A ZnO micron-wire heterojunction high-brightness red light emitting diode and its manufacturing method

Abstract

The present invention discloses a ZnO micrometer wire heterojunction high-brightness red light emitting diode and a method for manufacturing the same. The diode comprises a p-PGaAs substrate, a Ti / Pt / Au alloy electrode arranged on one side of the p-PGaAs substrate, an n-ZnO:Ga micrometer wire arranged on the p-PGaAs substrate, and AgNWs are spin-coated on the n-ZnO:Ga micrometer wire; the n-ZnO:Ga micrometer wire is covered with conductive glass. The present invention spin-coats AgNWs on the surface of the n-ZnO:Ga micrometer wire, and uses p-PGaAs as a substrate to construct a composite structure heterojunction light emitting diode. The present invention realizes a high-brightness red light emitting diode under forward bias by constructing an n-AgNWs@ZnO:Ga / p-PGaAs heterojunction structure, avoids lattice mismatch caused by directly growing a ZnO film on a GaAs substrate, and effectively realizes stable high-brightness red light emission of a heterojunction device.

Description

Technical Field

[0001] The invention relates to a light emitting diode and a preparation method thereof, in particular to a ZnO micron wire heterojunction high-brightness red light emitting diode and a preparation method thereof. Background Art

[0002] Red LED is the earliest commercial LED, but its development is not as good as the latest blue LED. Compared with red LED, the preparation of ZnO-based blue and green LED is more mature, which makes the preparation and research of red LED particularly important for the future realization of full-color display of LED. At present, red LED has been widely used in display, lighting and medical beauty. From clinical experimental data, it can be seen that red light can assist drugs in the treatment of many diseases such as dermatology, surgery, internal medicine, gynecology, burns, otolaryngology, etc.

[0003] ZnO is a II-VI group direct bandgap semiconductor with a relatively high bandgap width, and its bandgap width is 3.37eV at room temperature. At the same time, ZnO has a relatively high exciton binding energy (60meV), which is significantly higher than the thermal ionization energy (25meV) at room temperature. Therefore, ZnO has a relatively high exciton concentration at room temperature, which gives it a unique advantage in the field of optoelectronic devices. In addition, the micro-nano structure of ZnO has excellent single crystals, natural optical resonant cavities, and controllable structures and morphologies, and is widely used in semiconductor fields such as liquid crystal displays, detectors, and light-emitting diodes.

[0004] However, p-type ZnO doping is difficult, and the effective carrier injection rate and stability are poor, which limits the development of devices based on single ZnO materials. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a ZnO micron wire heterojunction high brightness red light emitting diode with high stability and excellent luminescence performance;

[0006] The second object of the present invention is to provide a method for preparing the above-mentioned ZnO micron-wire heterojunction high-brightness red light emitting diode.

[0007] Technical solution: The ZnO micron wire heterojunction high-brightness red light emitting diode of the present invention comprises a p-PGaAs substrate, a Ti / Pt / Au alloy electrode arranged on one side of the p-PGaAs substrate, an n-ZnO:Ga micron wire arranged on the p-PGaAs substrate, wherein the n-ZnO:Ga micron wire is spin-coated with AgNWs; and the n-ZnO:Ga micron wire is covered with conductive glass.

[0008] Wherein, the thicknesses of Ti, Pt and Au in the Ti / Pt / Au alloy electrode are 40-60nm, 40-60nm and 150-250nm respectively.

[0009] The method for preparing the above-mentioned ZnO micron-wire heterojunction high-brightness red light emitting diode comprises the following steps:

[0010] (1) Annealing and cleaning the p-PGaAs substrate;

[0011] (2) evaporating metal Ti / Pt / Au on one side of the p-PGaAs substrate to form a Ti / Pt / Au alloy electrode as an anode;

[0012] (3) spin coating AgNWs on n-ZnO:Ga microwires to obtain n-AgNWs@ZnO:Ga composite structures, which were then placed on p-PGaAs substrates;

[0013] (4) ITO was coated on the n-AgNWs@ZnO:Ga composite structure as the cathode.

[0014] Wherein, in step (1), the p-PGaAs substrate is annealed at a temperature of 700 to 900° C. for a time of 1 to 2 hours; after annealing, the p-PGaAs substrate is placed in a trichloroethylene solution and ultrasonically cleaned in an ultrasonic cleaning instrument; then ultrasonically cleaned in acetone, ethanol, and deionized water in sequence, and then blown dry with nitrogen.

