A kind of preparation of the LED structure of graded index nanostructure combination nano lens
Method
Technical field
The present invention relates to a kind of semiconductor electronic component preparation method, especially a kind of system of new and effective LED structure
Standby technique.
Background technique
As the substitute products of conventional lamp, solid-state semiconductor lighting source development prospect is wide, is known as a new generation
Light source [Science 308,1274-1278 (2005)].In recent years, nitride compound semiconductor device especially light emitting diode
(Light emitting diode, LED) illuminating device achieves great progress (Nobel Prize in 2014), answers extensively
For fields [Photonics Research 3,184 (2015)] such as white-light illuminating, indicator light, signal and colored displays.So
And LED will develop into a kind of light source of the versatility of high quality, substitute other light sources completely, it is also necessary to it solves to improve light efficiency,
The problems such as reducing cost, reducing chip calorific value, improve LED service life, and these problems are all imitated by quantum outside LED
Relatively low restriction [the Acta Materialia 61,945-951 of rate (external quantum efficiency, EQE)
(2013)].The EQE of LED is by internal quantum efficiency (internal quantum efficiency, IQE) and extraction efficiency (light
Extraction efficiency, LEE) it determines, expression is [Physics Reports 498,189-241 (2011)].Closely
Nian Lai, by improving the structure and growth pattern of active area, IQE obtains biggish promotion, it was reported that InGaN/GaN Quantum Well
The IQE of LED can achieve 90% or more [Applied Physics Letters 94,023101 (2009)].However, due to nitrogen
Compound LED material and air have biggish refringence, and only a small number of photon energy escapes into air, most of others
Photon is totally reflected at interface, is reabsorbed or is formed wave guide mode by material, cause the LEE of LED still lower, which has limited
Application and the development of LED.
Since GaN material has higher refractive index (n=2.5), so as to cause the lower extraction efficiency of LED, therefore, utilization is micro-
Nanotechnology prepares relevant micro nano structure (or coarse surface), to increase the critical angle of light output, it should be most straight
Connect the method for improving LED light extraction efficiency.The outermost layer of conventional LED chips is current extending, and indium tin oxide (indium
Tin oxide, ITO) material has been substituted current extending of traditional nickel gold material as LED at present.The refractive index of ITO is big
About 2, light is emitted to low-index material from high-index material, and be primarily present both sides loss: first is due to being all-trans
It penetrates and makes light output critical angle smaller;Second is Fresnel transmission loss.Dropping low-loss principle is using gradient index
Rate medium reduces Fresnel transmission loss, and design microlens array nanostructure increases light output critical angle, to further mention
The light extraction efficiency of high LED chip.
Summary of the invention
The purpose of the present invention is to provide a kind of preparations of the LED structure of graded index nanostructure combination nano lens
Method.Basic thinking is the ito transparent electrode of nano patterning LED light-emitting surface first, and then the PS of high-temperature digestion remnants receives
Rice ball, then again in the PS nanosphere of single layer prepared above, low-temperature heat forms semiglobe, forms microlens array.
Technical scheme is as follows.
A kind of preparation method of the LED structure of graded index nanostructure combination nano lens, comprising: in planar structure
The certain thickness ITO of LED deposition on substrate (about 100-300nm) be used as transparent electrode, then carry out conventional thickness gold electricity again
Pole preparation process, including resist coating expose for the first time, and wet etching ITO, ICP quarter GaN step removes photoresist, then resist coating;Second
Secondary exposure plates thick gold etc., to complete the production the production of thick gold electrode.
It is further comprising the steps of:
S1 protects thickness gold electrode by the method for photoetching, such as resist coating, and exposure is sunk at thick gold electrode
Product silica or metal, then remove photoresist, electrode protection are got up in this way.In the LED chip for having prepared thick gold electrode
Polystyrene (PS) nanosphere of upper production packed mono-layer, then utilizes oxygen rie PS nanosphere, can efficiently control
Its diameter, then ICP etching is carried out, it can be by periodic nano column array at transparent electrode ITO surface etch;By changing oxygen
Ion etching and ICP etch period can efficiently control the size and height of ITO nano column array, thus make sample have compared with
Good electrical and optical properties.Remaining PS nanosphere is remained, cannot be removed.
S2 heats the LED chip for having remaining PS nanosphere, and high-temperature heating melts PS nanosphere, so that PS penetrates into nanometer
Column gap forms the nanostructure of graded index.Such as 140 ° or more can be heated at high temperature, utilize sol evenning machine high-speed rotation
Chip, PS nanosphere can melt to penetrate into nano-pillar gap.
S3 selects suitable PS nanosphere, in the nanostructure of graded index further according to the emission wavelength of LED chip
Surface prepares the PS nanosphere of single layer.Such as near ultraviolet, blue-ray LED, it can choose the bead that diameter is about 450nm;It is right
In the LED of green light, the bead that diameter is about 550nm can choose;For the LED of feux rouges, can choose the period is the small of 650nm
Ball.Low-temperature heat PS nanosphere, so that nanosphere forms hemispherical configuration on the surface of graded index medium.Such as it can select
It selects in 80 ° of -100 ° of heating PS nanospheres, so that the lower surface of PS nanosphere melts, forms semiglobe.
S4 finally falls silica or coat of metal using pickling, so that thick gold electrode position is not any
Structure, and transparent electrode ITO layer has the nanostructure and hemispherical microlens array structure of gradually changed refractive index.
Further, in step S1, the transparent of the LED chip of transparent electrode ITO layer and thick gold electrode is being prepared
Electrode ITO layer prepares the PS nanometer ball array of packed mono-layer as exposure mask, then obtains nano-pillar battle array using ICP etching ITO layer
Column.
