CN102751418B - LED (light-emitting diode) tube core with ZnO-micron and nano composite structure and preparation method thereof - Google Patents

Abstract

The invention discloses an LED (light-emitting diode) tube core with a ZnO-micron and nano composite structure and a preparation method of the composite structure. The LED tube core is prepared in a way that a ZnO-micron graphic array grows on a luminous surface of the LED tube core and a nano rod vertically grows on the ZnO-micron graphic array.; The preparation method comprises the following steps: (1) planting an LED epitaxial wafer and preparing the LED tube core with a complete structure; (2) sputtering a layer of ZnO seed layer on the LED luminous surface; (3) preparing a photoresist micron periodic pattern on the LED surface; (4) taking the photoresist micron periodic pattern as a template to grow the ZnO-micron graphic array; (5) removing photoresist by glue removing liquid to obtain the ZnO-micron graphic array; (6) sputtering a layer of ZnO seed layer on the ZnO-micron graphic array, and (7) growing a ZnO nano rod array on the ZnO-micron graphic array. According to the invention, not only can the emitted light be extracted at higher ratio, but also the uniformity of light emitted from the entire light emitting surface of the light emitting diode is guaranteed.

Description

With the LED die and preparation method thereof of ZnO micron and nano composite structure

Technical field

The present invention relates to a kind of LED die, this tube core by with ZnO micro meter periodic figure and nanometer rods composite construction to improve its luminous efficiency, the invention still further relates to the preparation method of this LED die with ZnO micron graphic array and nanometer rods composite construction, belong to photoelectron technical field.

Background technology

LED is widely used, as fields such as various colorful display screen, LCD backlight, indicator light, white-light illuminating lamps in daily life due to advantages such as energy-saving and environmental protection.High efficiency, high-capacity LED have become the focus of research.Due to self refractive index of LED material high (GaN refractive index n ≈ 2.5), total internal reflection and Fresnel loss are very serious, only have small part light to extract from LED, limit the luminous efficiency of LED.For this problem, people carry out the method for micrometer structure or nanostructure process to improve light extraction efficiency to LED exiting surface, Chinese patent literature CN101110461 disclosed " utilizing the high efficiency light emitting diode with surface mini column array structure of diffraction effect ", at p-type GaN plasma coupled etch (ICP) micron pillar array structure, improve LED luminous efficiency by micron post diffraction effect.Have researcher to be used in recently extraction that mode micrometer structure making nanostructure strengthens LED light: the people such as Song are that template etches the micron array row in six side's cycles at the GaP exiting surface ICP of AlGaInP red-light LED with photoresist, be that template ICP etches sub-micron cone point with annealing Ag particle again, micron array row can improve LED light power 35%, sub-micron point structure can improve LED light power 32%, the composite construction of micron platform and sub-micron point improves the luminous power 72%(list of references Y.M.Song of LED, G.C.Park, S.J.Jang, J.H.Ha, J.S.Yu, and Y.T.Lee, Opt.Express, 19 (S2), A157-A165 (2011)).The people such as Lee nano impression in the ITO layer of GaN base LED makes polymethyl methacrylate (PMMA) six side's cycle micron pyramid figure (cycle 5um), nanoscale PMMA coarse surface is obtained again by high-density plasma bombardment, PMMA pyramid figure can improve LED light power 33%, nanometer alligatoring PMMA can improve LED light power 8%, PMMA micro-/nano compound structure can improve LED light power 37%(list of references Y.-C.Lee, C.-H.Ni, and C.-Y.Chen, Opt.Express, 18 (S4), A489-A498 (2010)).

Although the people such as Song carry out the micro-/nano compound structure of ICP etching at the GaP of AlGaInP red-light LED obtain good effect, but the voltage of LED die has certain rising, certain destruction is caused to LED die, the method is very thin for the p-type GaN of the thin LED(GaN base LED of epitaxial loayer, usually at about 200nm), very easily cause electric leakage after ICP etching or extremely manage, this method does not have universality, and etching depth is very shallow, alligatoring DeGrain, not obvious for raising LED luminous efficiency, moreover ICP equipment price is expensive, cost is high; The people such as Lee test LED surface made PMMA micro-/nano compound structure, but encapsulating material is also PMMA, this just cause original micro-/nano compound structure is submerged, and do not have the effect strengthening light and extract.

Summary of the invention

The defect existed for the various method of existing raising light extraction efficiency of LED and problem, the invention provides a kind of on LED electrical performance without impact, the LED die with ZnO micron and nano composite structure that can significantly improve LED luminous efficiency, a kind of preparation method of this LED die is provided simultaneously.

