Zinc oxide homojunction-based ultraviolet exciton polarization light-emitting diode and preparation method thereof

Abstract

The present invention discloses a method for preparing a homojunction-based ultraviolet exciton polarized light-emitting diode constructed based on antimony-doped p-type zinc oxide (p-ZnO:Sb) micrometer wire and an n-type ZnO film, including a method for preparing a p-type ZnO micrometer wire and constructing a light-emitting diode. The present invention uses high-quality p-ZnO:Sb micrometer wires with a hexagonal cross-section, combined with an n-ZnO film (n-ZnO substrate) to construct a ultraviolet light-emitting diode based on a ZnO homojunction. This light-emitting diode emits stable ultraviolet light under forward bias. Since the p-ZnO:Sb micrometer wire has high crystal quality and a naturally formed resonant cavity, the photons generated by the radiation recombination of electrons and holes interact with the excitons by coupling, showing typical exciton polarized light-emitting characteristics. The homogeneous structure used in the ultraviolet light-emitting diode provided by the present invention avoids the problems of lattice mismatch in traditional heterojunction-based devices, and exhibits good spectral stability and higher luminous efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor optoelectronic devices, and in particular to a zinc oxide homojunction-based ultraviolet exciton polarization light-emitting diode and a preparation method thereof. Background Art

[0002] In recent decades, ultraviolet light sources have been widely used in biological analysis, agricultural production, water purification, communications, medical diagnosis, etc. Although ultraviolet light sources based on organic materials have large output areas and diverse structures, their luminescence intensity is low, spectral stability is poor, and the corresponding luminescent materials are difficult to prepare, so their large-scale application is still limited. Thanks to the advantages of light weight, high response speed, and small size, wide bandgap semiconductor materials such as gallium nitride (GaN), cadmium sulfide (CdS), nickel oxide (NiO), zinc oxide (ZnO), etc. have been widely used. Among them, ZnO, as a typical wide bandgap semiconductor (band gap 3.37eV), has a higher exciton binding energy (60meV) than GaN-based materials, and can achieve exciton-related emission at room temperature or even above room temperature. In addition, ZnO also has rich micro-nano structures, excellent optoelectronic properties, and natural optical resonant cavities, and its manufacturing cost is low, so it is widely used in light-emitting diodes and detectors. Compared with common heterojunction-based optoelectronic devices, optoelectronic devices based on ZnO homojunction avoid the problems of lattice mismatch and defects caused by heterostructures. However, the p-type ZnO materials prepared by various methods (solution synthesis, molecular beam epitaxy, pulsed laser deposition, etc.) still have problems such as unstable output, poor repeatability, low carrier concentration, and poor crystal quality. These problems have also seriously restricted the development and large-scale application of ZnO homojunction-based optoelectronic devices. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a method for preparing ultraviolet exciton polarized light-emitting diodes based on ZnO homogeneous structures. Select p-ZnO:Sb micrometer wires with hexagonal cross-sections, uniform thickness, and smooth surface to combine with n-ZnO thin films to form high-quality homojunctions, thereby avoiding the lattice mismatch and defect problems generated during the growth or construction of conventional heterogeneous structures.

[0004] Technical solution: The zinc oxide homojunction-based ultraviolet exciton polarized light-emitting diode of the present invention comprises an n-ZnO substrate, a quartz plate, a p-ZnO:Sb micrometer wire, an MgO insulating layer, and an Au electrode; the MgO insulating layer is respectively deposited on the upper end, the lower end, and the left end of the n-ZnO substrate plane, the Au thin film electrode is respectively deposited on the MgO insulating layer at the left end and the right end of the n-ZnO substrate plane, the p-ZnO:Sb micrometer wire is fixed in the center of the n-ZnO substrate and the Au thin film electrode is prepared on one end thereof located on the MgO insulating layer, and finally the quartz plate is fixed above the p-ZnO:Sb micrometer wire.

[0005] The role of the p-ZnO:Sb microwire is to provide high-quality resonant cavities and holes, and its carrier concentration and mobility are lower than those of the n-ZnO film. Therefore, the radiative recombination of carriers occurs in the microwire, and the resulting photons are also confined in the p-ZnO:Sb microwire, thereby coupling and interacting with excitons (electron-hole pairs) to achieve exciton-polariton luminescence.

