CN102214738B - Method for preparing TiO2 (titanium dioxide) nano-pillar array on surface of LED (light-emitting diode) epitaxial wafer - Google Patents
Method for preparing TiO2 (titanium dioxide) nano-pillar array on surface of LED (light-emitting diode) epitaxial wafer Download PDFInfo
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- CN102214738B CN102214738B CN201110107701A CN201110107701A CN102214738B CN 102214738 B CN102214738 B CN 102214738B CN 201110107701 A CN201110107701 A CN 201110107701A CN 201110107701 A CN201110107701 A CN 201110107701A CN 102214738 B CN102214738 B CN 102214738B
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Abstract
The invention discloses a method for preparing a TiO2 (titanium dioxide) nano-pillar array on a surface of an LED (light-emitting diode) epitaxial wafer. The method comprises the following steps: (1) preparing a GaN (gallium nitride) epitaxial wafer on a sapphire substrate; (2) evaporating a titanium layer on a surface of a P-type GaN layer of the epitaxial wafer, and carrying out calcination to transform titanium into TiO2 which is taken as a seeding layer; (3) adopting a hydrothermal method to prepare the TiO2 nano-pillar array, placing an HCl (hydrogen chloride) solution into an autoclave, stirring at a room temperature and adding tetrabutyl titanate to prepare a mixture solution; placing an epitaxial wafer with the TiO2 seedling layer into the mixture solution, leaning against a lining wall of the autoclave in a heeling condition, reacting for 1-24 hours at 120 DEG C-180 DEG C and cooling to the room temperature. The method is simple and practicable and has the advantages of low cost, high controllability, good homogenization and a periodical array is easy to form; in addition, the method can be utilized to improve the light-emitting efficiency of an LED, and the photoluminescence intensity of the LED can be improved by 7-8 times.
Description
Technical field
The present invention relates to a kind of at LED (light-emitting diode) epitaxial wafer surface preparation titanium dioxide (TiO
2) method of nano column array, belong to the photoelectron technology field.
Background technology
Earlier 1990s is that the third generation wide bandgap semiconductor materials of representative has obtained historical breakthrough with the nitride, on the GaN sill, successfully prepares green, blueness and purple LED, makes the LED white-light illuminating become possibility.Along with improving constantly of GaN base LED performance, add the white light LEDs luminous efficiency that fluorescent material prepares with short wavelength LED and be greatly enhanced, at present by industry be known as be can replace incandescent, the so-called green illumination light source of traditional lighting light fixture such as fluorescent lamp.Be widely used at present view brightening, street lighting, room lighting and be the special lighting field of representative with the mine lamp.
The LED luminous efficiency is by LED internal quantum efficiency (η
Int) and light extraction efficiency (η
Extr) decision (but list of references M.K.Kwon, J.Y.Kim, K.S.II.Kyu Park, G.Y.Kim, S.J.Jung, J.W.Park, Kim, Y.C.Kim, Appl.Phys.Lett.92 (2008) 251110).The approach that improves the LED luminous efficiency generally has two kinds, and a kind of is the internal quantum efficiency that improves LED, and this quality and structure with epitaxial wafer is relevant; Second kind of approach is to improve the extraction efficiency of light.The light-emitting diode internal quantum efficiency is than higher, and the internal quantum efficiency of blue-ray LED can be reached for 60%-70%, and the internal quantum efficiency of red-light LED can be up to 99%.Therefore want to improve the luminous efficiency of LED, relatively effective method is the extraction efficiency that improves light.
The main cause that influences the extraction efficiency of LED light is; The refractive index of light-emitting diode semi-conducting material and air (the GaN refractive index n ≈ 2.5 that differs greatly; Air refraction n ≈ 1); Total internal reflection and Si Nieer loss cause SQW to produce the little and boundary reflection rate height of shooting angle of light, and the wide part that active area produces is owing to the total internal reflection of air and interface is limited in can't extracting in the semiconductor, for the GaN material; The critical angle of escape cone is approximately 23 °, the light outside the escape cone because of total reflection by substrate or active layer or electrode repeated reflection or absorb.Rough estimate has only 1/4n
2Light can be extracted out, for blue-ray LED, only have 4% light to be extracted out.