LED die with ZnO micron and nano composite structure of the present invention, be that growth has ZnO micron graphic array in the light-emitting area of LED die, on ZnO micron graphic array, vertical-growth has nanometer rods.

Described ZnO micron graphic array can be one-dimensional grating structure, or the two-dimensional grating structure of ZnO micron mesh composition, also can be the periodic array of micron ZnO post composition.Micron mesh or micron post are six sides or cubic periodic arrangement.

The diameter of described ZnO nanorod is 50nm-300nm, is highly 200nm-1.5 μm,

Above-mentioned LED die is by improving LED luminous efficiency by ZnO micro meter periodic figure and ZnO nanorod composite construction.

The preparation method of the above-mentioned LED die with ZnO micron and nano composite structure, comprises the following steps:

(1) by the method for metal organic chemical vapor deposition (MOCVD) at the complete epitaxial slice structure of substrate Epitaxial growth, make complete LED die structure;

(2) sputter in the light-emitting area of LED die the ZnO Seed Layer that thickness is 20nm-400nm;

(3) in a ZnO Seed Layer, by mask lithography technique (whirl coating, photoetching, exposure and development), photoresist micro meter periodic figure is obtained;

(4) with photoresist micro meter periodic figure for template growth ZnO micron graphic array: the LED die that step (3) obtains is inserted hydro-thermal reaction in the precursor mixed liquor of Treatment with High Concentration Zinc source, zinc source precursor mixed liquor is the mixed liquor of zinc nitrate or zinc acetate and ammoniacal liquor or hexamethylenetetramine solution, zinc nitrate or acetic acid zinc concentration are 0.1M-0.5M, ph value of mixture is 6-8, hydro-thermal reaction 1 hour-12 hours under 60 DEG C of-100 DEG C of water temperatures, then room temperature is down to, take out rear deionized water rinsing, dry up with nitrogen; ZnO grows and merges extension in the gap of photoresist, and close-packed arrays fills up the gap of photoresist;

(5) spend glue and remove photoresist, obtain the ZnO micron graphic array of photoresist anti-graphics;

(6) on ZnO micron graphic array, sputter by magnetic control sputtering device the 2nd ZnO Seed Layer that thickness is 20nm-200nm;

(7) on ZnO micron graphic array, the 2nd ZnO Seed Layer growing ZnO nanorod arrays is passed through: the LED die that step (6) obtains is inserted hydro-thermal reaction in the precursor mixed liquor of low concentration zinc source, zinc source precursor mixed liquor is the mixed liquor of zinc nitrate or zinc acetate and ammoniacal liquor or hexamethylenetetramine solution, zinc nitrate or acetic acid zinc concentration are 0.03M-0.07M, ph value of mixture is 6-8, hydro-thermal reaction 1 hour-6 hours under 60 DEG C of-100 DEG C of water temperatures, then room temperature is down to, take out rear deionized water rinsing, dry up with nitrogen, namely on ZnO micron graphic array, nanometer rods is grown, obtain ZnO micron graphic array and nanometer rods composite construction,

(8) by thinning, single led tube core is dissociated into.

(micron mesh or micron post are six sides or cubic periodic arrangement to the periodic arrangement mode of the ZnO micron graphic array in described step (5), one-dimensional grating is parallel stripe-arrangement), the cycle 0.5 μm-20 μm), figure duty ratio (0.2-0.8) and graphics shape (circular, square, hexagon or triangle etc.) the photoresist template that can be made by photoetching process regulates, pattern height (0.5 μm-10 μm) can be regulated by the ZnO hydrothermal growth time (1 hour-12 hours).

Template made by proposition figure photoresist of the present invention, ZnO micro meter periodic graphic structure is gone out in LED die superficial growth by hydro thermal method, again at ZnO micro meter periodic patterned surface growing ZnO nanorod, improve LED luminous efficiency by ZnO micro meter periodic figure and ZnO nanorod composite construction.The ZnO grown in the precursor solution of Treatment with High Concentration Zinc source is compact arranged entirety, ZnO micron graphic structure (grid or post) has obvious fiber waveguide effect, utilizing emitted light can be derived efficiently, ZnO micron graphic structure is also a kind of micron-sized photonic crystal or diffraction grating simultaneously, utilize diffraction and the scattering principle of ZnO micron graphic structure, high efficiency derivation utilizing emitted light; The separation ZnO nanorod energy alligatoring ZnO micro meter periodic patterned surface further simultaneously grown in low concentration solution, strengthen the Scattering and diffracting of light, the light be limited in the waveguide of ZnO figure is extracted further, not only can more a high proportion of extraction utilizing emitted light, also ensure that the uniformity of the whole light-emitting area bright dipping of light-emitting diode.The present invention makes simply, and cost is low; And only at exiting surface growth ZnO micron graphic array and the nanometer rods composite construction of LED, can not damage the electric property of LED die, the luminous efficiency about 75% of dull and stereotyped GaN base LED can be improved.