[0015] Wherein, in step (2), the metal Ti / Pt / Au is annealed after evaporation; the annealing temperature is 450-550°C and the time is 30-60s. The metal Ti / Pt / Au electrode is evaporated on one side of the p-PGaAs substrate: a portion of the p-PGaAs substrate is covered with a mask and a portion is exposed. The evaporation is performed by electron beam evaporation; the alloy electrode is an ohmic contact electrode.

[0016] Wherein, in step (3), the concentration of AgNWs is 0.01-0.03 mg / mL.

[0017] Wherein, in step (3), the length of the AgNWs is 2 to 90 um and the diameter is 20 to 120 nm.

[0018] Wherein, in step (3), the method of spin coating AgNWs on the n-ZnO:Ga micron wire is: using a pipette to drop the synthesized AgNWs on the ZnO:Ga micron wire, spin coating on a spin coater and drying for standby use; the volume of AgNWs spin coated by the pipette each time is ~3uL.

[0019] In step (4), the ITO is first cleaned. The method for cleaning the ITO is as follows: the ITO is placed in a glass beaker, cleaned with trichloroethylene, acetone, ethanol and ultrapure water respectively, and then blown dry with a nitrogen gun.

[0020] The method for constructing a single ZnO micron wire heterojunction-based high-brightness red light emitting diode comprises placing the composite structure micron wire on a p-PGaAs substrate under an optical microscope so that the micron wire and the substrate are in full contact, and then placing ITO as a cathode on the micron wire and fixing it, thereby achieving good contact of the device.

[0021] Principle of the invention: AgNWs are spin-coated on the surface of ZnO micron wires to construct AgNWs@n-ZnO:Ga / p-PGaAs composite structure heterojunction light-emitting diodes. The hot electrons induced by the local plasmon decay of AgNWs are used to improve the reinjection of carriers in the ZnO micron wires, regulate the surface defects of the ZnO micron wires, and thus realize high-brightness red light-emitting diodes.

[0022] Beneficial effects: Compared with the prior art, the present invention has achieved the following significant effects: 1. By constructing an n-ZnO:Ga / p-PGaAs heterojunction structure, a high-brightness red light-emitting diode with high stability is realized under forward bias. 2. The problem of lattice mismatch caused by direct growth of ZnO film on GaAs substrate, which seriously affects the stability of the device, is avoided, and the stable high-brightness red light emission of the n-ZnO:Ga / p-PGaAs heterojunction device is effectively realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of a single ZnO micron wire heterojunction-based high-brightness red light emitting diode device of the present invention;

[0024] Figure 2 Spectrum diagram and IV characteristic curve of the n-ZnO:Ga / p-PGaAs heterojunction light emitting diode of Example 1 of the present invention;

[0025] Figure 3 This is a bright red light photograph of the n-ZnO:Ga / p-PGaAs heterojunction light-emitting diode of Example 1 of the present invention;

[0026] Figure 4 This is a diagram of an IV test of a PGaAs substrate according to Example 1 of the present invention;

[0027] Figure 5 Spectrum diagram and IV characteristic curve of the n-Ag@ZnO:Ga / p-PGaAs heterojunction light emitting diode of Comparative Example 1;

[0028] Figure 6 This is a graph of the IV test of the PGaAs substrate under different electrode annealing conditions in Comparative Example 3. DETAILED DESCRIPTION

[0029] The present invention is described in further detail below.

[0030] Example 1

[0031] like Figure 1 As shown, the present invention provides a single ZnO micron wire heterojunction-based high-brightness red light-emitting diode, including a p-PGaAs substrate 4, which is arranged on a glass sheet 5; a Ti / Pt / Au alloy electrode 1 arranged on one side of the p-PGaAs substrate 4, an n-ZnO:Ga micron wire 2 arranged on the p-PGaAs substrate 4, on which AgNWs are spin-coated; and a conductive glass 3 is covered on the n-ZnO:Ga micron wire 2. The size of the substrate p-PGaAs 4 is 3cm*2cm, and the crystal orientation is <100> direction; the thickness of the Ti / Pt / Au electrode 1 on the p-PGaAs substrate 4 is 50nm / 50nm / 200nm respectively; the electron concentration range of the n-ZnO:Ga microwire 2 is 10 17 ~10 19 / cm 3 , the electron mobility range is 5 to 100 cm 2 / V·s; the ITO size used is 2cm*1.5cm.