Therefore, reduce total reflection, increase the critical angle of escape light cone, become the effective means that improves extraction efficiency.Surface coarsening is a kind of method commonly used.Utilize special epitaxial growth (but list of references W.Lee, J.Limb, J.H.Ryou; D.Yoo, T.Chung, R.D.Dupuis; Influence of growth temperature and growth rate of p-GaN layers on the characteristics of green light emitting diodes, J.Electron.Mater., 2006; 35,587-591.), dry etching P-GaN (can disclosed with reference to Chinese patent document CN101494272A " can make the manufacture method of the P-GaN laminar surface alligatoring of LED "), wet etching P-GaN (but list of references C.Huh, K.S.Lee; E.J.Kang, S.J.Park, Improved light-output and electrical performance of InGaN-based light-emitting diode by microroughening of the p-GaN surface; J.Appl.Phys.; 2003,93,9383-9385) etc. the method for acquisition surface coarsening all can improve the LED light extraction efficiency.But because the coarse P-GaN surface of epitaxial growth needs the extra epitaxial growth time, so cost is also than higher; The dry etching epitaxial loayer may cause damage to active area, thereby reduction even counteracting are to the effect of luminous enhancing; The wet etching method is because the GaN chemical property is more stable; Wet etching will be used corrosive solutions such as strong acid and strong base usually; To very inconvenience of operation; And because the isotropism of wet etching is easy to produce undercutting and crosses erosion, the size of alligatoring and the degree of depth receive certain restriction (usually less than 100nm).Method through nano impression such as Kyung-Min Yoon in the blue-ray LED surface preparation TiO
2Nano column array, improved effectively LED bright dipping (but list of references Kyung-Min Yoon, Ki-Yeon Yang; Kyeong-Jae Byeon; Heon Lee, Ffficient GaN slab vertical light-emitting diode covered wth a patterned high-index layer.APPLIED PHYSICS LETTERS 92,241118 (2008)); But this method cost is bigger; And have unicity, the corresponding a kind of nano column array of impression block is not easy to prepare difform nano column array.
Summary of the invention
The present invention is directed to the defective and the problem of the whole bag of tricks existence of the existing LED of raising luminous efficiency, provide a kind of method LED epitaxial wafer surface preparation TiO simple, with low cost
2The method of nano column array.
LED epitaxial wafer surface preparation TiO of the present invention
2The method of nano column array may further comprise the steps:
(1) method of applied metal organic chemical vapor deposition (MOCVD) epitaxial growth N type GaN layer, MQW active area and P type GaN layer successively on Sapphire Substrate forms epitaxial wafer;
(2) at the thick titanium of P type GaN laminar surface vapor deposition one deck 1nm-200nm, calcined 1 hour-5 hours down at 400 ℃-600 ℃ then, make titanium change TIO into
2, as Seed Layer;
(3) adopt Hydrothermal Preparation TiO
2Nano column array is put into autoclave with the HCl solution of 20mL concentration 3M-8M, stirs 1 minute-10 minutes under the room temperature, adds the 0.1mL-5mL butyl titanate, stirs 5 minutes, processes mixed solution; To have TiO
2The epitaxial wafer of Seed Layer is put into mixed solution and is leaned against on the inner liner wall of autoclave with heeling condition, reacts 1 hour-24 hours down at 120 ℃-180 ℃, then cool to room temperature.
The heeling condition of epitaxial wafer is that the angle of inclination with horizontal plane is the 5-80 degree in the said step (3).
The present invention adopts and prepares one deck Seed Layer at the P-GaN laminar surface earlier, uses the controlled TiO of Hydrothermal Growth pattern again
2Nano column array can obviously improve the luminous efficiency of LED, and its photoluminescence intensity can improve 7-8 doubly, and the present invention has that cost is low, simple, controllability is high, good uniformity, be prone to form the characteristics of cyclic array.