Accompanying drawing explanation

Fig. 1 is the schematic cross-section that growth has the coplanar electrode GaN base LED die of ZnO micro meter periodic figure/nanometer rods composite construction array.

Fig. 2 is the schematic cross-section that growth has the laser lift-off vertical stratification GaN base LED die of ZnO micro meter periodic graphic array/nanometer rods composite construction.

Fig. 3 is the cubic ZnO micron mesh grating in 5.5 μm of cycles and Scanning Electron microscope (SEM) picture of the composite construction of ZnO nanorod that make in LED surface.

Fig. 4 is the cubic ZnO micron mesh grating prepared of the present invention and nanometer rods composite construction LED(MM/NR-LED), cubic ZnO micron mesh optical grating construction LED(MM-LED), the electric current-optical output power curve comparison figure of ZnO nanorod LED (NR-LED) and traditional LED (C-LED).

Fig. 5 is voltage-to-current (V-I) the curve comparison figure of the present invention MM/NR-LED, MM-LED, NR-LED of preparing and traditional C-LED.

Wherein: 1, substrate, 2, u-shaped GaN resilient coating, 3, n-type GaN layer, 4, multi-quantum well active region, 5, P type GaN layer, 6, current extending, 7, ZnO Seed Layer, 8, p-electrode, 9, n-electrode, 10, ZnO micro meter periodic figure and nanometer rods composite construction, 11, metal electrode, 12, conductive silicon chip, 13, bonding metal layer, 14, reflector, 15, P type GaN layer, 16, multi-quantum well active region, 17, n-type GaN layer, 18, n-electrode, 19, ZnO Seed Layer, 20, ZnO micro meter periodic figure/nanometer rods composite construction.

Embodiment

LED die with ZnO micron graphic array of the present invention, as shown in Figure 1 or 2, its structure is the light-emitting area (current extending 6 of the coplanar electrode GaN base LED die shown in Fig. 1 in LED die, the n-type GaN layer 17 of the laser lift-off vertical stratification GaN base LED die shown in Fig. 2) upper sputtering has ZnO Seed Layer 7, in ZnO Seed Layer 7, growth has ZnO micron graphic array, on ZnO micron graphic array, growth has nanometer rods, forms ZnO micro meter periodic figure and nanometer rods composite construction 10.The growth course of the LED die with ZnO micro meter periodic figure and nanometer rods composite construction 10 is described for the coplanar electrode GaN base LED shown in Fig. 1 below, specifically comprises the steps:

(1) as shown in Figure 1, with the method complete epitaxial slice structure of epitaxial growth on substrate 1 of metal organic chemical vapor deposition (MOCVD), substrate 1 is provided with from bottom to top successively u-shaped GaN resilient coating 2, n-type GaN layer 3, multi-quantum well active region 4 and P type GaN layer 5; With electron beam evaporation plating one deck ITO(tin-doped indium oxide in P type GaN layer 5) current extending 6; Current extending 6 arranges p-electrode 8, N-shaped GaN3 arranges n-electrode 9, obtain complete coplanar electrode GaN base LED die structure;

(2) on the current extending 6 on LED die surface, first thick ZnO Seed Layer 7 of the good 20nm-400nm of one deck compact crystal is sputtered, see Fig. 1 with magnetic control sputtering device;

(3) in first ZnO Seed Layer 7, by mask lithography technique (Lithographic template four directions periodic structure, cycle 5.5 μm, whirl coating, photoetching, exposure and development), cycle 5.5 μm cubic photoresist micro meter periodic figure is obtained;

(4) with photoresist micro meter periodic figure for template growth ZnO micron graphic array: the LED die that step (3) obtains is inserted in the precursor mixed liquor of Treatment with High Concentration Zinc source, zinc source precursor mixed liquor is the mixed liquor of zinc nitrate or zinc acetate and ammoniacal liquor or hexamethylenetetramine solution, zinc nitrate or acetic acid zinc concentration are 0.1M-0.5M, ph value of mixture is 6-8, hydro-thermal reaction 1 hour-12 hours under 60 DEG C of-100 DEG C of water temperatures, then room temperature is down to, take out rear deionized water rinsing, dry up with nitrogen, ZnO grows and merges extension in the gap of photoresist, close-packed arrays fills up the gap of photoresist.

