Method for laser processing of group iii nitride micro- and nano-structures and light emitting device

Abstract

The application discloses a laser processing method of a group III nitride micro-nano structure and a light-emitting device, and the method comprises the following steps: S1, providing a group III nitride micro-nano structure, wherein the group III nitride micro-nano structure comprises a group III nitride thin film and a group III nitride nanowire array structure on the group III nitride thin film; and S2, continuously irradiating the group III nitride nanowire array structure by using an ultrafast femtosecond laser to improve the light-emitting performance of the group III nitride micro-nano structure. The continuous irradiation of the ultrafast femtosecond laser can improve the crystal quality of the group III nitride material, improve the light-emitting performance of the group III nitride material, and make the light-emitting intensity irreversibly enhanced. The application has the characteristics of low cost, simple operation and precise selected area irradiation, and can be applied to light-emitting devices such as Micro-LED and Nano-LED.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor materials technology, specifically relating to a laser processing method and light-emitting device for group III nitride micro / nano structures. Background Technology

[0002] Group III nitrides (such as GaN) have direct band gaps with continuously tunable band gap widths from 0.7 to 6.2 eV, covering a broad spectral range from ultraviolet to near-infrared. Therefore, Group III nitrides are widely used in optoelectronic devices. GaN-based light-emitting diodes (LEDs) are already widely used in daily life, such as in lighting, traffic signals, full-color displays, and LCD backlights. Currently, devices are increasingly miniaturized, with LED chip sizes shrinking to the micrometer and nanometer scale. Each pixel consists of only three chips (red, green, and blue), enabling independent pixel addressing and control. They also possess numerous advantages such as self-illumination, low power consumption, high integration, and high stability, meeting the demands of ultra-small and ultra-large displays. Therefore, Micro-LED and Nano-LED devices are gradually emerging as next-generation display technology light sources.

[0003] In the fabrication of GaN-based LED chips, a series of processes are required to treat the GaN epitaxial structure, including inductively coupled plasma etching (ICP), magnetron sputtering of ITO (CSL), and electron beam evaporation of metal layers (ELEC). Uncertain sidewall damage introduced during dry etching introduces deep-level defects at the device edges, forming non-radiative recombination centers. Micro-LED chips are typically smaller than 50 μm, and Nano-LED chips are smaller than 1 μm. As chip size decreases further, the ratio of damage area near the sidewalls to the total area increases dramatically. The introduced defects cause a rapid increase in the non-radiative recombination ratio, severely impacting the luminous efficiency of Micro-LED and Nano-LED devices. Furthermore, the high surface area to volume ratio in microstructures also leads to the introduction of more non-radiative recombination centers from surface states. Studies show that as LED chip size decreases from 100 μm to 10 μm, the external quantum efficiency decreases from 23% to 15%, exhibiting a sharp decline with size. Therefore, improving crystal quality and luminous efficiency during the miniaturization of LED devices is a pressing challenge.

[0004] Micro-LED and Nano-LED devices currently employ methods such as sidewall passivation, wet chemical processing, and thermal annealing to reduce the impact of sidewall etching damage. While these methods can improve luminous efficiency to some extent, the improvement is relatively small and the operations are relatively complex. In addition, efforts are underway to explore alternative etching methods with less damage to replace ICP etching, or to use other fabrication methods to avoid etching GaN altogether, but this requires extensive process development and refinement.

[0005] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a laser processing method and light-emitting device for group III nitride micro / nano structures. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a laser processing method and a light-emitting device for group III nitride micro / nano structures.

[0007] To achieve the above objectives, an embodiment of the present invention provides the following technical solution:

[0008] A laser processing method for group III nitride micro / nano structures, the method comprising:

[0009] S1. Provide a group III nitride micro / nano structure, wherein the group III nitride micro / nano structure includes a group III nitride thin film and a group III nitride nanowire array structure located on the group III nitride thin film;

[0010] S2. The group III nitride nanowire array structure is continuously irradiated with an ultrafast femtosecond laser to improve the luminescence performance of the group III nitride micro / nano structure.

[0011] In one embodiment, the wavelength of the ultrafast femtosecond laser is less than or equal to the wavelength corresponding to the group III nitride bandgap.