Description of drawings
Fig. 1 is that the present invention prepares TiO
2The flow chart of nano column array.
Fig. 2 is the TiO that the present invention prepares
2The structural representation of nano column array.
Fig. 3 is the TiO that the present invention prepares
2The SEM of nano column array (scanning electron microscopy) picture.
Fig. 4 is the TiO that the present invention prepares
2The photoluminescence intensity comparison diagram of nano column array LED epitaxial wafer (NR-LED) and traditional LED epitaxial wafer (C-LED).
Wherein: 1, Sapphire Substrate, 2, N type GaN layer, 3, the MQW active area, 4, P type GaN layer, 5, TiO
2Seed Layer, 6, TiO
2Nano column array.
Embodiment
Embodiment 1
As shown in Figure 1, the present invention uses TiO
2Nano column array improves LED epitaxial wafer photoluminescence efficiency, this TiO
2The preparation method of nano column array, because GaN is a hexagonal structure, TiO
2Be tetragonal, so the TiO that on GaN, grows earlier
2Need growth one deck Seed Layer earlier during array.Specifically comprise the steps:
(1) method of applied metal organic chemical vapor deposition (MOCVD) epitaxial growth N type GaN layer 2, MQW active area 3 and P type GaN layer 4 successively on Sapphire Substrate 1 forms epitaxial wafer;
(2), calcined 3 hours down, make titanium change TiO into for 500 ℃ at the thick titanium of P type GaN surface vapor deposition one deck 50nm
2, become TiO
2As Seed Layer 5;
(3) Hydrothermal Preparation TiO
2 Nano column array 6 is put into autoclave with the HCl solution 20mL of 4M, stirs 5min under the room temperature, adds the 1mL butyl titanate, stirs 5min, processes mixed solution; To have TiO
2The GaN substrate of Seed Layer 5 is put into mixed solution and is leaned against on the inner liner wall with the heeling condition horizontal by 30 degree, and 180 ℃ are reacted 4h, cool to room temperature down.
The TiO of present embodiment preparation
2The structure of nano column array 6 is as shown in Figure 2.The TiO that obtains
2Nano-pillar is a rutile structure, and its SEM pattern is as shown in Figure 3.
Fig. 4 has provided has TiO of the present invention
2The LED epitaxial wafer (NR-LED) of nano column array and the contrast of the photoluminescence intensity of traditional LED epitaxial wafer (C-LED) are shown, can be known to have TiO of the present invention by Fig. 4
2The photoluminescence intensity of the LED epitaxial wafer of nano column array significantly improves.
Embodiment 2
What present embodiment and embodiment 1 were different is:
At the thick titanium of P type GaN laminar surface vapor deposition one deck 1nm, calcined 1 hour down, make titanium change TiO into for 400 ℃ in the step (2)
2
HCl solution 20mL with 3M in the step (3) puts into autoclave, stirs 1min under the room temperature, adds the 1mL butyl titanate, stirs 5min, processes mixed solution; To have TiO
2The GaN substrate of Seed Layer 5 is put into mixed solution and is leaned against on the inner liner wall with the heeling condition horizontal by 5 degree, and 120 ℃ are reacted 24h, cool to room temperature down.
Embodiment 3
What present embodiment and embodiment 1 were different is:
At the thick titanium of P type GaN surface vapor deposition one deck 200nm, calcined 2 hours down, make titanium change TiO into for 600 ℃ in the step (2)
2
HCl solution 20mL with 8M in the step (3) puts into autoclave, stirs 10min under the room temperature, adds the 5mL butyl titanate, stirs 5min, processes mixed solution; To have TiO
2The GaN substrate of Seed Layer 5 is put into mixed solution and is leaned against on the inner liner wall with the heeling condition horizontal by 80 degree, and 150 ℃ are reacted 1h, cool to room temperature down.
