N-ZNO/N-GAN/N-ZNO HETEROJUNCTION-BASED BIDIRECTIONAL ULTRAVIOLET LIGHT-EMITTING DIODE AND PREPARATION METHOD THEREFOR

Abstract

The present invention discloses a bidirectional ultraviolet light emitting diode (UV LED) based on N—ZnO/N—GaN/N—ZnO heterojunction as well as its preparation method. The LED includes: N—ZnO microwires, a N—GaN film, a PMMA protective layer and alloy electrodes; and its preparation method includes the following steps: lay two N—ZnO microwires on the N—GaN film, then spin-coat a PMMA protective layer on the film to fix the N—ZnO microwires until the PMMA protective layer spreads over the N—ZnO microwires, and then place the film on a drying table to solidify the PMMA protective layer; then etch the PMMA protective layer with O.sub.2 to expose the N—ZnO microwires, and prepare alloy electrodes on different N—ZnO microwires to construct a N—ZnO/N—GaN/N—ZnO heterojunction to constitute a complete device. The present invention constructs an N/N/N symmetrical structure; the device is composed of N—ZnO and N—GaN, emits light in the ultraviolet region and has a small turn-on voltage.

Claims

1. A bidirectional ultraviolet light emitting diode (UV LED) based on N—ZnO/N—GaN/N—ZnO heterojunction is characterized by: it includes: N—ZnO microwires, a N—GaN film, a PMMA protective layer and alloy electrodes; two N—ZnO microwires are laid on the N—GaN film, and a PMMA protective layer is then spin-coated on the film to fix the N—ZnO microwires, and alloy electrodes are prepared on different N—ZnO microwires, respectively; the electron concentration of the N—ZnO micronwires is 10.sup.16-10.sup.19/cm.sup.3, and their electron mobility is 5-40 cm.sup.2/V.s.

2. (canceled)

3. A bidirectional UV LED based on N—ZnO/N—GaN/N—ZnO heterojunction described in claim 1 is characterized by: the N—GaN film is 0.5-10 μm thick, its electron concentration is 10.sup.17-10.sup.19/cm.sup.3, and its electron mobility is 20-100 cm.sup.2/V.s.

4. A bidirectional UV LED based on N—ZnO/N—GaN/N—ZnO heterojunction described in claim 1 is characterized by: the electrodes are all located on the N—ZnO microwires and are Ni/Au alloy electrodes or Ti/Au alloy electrodes.

5. The preparation method of a bidirectional UV LED based on N—ZnO/N—GaN/N—ZnO heterojunction is characterized by: it includes the following steps: (1) Mix and grind ZnO powder having a purity of 99.97-99.99% and 500 nm-2,000 nm carbon powder in a mass ratio of 1:1-1:1.3, and then fill the mixture into a ceramic boat; cut the silicon slice substrate into 3.2 cm×3 cm slices, then ultrasonically clean the silicon slices with a mixed solution of acetone and absolute ethanol and then dry them with nitrogen. Used as a type of growth substrate, the silicon slices are placed in a quartz tube having a length of 20 cm and a diameter of 8 cm with openings at both ends. The cleaned sapphire slice substrate is also placed in the quartz tube and is 10 cm away from the mouth of the tube. The entire quartz tube is pushed horizontally into a tube furnace for high temperature reaction and is infused with 150 sccm argon gas and 15 sccm oxygen gas; the substrate is composed of silicon slices or sapphire slices; (2) After the reaction, the N—GaN substrate is ultrasonically cleaned with acetone, absolute ethanol and deionized water in sequence and then dried with nitrogen; (3) Pick out two N—ZnO microwires from the reactant in Step (1), lay the two N—ZnO microwires on the N—GaN film, then spin-coat a PMMA protective layer on the film to fix the N—ZnO microwires until the PMMA protective layer spreads over the N—ZnO microwires, and then place the film on a drying table to solidify the PMMA protective layer; then etch the PMMA protective layer with O.sub.2 to expose the N—ZnO microwires, and prepare alloy electrodes on different N—ZnO microwires, respectively; (4) Measure the electrical properties of the N—ZnO/N—GaN/N—ZnO heterojunction-based LED finally produced in Step (3), and measure its electrically pumped luminescence spectrum.

6. The preparation method of a bidirectional UV LED based on N—ZnON—GaN/N—ZnO heterojunction described in claim 5 is characterized by: In Step (1), the temperature for high-temperature reaction is 1,000-1,100° C., and the reaction time is 90-180 minutes.

7. The preparation method of a bidirectional UV LED based on N—ZnON—GaN/N—ZnO heterojunction described in claim 5 is characterized by: In Step (3), the metal plating method is magnetron sputtering, thermal evaporation or electron beam evaporation, and the plating thickness is 20-60 nm.

Description

DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0018] FIG. 1 shows a scanning electron microscope image of the N—ZnO microrod synthesized in Embodiment case 1 of the present invention after etching.

[0019] FIG. 2 shows a schematic diagram of the structure of N—ZnO/N—GaN/N—ZnO heterojunction-based LED provided by the present invention.

[0020] FIG. 3 shows the electroluminescence (EL) spectra of the N—ZnO/N—GaN/N—ZnO heterojunction-based LED synthesized in Embodiment case 1 of the present invention under different injection AC voltages at room temperature.