[0012] In one embodiment, the group III nitride micro / nanostructure is a GaN micro / nanostructure, which includes a GaN thin film and a GaN nanowire array structure located on the GaN thin film.

[0013] In one embodiment, the ultrafast femtosecond laser has a wavelength less than or equal to 365 nm, a pulse width less than or equal to 1 ps, and a pulse energy density greater than or equal to 10 μJ / cm². 2 The irradiation time is 5 min to 90 min.

[0014] In one embodiment, the GaN nanowire array structure is a GaN random nanowire array structure.

[0015] In one embodiment, the diameter of the nanowires in the GaN random nanowire array structure is 50–300 nm, the spacing between the nanowires is less than or equal to 100 nm, and the height of the nanowires is 600–1000 nm.

[0016] In one embodiment, the method for fabricating the GaN random nanowire array structure is as follows:

[0017] GaN thin films were epitaxially grown on a substrate using the HVPE process;

[0018] A metal film is formed on a GaN thin film, and then annealed to form a metal nanosphere mask;

[0019] GaN thin films are etched using ICP etching to form random GaN nanowires;

[0020] The residual metal nanosphere mask on the surface of GaN random nanowires was cleaned to obtain the GaN random nanowire array structure.

[0021] In one embodiment, step S2 further includes:

[0022] All or part of the group III nitride nanowire array structure was irradiated with an ultrafast femtosecond laser.

[0023] Another embodiment of the present invention provides the following technical solution:

[0024] A light-emitting device comprising the aforementioned group III nitride micro / nano structure processed by ultrafast femtosecond laser.

[0025] In one embodiment, the light-emitting device is a GaN-based Micro-LED device or a GaN-based Nano-LED device.

[0026] The present invention has the following beneficial effects:

[0027] This invention utilizes continuous ultrafast femtosecond laser irradiation to improve the crystal quality of group III nitride materials, enhance their luminescence performance, and achieve an irreversible increase in luminescence intensity.

[0028] This invention features low cost, simple operation, and precise selective irradiation, and can be applied to light-emitting devices such as Micro-LED and Nano-LED. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic flowchart of the laser processing method for group III nitride micro / nano structures in this invention;

[0031] Figure 2a , Figure 2b The images shown are scanning electron microscope images of a GaN random nanowire array structure in a specific embodiment of the present invention (magnifications of 40k and 80k, respectively).

[0032] Figure 3aThe figure shows the change in PL intensity of the photoluminescence (PL) spectrum of the GaN random nanowire array structure during continuous irradiation with an ultrafast femtosecond laser in a specific embodiment of the present invention;

[0033] Figure 3b The figure shows the change in peak position of the photoluminescence (PL) spectrum of the GaN random nanowire array structure during continuous irradiation with an ultrafast femtosecond laser in a specific embodiment of the present invention;

[0034] Figure 4a The figure shows the normalized curve of the minimum value of the peak intensity of the photoluminescence (PL) spectrum of the GaN random nanowire array structure during continuous irradiation with an ultrafast femtosecond laser in a specific embodiment of the present invention;

[0035] Figure 4b The figure shows the normalized curve of the minimum value of the peak intensity of the photoluminescence (PL) spectrum of the GaN random nanowire array structure during continuous laser irradiation in a comparative example of the present invention;

[0036] Figure 5 The figure shows the change in the intensity of the band-edge peak in the photoluminescence (PL) spectrum of the GaN random nanowire array structure after intermittent irradiation with an ultrafast femtosecond laser in a specific embodiment of the present invention. Detailed implementation manners

[0037] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] Refer Figure 1 As shown, the present invention discloses a laser processing method for group III nitride micro-nano structures, including:

[0039] S1. Provide a group III nitride micro-nano structure, where the group III nitride micro-nano structure includes a group III nitride thin film and a group III nitride nanowire array structure located on the group III nitride thin film;

[0040] S2. Continuously irradiate the group III nitride nanowire array structure with an ultrafast femtosecond laser to improve the luminescence performance of the group III nitride micro-nano structure.

[0041] Among them, the wavelength of the ultrafast femtosecond laser is less than or equal to the wavelength corresponding to the bandgap of the group III nitride.

[0042] Taking GaN as an example, the micro-nano structure of group III nitrides is the GaN micro-nano structure, which includes GaN thin films and GaN nanowire array structures located on GaN thin films.