[0032] The method for preparing the above-mentioned single ZnO micron wire heterojunction-based high-brightness red light emitting diode comprises the following steps:

[0033] Step 1: anneal the p-PGaAs substrate 4 in a high temperature furnace at 800° C. for 1.5 h, then use trichloroethylene, acetone, ethanol and deionized water to ultrasonically clean the annealed p-PGaAs substrate 4 in an ultrasonic instrument for 15 min, and then blow dry with nitrogen;

[0034] Step 2: partially cover the p-PGaAs substrate 4 with a mask plate and expose a portion of it, and use electron beam evaporation to plate Ti / Pt / Au alloy electrodes 1 with thicknesses of 50nm / 50nm / 200nm respectively on the exposed portion of the p-PGaAs substrate 4, and put the evaporated Ti / Pt / Au alloy electrodes into a high-temperature tube furnace for annealing at a temperature of 500°C for 30s, and test the ohmic characteristics of the electrodes;

[0035] Step 3: Take a hexagonal n-ZnO:Ga micron wire 2, make sure it has good crystal quality, place it on a clean glass slide, put it under an optical microscope, use a pipette to take a drop of AgNWs sample and drop it on the n-ZnO:Ga micron wire, spin-coat and dry it for later use;

[0036] Step 4: Take a piece of ITO 3 with a size of 2cm*1.5cm, wipe its surface with a dust-free cloth and place it in a clean beaker. Ultrasonic clean it with trichloroethylene, acetone, ethanol and ultrapure water for 15 minutes respectively, then blow dry with a nitrogen gun and put it in a drying cabinet for later use;

[0037] Step 5: Take a p-PGaAs substrate 4 with an electrode evaporated on it and place it under a microscope. Use tweezers to take a hexagonal micrometer wire with spin-coated AgNWs and place it on the p-PGaAs substrate 4. Ensure that there is sufficient contact between the n-ZnO:Ga micrometer wire and the p-PGaAs substrate 4. Then, take a clean ITO and press it on the composite structure micrometer wire to fix it. Ensure good contact between the n-ZnO:Ga micrometer wire and ITO, and between the n-ZnO:Ga micrometer wire and the p-PGaAs substrate, thus constructing a single ZnO micrometer wire heterojunction-based high-brightness red light-emitting diode.

[0038] The n-ZnO:Ga / p-PGaAs heterojunction light-emitting diode formed in step 4 was electrically tested, and the luminescence video and luminescence spectrum were taken, as shown in FIG. Figure 2 , 3 As shown. Figure 2 It can be seen that under the drive of forward injection current (15mA-30mA), spectrum graph a shows that the main emission peak of the heterojunction device is concentrated around 642nm, and graph b shows that the heterojunction device has good rectification characteristics. Figure 3 It can be seen that under the drive of forward injection current (15mA-30mA), the heterojunction diode begins to emit red light, and as the injection current increases, the brightness and emission area increase, showing a stable high-brightness red light emission. Therefore, based on a single ZnO micron wire heterojunction, a high-brightness red light-emitting diode is realized.

[0039] Depend on Figure 4 It can be seen that the evaporated Ti / Pt / Au electrode is placed in a high-temperature tube furnace at 500°C and annealed for 30 seconds, and its IV test result shows ohmic contact.

[0040] Example 2

[0041] On the basis of Example 1, the difference from Example 1 is that the thicknesses of Ti, Pt and Au in the Ti / Pt / Au alloy electrode are 60nm, 60nm and 250nm respectively; the annealing temperature of the alloy electrode is 450℃, and the time is 60s; the annealing temperature of the p-PGaAs substrate is 900℃, and the annealing time is 1h; and the concentration of AgNWs is 0.03mg / mL.

[0042] Example 3

[0043] On the basis of Example 1, different from Example 1, the thicknesses of Ti, Pt and Au in the Ti / Pt / Au alloy electrode are 40 nm, 40 nm and 150 nm respectively; the annealing temperature of the alloy electrode is 550°C and the time is 30 s; the annealing temperature of the p-PGaAs substrate is 700°C and the annealing time is 2 h; and the concentration of AgNWs is 0.01 mg / mL.

