Preparation method of Eu-doped single crystal β-gallium oxide thin film with distributed Bragg reflector

Abstract

The present invention discloses a method for preparing a Eu-doped single-crystal β-gallium oxide film with a distributed Bragg reflector. The method comprises growing a GaN buffer layer and an n-GaN / u-GaN periodic structure on a substrate using metal organic chemical vapor deposition technology, and then etching the n-GaN / u-GaN periodic structure in a solution to prepare a nanoporous GaN distributed Bragg reflector. The nanoporous GaN distributed Bragg reflector is used as a substrate, and a Eu-doped gallium oxide film is grown using a pulsed laser deposition technology to prepare a Eu-doped gallium oxide film with a distributed Bragg reflector. The gallium oxide film is converted into a single-crystal β-gallium oxide film with different Eu doping levels using an annealing technique. The preparation method of the present invention can produce a single-crystal β-gallium oxide film with stress relaxation, high crystal quality, strong heat dissipation capability, large area, high luminous efficiency, and adjustable Eu concentration.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor optoelectronic materials, and in particular relates to a method for preparing a Eu-doped single crystal beta-gallium oxide thin film with a distributed Bragg reflector. Background Art

[0002] Rare earth ions and semiconductor crystals are important luminescent materials. In recent years, the use of rare earth elements such as Eu to dope β-gallium oxide (GaO) for the fabrication of optoelectronic devices such as light-emitting diodes (LEDs), lasers, and detectors has garnered widespread attention. β-GaO thin films offer advantages such as wide bandgap, high thermal conductivity, and chemical stability, making them ideal hosts for rare earth ions. Generally speaking, dopants can not only effectively modulate the photophysical behavior of wide-bandgap semiconductor materials but also improve their luminescence efficiency, electrical conductivity, and carrier mobility. However, β-GaO thin films suffer from high stress, high defect density, and low light extraction efficiency, resulting in low luminescence efficiency. To improve the luminescence efficiency of Eu-doped β-GaO thin films, the gallium oxide film can be grown on a nanoporous film. Various substrate structures have been explored, but even when exfoliation is achieved, the luminescence efficiency remains low due to high stress, high defect density, and low light extraction efficiency. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing a Eu-doped single-crystal β-gallium oxide film with a distributed Bragg reflector, which solves the key common problems of gallium oxide films in the prior art, such as high stress, poor crystal quality, and low luminous efficiency.

[0004] The technical solution adopted by the present invention is a method for preparing a Eu-doped single-crystalline β-gallium oxide thin film with a distributed Bragg reflector, which is specifically implemented according to the following steps:

[0005] Step 1: Growing a GaN buffer layer and an n-GaN / u-GaN periodic structure on a substrate using metal organic chemical vapor deposition technology, and etching the n-GaN / u-GaN periodic structure in a solution to prepare a nanoporous GaN distributed Bragg reflector;

[0006] Step 2: Using the nanoporous GaN distributed Bragg reflector as a new substrate, a Eu-doped gallium oxide thin film is grown by pulsed laser deposition technology to prepare a Eu-doped gallium oxide thin film with a nanoporous GaN distributed Bragg reflector;

[0007] Step 3: setting annealing process parameters to transform the Eu-doped gallium oxide thin film with the nanoporous GaN distributed Bragg reflector into a Eu-doped single crystal β-gallium oxide thin film.

[0008] The present invention is also characterized in that:

[0009] In step 1, the substrate is any one of C-plane sapphire, silicon carbide and quartz.

[0010] In step 1, the n-GaN / u-GaN periodic structure includes an undoped GaN layer, i.e., u-GaN, and a doped GaN layer, i.e., n-GaN. The thickness of the u-GaN layer is 30-70 nm, the thickness of the n-GaN layer is 75-125 nm, and the doping concentration is 3.2×10 18 -3.8×10 19 cm -3 , the number of cycles is 7-18.

[0011] The solution in step 1 is any one of aqueous solutions of oxalic acid, sulfuric acid, and nitric acid with a concentration in the range of 0.25-0.45 mol / ·L.

