A method for preparing a metal oxide passivation film on a gallium nitride surface

Abstract

The application discloses a preparation method of a metal oxide passivation film on a gallium nitride surface; the method comprises the following steps: mixing a metal nitrate precursor solution and a hole sacrificial agent to obtain a mixed solution; placing a substrate containing a GaN layer into the mixed solution and performing photochemical deposition under ultraviolet light to obtain a metal oxide passivation film formed on the surface of the GaN layer. The preparation method uses a metal nitrate as a precursor, and under ultraviolet light, photo-generated electrons and holes of the GaN are used to initiate a redox reaction at a solid / liquid interface to form a uniform and dense metal oxide passivation film. The method is simple in process, is performed at room temperature, does not need vacuum, has small interface damage, can be used to reduce the trap state density of the GaN surface, improve the interface stability and reliability of a device, and is suitable for surface / interface passivation treatment of power electronic and ultraviolet photoelectric devices.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a method for preparing a gallium nitride surface metal oxide passivation film. Background Technology

[0002] GaN is a typical wide-bandgap semiconductor material widely used in power electronics and ultraviolet optoelectronic devices. The electrical and optical performance of GaN devices is largely limited by the defect state density at the surface and interface. Unpassivated or insufficiently passivated GaN surfaces contain dangling bonds, defects, and impurity adsorption, which can easily lead to carrier recombination, Fermi level pinning, increased interface leakage current, and increased signal noise, thereby reducing the efficiency and stability of the device.

[0003] To suppress the aforementioned adverse factors, ultrathin (<5 nm) metal oxide passivation films (such as Al2O3, ZrO2, HfO2, SiOx, TiOx, etc.) are commonly used to passivate GaN surfaces. Currently, common GaN surface passivation methods include chemical solution treatment, organic molecule modification, atomic layer deposition (ALD), and magnetron sputtering. However, these methods usually have the following shortcomings: (1) they rely on high vacuum or high-energy equipment, resulting in complex processes and high costs; (2) high-temperature or plasma processes easily introduce interface damage; and (3) some low-density passivation films have insufficient stability, and the passivation effect decays over long-term operation.

[0004] Therefore, it is necessary to develop a new method for preparing metal oxide passivation films on GaN surfaces. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a method for preparing a metal oxide passivation film on a gallium nitride surface. This method utilizes photogenerated carriers generated by GaN under ultraviolet light irradiation to trigger a redox reaction at the solid / liquid interface, realizing the directional transformation and controlled deposition of the metal precursor at the interface, thereby forming a dense, uniform, ultrathin metal oxide passivation film on the GaN surface.

[0006] According to an embodiment of the present invention, a method for preparing a metal oxide passivation film on a gallium nitride surface is provided, comprising the following steps: A metal nitrate precursor solution and a hole sacrificial agent are mixed to obtain a mixture; a substrate containing a GaN layer is placed in the mixture, and photochemical deposition is performed under ultraviolet light to obtain a metal oxide passivation film formed on the surface of the GaN layer.

[0007] According to a preferred embodiment of the present invention, the concentration of metal ions of the metal nitrate precursor in the mixture is 5 × 10⁻⁶. -6 ~1 mol / L. For example, a concentration of 5 × 10⁻⁶-6 mol / L, 5.33×10 -5 mol / L, 5×10 - 4 mol / L, 5×10 -3 0.01 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, or any two of the above values ​​forming a subrange.

[0008] It is understandable that, in order to avoid precipitation of the metal nitrate precursor solution, the solution pH can be adjusted to weakly acidic or neutral to stabilize the metal complex morphology and prevent bulk precipitation.

[0009] According to a preferred embodiment of the present invention, the wavelength of the ultraviolet light source is 200~365nm. For example, it includes 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 280nm, 300nm, 320nm, 340nm, 350nm, 365nm, or any sub-range composed of any two of the above values.

[0010] More preferably, the wavelength of the ultraviolet light source is 300~365nm. For example, it includes 300nm, 310nm, 320nm, 330nm, 340nm, 350nm, 365nm, or any sub-range composed of two of the above values.

[0011] According to a preferred embodiment of the present invention, the optical power density of the ultraviolet light is 1~100 mW / cm². 2 For example, including 1mW / cm 2 10mW / cm 2 20mW / cm 2 30mW / cm 2 40mW / cm 2 50mW / cm 2 60mW / cm 2 70mW / cm 2 80mW / cm 2 90mW / cm 2 100mW / cm 2 Or a subrange consisting of any two of the above values.