EMBODIMENTS

[0021] As shown in FIG. 1 and FIG. 2, a bidirectional UV LED based on N—ZnO/N—GaN/N—ZnO heterojunction, including: N—ZnO microwires, a N—GaN film, a PMMA protective layer and alloy electrodes; two N—ZnO microwires are laid on the N—GaN film, and a PMMA protective layer is then spin-coated on the film to fix the N—ZnO microwires, and alloy electrodes are prepared on different N—ZnO microwires, respectively.

[0022] The electron concentration of the N—ZnO micronwires is 10.sup.16-10.sup.19/cm.sup.3, and their electron mobility is 5-40 cm.sup.2/V.s. The N—GaN film is 0.5-10 μm thick, its electron concentration is 10.sup.17-10.sup.19/cm.sup.3, and its electron mobility is 20-100 cm.sup.2/V.s. The electrodes are all located on the N—ZnO microwires and are Ni/Au alloy electrodes or Ti/Au alloy electrodes.

[0023] Correspondingly, the preparation method of a bidirectional UV LED based on N—ZnO/N—GaN/N—ZnO heterojunction includes the following steps: [0024] (1) Mix and grind ZnO powder having a purity of 99.97-99.99% and 500 nm-2,000 nm carbon powder in a mass ratio of 1:1-1:1.3, and then fill the mixture into a ceramic boat; cut the silicon slice substrate into 3.2 cm×3 cm slices, then ultrasonically clean the silicon slices with a mixed solution of acetone and absolute ethanol and then dry them with nitrogen. Used as a type of growth substrate, the silicon slices are placed in a quartz tube having a length of 20 cm and a diameter of 8 cm with openings at both ends. The cleaned sapphire slice substrate is also placed in the quartz tube and is 10 cm away from the mouth of the tube. The entire quartz tube is pushed horizontally into a tube furnace for high temperature reaction and is infused with 150 sccm argon gas and 15 sccm oxygen gas. [0025] (2) After the reaction, the N—GaN substrate is ultrasonically cleaned with acetone, absolute ethanol and deionized water in sequence and then dried with nitrogen; [0026] (3) Pick out two N—ZnO microwires from the reactant in Step (1), lay the two N—ZnO microwires on the N—GaN film, then spin-coat a PMMA protective layer on the film to fix the N—ZnO microwires until the PMMA protective layer spreads over the N—ZnO microwires, and then place the film on a drying table to solidify the PMMA protective layer; then etch the PMMA protective layer with O.sub.2 to expose the N—ZnO microwires, and prepare alloy electrodes on different N—ZnO microwires, respectively; [0027] (4) Measure the electrical properties of the N—ZnO/N—GaN/N—ZnO heterojunction-based LED finally produced in Step (3), and measure its electrically pumped luminescence spectrum.

[0028] In Step (1), the temperature for high-temperature reaction is 1,000-1,100° C., and the reaction time is 90-180 minutes. In Step (3), the metal plating method is magnetron sputtering, thermal evaporation or electron beam evaporation, and the plating thickness is 20-60 nm.

[0029] Embodiment case 1: [0030] (1) Mix and grind ZnO powder having a purity of 99.99% and 500 nm-2,000 nm carbon powder in a mass ratio of 1:1, and then fill the mixture into a ceramic boat; cut the silicon slice substrate into 3.2 cm×3 cm slices, then ultrasonically clean the silicon slices with a mixed solution of acetone and absolute ethanol and then dry them with nitrogen. Used as a type of growth substrate, the silicon slices are placed in a quartz tube having a length of 20 cm and a diameter of 8 cm with openings at both ends. The cleaned sapphire slice substrate is also placed in the quartz tube and is 10 cm away from the mouth of the tube. The entire quartz tube is pushed horizontally into a tube furnace for high temperature reaction and is infused with 150 sccm argon gas and 15 sccm oxygen gas. [0031] (2) After the reaction, the N—GaN substrate is ultrasonically cleaned with acetone, absolute ethanol and deionized water in sequence and then dried with nitrogen; [0032] (3) Pick out two N—ZnO microwires from the reactant in Step (1), lay the two N—ZnO microwires on the N—GaN film, then spin-coat a PMMA protective layer on the film to fix the N—ZnO microwires until the PMMA protective layer spreads over the N—ZnO microwires, and then place the film on a drying table to solidify the PMMA protective layer; then etch the PMMA protective layer with O.sub.2 to expose the N—ZnO microwires, and prepare alloy electrodes on different N—ZnO microwires, respectively; [0033] (4) Measure the electrical properties of the N—ZnO/N—GaN/N—ZnO heterojunction-based LED finally produced in Step (3), and measure its electrically pumped luminescence spectrum. Under different voltages at 100 Hz, the light-emitting positions of the LED are 371 nm and 385 nm, and the ultraviolet luminescence accounts for more than 85% of the total luminescence of the LED.

[0034] In Step (1), the temperature for high-temperature reaction is 1,000-1,100° C., and the above-mentioned reaction time is 120 minutes. In Step (3), the metal plating method is magnetron sputtering, thermal evaporation or electron beam evaporation, and the plating thickness is 45 nm.

[0035] FIG. 3 shows the electrically pumped luminescence spectrum of the N—ZnO/N—GaN/N—ZnO heterojunction-based LED synthesized in Embodiment case 1 under different AC voltages. The light-emitting positions of the LED are located at 371 nm and 385 nm and do not change with voltage.