[0012] In step 1, the etching voltage for etching the n-GaN / u-GaN periodic structure is 7-48 V, and the etching time ranges from 7 to 70 minutes.

[0013] The specific process of step 2 is as follows: using a nanoporous GaN distributed Bragg reflector as a new substrate, using a 248nm KrF excimer laser, setting the frequency range to 1-5Hz, the energy range to 200-600mJ, the growth temperature to 450-850℃, the growth time to 30min-400min, and the volume ratio of Eu in the target material to 0-6%, to obtain a film with a growth thickness of 60-400nm, that is, a Eu-doped gallium oxide film with a nanoporous GaN distributed Bragg reflector.

[0014] In step 3, the annealing process parameters are set as follows: annealing temperature is 800-1100° C., annealing time is 10-120 min, and annealing atmosphere is any one of air, nitrogen, oxygen, and a mixture of nitrogen and oxygen.

[0015] The beneficial effects of the present invention are:

[0016] 1) Nanoporous GaN distributed Bragg reflectors (DBRs) have a unique mesoporous structure, high light reflection effect, large stress relaxation, and low defect density. Using them as substrates, the gallium oxide films grown exhibit large stress relaxation and high crystal quality, which is expected to significantly improve the luminous efficiency, service life, and heat dissipation capacity of gallium oxide films.

[0017] 2) The annealing temperature of the gallium oxide film can affect its light reflectivity, crystal form, and crystal quality. When the annealing temperature of the gallium oxide film is between 800-1100°C, the nanoporous GaN DBR maintains a high reflectivity and the crystal quality of the film is significantly improved, which is conducive to improving the luminous efficiency of the DBR-based gallium oxide film.

[0018] 3) The process conditions in the present invention are easy to precisely control, and the prepared Eu-doped single-crystalline β-gallium oxide thin film with distributed Bragg reflectors has good uniformity and repeatability, which is convenient for industrial production. In addition, it also has excellent characteristics such as continuously adjustable doping concentration, high stability, long service life, high luminous efficiency and strong heat dissipation capacity, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a scanning electron microscope image of a cross section of the nanoporous GaN DBR prepared in Example 1, where the scale bar is 1 μm;

[0020] Figure 2 is the reflection spectrum of the n-GaN / u-GaN periodic structure and nanoporous GaN DBR prepared in Example 1;

[0021] Figure 3 1 is the EDS spectrum of the single crystal β-gallium oxide thin films with different Eu doping and distributed Bragg reflectors prepared in Example 1;

[0022] Figure 4 1 is an XRD pattern of the single crystal β-gallium oxide thin films with different Eu doping and distributed Bragg reflectors prepared in Example 1;

[0023] Figure 5 is a Raman image of a single crystal β-gallium oxide thin film with different Eu doping and a distributed Bragg reflector prepared in Example 1;

[0024] Figure 6 is a photoluminescence image of a single crystal β-gallium oxide thin film with a distributed Bragg reflector and different Eu doping prepared in Example 1;

[0025] Figure 7 This is a surface SEM image of a single-crystalline β-gallium oxide thin film with a Eu doping concentration of 4 wt% and a distributed Bragg reflector prepared in Example 1, where the scale bar is 500 nm;

[0026] Figure 8 This is a cross-sectional SEM image of a single-crystalline β-gallium oxide thin film with a Eu doping concentration of 4 wt% and a distributed Bragg reflector prepared in Example 1, where the scale bar is 500 nm;

[0027] Figure 9 is the XRD pattern of the control single crystal β-gallium oxide film and the single crystal β-gallium oxide film with distributed Bragg reflector;

[0028] Figure 10 is the half-height width of the Ga2O3(-201) XRD rocking curves of the control single crystal β-gallium oxide film and the single crystal β-gallium oxide film with a distributed Bragg reflector;

[0029] Figure 11 1 is a photoluminescence image of a control single crystal β-gallium oxide thin film and a single crystal β-gallium oxide thin film with a distributed Bragg reflector. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] The preparation method of the Eu-doped single crystal β-gallium oxide thin film having a distributed Bragg reflector of the present invention is specifically implemented according to the following steps:

[0032] Step 1: Growing a GaN buffer layer and an n-GaN / u-GaN periodic structure on a substrate using metal organic chemical vapor deposition technology, and etching the n-GaN / u-GaN periodic structure in a solution to prepare a nanoporous GaN distributed Bragg reflector;

[0033] The substrate is any one of C-plane sapphire, silicon carbide and quartz.

