800 nm on the GaN epitaxial layer as the first Al.sub.1-mGa.sub.mN nanopillar 121, in which m=1.

[0094] Step 4, growing a layer of Al.sub.0.3Ga.sub.0.7N nanopillars having a thickness of 100 nm on the GaN nanopillar as the second Al.sub.1-xGa.sub.xN nanopillar 122, in which x=0.7; then growing a layer of p-type Mg-doped GaN nanopillars having a thickness of 80 nm as the third Al.sub.1-zGa.sub.zN nanopillar 123, in which z=1.

[0095] Step 5, introducing electrodes to a rear side (bottom surface) of the Si substrate, performing an electrochemical etching in an HNO.sub.3 solution using a voltage of about 10 V to etch the AlN sacrificial layer 2, and transferring the epitaxial film on the sacrificial layer to a surface of an ITO conductive film.

Third Embodiment

[0096] The present embodiment is basically identical to the first embodiment, except that the second Al.sub.1-xGa.sub.xN nanopillar 122 in the present embodiment includes a plurality of superlattice-like structures arranged in a stacked manner, Al.sub.1-xGa.sub.xN material layers with different x values are stacked in each of the superlattice-like structures, and the Al.sub.1-xGa.sub.xN material layers with different x values are periodically and alternately stacked to form the second Al.sub.1-xGa.sub.xN nanopillar 122.

[0097] Specifically, the second Al.sub.1-xGa.sub.xN nanopillar 122 has 5 Al.sub.0.1Ga.sub.0.9N (10 nm)/GaN (3 nm) superlattice-like structures, i.e., Al.sub.0.1Ga.sub.0.9N (10 nm) alternates with GaN (3 nm) with 5 cycles, in which x values of adjacent two layers of Al.sub.1-xGa.sub.xN materials are 0.9 and 1 respectively.

Fourth Embodiment

[0098] The present embodiment is basically identical to the second embodiment, except that the epitaxial substrate 1 in the present embodiment is a sapphire substrate having a TiN metal film with a thickness of 500 nm.

Fifth Embodiment

[0099] The present embodiment is basically identical to the first embodiment, except that an epitaxial device in the present embodiment is a metal-organic chemical vapor deposition (MOCVD) device.

Sixth Embodiment

[0100] The present embodiment provides another preparation method of a super-flexible transparent semiconductor film.

[0101] First, taking a sheet of n-type Si substrate as the epitaxial substrate 1, and cleaning a surface of the Si substrate with HF acid, acetone, and ethanol solution respectively for 3 minutes.

[0102] Then, placing the Si substrate in an MBE growth chamber for epitaxial growth and forming an epitaxial structure, specifically including the following steps:

[0103] Step 1, growing an AlN sacrificial layer having a thickness of about 4 nm on the Si substrate, i.e., Al.sub.1-bGa.sub.bN materials, in which b=0.

[0104] Step 2, growing a layer of n-type Si-doped GaN epitaxial layer having a height of about 100 nm on the AlN sacrificial layer, i.e., a lower Al.sub.1-nGa.sub.nN epitaxial layer 111, in which n=1; then growing a layer of n-type Si-doped Al.sub.0.4Ga.sub.0.6N epitaxial layer having a height of about 80 nm, i.e., an upper Al.sub.1-nGa.sub.nN epitaxial layer 112, in which n=0.6, which is used to regulate stress of film after peeling so as to form a curly film.

[0105] Step 3, growing a layer of n-type Si-doped GaN nanopillars having a height of about 400 nm on the GaN epitaxial layer as the first Al.sub.1-mGa.sub.mN nanopillar 121, in which m=1.

[0106] Step 4, growing a layer of In.sub.0.1Ga.sub.0.9N (4 nm)/GaN (15 nm) with a plurality of cycles (e.g., 10 cycles) on the GaN nanopillar as the second Al.sub.1-xGa.sub.xN nanopillar 122, in which x is 0.9 and 1 respectively; and growing a p-type Mg-doped GaN nanopillar having a thickness of 120 nm as the third Al.sub.1-zGa.sub.zN nanopillar 123, in which z=1.

[0107] As shown in FIG. 8, a grid in the form of a rectangular array can be etched on an epitaxial sample in a photolithographic manner, in which a single rectangle has a length of 30 μm and a width of 20 μm, each rectangle is separated by etched grooves C, i.e., an etching pattern is formed, and the grooves C are engraved onto the epitaxial substrate 1 to separate the epitaxial structure into several portions that are independent of each other.

[0108] Step 5, introducing electrodes to a rear side of the Si substrate, performing an electrochemical etching in an HNO.sub.3 solution using a voltage of about 15 V to etch the AlN sacrificial layer 2, and transferring the epitaxial film on the sacrificial layer to a surface of an ITO conductive film, in which the film forms a micron roll structure having nanopillars due to stress as shown in FIG. 9.

Seventh Embodiment

[0109] The present embodiment is basically identical to the sixth embodiment, except that a grid in the form of a circular array is etched on the epitaxial sample in a photolithographic manner, in which a single circle has a diameter of 50 μm, an electrochemical etching is performed in a KOH solution using a voltage of about 20V, and the epitaxial film on the sacrificial layer is transferred to two-dimensional material graphene.

[0110] In view of the above, the present invention has at least the following beneficial effects as compared to the prior art.

[0111] (1) Low cost: A total thickness of the buffer layer and the sacrificial layer required by preparing the epitaxial structure of the super-flexible transparent semiconductor film according to the present invention is small (<200 nm), and the nanopillar array is directly grown without additional catalyst during an epitaxy process, which is beneficial for reducing epitaxial costs; in addition, both electrochemical etching and photolithography necessary for a preparation solution are common etching processes, and the costs are low.

[0112] (2) High crystal quality: The super-flexible transparent semiconductor film prepared by the present invention mainly includes a nanopillar array, which facilitates release of epitaxial stress and improves crystal quality as compared to traditional film structures; and the buffer layer and the sacrificial layer that are grown at the bottom facilitate further relieving the stress due to crystal lattice and thermal mismatch and facilitate formation of a nanopillar nucleation layer.

[0113] (3) Simple and controllable in process and practical in use; The super-flexible transparent film is directly grown without additional catalyst during an epitaxy process, which reduces process difficulty; both electrochemical etching and photolithography necessary for the preparation process are common etching processes, and requirements for accuracy are not high, so that practicability is facilitated.

[0114] (4) Good flexibility and high transparency: A connecting portion of the nanopillar array prepared by the present invention is a Al.sub.1-nGa.sub.nN epitaxial layer having a low absorbance of visible light and a high transparency; the connecting portion Al.sub.1-nGa.sub.nN epitaxial layer has a small thickness, there is a large gap between the nanopillar arrays, which improves the flexibility of the film while avoiding compression and damage between the epitaxial structures during the epitaxy process; the nanopillar array has higher transmittance in a visible light range, thereby improving the transparency of prepared samples as required.

[0115] The above are only descriptions of embodiments of the present application. It should be noted that for those skilled in the art, a variety of modifications and polishing are possible without departing from the principles of the present application and should also fall within the scope of the present application.