[0012] More preferably, the optical power density of the ultraviolet light is 10~50 mW / cm². 2 For example, including 10mW / cm2 15mW / cm 2 20mW / cm 2 25mW / cm 2 30mW / cm 2 35mW / cm 2 40mW / cm 2 45mW / cm 2 50mW / cm 2 Or a subrange consisting of any two of the above values.

[0013] According to a preferred embodiment of the present invention, the ultraviolet light irradiation time is 1 to 60 minutes. For example, it includes 1 minute, 2 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, or any sub-range composed of two of the above values.

[0014] According to a preferred embodiment of the present invention, the ultraviolet light irradiation time is 5 to 20 minutes. For example, it includes 5 minutes, 7 minutes, 10 minutes, 12 minutes, 15 minutes, 18 minutes, 20 minutes, or any sub-range consisting of two of the above values.

[0015] According to a preferred embodiment of the present invention, the hole sacrificial agent includes at least one of methanol, ethanol or acetonitrile.

[0016] According to a preferred embodiment of the present invention, the metal nitrate precursor includes at least one of zirconium nitrate, aluminum nitrate, chromium nitrate, or gallium nitrate.

[0017] According to a preferred embodiment of the present invention, the thickness of the GaN layer is 1~10 μm, and the room temperature carrier concentration is 1×10⁻⁶. 15 ~5×10 17 cm -3 .

[0018] According to a preferred embodiment of the present invention, the thickness of the metal oxide passivation film is 0.5~10 nm. For example, the thickness includes 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or any sub-range composed of any two of the above values.

[0019] According to a preferred embodiment of the present invention, the substrate containing the GaN layer further includes a pretreatment step. The pretreatment step is as follows: The solution was ultrasonically cleaned sequentially with acetone, ethanol, and deionized water, then treated with a mixture of sulfuric acid and hydrogen peroxide solution at room temperature, followed by thorough rinsing with deionized water and drying with nitrogen gas.

[0020] The preparation method according to embodiments of the present invention has at least the following beneficial effects: The preparation method of the present invention uses metal nitrate as a precursor. Under ultraviolet light irradiation, the photogenerated electrons and holes of GaN initiate a redox reaction at the solid / liquid interface to form a uniform and dense metal oxide passivation film.

[0021] Furthermore, the method of the present invention is mild and does not require vacuum: it uses a whole solution system and completes the reaction at room temperature, without the need for high vacuum or plasma equipment, which significantly reduces equipment investment and operating costs.

[0022] Furthermore, it exhibits interface-free operation: avoiding high-temperature and ion / plasma bombardment processes, it significantly reduces additional interface damage defects and deep-level traps, improving interface chemical stability. It can be used to reduce the trap state density on the GaN surface, enhancing device interface stability and reliability, and is suitable for surface / interface passivation treatment of power electronics and ultraviolet optoelectronic devices.

[0023] It is understood that the mechanism of this invention is as follows: Under ultraviolet irradiation, conduction band electrons and valence band holes in GaN are separated in the interfacial reaction region. Photogenerated electrons preferentially reduce the strong oxidizing anion nitrate in the solution, and the resulting OH- ions rapidly complex with metal cations at the interface to form a hydroxyl intermediate. This intermediate undergoes a dehydration reaction to transform into a metal oxide film. Simultaneously, photogenerated holes oxidize alcohol molecules, forming an equilibrium reaction cycle. This solid / liquid interfacial selective reaction enables directional nucleation and controlled growth on the GaN surface, avoiding bulk precipitation and particulate contamination, thereby obtaining an atomically smooth and chemically well-bonded ultrathin metal oxide passivation film.

[0024] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 The diagram shows the process flow and structural schematic of the preparation method of the present invention. Figure 2 XPS characterization of ZrO2 prepared by photodeposition on GaN surface in Example 1 of this invention.

[0026] Figure 3 This is a TEM characterization image of the ZrO2 cross-section prepared by photodeposition on the GaN surface in Example 1 of the present invention.

[0027] Figure 4 The surface photovoltage spectrum (SPV) before and after ZrO2 was prepared by photodeposition on GaN surface in Example 1 of the present invention.