[0034] The n-GaN / u-GaN periodic structure includes an undoped GaN layer, i.e., u-GaN, and a doped GaN layer, i.e., n-GaN. The thickness of the u-GaN layer is 30-70 nm, the thickness of the n-GaN layer is 75-125 nm, and the doping concentration is

[0035] 3.2×10 18 -3.8×10 19 cm -3 , the number of cycles is 7-18.

[0036] The solution is any one of aqueous solutions of oxalic acid, sulfuric acid, and nitric acid with a concentration within the range of 0.25-0.45 mol / ·L.

[0037] The etching voltage for etching the n-GaN / u-GaN periodic structure is 7-48V, and the etching time ranges from 7 to 70 minutes.

[0038] Step 2: Using the nanoporous GaN distributed Bragg reflector as a new substrate, a pulsed laser deposition technology is used to grow a Eu-doped gallium oxide thin film to prepare a Eu-doped gallium oxide thin film with a nanoporous GaN distributed Bragg reflector. The specific process is as follows: using the nanoporous GaN distributed Bragg reflector as a new substrate, using a 248nm KrF excimer laser, setting the frequency range to 1-5Hz, the energy range to 200-600mJ, the growth temperature to 450-850°C, the growth time to 30min-400min, and the volume ratio of Eu in the target material to 0-6%, to obtain a thin film with a growth thickness of 60-400nm, that is, a Eu-doped gallium oxide thin film with a nanoporous GaN distributed Bragg reflector.

[0039] Step 3: Set the annealing process parameters to: annealing temperature of 800-1100°C, annealing time of 10-120 minutes, and annealing atmosphere of air, nitrogen, oxygen, or a mixture of nitrogen and oxygen. The Eu-doped gallium oxide film with the nanoporous GaN distributed Bragg reflector is converted into a Eu-doped single-crystalline β-gallium oxide film.

[0040] Example 1

[0041] The present invention provides a method for preparing a Eu-doped single crystal β-gallium oxide thin film having a distributed Bragg reflector, which is specifically implemented according to the following steps:

[0042] Step 1: A GaN buffer layer and a 10-periodic n-GaN / u-GaN periodic structure are grown on a C-plane sapphire substrate using metal organic chemical vapor deposition technology, where the n-GaN is Si-doped with a doping concentration of 1×10 19 cm -3 The thickness of the n-GaN and u-GaN layers was 100nm and 50nm, respectively. Subsequently, the layers were etched in a 0.3mol / L HNO3 solution at a constant voltage of 15V for 15 minutes, using the n-GaN / u-GaN periodic structure as the anode. After etching, the instrument was turned off, the sample removed, and immersed in deionized water for 6 minutes before being dried with nitrogen to create a nanoporous GaN DBR.

[0043] Step 2: Using the nanoporous GaN distributed Bragg reflector as a new substrate, pulsed laser deposition was used to grow gallium oxide films with varying Eu doping concentrations, producing gallium oxide films with Eu doping concentrations similar to those of the nanoporous GaN distributed Bragg reflector. The laser used was a 248nm KrF excimer laser with a frequency of 2Hz, an energy of 500mJ, a growth temperature of 700°C, and a growth time of 90min. The volume ratios of Eu in the five gallium oxide targets were 0wt%, 1wt%, 2wt%, 3wt%, and 4wt%, respectively, and the grown films had a thickness of 85nm.