What present embodiment and embodiment 1 were different is:
At the thick titanium of P type GaN surface vapor deposition one deck 100nm, calcined 2.5 hours down, make titanium change TiO into for 450 ℃ in the step (2)
2
HCl solution 20mL with 6M in the step (3) puts into autoclave, stirs 8min under the room temperature, adds the 3mL butyl titanate, stirs 5min, processes mixed solution; To have TiO
2The GaN substrate of Seed Layer 5 is put into mixed solution and is leaned against on the inner liner wall with the heeling condition horizontal by 60 degree, and 160 ℃ are reacted 15h, cool to room temperature down.
Claims (2)
1. LED epitaxial wafer surface preparation TiO
2The method of nano column array is characterized in that, may further comprise the steps:
(1) method of applied metal organic chemical vapor deposition epitaxial growth N type GaN layer, MQW active area and P type GaN layer successively on Sapphire Substrate forms epitaxial wafer;
(2) at the thick titanium of P type GaN laminar surface vapor deposition one deck 1nm-200nm, calcined 1 hour-5 hours down at 400 ℃-600 ℃ then, make titanium change TiO into
2, as Seed Layer;
(3) adopt Hydrothermal Preparation TiO
2Nano column array is put into autoclave with the HCl solution of 20mL 3M-8M, stirs 1 minute-10 minutes under the room temperature, adds the 0.1mL-5mL butyl titanate, stirs 5 minutes, processes mixed solution; To have TiO
2The epitaxial wafer of Seed Layer is put into mixed solution and is leaned against on the inner liner wall of autoclave with heeling condition, reacts 1 hour-24 hours down at 120 ℃-180 ℃, then cool to room temperature.
2. LED epitaxial wafer surface preparation TiO according to claim 1
2The method of nano column array is characterized in that, the heeling condition of epitaxial wafer is that the angle of inclination with horizontal plane is the 5-80 degree in the said step (3).
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| CN103165779B (en) * | 2013-02-08 | 2016-04-06 | 芜湖德豪润达光电科技有限公司 | LED semiconductor element and manufacture method thereof |
| CN103500778B (en) * | 2013-10-23 | 2016-01-20 | 山东大学 | A kind of embedding TiO 2nanometer rods graphic array improves the method for LED luminous efficiency |
| CN103681989B (en) * | 2013-12-09 | 2016-04-06 | 广州有色金属研究院 | A kind of preparation method of LED light output surface nano barium titanate salt deposit |
| CN104659179A (en) * | 2015-03-10 | 2015-05-27 | 江苏新广联半导体有限公司 | Anti-reflection transparency electrode structure for GaN-based LED and method for processing the structure |
| CN106784183B (en) * | 2016-12-19 | 2019-06-11 | 华灿光电（浙江）有限公司 | A kind of LED chip and preparation method thereof |
| CN106653973B (en) * | 2016-12-19 | 2019-06-11 | 华灿光电（浙江）有限公司 | A kind of LED chip and preparation method thereof |
| CN106981552B (en) * | 2017-02-15 | 2019-04-12 | 华灿光电（浙江）有限公司 | A kind of chip of light emitting diode and preparation method thereof |
| CN108198914B (en) * | 2017-12-29 | 2019-08-02 | 青岛科技大学 | A kind of inserted TiO2The method of nanometer rods cluster periodic array raising LED luminous efficiency |
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| CN101899709A (en) * | 2010-08-13 | 2010-12-01 | 浙江大学 | Method for preparing titanium dioxide nano rod array with adjustable size and density on titanium surface |
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| CN101899709A (en) * | 2010-08-13 | 2010-12-01 | 浙江大学 | Method for preparing titanium dioxide nano rod array with adjustable size and density on titanium surface |
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Application publication date: 20111012 Assignee: Shandong Keheng Crystal Material Technologies Co., Ltd. Assignor: Shandong University Contract record no.: 2013370000074 Denomination of invention: Method for preparing TiO2 nano column array on surface of LED epitaxial wafer Granted publication date: 20121017 License type: Exclusive License Record date: 20130407 |
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