[0006] Furthermore, the p-ZnO:Sb micron wire has a hexagonal cross section, a diameter of about 10 to 15 μm, and a carrier concentration of 10 17 ~10 18 / cm 3 , the carrier mobility is 1~5cm 2 / V·s. It is ensured that the carrier mobility is lower than that of the n-ZnO substrate; in addition, the p-ZnO:Sb micrometer wire used in the present invention has high crystal quality, can realize optical pumping laser, and its natural resonant cavity can also ensure a longer exciton lifetime, thereby increasing the probability of photon-exciton coupling interaction.

[0007] Furthermore, the thickness of the n-ZnO substrate is 440-460 μm, the thickness of the ZnO layer is 2.5-3 μm, the size is 1.2 cm×0.6 cm, and the carrier concentration is 10 19 / cm 3 , the carrier mobility is 25~50cm 2 / V·s, and the band gap is 3.37eV.

[0008] Furthermore, the thickness of the MgO insulating layer at the left end is 0.08-0.1 μm, and the evaporation rate is The thickness of the MgO insulating layer at the upper and lower ends is 5 to 6 μm, and the evaporation rate is

[0009] Furthermore, the thickness of the Au thin film electrode evaporated on the n-ZnO substrate and the MgO insulating layer is 40-60 nm, and the evaporation rate is

[0010] Furthermore, the thickness of the Au electrode deposited on the p-ZnO:Sb microwire is 0.1 to 0.15 μm, and the deposition rate is Au electrodes are provided on both the upper and lower surfaces of the microwire, which can better ensure the injection of carriers. Furthermore, the quartz plate is fixed on the p-ZnO:Sb microwire using a metal clip.

[0011] The present invention also discloses a method for preparing a zinc oxide homojunction-based ultraviolet exciton polarized light-emitting diode, comprising the following steps:

[0012] Step 1, selecting p-ZnO:Sb micron wire;

[0013] Step 2, cleaning the quartz plate and the n-ZnO substrate;

[0014] Step 3, placing the p-ZnO:Sb microwire on the n-ZnO substrate, and preparing an Au electrode on the p-ZnO:Sb microwire;

[0015] Step 4: Place the quartz plate on top of the p-ZnO:Sb micrometer wire and fix it with a metal clip to complete the preparation of the p-ZnO:SbMW / n-ZnO homojunction ultraviolet exciton polariluminescent diode.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0017] 1) The p-ZnO:Sb microwires selected in the present invention have good electrical conductivity and a natural high-quality resonant cavity. By selecting p-ZnO:Sb microwires whose carrier concentration and mobility are lower than those of n-ZnO films, the radiative recombination of carriers occurs in the microwires, achieving light confinement, and providing good conditions for the coupling interaction between photons and excitons (electron-hole pairs).

[0018] 2) The present invention combines p-ZnO:Sb micron wires with n-ZnO substrates to successfully construct a ZnO homojunction, achieving stable ultraviolet light emission under forward bias, avoiding the problems of lattice mismatch and poor device spectrum stability caused by the construction or growth of traditional heterostructure devices, significantly improving the reliability of light-emitting diodes, and providing a new solution for building a stable and reliable ultraviolet light source;

[0019] 3) The p-ZnO:Sb MW / n-ZnO homojunction device constructed in the present invention exhibits typical exciton-polariton luminescence characteristics under forward bias, which provides an important reference for the design and construction of short-wavelength low-threshold coherent light sources, homojunction lasers and nonlinear optoelectronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Optical photos and SEM images of p-ZnO:Sb micrometer wires prepared by chemical vapor deposition in the present invention;

[0021] Figure 2 The optically pumped laser excited by the p-ZnO:Sb micron wire prepared by the present invention;

[0022] Figure 3 The present invention is a flow chart of the preparation of the p-ZnO:Sb MW / n-ZnO homojunction ultraviolet light-emitting diode;

[0023] Figure 4 The IV characteristic curve of the p-ZnO:Sb MW / n-ZnO homojunction UV light emitting diode prepared in Example 1 of the present invention;