[0044] Step 3: Using annealing technology, the gallium oxide films with different Eu doping levels are transformed into single-crystalline β-gallium oxide films with different Eu doping levels. The annealing temperature is 850° C., the annealing time is 30 minutes, and the annealing atmosphere is air.

[0045] Example 2

[0046] The preparation method of the Eu-doped single crystal β-gallium oxide thin film having a distributed Bragg reflector of the present invention is specifically implemented according to the following steps:

[0047] Step 1: A GaN buffer layer and a 7-periodic n-GaN / u-GaN periodic structure are grown on a silicon carbide substrate using metal organic chemical vapor deposition technology, where the n-GaN is Si-doped with a doping concentration of 8×10 18 cm -3 The thickness of the n-GaN and u-GaN layers was 80nm and 45nm, respectively. Subsequently, the nanoporous GaN DBR was fabricated in a 0.25mol / L HNO3 solution, using the n-GaN / u-GaN periodic structure as the anode at a constant voltage of 13V for 18 minutes. After etching, the instrument was turned off, the sample removed, and immersed in deionized water for 6 minutes before being dried with nitrogen.

[0048] Step 2: Using the nanoporous GaN distributed Bragg reflector as a new substrate, pulsed laser deposition was used to grow gallium oxide thin films with varying Eu doping concentrations, thereby preparing Eu-doped gallium oxide thin films with nanoporous GaN distributed Bragg reflectors. The laser used was a 248nm KrF excimer laser with a frequency of 1Hz, an energy of 400mJ, a growth temperature of 600°C, and a growth time of 90min. The volume ratios of Eu in the five gallium oxide targets were 0wt%, 1wt%, 2wt%, 3wt%, and 4wt%, respectively.

[0049] Step 3: Using annealing technology, the gallium oxide film is transformed into a single-crystal β-gallium oxide film doped with different Eu. The annealing temperature is 800° C., the annealing time is 30 minutes, and the annealing atmosphere is oxygen.

[0050] Example 3

[0051] The present invention provides a method for preparing a Eu-doped single crystal β-gallium oxide thin film having a distributed Bragg reflector, which is specifically implemented according to the following steps:

[0052] Step 1: A GaN buffer layer and a 14-periodic n-GaN / u-GaN periodic structure are grown on a quartz substrate using metal organic chemical vapor deposition technology, where the n-GaN is doped with Si at a doping concentration of 2×10 19 cm -3 The thickness of the n-GaN and u-GaN layers was 120nm and 60nm, respectively. Subsequently, the nanoporous GaN DBR was fabricated in a 0.4mol / L HNO3 solution, using the n-GaN / u-GaN periodic structure as the anode at a constant voltage of 17V for 12 minutes. After etching, the instrument was turned off, the sample was removed, and the etched sample was immersed in deionized water for 6 minutes before being dried with nitrogen.

[0053] Step 2: Using five nanoporous GaN distributed Bragg reflectors as substrates, pulsed laser deposition was used to grow gallium oxide thin films with varying Eu doping concentrations, thereby preparing Eu-doped gallium oxide thin films with nanoporous GaN distributed Bragg reflectors. The laser used was a 248 nm KrF excimer laser with a frequency of 3 Hz, an energy of 600 mJ, a growth temperature of 800°C, and a growth time of 90 minutes. The volume ratios of Eu in the five gallium oxide targets were 0 wt%, 1 wt%, 2 wt%, 3 wt%, and 4 wt%, respectively.

[0054] Step 3: Using annealing technology, the gallium oxide film is transformed into a single-crystal β-gallium oxide film doped with different Eu. The annealing temperature is 900° C., the annealing time is 30 minutes, and the annealing atmosphere is a mixture of nitrogen and oxygen.

[0055] Comparative Example 1

[0056] A GaN buffer layer, an n-GaN / u-GaN periodic structure, and a Eu-doped gallium oxide thin film were grown on a C-plane sapphire substrate using the method of step 1 in Example 1. Single crystal β-gallium oxide thin films with different Eu doping levels were prepared using exactly the same process conditions as step 3 in Example 1.