[0043] Preferably, the GaN nanowire array structure is a GaN random nanowire array structure, with the nanowire diameter being 50–300 nm, the nanowire spacing being less than or equal to 100 nm, and the nanowire height being 600–1000 nm.

[0044] The fabrication method of GaN random nanowire array structure is as follows:

[0045] GaN thin films were epitaxially grown on a substrate using the HVPE process;

[0046] A metal film is formed on a GaN thin film, and then annealed to form a metal nanosphere mask;

[0047] GaN thin films are etched using ICP etching to form random GaN nanowires;

[0048] The residual metal nanosphere mask on the surface of GaN random nanowires was cleaned to obtain the GaN random nanowire array structure.

[0049] Ultrafast femtosecond lasers have pulse widths on the femtosecond scale (10^6 Hz). -15 For the pulsed laser of s), the parameters of the ultrafast femtosecond laser continuous irradiation in this invention must meet the following requirements: the wavelength of the ultrafast femtosecond laser is less than or equal to 365 nm, the pulse width is less than or equal to 1 ps, and the pulse energy density is greater than or equal to 10 μJ / cm². 2 The irradiation time is 5 min to 90 min, preferably 10 min to 46 min.

[0050] It should be understood that the present invention can use ultrafast femtosecond laser to continuously irradiate the entire region of the group III nitride nanowire array structure, or it can perform selective irradiation processing and use ultrafast femtosecond laser to continuously irradiate a portion of the group III nitride nanowire array structure.

[0051] The present invention also discloses a light-emitting device, which can be a GaN-based Micro-LED, Nano-LED, etc. The group III nitride micro-nano structure in the light-emitting device can be greatly improved by ultrafast femtosecond laser treatment.

[0052] This invention uses ultrafast femtosecond laser to continuously irradiate group III nitride nanomaterials to improve their luminescence properties, thereby improving the crystal quality of group III nitride nanomaterials and achieving an irreversible enhancement in luminescence intensity.

[0053] The present invention can be applied to light-emitting devices (such as Micro-LED, Nano-LED, etc.), and it is expected to improve their luminous efficiency. Compared with methods such as sidewall passivation, wet chemical treatment, and thermal annealing of group III nitride nanomaterials, the treatment method of the present invention not only has low cost and simple operation, but can also perform local precise laser irradiation treatment on the nanomaterials, thereby effectively improving the luminous efficiency of the light-emitting devices.

[0054] The following further illustrates the present invention with specific embodiments.

[0055] 1. Provide a GaN micro-nano structure, where the GaN micro-nano structure includes a GaN thin film and a GaN nanowire array structure located on the GaN thin film;

[0056] In this embodiment, the group III nitride is GaN, and the GaN micro-nano structure includes a GaN thin film and a GaN random nanowire array structure located on the GaN thin film.

[0057] The preparation method of the GaN random nanowire array structure is as follows:

[0058] Use the HVPE (hydride vapor phase epitaxy) process to epitaxially grow a GaN thin film on a sapphire substrate;

[0059] Form a layer of Ni metal film on the GaN thin film and anneal it to form a Ni metal nanosphere mask;

[0060] Use the ICP (inductively coupled plasma) etching process to etch the GaN thin film to form GaN random nanowires;

[0061] Clean the residual Ni metal nanosphere mask on the surface of the GaN random nanowires to obtain the GaN random nanowire array structure.

[0062] See Figure 2a 、 Figure 2b The scanning electron microscope image of the GaN random nanowire array structure in this embodiment is shown. The diameter of the nanowires is 50 - 300 nm, the nanowire spacing is less than 100 nm, and the nanowire height is about 800 nm.

[0063] 2. Use an ultrafast femtosecond laser to continuously irradiate the GaN nanowire array structure to improve the luminous performance of the GaN micro-nano structure.

[0064] The parameters of the continuous irradiation of the ultrafast femtosecond laser in this embodiment are: the wavelength of the ultrafast femtosecond laser is 224 nm, the pulse width is 640 fs, the repetition frequency is 80 MHz, and the pulse energy density is 0.76 mJ / cm 2 , and the irradiation time is 10 min - 46 min (10 min, 16 min, 22 min, 34 min, 46 min).