Further, in step sl, transparent electrode ITO layer prepares the nanosphere of packed mono-layer, and PS nanosphere is single point
Scattered polystyrene microsphere, monodispersed polystyrene microsphere diameter is between 100nm-2um.
Further, in step s 2, heating temperature is at 120 ° or more.
Further, in step s3, PS nanosphere is monodispersed polystyrene microsphere, and monodispersed polystyrene is micro-
Bulb diameter is between 100nm-2um.
Further, in step s3, heating temperature is between 80 ° -100 °.
By above-mentioned technical proposal, present invention has the advantage that
1, method proposed by the present invention can prepare a kind of graded index medium, reduce emergent light and be situated between from high refractive index
Matter increases the novel of light output critical angle to the Fresnel transmission loss of low refractive index dielectric, with microlens array nanostructure
LED chip.
2, preparation method of the present invention is ingenious, and principle is simple, is a kind of novel micro nanometer structure LED preparation process.
Detailed description of the invention
Fig. 1 is the method for the present invention preparation flow figure.
The structure change figure of LED in the method for the present invention preparation process is shown in Fig. 2 (a)~Fig. 2 (f).
Fig. 2 (a) is the LED substrate schematic diagram for preparing transparent electrode ITO layer and thick gold electrode;
Fig. 2 (b) is the LED substrate schematic diagram for increasing PS nanosphere;
Fig. 2 (c) is the structural schematic diagram heated in PS nanosphere;
Fig. 2 (d) is the structural schematic diagram for etching nano column array;
Fig. 2 (e) is to be filled with the structural schematic diagram of PS material in nano-pillar gap;
Fig. 2 (f) is the LED structure schematic diagram generated after microlens array;
Wherein: 101, substrate;102, undoped GaN;103, n adulterates GaN;104, multiple quantum wells;105, p adulterates GaN;
106, ito transparent electrode;107, p thickness metal electrode;111, n thickness metal electrode;110, ITO nanometers of rod structures;108, polyphenyl second
Alkene (PS) nanosphere;109, it is seeped into the PS film of nanometer rod structure;112, hemispherical PS nanosphere.
Fig. 3 be a process for preparing LED structure, preparing graded index and surface on surface is array structure thereof
When, the ratio curve table for going out luminous intensity with no structure sample.Wherein x-axis is emission wavelength, and y-axis is intensification factor.
Specific embodiment
With reference to the accompanying drawings and examples to a kind of system of the LED structure of graded index nanostructure combination nano lens
Preparation Method further illustrates.The structure of LED substrate is as follows: one layer of undoped GaN102 of deposition on substrate 101, and one layer of regrowth
N adulterates GaN103, then grows multiple quantum wells 104, finally grows p and adulterates GaN105.Deposit certain thickness ito transparent electrode
106 are used as transparent electrode, then carry out conventional plus Electrode treatment, such as resist coating again, expose for the first time, wet etching ITO is saturating
Prescribed electrode 106, ICP carve GaN step, remove photoresist, then resist coating, second of exposure, thick gold 111 of 107 and n of the thick gold of plating p etc., as schemed
Shown in 2 (a).
The step of the method for the present invention, is as follows:
First by the method for photoetching, thickness gold electrode is protected, such as resist coating, exposure, at thick gold electrode
Silica or metal are deposited, then removes photoresist, electrode protection is got up in this way.By polystyrene (PS) nanometer of packed mono-layer
Ball 108 is distributed in the surface of LED substrate, as shown in Fig. 2 (b);Then oxygen rie polystyrene PS nanosphere is utilized, it can be with
Its diameter is efficiently controlled, as shown in Fig. 2 (c);Inductive couple plasma (ICP) etching is carried out again, it can be by LED substrate
Ito transparent electrode 106 etches periodic ITO nano column array 110, as shown in Fig. 2 (d);There to be remaining polystyrene PS
The LED chip of nanosphere 108 heats, and to 140 ° or more, polystyrene PS nanosphere 108 can melt to form infiltration high-temperature heating
To the PS film 109 of nanometer rod structure, as shown in Fig. 2 (e);The blue-ray LED for being 450nm for emission wavelength selects diameter about
For the polystyrene PS nanosphere of 450nm, PS nanometers of polystyrene of single layer are prepared in the nanostructured surface of graded index
Ball, low-temperature heat polystyrene PS nanosphere, so that nanosphere forms the PS nanometer of hemisphere on the surface of graded index medium
Ball 112, as shown in Fig. 2 (f).
By change oxygen rie and ICP etch period can efficiently control ITO layer nano column array size and
Highly, to make sample that there are preferable electrical and optical properties.According to the emission wavelength of LED chip, suitable PS is selected to receive
Rice ball, what we designed is blue-light LED chip, the PS nanosphere having a size of 450nm is selected at this time, in graded index medium
Surface prepares the PS nanosphere of single layer, as shown in Fig. 2 (f).
Fig. 3 is to go out light with without structure sample when LED surface prepares graded index and surface is array structure thereof
The ratio of intensity, wherein x-axis is emission wavelength, and y-axis is intensification factor.Such as the near ultraviolet for being 400nm for emission wavelength
The intensification factor of LED, Fig. 3 are 1.4, can effectively improve the light extraction efficiency of LED.
The above described is only a preferred embodiment of the present invention, not to the limitation made of the present invention, it is all without departing from
Technical solution of the present invention content, according to the technical essence of the invention any simple modification to the above embodiments, equivalent change
Change and modification, in the range of still falling within technical solution of the present invention.