[0028] Figure 5 The light and dark current-voltage curves of the ultraviolet detector before and after ZrO2 photodeposition on the GaN surface are shown in Example 1 of the present invention.

[0029] Figure 6 This is an XPS characterization image of Ga2O3 prepared by photodeposition on the GaN surface in Example 2 of the present invention.

[0030] Figure 7 This is an XPS characterization image of Al2O3 prepared by photodeposition on GaN surface in Example 3 of the present invention. Detailed Implementation

[0031] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0032] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0033] In some embodiments of the present invention, a method for preparing a gallium nitride surface metal oxide passivation film is provided, comprising the following steps: A metal nitrate precursor solution and a hole sacrificial agent are mixed to obtain a mixture; a substrate containing a GaN layer is placed in the mixture, and photochemical deposition is performed under ultraviolet light to obtain a metal oxide passivation film formed on the surface of the GaN layer.

[0034] It is understood that the preparation method of the present invention uses metal nitrate as a precursor, and under ultraviolet light irradiation, utilizes the photogenerated electrons and holes of GaN to initiate a redox reaction at the solid / liquid interface to form a uniform and dense metal oxide passivation film.

[0035] Furthermore, the method of the present invention is mild and does not require vacuum: it uses a whole solution system and completes the reaction at room temperature, without the need for high vacuum or plasma equipment, which significantly reduces equipment investment and operating costs.

[0036] Furthermore, it exhibits interface-free operation: avoiding high-temperature and ion / plasma bombardment processes, it significantly reduces additional interface damage defects and deep-level traps, improving interface chemical stability. It can be used to reduce the trap state density on the GaN surface, enhancing device interface stability and reliability, and is suitable for surface / interface passivation treatment of power electronics and ultraviolet optoelectronic devices.

[0037] It is understood that the mechanism of this invention is as follows: Under ultraviolet irradiation, conduction band electrons and valence band holes in GaN are separated in the interfacial reaction region. Photogenerated electrons preferentially reduce the strong oxidizing anion nitrate in the solution, and the resulting OH- ions rapidly complex with metal cations at the interface to form a hydroxyl intermediate. This intermediate undergoes a dehydration reaction to transform into a metal oxide film. Simultaneously, photogenerated holes oxidize alcohol molecules, forming an equilibrium reaction cycle. This solid / liquid interfacial selective reaction enables directional nucleation and controlled growth on the GaN surface, avoiding bulk precipitation and particulate contamination, thereby obtaining an atomically smooth and chemically well-bonded ultrathin metal oxide passivation film.

[0038] It is understood that the present invention Figure 1 These are process flow diagrams and structural schematic diagrams of the preparation method of the present invention, as shown below. Figure 1 As shown, the sample involved in this invention includes a substrate layer (100), a semiconductor layer (200) (GaN layer), and a metal oxide passivation film (300).

[0039] In some embodiments of the present invention, the concentration of metal ions of the metal nitrate precursor in the mixture is 5 × 10⁻⁶. -6 ~1 mol / L. For example, a concentration of 5 × 10⁻⁶ -6 mol / L, 5.33×10 -5 mol / L, 5×10 -4 mol / L, 5×10 -3 0.01 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, or any two of the above values ​​forming a subrange.

[0040] It is understandable that, in order to avoid precipitation of the metal nitrate precursor solution, the solution pH can be adjusted to weakly acidic or neutral to stabilize the metal complex morphology and prevent bulk precipitation.

[0041] In some embodiments of the present invention, the wavelength of the ultraviolet light source is 200~365nm. For example, it includes 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 280nm, 300nm, 320nm, 340nm, 350nm, 365nm, or any sub-range composed of any two of the above values.

[0042] More preferably, the wavelength of the ultraviolet light source is 300~365nm. For example, it includes 300nm, 310nm, 320nm, 330nm, 340nm, 350nm, 365nm, or any sub-range composed of two of the above values.

[0043] In some embodiments of the present invention, the optical power density of the ultraviolet light is 1~100 mW / cm². 2 For example, including 1mW / cm 2 10mW / cm 2 20mW / cm 2 30mW / cm 2 40mW / cm 2 50mW / cm 2 60mW / cm 2 70mW / cm 2 80mW / cm 2 90mW / cm 2 100mW / cm 2 Or a subrange consisting of any two of the above values.