[0024] Figure 5 The electroluminescence spectrum of the p-ZnO:Sb MW / n-ZnO homojunction UV light-emitting diode prepared in Example 1 of the present invention;

[0025] Figure 6 To take a light-emitting image of the p-ZnO:Sb MW / n-ZnO homojunction ultraviolet light-emitting diode prepared in Example 1 of the present invention under a microscope;

[0026] Figure 7 The group refractive index of the p-ZnO:Sb micrometer wire in the p-ZnO:Sb MW / n-ZnO homojunction UV light-emitting diode prepared in Example 1 of the present invention;

[0027] Figure 8 The energy-wave vector dispersion curve of the p-ZnO:Sb MW / n-ZnO homojunction UV light-emitting diode prepared in Example 1 of the present invention, wherein the data points correspond to the resonance peak values ​​one by one;

[0028] Fig. 9 The electroluminescence spectrum of the p-ZnO:Sb MW / n-ZnO homojunction UV light-emitting diode prepared in Example 2 of the present invention;

[0029] Fig.10 is the group refractive index of the p-ZnO:Sb micrometer wire in the p-ZnO:Sb MW / n-ZnO homojunction UV light-emitting diode prepared in Example 2 of the present invention;

[0030] Fig.11 This is the energy-wave vector dispersion curve of the p-ZnO:Sb MW / n-ZnO homojunction UV light-emitting diode prepared in Example 2 of the present invention, wherein the data points correspond one-to-one to the peak values ​​of the resonance peaks;

[0031] Fig.12The electroluminescence spectrum of the p-ZnO:Sb MW / n-ZnO homojunction UV light-emitting diode prepared in Example 3 of the present invention;

[0032] Fig.13 is the group refractive index of the p-ZnO:Sb micrometer wire in the p-ZnO:Sb MW / n-ZnO homojunction UV light-emitting diode prepared in Example 3 of the present invention;

[0033] Fig.14 This is the energy-wave vector dispersion curve of the p-ZnO:Sb MW / n-ZnO homojunction ultraviolet light-emitting diode prepared in Example 3 of the present invention, wherein the data points correspond one-to-one to the peak values ​​of the resonance peaks. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0035] Embodiment 1:

[0036] The total thickness of the selected n-ZnO substrate is 450 μm, of which the ZnO layer is 3 μm thick, the size is 1.2 cm × 0.6 cm, and the carrier concentration is 2.6 × 10 19 / cm 3 , the carrier mobility is 35cm 2 / V·s; the p-ZnO:Sb microwire has a diameter of 10 μm, a length of 0.35 cm, and a carrier (hole) concentration of 5.8×10 17 / cm 3 , the carrier mobility is 3cm 2 / V·s; the anode and cathode electrodes of the device are both Au electrodes.

[0037] The following is the specific method for preparing the device:

[0038] Step 1: Select p-ZnO:Sb microwires with a hexagonal cross section, uniform thickness, and smooth surface, with a diameter of 10 μm, a length of 0.35 cm, and a carrier (hole) concentration of 5.8×10 17 / cm 3 , the carrier mobility is 3cm 2 / V·s, its optical photograph and SEM image are as follows Figure 1 shown.

[0039] Step 2: Use trichloroethylene solution, acetone, ethanol, and deionized water to ultrasonically clean the n-ZnO substrate and quartz wafer for 20 minutes, then use a nitrogen gun to blow off the surface moisture, and finally put them in a drying oven to dry for use.

[0040] Step 3: Use electron beam evaporation to deposit the ZnO on a dry and clean n-ZnO substrate (carrier concentration 2.6×1019 / cm 3 , electron mobility 35cm 2 / V·s) to prepare the MgO insulating layer, and the specific location is as follows Figure 3 As shown in ① (the thickness at 1 is 100nm and the rate is The thickness at 2 and 3 is 5 μm, and the rate is ), then depositing Au thin film with a thickness of 50 nm on the MgO insulating layer and the n-ZnO substrate at a rate of The specific location can be seen Figure 3 Middle②.