[0065] In this embodiment, the irradiation time within the range of 5 min to 90 min can improve the luminescence performance of the GaN random nanowire array structure, and the luminescence performance is more significantly improved when the irradiation time is within the range of 10 min to 46 min.

[0066] Refer Figure 3a 、 Figure 3b As shown in

[0067] Refer Figure 4a 、 Figure 4b As shown, during the continuous irradiation of the ultrafast femtosecond laser, the intensity of the band-edge peak in the photoluminescence (PL) spectrum (362.7 nm) gradually increases after 10 min and gradually increases within 46 min. The PL intensity increases to about 3 times the lowest value. In addition, the peak position remains basically stable (the change range is 0.5 nm) during the increase of the PL intensity.

[0068] Refer Figure 5 As shown is the change diagram of the band-edge peak intensity in the photoluminescence (PL) spectrum of the GaN random nanowire array structure after the intermittent irradiation of the ultrafast femtosecond laser. The ultrafast femtosecond laser continuously irradiates the sample and intermittently disconnects the laser, and the disconnection time for each interval is 5 minutes.

[0069] It can be seen that although there is a certain change in intensity after the laser is turned off and then turned on again, its intensity change is consistent with the stable rising stage of the irradiation time (such as Figure 5 the AB segment, CD segment, and EF segment in

[0070] From the above technical solutions, it can be seen that the present invention has the following advantages:

[0071] The present invention uses continuous irradiation of the ultrafast femtosecond laser to improve the crystal quality of the group III nitride material, improve its luminescence performance, and obtain an irreversible enhancement of the luminescence intensity;

[0072] The present invention has the characteristics of low cost, simple operation, and precise selective area irradiation, and can be applied to light-emitting devices such as Micro-LED and Nano-LED.

[0073] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0074] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A laser processing method for group III nitride micro / nano structures, characterized in that, The method includes: S1. Provide a group III nitride micro / nano structure, wherein the group III nitride micro / nano structure includes a group III nitride thin film and a group III nitride nanowire array structure located on the group III nitride thin film; S2. The group III nitride nanowire array structure is continuously irradiated with ultrafast femtosecond laser to improve the luminescence performance of the group III nitride micro / nano structure. The ultrafast femtosecond laser has a wavelength less than or equal to 365 nm, a pulse energy density greater than or equal to 10 μJ / cm², an irradiation time of 5 min to 90 min, and a pulse width less than or equal to 1 ps. The group III nitride micro / nanostructure is a GaN micro / nanostructure, which includes a GaN thin film and a GaN nanowire array structure located on the GaN thin film. The fabrication method of the GaN nanowire array structure includes: etching the GaN thin film using an ICP etching process to form GaN random nanowires.

2. The laser processing method for group III nitride micro / nano structures according to claim 1, characterized in that, The wavelength of the ultrafast femtosecond laser is less than or equal to the wavelength corresponding to the band gap of group III nitrides.

3. The laser processing method for group III nitride micro / nano structures according to claim 1, characterized in that, The GaN nanowire array structure is a GaN random nanowire array structure.

4. The laser processing method for group III nitride micro / nano structures according to claim 3, characterized in that, The GaN random nanowire array structure has nanowires with diameters of 50-300 nm, nanowire spacing of less than or equal to 100 nm, and nanowire height of 600-1000 nm.

5. The laser processing method for group III nitride micro / nano structures according to claim 3, characterized in that, The method for preparing the GaN random nanowire array structure is as follows: GaN thin films were epitaxially grown on a substrate using the HVPE process; A metal film is formed on a GaN thin film, and then annealed to form a metal nanosphere mask; GaN thin films are etched using ICP etching to form random GaN nanowires; The residual metal nanosphere mask on the surface of GaN random nanowires was cleaned to obtain the GaN random nanowire array structure.

6. The laser processing method for group III nitride micro / nano structures according to claim 1, characterized in that, Step S2 further includes: All or part of the group III nitride nanowire array structure was irradiated with an ultrafast femtosecond laser.

7. A light-emitting device, characterized in that, The light-emitting device includes a group III nitride micro / nano structure processed by the laser processing method according to any one of claims 1 to 6.

8. The light-emitting device according to claim 7, characterized in that, The light-emitting device is a GaN-based Micro-LED device or a GaN-based Nano-LED device.

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