[0044] More preferably, the optical power density of the ultraviolet light is 10~50 mW / cm². 2 For example, including 10mW / cm 2 15mW / cm 2 20mW / cm 2 25mW / cm 2 30mW / cm 2 35mW / cm 2 40mW / cm 2 45mW / cm 2 50mW / cm 2 Or a subrange consisting of any two of the above values.

[0045] In some embodiments of the present invention, the ultraviolet light irradiation time is 1 to 60 minutes. For example, it includes 1 minute, 2 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, or any sub-range composed of any two of the above values.

[0046] In some embodiments of the present invention, the ultraviolet light irradiation time is 5 to 20 minutes. For example, it includes 5 minutes, 7 minutes, 10 minutes, 12 minutes, 15 minutes, 18 minutes, 20 minutes, or any sub-range consisting of any two of the above values.

[0047] In some embodiments of the present invention, the hole sacrificial agent comprises at least one of methanol, ethanol, or acetonitrile. Thus, its function is to maintain charge balance.

[0048] In some embodiments of the present invention, the metal nitrate precursor includes at least one of zirconium nitrate, aluminum nitrate, chromium nitrate, or gallium nitrate.

[0049] In some embodiments of the present invention, the thickness of the GaN layer is 1~10 μm, and the room temperature carrier concentration is 1×10⁻⁶. 15 ~5×10 17 cm -3 .

[0050] In some embodiments of the present invention, the thickness of the metal oxide passivation film is 0.5 to 10 nm. For example, the thickness includes 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or any subrange consisting of two of the above values.

[0051] In the embodiments and comparative examples of the present invention, the substrate containing the GaN layer (the thickness of the GaN layer is 5 μm, and the room temperature carrier concentration is 1.2 × 10⁻⁶) is used. 17 cm -3 The preprocessing steps are as follows: The sample was ultrasonically cleaned sequentially with acetone, ethanol, and deionized water for 15 minutes each. It was then treated with a mixture of sulfuric acid and hydrogen peroxide solution at room temperature, followed by thorough rinsing with deionized water and drying with nitrogen.

[0052] Example 1 This example provides a method for preparing a zirconium oxide (ZrO2) passivation film, the steps of which are as follows: Weigh 0.43 g of zirconium nitrate (Zr(NO3)4) and dissolve it in 5 mL of deionized water to prepare a 0.2 mol / L zirconium nitrate stock solution; add 60 mL of deionized water and 15 mL of methanol to a beaker, add 20 μL of zirconium nitrate stock solution (zirconium ion concentration of 0.943 mol / L), and stir until clear and homogeneous.

[0053] The pretreated substrate containing the GaN layer was placed in a culture dish with the GaN film side facing up. A 365 nm ultraviolet lamp (optical density of 32 mW / cm²) was then used. 2 Place it at a distance of about 6 cm from the mixed solution and irradiate for 60 minutes.

[0054] After deposition, the sample was thoroughly rinsed with deionized water and dried with nitrogen to obtain a zirconia passivation film.

[0055] The obtained zirconia passivation film was first subjected to XPS and cross-sectional TEM tests, and the results are as follows:Figure 2 and Figure 3 As shown, the obtained film is ZrO2, with a thickness of approximately 3 nm. The interface is smooth, continuous, and free of obvious defects. XPS spectroscopy reveals typical Zr-O chemical coordination, and no Zr-N characteristic peaks were detected, indicating that no nitrides were formed during the deposition process.

[0056] Furthermore, surface photovoltage spectroscopy (SPV) tests were performed on the GaN layer substrate before and after photodepositing to prepare a zirconia passivation film. The results are as follows: Figure 4 As shown, after photodeposition of ZrO2, GaN exhibits a significant increase in surface velocity (SPV) in the short wavelength range, with a sharper peak at approximately 350 nm, while the untreated sample shows a lower SPV and rapid decay. In the 500-600 nm range, the untreated sample shows a defect-related peak at approximately 570 nm, which disappears after photodeposition. These phenomena indicate that ZrO2 effectively passivates surface defects / traps, reduces surface recombination, and enhances carrier separation, thereby increasing the SPV induced by intrinsic interband excitation and suppressing the defect-state-related subbandgap response.