[0041] Step 4: Fix the p-ZnO:Sb micron wire on the n-ZnO substrate, cover 4 / 5 of the length with a mask, and then use an electron beam evaporator to deposit Au electrodes on the exposed parts of the p-ZnO:Sb micron wires with a thickness of about 100nm at a rate of As hole injection electrode, Figure 3 As shown in ③.

[0042] Step 5: Place a quartz plate (0.7cm×0.5cm×0.05cm) on the p-ZnO:Sb micron-wire, and use a metal clamp to clamp the quartz plate and the n-ZnO substrate to ensure good contact between the n-ZnO substrate and the p-ZnO:Sb micron-wire, thereby constructing a single ZnO heterojunction light-emitting diode. Figure 3 Figure ④ shows a three-dimensional schematic diagram of a homojunction light-emitting diode.

[0043] Step 6: Connect the single ZnO homojunction UV LED prepared in the fourth step to a power source, shoot a light-emitting video and measure the volt-ampere characteristic (IV) curve, and collect and analyze relevant light-emitting characteristics such as the electroluminescence spectrum.

[0044] The device constructed by the above steps has typical rectification characteristics, such as Figure 4 Its electroluminescence spectrum is shown in Figure 5 As shown, the photon energy at the peak is 3.28 eV, which can be confirmed to be typical ZnO near-band edge luminescence. In addition, a series of peaks can be observed from the spectrum image, and they are broadened in the long wavelength direction.

[0045] As the injection current increases, the luminescence can be seen under a microscope on the p-ZnO:Sb micrometer line, such as Figure 6 shown.

[0046] The change of group refractive index in p-ZnO microwires is calculated based on experimental data, such as Figure 7As shown, it can be seen that the refractive index of the microwire in the long-wave region is about 2.1, and as the wavelength approaches the main emission wavelength of the device (378nm), the refractive index of the microwire rises sharply, reaching a refractive index range far exceeding that of normal ZnO crystals. This abnormal refractive index increase indicates that there is a strong light-matter interaction in the p-ZnO microwires prepared by the present invention, and further confirms the occurrence of strong coupling between excitons and photons in the microwires. This phenomenon can be attributed to the fact that the p-ZnO:Sb microwires selected by the present invention have good conductivity and a natural high-quality resonant cavity, and their carrier concentration and mobility are lower than those of the n-ZnO film. Therefore, the radiative recombination of carriers occurs in the microwires, achieving the confinement of light. The high-quality resonant cavity also ensures a long lifetime of excitons (electron-hole pairs), providing good conditions for the coupling interaction between photons and excitons. In addition, as Figure 8 As shown in the figure, the peak value of the resonance peak in the luminescence spectrum is fitted and calculated, and the energy-wave vector dispersion curve is drawn. The minimum energy difference between the upper polarization branch (UP) and the lower polarization branch (LP) is the coupling strength (Rabi splitting energy) between the exciton and the photon in the light-emitting diode. The Rabi splitting energy is calculated to be 401 meV. The higher Rabi splitting energy also confirms the strong coupling interaction between the exciton and the photon in the light-emitting diode.

[0047] Embodiment 2:

[0048] The total thickness of the selected n-ZnO substrate is 450 μm, of which the ZnO layer is 3 μm thick, the size is 1.2 cm × 0.6 cm, and the carrier concentration is 1.4 × 10 19 / cm 3 , the carrier mobility is 25cm 2 / V·s; the p-ZnO:Sb microwire has a diameter of 10 μm, a length of 0.35 cm, and a carrier (hole) concentration of 2.2×10 18 / cm 3 , the carrier mobility is 2.4 cm 2 / V·s; the anode and cathode electrodes of the device are both Au electrodes.

[0049] Step 1: Select p-ZnO:Sb microwires with a hexagonal cross section, uniform thickness, and smooth surface, with a diameter of 10 μm, a length of 0.35 cm, and a carrier (hole) concentration of 2.2×10 18 / cm 3 , the carrier mobility is 2.4 cm 2 / V·s.

[0050] Step 2: Use trichloroethylene solution, acetone, ethanol, and deionized water to ultrasonically clean the n-ZnO substrate and quartz wafer for 20 minutes, then use a nitrogen gun to blow off the surface moisture, and finally put them in a drying oven to dry for use.

