Silicon-doped gallium oxide conductive electrode suitable for gallium nitride-based deep ultraviolet photoelectric device and preparation method of silicon-doped gallium oxide conductive electrode

Abstract

The invention discloses a silicon-doped gallium oxide conductive electrode suitable for a gallium nitride-based deep ultraviolet photoelectric device and a preparation method of the silicon-doped gallium oxide conductive electrode. Excellent ohmic contact is formed between the silicon-doped gallium oxide epitaxial layer of the silicon-doped gallium oxide conductive electrode and the n-type gallium nitride substrate, the interface contact resistance is low, the transmittance of a deep ultraviolet band (280-400 nm) can reach 85%, the requirement of a gallium nitride-based deep ultraviolet photoelectric device on a transparent electrode can be met, and the transparent electrode has a wide application prospect. The problem of low device quantum efficiency caused by serious absorption of a traditional ITO electrode in a deep ultraviolet region is solved.

Description

Technical Field

[0001] This invention belongs to the field of transparent oxide semiconductor materials, specifically relating to a silicon-doped gallium oxide conductive electrode suitable for gallium nitride-based deep ultraviolet optoelectronic devices and its preparation method. Background Technology

[0002] Gallium nitride (GaN)-based optoelectronic devices offer advantages such as low operating voltage, tunable wavelength, and ease of integration, playing a crucial role in disinfection, water purification, skin disease treatment, and optical communication systems. With the development of optoelectronic information technology and ultraviolet optoelectronics, the development of GaN-based ultraviolet light-emitting diodes (UV-LEDs) and solar-blind ultraviolet photodetectors (SBPDs) has made continuous progress, not only promoting the development of the LED industry but also extending the emission wavelength to the deep ultraviolet band (200-300 nm). Transparent conductive oxides, due to their high transmittance and low resistance, are often used as transparent electrodes in optoelectronic devices and have attracted widespread attention. As one of the core components of deep ultraviolet optoelectronic devices, transparent electrodes need to possess both excellent interfacial ohmic contacts for injecting or collecting charge carriers and high deep ultraviolet light transmittance. Their optical transmittance directly affects the light extraction efficiency of the device and is a key factor limiting the overall efficiency (such as external quantum efficiency) of deep ultraviolet optoelectronic devices.

[0003] However, the external quantum efficiency of existing deep ultraviolet (DUV) optoelectronic devices remains extremely low (< 1%), primarily due to the widely used transparent electrode material—ITO (Sn-doped In₂O₃). ITO's band gap is below 4.0 eV, resulting in extremely low transparency in the ultraviolet region (especially the deep UV band), with a transmittance of only 10% at 280 nm. This property severely restricts the development of gallium nitride (GaN) DUV optoelectronic devices. Furthermore, the reserves of indium raw materials are decreasing year by year, and prices are continuously rising. Coupled with my country's heavy reliance on imported ITO targets, this further exacerbates the risk to material supply. Therefore, developing novel transparent electrode materials that combine high deep UV transparency with low resistance has become an urgent direction to meet the needs of next-generation DUV optoelectronic devices. Summary of the Invention

[0004] The purpose of this invention is to provide a silicon-doped gallium oxide conductive electrode suitable for gallium nitride-based deep ultraviolet optoelectronic devices and its preparation method. The prepared conductive electrode has low contact resistance and high transparency in the deep ultraviolet band, which can meet the requirements of gallium nitride-based deep ultraviolet optoelectronic devices for transparent electrodes.

[0005] The technical solution of the present invention is as follows:

[0006] A method for fabricating a gallium oxide-doped silicon conductive electrode suitable for gallium nitride-based deep ultraviolet optoelectronic devices includes the following steps:

[0007] (1) The n-type gallium nitride (n-GaN) substrate is etched with buffered oxide etchant to make its surface roughness less than 0.5 nm;

[0008] (2) A mask is applied to the etched n-type gallium nitride substrate, and a silicon-doped gallium oxide target is used to perform vapor deposition on the n-type gallium nitride substrate to generate a silicon-doped gallium oxide epitaxial layer;

[0009] The concentration of Si doping in the silicon-doped gallium oxide target is 0.01~5 mol%, and the thickness of the silicon-doped gallium oxide epitaxial layer is 0.03~0.25 μm.