[0057] Furthermore, dark current-voltage curve tests were performed on the GaN layer substrate with a zirconia passivation film photodeposited in Example 1 of the present invention and the GaN layer substrate. The results are as follows: Figure 5 As shown, it is evident that the dark current is suppressed and the photocurrent is increased after photodeposition of ZrO2. At 4 V, the light / dark on / off ratio is 2.13 × 10⁻⁶ compared to the undeposited ZrO2. 3 Upgraded to 6.00×10 6 After passivation, the device performance is greatly improved.

[0058] Example 2 This example provides a method for preparing a gallium oxide (Ga2O3) passivation film, the steps of which are as follows: Weigh 0.40 g of gallium nitrate (Ga(NO3)3) and dissolve it in 5 mL of deionized water to prepare a 0.2 mol / L gallium nitrate stock solution. Mix 60 mL of deionized water with 15 mL of methanol, and add 20 μL of the stock solution (gallium ion concentration of 5.33 × 10⁻⁶). 5 (mol / L), stir until homogeneous.

[0059] Photochemical deposition was performed under the same process conditions as in Example 1, i.e., 365 nm ultraviolet light (32 mW / cm²). 2 Irradiate the liquid with the light source about 6 cm above the liquid surface for 60 minutes.

[0060] After deposition, the film was rinsed with deionized water and dried with nitrogen to obtain a gallium oxide passivation film.

[0061] XPS tests were performed on the obtained gallium oxide passivation film, and the results are as follows:Figure 6 As shown, XPS analysis indicates that the deposited film is Ga2O3 with obvious Ga-O chemical coordination, indicating that a uniform and stable gallium oxide passivation layer was successfully formed on the GaN surface.

[0062] Example 3 This example provides a photochemical deposition method for preparing an alumina (Al2O3) passivation film, the steps of which are as follows: Weigh 0.37 g of aluminum nitrate (Al(NO3)3) and dissolve it in 5 mL of deionized water to prepare a 0.2 mol / L aluminum nitrate stock solution. Mix 60 mL of deionized water with 15 mL of methanol, and add 20 μL of the stock solution (aluminum ion concentration of 5.33 × 10⁻⁶). 5 (mol / L), stir until the solution is clear and homogeneous.

[0063] Photochemical deposition was performed under the same conditions as in Example 1 (365 nm, light source approximately 6 cm from the liquid surface, illumination for 60 minutes).

[0064] After deposition, the film was washed with deionized water and dried with nitrogen to obtain an alumina passivation film.

[0065] XPS testing was performed on the obtained alumina passivation film, and the results are as follows: Figure 7 As shown, XPS test results indicate that the deposited film is Al2O3, with obvious Al-O coordination peaks, and the surface passivation layer has uniform thickness and strong adhesion, indicating that this method can achieve stable alumina coverage on the GaN surface.

[0066] The present invention has been described in detail above with reference to the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing a metal oxide passivation film on a gallium nitride surface, characterized in that, Includes the following steps: A metal nitrate precursor solution and a hole sacrificial agent are mixed to obtain a mixture; a substrate containing a GaN layer is placed in the mixture, and photochemical deposition is performed under ultraviolet light to obtain a metal oxide passivation film formed on the surface of the GaN layer.

2. The preparation method according to claim 1, characterized in that, In the mixture, the concentration of metal ions in the metal nitrate precursor is 5 × 10⁻⁶. -6 ~1mol / L.

3. The preparation method according to claim 1, characterized in that, The wavelength of the ultraviolet light source is 200~365nm.

4. The preparation method according to claim 1, characterized in that, The optical power density of the ultraviolet light is 1~100mW / cm². 2 .

5. The preparation method according to claim 1, characterized in that, The duration of ultraviolet light irradiation is 1 to 60 minutes.

6. The preparation method according to claim 1 or 5, characterized in that, The duration of ultraviolet light irradiation is 5 to 20 minutes.

7. The preparation method according to claim 1, characterized in that, The hole sacrificial agent includes at least one of methanol, ethanol, or acetonitrile.

8. The preparation method according to claim 1, characterized in that, The metal nitrate precursor includes at least one of zirconium nitrate, aluminum nitrate, chromium nitrate, or gallium nitrate.

9. The preparation method according to claim 1, characterized in that, The GaN layer has a thickness of 1~10 μm and a room temperature carrier concentration of 1×10⁻⁶. 15 ~5×10 17 cm -3 .

10. The preparation method according to claim 1, characterized in that, The thickness of the metal oxide passivation film is 0.5~10 nm.

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