[0051] Step 3: Use electron beam evaporation to deposit the ZnO on a dry and clean n-ZnO substrate (carrier concentration 1.4×10 19 / cm 3 , electron mobility 25cm 2 / V·s), and the preparation process of the MgO insulating layer can be completely referred to Example 1.

[0052] The fourth and fifth steps can refer to the first embodiment.

[0053] After the device is prepared, the prepared single ZnO homojunction ultraviolet light-emitting diode is connected to a power source, and the electroluminescence spectrum and other related light-emitting characteristics are collected and analyzed.

[0054] like Fig. 9 As shown, the electroluminescence spectrum of the light-emitting diode prepared in Example 2 shows fewer oscillation peaks and the oscillation is weaker. This is because the selected p-ZnO:Sb microwire has a higher hole concentration than that of Example 1, which leads to a higher probability of recombination between electrons injected from the n-ZnO substrate and holes in the p-ZnO:Sb microwire, thereby reducing the average lifetime of the excitons. In addition, the reduction in the electron concentration of the n-ZnO substrate also affects the formation of excitons in the p-ZnO:Sb microwire. Therefore, the light-emitting diode prepared in Example 2 shows a lower exciton-photon coupling intensity, which can also be seen from the lower group refractive index ( Fig.10 )as well as( Fig.11 ) is confirmed by the lower Rabi splitting energy (379 meV) shown in the energy-wave-vector dispersion curve.

[0055] Embodiment three:

[0056] The total thickness of the selected n-ZnO substrate is 450 μm, of which the ZnO layer is 3 μm thick, the size is 1.2 cm × 0.6 cm, and the carrier concentration is 3.7 × 10 19 / cm 3 , the carrier mobility is 31cm 2 / V·s; the p-ZnO:Sb microwire has a diameter of 10 μm, a length of 0.35 cm, and a carrier (hole) concentration of 5.8×10 17 / cm 3 , the carrier mobility is 3cm 2 / V·s; the anode and cathode electrodes of the device are both Au electrodes.

[0057] Step 1: Select p-ZnO:Sb microwires with a hexagonal cross section, uniform thickness, and smooth surface, with a diameter of 10 μm, a length of 0.35 cm, and a carrier (hole) concentration of 4.2×10 17 / cm 3 , the carrier mobility is 3.6 cm 2 / V·s.

[0058] Step 2: Use trichloroethylene solution, acetone, ethanol, and deionized water to ultrasonically clean the n-ZnO substrate and quartz wafer for 20 minutes, then use a nitrogen gun to blow off the surface moisture, and finally put them in a drying oven to dry for use.

[0059] Step 3: Use electron beam evaporation to deposit the ZnO on a dry and clean n-ZnO substrate (carrier concentration 3.7×10 19 / cm 3 , electron mobility 31cm 2 / V·s), and the preparation process of the MgO insulating layer can be completely referred to Example 1.

[0060] The fourth and fifth steps can be completely referred to in Example 1.

[0061] After the device is prepared, the prepared single ZnO homojunction ultraviolet light-emitting diode is connected to a power source, and the electroluminescence spectrum and other related light-emitting characteristics are collected and analyzed.

[0062] like Fig.12 As shown, compared with Example 1 and Example 2, the electroluminescence spectrum of the light-emitting diode prepared in Example 3 shows more and stronger oscillation peaks. This can be attributed to the higher carrier concentration in the n-ZnO substrate. When the device is operated under forward bias, a large number of electrons are injected into the p-ZnO:Sb microwires from one side of the n-ZnO substrate. The probability of electrons and holes forming excitons due to Coulomb interaction increases, and the average lifetime of the excitons becomes longer. Therefore, exciton-photon coupling interaction is more likely to occur in the light-emitting diode prepared in Example 3, showing a stronger exciton-photon coupling intensity. Similarly, Fig.13 The higher group refractive index in the high energy region shown in Fig.14 The calculated higher Rabi splitting energy (437 meV) can also prove the stronger exciton-photon coupling intensity compared with the first and second embodiments.