[0010] (3) Perform in-situ high-temperature high-vacuum annealing to obtain silicon-doped gallium oxide electrode substrate;

[0011] The pressure for in-situ high-temperature high-vacuum annealing is 10. -5 Pa, the temperature of in-situ high temperature high vacuum annealing is 500~800℃, and the time of in-situ high temperature high vacuum annealing is 10~30min;

[0012] (4) Photolithography and development of the preset electrode pattern are performed on the silicon-doped gallium oxide electrode substrate, and then an electron beam evaporation metal electrode layer is deposited on the electrode pattern to obtain a silicon-doped gallium oxide conductive electrode.

[0013] Optionally, the concentration of Si doping in the silicon-doped gallium oxide target is 0.1~1 mol.

[0014] Optionally, the preparation method of silicon-doped gallium oxide target is as follows: high-purity SiO2 and Ga2O3 powders are mixed and pressed into sheets under a pressure of 5~15MPa, and then calcined at 1250~1450℃ for 12~36h to obtain the target.

[0015] Optionally, the heating rate of calcination is 5~20℃ / min, and the cooling rate is 3~5℃ / min.

[0016] Optionally, the n-type gallium nitride substrate includes a sapphire base substrate and an undoped n-type gallium nitride layer grown on the sapphire base substrate, the thickness of the undoped n-type gallium nitride layer being 4~6 μm; the n-type gallium nitride substrate is pre-cleaned by ultrasonic cleaning in acetone, isopropanol and deionized water for 1~5 min, and then etched by the buffer oxide etchant; a silicon-doped gallium oxide epitaxial layer is grown on the surface of the undoped n-type gallium nitride layer.

[0017] Optionally, the buffer oxide etching solution includes HF and NH4F in a volume ratio of 1:10~20, and the etching time is 30s~5min.

[0018] Optionally, the vapor deposition employs pulsed laser deposition (PLD) technology, wherein the deposition temperature of PLD is 500–700 °C, the oxygen partial pressure in the growth atmosphere is 0.5–10 Pa, and the laser energy density is 1.2–2 J / cm³. 2 The pulse number of pulses in pulsed laser deposition technology is 3,000 to 30,000, and the pulse frequency is 2 to 6 Hz. In other alternative embodiments, vapor deposition can also be achieved using radio frequency magnetron sputtering (RFMS), molecular beam epitaxy (MBE), or metal-organic chemical vapor deposition (MOCVD).

[0019] Optionally, the electrode pattern consists of several parallel rectangles, wherein the width of the rectangle is 400~700 μm, the length of the rectangle is 2~4.5 mm, and the distance between two adjacent rectangles is 500~1800 μm.

[0020] Optionally, the metal electrode layer is a titanium layer and / or a gold layer, and the background vacuum of the electron beam evaporation growth chamber is 10. -8 ~10 -6 Pa, the thickness of the titanium layer is 5~50 nm, and the thickness of the gold layer is 50~100 nm.

[0021] A silicon-doped gallium oxide conductive electrode suitable for gallium nitride-based deep ultraviolet optoelectronic devices is prepared by the above-described method.

[0022] The present invention has at least the following beneficial effects:

[0023] (1) This invention discloses a method for fabricating a silicon-doped gallium oxide conductive electrode suitable for gallium nitride-based deep ultraviolet optoelectronic devices. Using this method, a silicon-doped gallium oxide epitaxial layer with high crystallinity can be obtained on an n-type gallium nitride substrate. The obtained silicon-doped gallium oxide epitaxial layer forms a good ohmic contact with the n-type gallium nitride substrate, with a contact resistance of only 1.41 Ω and a specific contact resistivity as low as 1.96 × 10⁻⁶. -4 Ω·cm 2 It has an average transmittance of up to 92% in the visible to near-infrared band (400~1200nm) and up to 85% in the deep ultraviolet band (280~400 nm), which can meet the requirements of gallium nitride-based deep ultraviolet optoelectronic devices for transparent electrodes.

[0024] (2) This invention promotes atomic rearrangement within the gallium oxide-doped silicon epitaxial layer by in-situ high-temperature and high-vacuum annealing, reducing endogenous defects and improving the crystal quality and conductivity of the gallium oxide-doped silicon epitaxial layer. The resulting gallium oxide-doped silicon epitaxial layer has good crystal quality, which is beneficial for the continued growth of other high-quality Ga2O3-based doped and alloy thin films and superlattice structures on this gallium oxide-doped silicon epitaxial layer.