(5) spend glue and remove photoresist, namely obtain the ZnO micron graphic array of photoresist anti-graphics, the cycle 5.5 μm (cycle regulates by Lithographic template in 0.5 μm-20 μm) of ZnO micron graphic array.

The photoresist template graphics that the concrete figure duty ratio (0.2-0.8) of ZnO micron graphic array and graphics shape (circular, square, hexagon or triangle etc.) can be made by photoetching process regulates.The ZnO micron graphic array obtained can be two-dimensional grating structure (the photoresist template cycle micron rod structure of ZnO micron mesh or grid composition, namely anti-graphics is micron mesh or grid), also can be the periodic array (photoresist template cycle micron mesh or grid, namely anti-graphics is a micron post) of micron ZnO post composition.The shape of ZnO micron graphic array can be six sides or cubic periodic structure, or one-dimensional grating structure.The concrete pattern height (0.5 μm-10 μm) of ZnO micron graphic array can by ZnO hydrothermal growth Timing.

(6) on ZnO micron graphic array, second thick ZnO Seed Layer of one deck 20nm-200nm is sputtered with magnetic control sputtering device.

(7) on ZnO micron graphic array, second ZnO Seed Layer growing ZnO nanorod arrays is passed through: the LED die that step (6) obtains is inserted in the precursor mixed liquor of low concentration zinc source, zinc source precursor mixed liquor is the mixed liquor of zinc nitrate or zinc acetate and ammoniacal liquor or hexamethylenetetramine solution, zinc nitrate or acetic acid zinc concentration are 0.03M-0.07M, ph value of mixture is 6-8, hydro-thermal reaction 1 hour-6 hours under 60 DEG C of-100 DEG C of water temperatures, then room temperature is down to, take out rear deionized water rinsing, dry up with nitrogen; Namely long on ZnO micron graphic array have ZnO nanorod, obtains ZnO micro meter periodic figure and nanometer rods composite construction 10.

Fig. 3 gives the cubic ZnO micron mesh grating in 5.5 μm of cycles and Scanning Electron microscope (SEM) figure of ZnO nanorod composite construction array that make in LED surface.

(8) by thinning, be dissociated into singulated dies, be made into device.

Fig. 2 gives the cross section structure that growth has the laser lift-off vertical stratification GaN base LED of ZnO micro meter periodic figure and nanometer rods composite construction, bonding metal layer 13, reflector 14, P type GaN layer 15, multi-quantum well active region 16, n-type GaN layer 17, ZnO Seed Layer 19 and ZnO micro meter periodic figure and nanometer rods composite construction 20 is provided with successively on conductive silicon chip 12, n-type GaN layer 17 is provided with n-electrode 18, the bottom surface of conductive silicon chip 12 is provided with metal electrode 11.Wherein the process of making ZnO micro meter periodic figure and nanometer rods composite construction 20 is the same with above-mentioned steps (2), (3), (4), (5), (6) and (7).

ZnO micro meter periodic figure prepared by the present invention and nanometer rods composite construction LED (MM-LED), ZnO micron graphic array coplanar electrode GaN base LED(MM-LED), ZnO nano-rod array LED(NR-LED) and traditional coplanar electrode GaN base LED (C-LED) electric current--optical output power curve comparison as shown in Figure 4, under 20mA electric current, ZnO micron graphic array can improve LED light power 42.1%, ZnO nano-rod array can improve LED light power 49.7%, ZnO micro meter periodic figure/nanometer rods composite construction array can improve LED light power 75.7%, under 100mA electric current, ZnO micron graphic array can improve LED light power 39.5%, ZnO nano-rod array can improve LED light power 50.7%, ZnO micro meter periodic figure/nanometer rods composite construction array can improve LED light power 72.7%, as shown in Figure 5, ZnO micro meter periodic figure/nanometer rods composite construction array LED and traditional LED current voltage curve overlap voltage--electric current (V-I) curve comparison.From Fig. 4 and Fig. 5, ZnO micro meter periodic figure prepared by the present invention and the luminous efficiency of nanometer rods composite construction array to GaN base LED are significantly increased, and do not have a significant effect to the electric property of LED.