[0063] From the above three embodiments, we can see that the present invention uses p-ZnO:Sb micrometer wires with high crystal quality and hexagonal cross-section, combined with n-ZnO substrates with high carrier concentration and mobility to construct p-ZnO:Sb MW / n-ZnO homojunctions, which ensures the effective injection of electrons from the n-ZnO substrate to the p-ZnO:Sb micrometer wires. And by utilizing the natural resonant cavity of the p-ZnO:Sb micrometer wire to confine light, the interaction between light and matter is realized. Analysis of the luminescence spectrum and group refractive index of the device confirms the strong coupling interaction between excitons and photons. The preparation method of the ZnO homojunction-based ultraviolet light-emitting diode provided by the present invention provides an important reference for the design and construction of short-wavelength low-threshold coherent light sources, homojunction lasers and nonlinear optoelectronic devices.

Claims

1. A zinc oxide homojunction-based ultraviolet exciton polarization light-emitting diode, characterized in that: The invention comprises an n-ZnO substrate, a quartz sheet, a p-ZnO:Sb micrometer wire, a MgO insulating layer and an Au electrode; the MgO insulating layer is respectively deposited on the upper end, the lower end and the left end of the plane of the n-ZnO substrate, the Au thin film electrode is respectively deposited on the MgO insulating layer at the left end and the right end of the plane of the n-ZnO substrate, the p-ZnO:Sb micrometer wire is fixed in the center of the n-ZnO substrate and the Au thin film electrode is prepared on one end of the p-ZnO:Sb micrometer wire which is located on the left MgO insulating layer, and finally the quartz sheet is fixed above the p-ZnO:Sb micrometer wire.

2. The zinc oxide homojunction-based ultraviolet exciton polarized light-emitting diode according to claim 1, characterized in that: The p-ZnO:Sb micron wire has a hexagonal cross section with a diameter of 10 to 15 μm and a carrier concentration of 10 17 ~10 18 / cm 3 , the carrier mobility is 1~5cm 2 / V·s.

3. The zinc oxide homojunction-based ultraviolet exciton polarized light-emitting diode according to claim 1, characterized in that: The thickness of the n-ZnO substrate is 440-460 μm, the thickness of the ZnO layer is 2.5-3 μm, the size is 1.2 cm×0.6 cm, and the carrier concentration is 10 19 / cm 3 , the carrier mobility is 25~50cm 2 / V·s, and the band gap is 3.37eV.

4. The zinc oxide homojunction-based ultraviolet exciton polarized light-emitting diode according to claim 1, characterized in that: The thickness of the MgO insulating layer on the left side is 0.08 to 0.1 μm, and the evaporation rate is The thickness of the MgO insulating layer at the upper and lower ends is 5 to 6 μm, and the evaporation rate is 5. The zinc oxide homojunction-based ultraviolet exciton polariton light-emitting diode according to claim 1, characterized in that: The thickness of the Au thin film electrode evaporated on the n-ZnO substrate and the MgO insulating layer is 40-60 nm, and the evaporation rate is 6. The zinc oxide homojunction-based ultraviolet exciton polariton light-emitting diode according to claim 1, characterized in that: The thickness of the Au electrode deposited on the p-ZnO:Sb microwire is 0.1 to 0.15 μm, and the deposition rate is 7. The zinc oxide homojunction-based ultraviolet exciton polarized light-emitting diode according to claim 1, characterized in that: The quartz plate was fixed on top of the p-ZnO:Sb microwires by metal clips.

8. A method for preparing a zinc oxide homojunction-based ultraviolet exciton polarized light-emitting diode according to claim 1, characterized in that: The steps include: Step 1, selecting p-ZnO:Sb micron wire; Step 2, cleaning the quartz plate and the n-ZnO substrate; Step 3: using an electron beam evaporator to prepare a MgO insulating layer on the cleaned n-ZnO substrate; Step 4, depositing an Au film on the left end MgO insulating layer and the right end of the n-ZnO substrate plane; Step 5, placing the p-ZnO:Sb microwire on the n-ZnO substrate, and preparing an Au electrode on the p-ZnO:Sb microwire; Step 6: Place the quartz plate on top of the p-ZnO:Sb micrometer wire and fix it with a metal clip to complete the preparation of the p-ZnO:Sb MW / n-ZnO homojunction ultraviolet exciton polariton light-emitting diode.

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