[0025] (3) In some optional embodiments, the present invention provides a method for preparing silicon-doped gallium nitride targets by high-temperature sintering and uses pulsed laser deposition technology to deposit the silicon-doped gallium oxide target on an n-type gallium nitride substrate. The prepared silicon-doped gallium nitride target meets the high-performance film formation requirements of the PLD process, and its physical properties (such as target density and geometry) are also compatible with magnetron sputtering equipment widely used in industrial applications. This design, which is compatible with both PLD and magnetron sputtering processes, can significantly reduce the technical barriers and industrialization costs of preparing large-size transparent electrode films based on this material system in the future, and is conducive to accelerating the large-scale production and application of deep ultraviolet optoelectronic devices. Attached Figure Description

[0026] Figure 1 This is a front view of the silicon-doped gallium oxide conductive electrode provided in Embodiment 1 of the present invention;

[0027] Figure 2 This is a top view of the silicon-doped gallium oxide conductive electrode provided in Embodiment 1 of the present invention;

[0028] Figure 3 These are XRD patterns of the Si-doped Ga2O3 epitaxial layers prepared in Examples 1-3 of this invention and the Sn-doped In2O3 epitaxial layer prepared in Comparative Example 1, wherein "0.1% Si:GO" is Example 2, "0.5% Si:GO" is Example 1, "1% Si:GO" is Example 3, and "3% Sn:INO" is Comparative Example 1.

[0029] Figure 4 The test graphs are calculated using TLM fitting to measure the contact resistance of the Si-doped Ga2O3 conductive electrode prepared in Examples 1-3 of this invention and the Sn-doped In2O3 conductive electrode prepared in Comparative Example 1.

[0030] Figure 5 These are optical transmittance diagrams of the Si-doped Ga2O3 epitaxial layers prepared in Examples 1-3 and the Sn-doped In2O3 epitaxial layer prepared in Comparative Example 1.

[0031] The reference numerals in the figure are: 1-sapphire base substrate; 2-undoped n-type gallium nitride layer; 3-Si-doped Ga2O3 epitaxial layer; 4-titanium layer; 5-gold layer. Detailed Implementation

[0032] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0033] In the following embodiments, unless otherwise specified, the water used may be one or more of distilled water, purified water, and drinking water; the detection methods in the following embodiments are conventional detection methods unless otherwise specified; the reagents in the following embodiments are commercially available unless otherwise specified.

[0034] Example 1

[0035] The specific fabrication method of the silicon-doped gallium oxide conductive electrode for gallium nitride-based deep ultraviolet optoelectronic devices in this embodiment is as follows:

[0036] (1) Si-doped Ga2O3 thin films were epitaxially deposited using pulsed laser deposition. A 0.5 mol% Si-doped Ga2O3 target was selected and sent into the sputtering chamber.

[0037] (2) Clean an n-GaN substrate sequentially with acetone, isopropanol and deionized water for 5 min, then etch the substrate with buffer oxide etchant (BOE), clean it with deionized water and dry it with a nitrogen gun; fix the n-GaN substrate and the special tantalum mask on the heating stage with silver paste, and send the heating stage into the sputtering chamber.

[0038] (3) After heating the heating stage to 550°C and maintaining the temperature constant, oxygen is introduced into the sputtering chamber to maintain the oxygen partial pressure in the chamber at 1 Pa.

[0039] (4) Turn on the laser to deposit Si-doped Ga2O3 electrodes; the epitaxial thickness is approximately 200 nm, and the pulsed laser energy density is 1.6 J / cm. 2 The growth temperature was 550℃, the oxygen pressure was 1 Pa, and the pulse frequency was 5Hz. Before growth, the target material was bombarded with laser for 5 minutes to remove surface contaminants.

[0040] (5) After deposition, the sputtering chamber is restored to a background vacuum of 10°C using a molecular pump. -5 Pa, and the heating stage was heated to 750℃, and the film was subjected to in-situ high temperature and high vacuum annealing for 10 min to obtain Si-doped Ga2O3 electrode substrate;

[0041] (6) The Si-doped Ga2O3 electrode substrate after annealing is subjected to standard photolithography process by laser direct writing photolithography system to obtain the preset electrode pattern. The electrode pattern includes several parallel rectangles, wherein the width of the rectangle is 400~700 μm, the length is 2~4.5 mm, and the distance between two adjacent rectangles is 500~1800 μm.

[0042] (7) A metal electrode layer is prepared on a rectangular electrode pattern using an electron beam evaporation device. First, a titanium layer is deposited. The background vacuum of the electron beam evaporation growth chamber is 5 × 10⁻⁶. -8Pa, with a titanium layer thickness of 20 nm, followed by a gold layer with a thickness of 80 nm. After electrode deposition, the remaining mask portion is washed away with acetone to obtain a Si-doped Ga2O3 conductive electrode.