[0057] Comparing Example 1 with Comparative Example 1, the LED prepared in Example 1 has a luminous efficiency increased by 2-10 times, a stability increased by more than 1.6 times, and a smooth surface compared to the single crystal β-gallium oxide thin film obtained in Comparative Example 1.

[0058] Comparative Example 2

[0059] The preparation method is the same as that of Example 1, except that the etching voltage is increased from 15V to 30V.

[0060] The surface of the Eu-doped single-crystal β-gallium oxide film with distributed Bragg reflectors exhibited obvious peeling and became uneven.

[0061] Comparing Example 2 with Comparative Example 2, the LED prepared in Example 2 has a luminous efficiency increased by 2-10 times, a stability increased by more than 1.6 times, and a smooth surface compared to the Eu-doped single crystal β-gallium oxide thin film with a distributed Bragg reflector obtained in Comparative Example 2.

[0062] Comparative Example 3

[0063] The preparation method is the same as that of Example 1, except that the annealing temperature of the gallium oxide film in step 3 is 1100° C. Although the surface of the prepared LED is flat and smooth, the surface color becomes black and metallic gallium is precipitated.

[0064] Comparing Example 3 with Comparative Example 3, the LED prepared in Example 3 has a luminous efficiency increased by 2-10 times, a stability increased by more than 1.6 times, and a smooth surface compared to the Eu-doped single crystal β-gallium oxide thin film with a distributed Bragg reflector obtained in Comparative Example 3.

[0065] Figure 1 This is a SEM photograph of a cross section of the nanoporous GaN DBR prepared in Example 1, with a period number of 10. Figure 2 This is the reflection spectrum of the n-GaN / u-GaN periodic structure and nanoporous GaN DBR prepared in Example 1. The reflectivity of the nanoporous GaN DBR is significantly improved, and the reflectivity between 530nm and 650nm exceeds 99%. Figure 3 The EDS spectrum of the single crystal β-gallium oxide thin film with different Eu doping and distributed Bragg reflectors prepared in Example 1 shows peaks of Ga, O, and Eu. In addition, the peak value of Eu increases with the increase of Eu doping concentration. Figure 4 and Figure 5 The XRD patterns and Raman patterns are respectively of the single crystal β-gallium oxide thin films with different Eu doping and distributed Bragg reflectors prepared in Example 1, which confirm that the prepared films are all single crystal β-gallium oxide thin films with (-201) crystal plane, and the films exhibit stress relaxation. Figure 6 This is the photoluminescence image of the single crystal β-gallium oxide thin film with different Eu doping and distributed Bragg reflectors prepared in Example 1. The strongest peak appears at 610 nm, which is related to Eu ions.

[0066] The Eu-doped single-crystalline β-gallium oxide film with distributed Bragg reflectors prepared in Example 1 has the following characteristics compared to the single-crystalline β-gallium oxide film obtained in Comparative Example 1: Surface and cross-sectional SEM images of the single-crystalline β-gallium oxide film with a Eu doping concentration of 4 wt% and distributed Bragg reflectors prepared in Example 1 Figure 7 and Figure 8 As shown, the scale bar is 500nm. Figure 7 It can be seen that the grain size of single crystal β-gallium oxide is 99nm; according to Figure 8 It can be seen that the nanoporous GaN DBR of the single crystal β-gallium oxide thin film prepared in the present invention has good integrity. Figure 9 1 is an XRD pattern of a control single crystal β-gallium oxide thin film and a single crystal β-gallium oxide thin film with a distributed Bragg reflector. Both Example 1 and Comparative Example 1 are single crystal β-gallium oxide thin films with a (-201) crystal plane. Figure 10 It is the half-height width of the Ga2O3(-201) XRD rocking curve of the control single crystal β-gallium oxide film and the single crystal β-gallium oxide film with a distributed Bragg reflector. Compared with comparative example 1, its line width is significantly reduced, indicating that its crystal quality is significantly improved. Figure 11 These are photoluminescence images of two single-crystal β-gallium oxide thin films. Compared with the film obtained in Comparative Example 1, the luminescence peak is significantly increased.