The present invention has the following advantages:

(1) micron and nanometer secondary structure fully improve the light extraction efficiency of light-emitting diode.ZnO refractive index (n ≈ 2.0) is between air and LED material (GaN n ≈ 2.5, GaP n ≈ 3.2) between, play the effect of gradually changed refractive index, and this design takes full advantage of the fiber waveguide effect of light in ZnO micro meter periodic mesh or micron post and diffraction effect makes utilizing emitted light efficiently derive, ZnO nanorod energy alligatoring ZnO micro meter periodic patterned surface further, increase the scattering of light, the transversal waveguides light scattering be limited in ZnO micro meter periodic figure is derived, thus clearly enhances the light extraction efficiency of LED.Compared with the LED of traditional employing surface roughening process, this structure can obtain higher optical efficiency.

(2) technique is simple, and cost is low.Photoresist template is made owing to adopting traditional photoetching process, with traditional hydro-thermal reflection growth ZnO micron graphic array and ZnO nanorod, relative traditional IC P etching makes photonic crystal or optical grating construction, and making step is simple, equipment cost is low, and material therefor ZnO is with low cost.

(3) on LED electrical performance without impact.ZnO micron graphic array and nanometer rods composite construction are long in LED light-emitting area, and production environment is gentle, to LED die structure itself without changing, avoid ICP, corrode destruction to LED structure, before and after structure fabrication, LED electrical performance is highly stable, to LED electrical performance without any harmful effect.

(4) the present invention is not only applicable to GaN base flat LED, PSS substrate LED, vertical structure LED, inverted structure LED, is also applicable to other visible light wave ranges, the semiconductor LED of material system and the making of Organic Light Emitting Diode.

Claims (2)

1. with a LED die for ZnO micron and nano composite structure, it is characterized in that: in the light-emitting area of LED die, growth has ZnO micron graphic array, and on ZnO micron graphic array, vertical-growth has nanometer rods; Described ZnO micron graphic array is one-dimensional grating structure, or the two-dimensional grating structure of ZnO micron mesh composition, or the periodic array of micron ZnO post composition; Described micron mesh or micron post are six sides or cubic periodic arrangement; The diameter of described ZnO nanorod is 50nm-300nm, is highly 200nm-1.5 μm.

2. described in claim 1 with a preparation method for the LED die of ZnO micron and nano composite structure, it is characterized in that, comprise the following steps:

(1) by the method for metal organic chemical vapor deposition at the complete epitaxial slice structure of substrate Epitaxial growth, make complete LED die structure;

(2) sputter in the light-emitting area of LED die the ZnO Seed Layer that thickness is 20nm-400nm;

(3) in a ZnO Seed Layer, by mask lithography technique, photoresist micro meter periodic figure is obtained;

(4) with photoresist micro meter periodic figure for template growth ZnO micron graphic array: the LED die that step (3) obtains is inserted hydro-thermal reaction in the precursor mixed liquor of Treatment with High Concentration Zinc source, zinc source precursor mixed liquor is the mixed liquor of zinc nitrate or zinc acetate and ammoniacal liquor or hexamethylenetetramine solution, zinc nitrate or acetic acid zinc concentration are 0.1M-0.5M, ph value of mixture is 6-8, hydro-thermal reaction 1 hour-12 hours under 60 DEG C of-100 DEG C of water temperatures, then room temperature is down to, take out rear deionized water rinsing, dry up with nitrogen; ZnO grows and merges extension in the gap of photoresist, and close-packed arrays fills up the gap of photoresist;

(5) spend glue and remove photoresist, obtain the ZnO micron graphic array of photoresist anti-graphics;

(6) on ZnO micron graphic array, sputter by magnetic control sputtering device the 2nd ZnO Seed Layer that thickness is 20-200nm;

(7) on ZnO micron graphic array, the 2nd ZnO Seed Layer growing ZnO nanorod arrays is passed through: the LED die that step (6) obtains is inserted hydro-thermal reaction in the precursor mixed liquor of low concentration zinc source, zinc source precursor mixed liquor is the mixed liquor of zinc nitrate or zinc acetate and ammoniacal liquor or hexamethylenetetramine solution, zinc nitrate or acetic acid zinc concentration are 0.03M-0.07M, ph value of mixture is 6-8, hydro-thermal reaction 1 hour-6 hours under 60 DEG C of-100 DEG C of water temperatures, then room temperature is down to, take out rear deionized water rinsing, dry up with nitrogen, namely on ZnO micron graphic array, nanometer rods is grown, obtain ZnO micron graphic array and nanometer rods composite construction,

(8) by thinning, single led tube core is dissociated into.