[0043] The structure of a silicon gallium oxide-doped conductive electrode is as follows: Figure 1 and Figure 2 As shown, it includes an n-GaN substrate, a 0.5 mol% Si-doped Ga2O3 epitaxial layer 3, and a metal electrode layer arranged sequentially. The n-GaN substrate includes a sapphire base substrate 1 and an undoped n-type gallium nitride layer 2, and the metal electrode layer includes a titanium layer 4 and a gold layer 5.

[0044] Example 2

[0045] The Si-doped Ga2O3 conductive electrode was prepared using a method that was essentially the same as in Example 1, except that in step (1), a 0.1 mol% Si-doped Ga2O3 target was selected to obtain a Si-doped Ga2O3 epitaxial layer with a thickness of about 200 nm.

[0046] Example 3

[0047] The Si-doped Ga2O3 conductive electrode was prepared in basically the same way as in Example 1, except that in step (1), a 1 mol% Si-doped Ga2O3 target was selected to obtain a Si-doped Ga2O3 epitaxial layer with a thickness of about 200 nm.

[0048] Comparative Example 1

[0049] The Sn-doped In2O3 conductive electrode for comparison was prepared in basically the same way as in Example 1, except that in step (1), a 3 mol% Sn-doped In2O3 target was selected to obtain a Sn-doped In2O3 epitaxial layer with a thickness of 200 nm. This tin-doped indium oxide conductive electrode is a commonly used transparent electrode material.

[0050] Performance testing

[0051] 1. X-ray diffraction was performed on the Si-doped Ga2O3 epitaxial layers prepared in Examples 1-3 and the Sn-doped In2O3 epitaxial layer prepared in Comparative Example 1. The results are as follows: Figure 3As shown in the figure, the XRD patterns near the diffraction peaks of Ga2O3 (-201), (-402) and (-603) of the thin film sample, the (222) diffraction peak of In2O3, GaN (002) and Al2O3 (0006) substrate are marked. It can be seen that in Examples 1 to 3, except for the GaN (002) and Al2O3 (0001) substrate peaks, only Ga2O3 (-201), (-402) and (-603) diffraction peaks exist in the Si-doped Ga2O3 thin film sample, and only the In2O3 (222) diffraction peak exists in the Sn-doped In2O3 thin film sample of Comparative Example 1. There are no other impurity phases, which proves that Si-doped Ga2O3 epitaxial layers or Sn-doped In2O3 epitaxial layers with good epitaxial relationship can be grown on the n-GaN substrate.

[0052] 2. The relationship between the resistance and the electrode spacing (including the spacing between the Si-doped Ga2O3 epitaxial layer / Sn-doped In2O3 epitaxial layer + titanium layer / gold layer) in the Si-doped Ga2O3 conductive electrodes prepared in Examples 1-3 and the Sn-doped In2O3 conductive electrode prepared in Comparative Example 1 was measured as follows: Figure 4 The contact resistance ratio between the Si-doped Ga2O3 epitaxial layers prepared in Examples 1-3 and the Sn-doped In2O3 epitaxial layer prepared in Comparative Example 1 and the n-GaN substrate was calculated using TLM fitting. The calculated contact resistance of Example 1 was only 1.41 Ω, and the specific contact resistivity was 1.96 × 10⁻⁶. -4 Ω·cm 2 The contact resistances of Examples 2, 3, and Comparative Example 1 were 15.73 Ω, 1.81 Ω, and 6.07 Ω, respectively, and their specific contact resistivity was 3.63 × 10⁻⁶, respectively. -3 Ω·cm 2 3.48×10 -4 Ω·cm 2 and 2.51×10 -2 Ω·cm 2 The results show that Examples 1 and 3 exhibit low contact resistance and specific contact resistivity, achieving good ohmic contact. Furthermore, the specific contact resistivity levels of Examples 1-3 are superior to those of existing commercially available transparent electrodes (~10). -2 Ω·cm 2 (e.g., Comparative Example 1).