[0067] The nanoporous GaN DBR prepared by the preparation method of Eu-doped single crystal β-gallium oxide film with distributed Bragg reflector in the above manner has unique high light reflection ability, stress relaxation and high crystal quality. With it as the substrate, the grown gallium oxide film shows stress relaxation and low defect density, which is expected to significantly improve the luminous efficiency, service life and heat dissipation capacity of the Eu-doped gallium oxide film; the annealing temperature of the Eu-doped gallium oxide film can affect the light reflection effect of the nanoporous GaN DBR and the crystal quality of the gallium oxide film; when the annealing temperature of the gallium oxide film is between 800-1100°C, the nanoporous GaN DBR has a high reflectivity and significantly reduces the defect density of the film, which is beneficial to improving the luminous efficiency of the single-crystal β-gallium oxide film. The process conditions in the present invention are easy to accurately control, and the prepared Eu-doped single-crystal β-gallium oxide film with a distributed Bragg reflector has good uniformity and repeatability, which is convenient for industrial production. The prepared Eu-doped single-crystal β-gallium oxide film with a distributed Bragg reflector also has excellent characteristics such as high stability, high luminous efficiency, long service life and strong heat dissipation capability, and has broad application prospects.

Claims

1. A method for preparing a Eu-doped single-crystal β-gallium oxide thin film having a distributed Bragg reflector, characterized in that: Please follow the steps below to implement it: Step 1: Growing a GaN buffer layer and an n-GaN / u-GaN periodic structure on a substrate using metal organic chemical vapor deposition technology, and etching the n-GaN / u-GaN periodic structure in a solution to prepare a nanoporous GaN distributed Bragg reflector; Step 2: Using the nanoporous GaN distributed Bragg reflector as a new substrate, a Eu-doped gallium oxide thin film is grown by pulsed laser deposition technology to prepare a Eu-doped gallium oxide thin film with a nanoporous GaN distributed Bragg reflector; Step 3: setting annealing process parameters to transform the Eu-doped gallium oxide film with the nanoporous GaN distributed Bragg reflector into a Eu-doped single crystal β-gallium oxide film; The n-GaN / u-GaN periodic structure in step 1 includes an undoped GaN layer, i.e., u-GaN, and a doped GaN layer, i.e., n-GaN. The thickness of the u-GaN layer is 30-70 nm, the thickness of the n-GaN layer is 75-125 nm, and the doping concentration is 3.2×10 18 -3.8×10 19 cm -3 , the number of cycles is 7-18; The specific process of step 2 is as follows: using a nanoporous GaN distributed Bragg reflector as a new substrate, using a 248nm KrF excimer laser, setting the frequency range to 1-5Hz, the energy range to 200-600mJ, the growth temperature to 450-850°C, the growth time to 30min-400min, and the volume ratio of Eu in the target material to 0-6%, to obtain a film with a thickness of 60-400nm, i.e., a Eu-doped gallium oxide film with a nanoporous GaN distributed Bragg reflector; The annealing process parameters set in step 3 are: annealing temperature is 850-1100° C., annealing time is 10-120 min, and annealing atmosphere is any one of air, nitrogen, and a mixture of nitrogen and oxygen; The solution in step 1 is any one of aqueous solutions of oxalic acid, sulfuric acid, and nitric acid with a concentration in the range of 0.25-0.45 mol / ·L.

2. The method for preparing a Eu-doped single crystal β-gallium oxide thin film having a distributed Bragg reflector according to claim 1, characterized in that: The substrate in step 1 is any one of silicon carbide and quartz.

3. The method for preparing a Eu-doped single crystal β-gallium oxide thin film having a distributed Bragg reflector according to claim 1, characterized in that: The etching voltage for etching the n-GaN / u-GaN periodic structure in step 1 is 7-48 V, and the etching time ranges from 7 to 70 minutes.

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