[0044] Comparative Example 1

[0045] Based on Example 1, the difference from Example 1 is that the n-ZnO:Ga microwire is loaded with an Ag film. The IV test curve of the obtained light-emitting diode is as follows: Figure 5 As shown, it can be seen that under the drive of forward injection current (10mA-25mA), spectrum graph a shows that the main emission peak of the heterojunction device is concentrated around 630nm. Compared with the composite heterojunction structure of n-AgNWs@ZnO:Ga / p-PGaAs, the luminescence spectrum is blue-shifted. Figure b shows the IV characteristic curve of the heterojunction device. Compared with the IV characteristic curve of the n-AgNWs@ZnO:Ga / p-PGaAs device, its rectification characteristics are poor.

[0046] Comparative Example 2

[0047] On the basis of Example 1, the difference from Example 1 is that the Ti / Pt / Au alloy electrode is replaced by a Ni / Au electrode with thicknesses of 30 nm / 30 nm respectively.

[0048] The PGaAs substrate with evaporated Ni / Au electrodes was tested by IV using a semiconductor analyzer. Analysis of the IV curve showed that it was not an ohmic contact, while the PGaAs substrate with evaporated Ti / Pt / Au electrodes was an obvious ohmic contact.

[0049] Comparative Example 3

[0050] On the basis of Example 1, the difference from Example 1 is that the temperature and time of electrode annealing are changed. The experimental groups set are: 300℃-30s, 300℃-60s, 400℃-30s, 400℃-60s, and no electrode annealing. The IV test curve of the obtained PGaAs substrate is as follows: Figure 6 As shown, it can be seen that in the cases of 300℃-30s, 300℃-60s, 400℃-30s, 400℃-60s and without annealing the electrode, the IV test of the PGaAs substrate is not an ohmic contact.

Claims

1. A ZnO micron-wire heterojunction high-brightness red light emitting diode, characterized in that: It comprises a p-PGaAs substrate, a Ti / Pt / Au alloy electrode arranged on one side of the p-PGaAs substrate, an n-ZnO:Ga micron wire arranged on the p-PGaAs substrate, wherein AgNWs are spin-coated on the n-ZnO:Ga micron wire; and the n-ZnO:Ga micron wire is covered with conductive glass; The thicknesses of Ti, Pt and Au in the Ti / Pt / Au alloy electrode are 40-60 nm, 40-60 nm and 150-250 nm respectively; The method for preparing the ZnO micron-wire heterojunction high-brightness red light emitting diode comprises the following steps: (1) Annealing and cleaning the p-PGaAs substrate; (2) vapor-depositing metal Ti / Pt / Au on one side of the p-PGaAs substrate to form a Ti / Pt / Au alloy electrode as an anode; annealing is performed after the metal Ti / Pt / Au is vapor-deposited; the annealing temperature is 450-550° C. and the time is 30-60 seconds; (3) Spin-coating AgNWs on n-ZnO:Ga microwires to obtain n-AgNWs@ZnO:Ga composite structures, which were then placed on p-PGaAs substrates. (4) ITO is coated on the n-AgNWs@ZnO:Ga composite structure as a cathode.

2. The ZnO micron-wire heterojunction high-brightness red light emitting diode according to claim 1, characterized in that: In step (1), the p-PGaAs substrate is annealed at a temperature of 700-900° C. and for a time of 1-2 h.

3. The ZnO micron-wire heterojunction high-brightness red light emitting diode according to claim 1, characterized in that: In step (3), the AgNWs concentration is 0.01-0.03 mg / mL.

4. The ZnO micron-wire heterojunction high-brightness red light emitting diode according to claim 1, characterized in that: In step (3), the length of the AgNWs is 2 to 90 um and the diameter is 20 to 120 nm.

5. The ZnO micron-wire heterojunction high-brightness red light emitting diode according to claim 1, characterized in that: In step (3), the method of spin coating AgNWs on the n-ZnO:Ga micron wire is as follows: using a pipette to drop the synthesized AgNWs on the ZnO:Ga micron wire, spin coating on a spin coater, and then drying for later use.

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