[0053] 3. The optical transmittance of the Si-doped Ga2O3 epitaxial layers prepared in Examples 1-3 and the Sn-doped In2O3 epitaxial layer prepared in Comparative Example 1 were tested, and the results are as follows: Figure 5As shown, the Si-doped Ga2O3 epitaxial layers of Examples 1-3 exhibit an average transmittance of up to 92% in the visible to near-infrared light band (400-1200 nm) and up to 85% in the deep ultraviolet band (280-400 nm), meeting the requirements for deep ultraviolet transparent electrodes. In contrast, the Sn-doped In2O3 epitaxial layer of Comparative Example 1 has a lower transmittance in the visible to near-infrared light band than the Si-doped Ga2O3 epitaxial layer, and its transmittance at 280 nm is less than 10%. Deep ultraviolet transmittance is a key indicator for evaluating the optical performance of transparent conductive oxides. The results show that the Si-doped Ga2O3 epitaxial layers obtained in Examples 1-3 have higher deep ultraviolet transmittance, better meeting the requirements for transparent electrodes in GaN-based deep ultraviolet optoelectronic devices, and have great application potential.

[0054] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for fabricating a silicon-doped gallium oxide conductive electrode suitable for gallium nitride-based deep ultraviolet optoelectronic devices, characterized in that, Includes the following steps: (1) The n-type gallium nitride substrate is etched with buffered oxide etchant to make its surface roughness less than 0.5 nm; (2) A mask is applied to the etched n-type gallium nitride substrate, and a silicon-doped gallium oxide target is used to perform vapor deposition on the n-type gallium nitride substrate to generate a silicon-doped gallium oxide epitaxial layer; The concentration of Si doping in the silicon-doped gallium oxide target is 0.01~5 mol%, and the thickness of the silicon-doped gallium oxide epitaxial layer is 0.03~0.25 μm. (3) Perform in-situ high-temperature high-vacuum annealing to obtain silicon-doped gallium oxide electrode substrate; The gas pressure for the in-situ high-temperature high-vacuum annealing is 10. -5 Pa, the temperature of the in-situ high temperature high vacuum annealing is 500~800℃, and the time of the in-situ high temperature high vacuum annealing is 10~30min; (4) Photolithography and development of a preset electrode pattern are performed sequentially on the silicon-doped gallium oxide electrode substrate, and then an electron beam evaporation of a metal electrode layer is performed on the electrode pattern to obtain the silicon-doped gallium oxide conductive electrode.

2. The preparation method according to claim 1, characterized in that, The concentration of Si doping in the silicon-doped gallium oxide target is 0.1~1 mol.

3. The preparation method according to claim 1, characterized in that, The method for preparing the silicon-doped gallium oxide target is as follows: high-purity SiO2 and Ga2O3 powders are mixed and pressed into sheets under a pressure of 5~15 MPa, and then calcined at 1250~1450℃ for 12~36h to obtain the target.

4. The preparation method according to claim 3, characterized in that, The heating rate of the calcination is 5~20℃ / min, and the cooling rate is 3~5℃ / min.

5. The preparation method according to claim 1, characterized in that, The n-type gallium nitride substrate includes a sapphire base substrate and an undoped n-type gallium nitride layer grown on the sapphire base substrate, the thickness of the undoped n-type gallium nitride layer being 4~6 μm; the n-type gallium nitride substrate is pre-cleaned by ultrasonic cleaning in acetone, isopropanol and deionized water for 1~5 min, and then etched by the buffer oxide etching solution; the silicon-doped gallium oxide epitaxial layer is grown on the surface of the undoped n-type gallium nitride layer.

6. The preparation method according to claim 1, characterized in that, The buffer oxide etching solution comprises HF and NH4F in a volume ratio of 1:10~20, and the etching time is 30s~5min.

7. The preparation method according to claim 1, characterized in that, The vapor deposition employs pulsed laser deposition technology, wherein the deposition temperature is 500~700℃, the oxygen partial pressure in the growth atmosphere is 0.5~10 Pa, and the laser energy density is 1.2~2 J / cm³. 2 The pulse number of the pulsed laser deposition technology is 3000~30000, and the pulse frequency of the pulsed laser deposition technology is 2~6 Hz.

8. The preparation method according to claim 1, characterized in that, The electrode pattern consists of several parallel rectangles, wherein the width of the rectangle is 400~700 μm, the length of the rectangle is 2~4.5 mm, and the distance between two adjacent rectangles is 500~1800 μm.

9. The preparation method according to claim 1, characterized in that, The metal electrode layer is a titanium layer and / or a gold layer, and the background vacuum of the electron beam evaporation growth chamber is 10. -8 ~10 -6 Pa, wherein the thickness of the titanium layer is 5~50 nm and the thickness of the gold layer is 50~100 nm.

10. A silicon-doped gallium oxide conductive electrode suitable for gallium nitride-based deep ultraviolet optoelectronic devices, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 9.

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