CN101604721B

CN101604721B - High-efficiency (B,Al,Ga,In)N group light-emitting diode by surface roughness treatment

Info

Publication number: CN101604721B
Application number: CN200910142642.4A
Authority: CN
Inventors: T·藤井; Y·高; E·L·胡; S·中村
Original assignee: Japan Science and Technology Agency; University of California
Current assignee: Japan Science and Technology Agency; University of California
Priority date: 2003-12-09
Filing date: 2003-12-09
Publication date: 2014-11-26
Anticipated expiration: 2023-12-09
Also published as: CN101604721A

Abstract

The invention discloses a (B,Al,Ga,In)N group light-emitting diode (LED). Light is extracted through a nitrogen surface (N surface) (42) of the LED; and the surface of the N surface is roughened into one or more hexagon conical surfaces. The roughened surface reduces the repeat occurrence of light reflection in the LED, so that more lights are extracted from the outer part of the LED. The surface of the N surface is roughened by anisotropic etching, and the etching comprises dry etching or photoinduced chemistry (PEC) etching.

Description

Through efficient (B, Al, Ga, In) N based light-emitting diode of surface coarsening

The application is that the name of submitting on December 9th, 2003 is called: the divisional application of the Chinese patent application 200380110945.9 of " through efficient (B, Al, Ga, In) N based light-emitting diode of surface coarsening ".

Technical field

The present invention relates to light-emitting diode, and relate in particular to through (B, Al, Ga, the In) of surface coarsening N base efficient LED.

Background technology

(note: the application is with reference to a large amount of different publications, and it represents in this specification and with one or more reference numbers.Can in the part for " list of references ", find at following autograph according to tactic these the different publications of these reference numbers.Each in these publications is all by reference in conjunction with in this manual.)

The wide band gap semiconducter light-emitting diode (LED) of gallium nitride (GaN) base has come into operation approximately ten years.Along with the realization of Full color LED display screen, LED traffic signals, white light LEDs etc., the process of LED exploitation has been brought great variety in LED technical field.

Recently, high efficiency white light LEDs, due to possibility replace fluorescent lamps, has caused very big interest.Particularly, the efficiency of white light LEDs (74lm/W) (document that sees reference [1]) is approaching the efficiency (75lm/W) of conventional fluorescent lamps.Even so, aspect efficiency, be also necessary to do more improvement.

There are in principle two kinds of approach to improve the efficiency of LED.The first approach is to improve internal quantum (internal quantum efficiency, η _i), it is decided by crystal mass and epitaxial layer structure, and the second approach is to increase light extraction efficiency (light extractionefficiency, η _extraction).

Improving internal quantum is difficult for accomplishing.For blue-ray LED, typical η _ivalue is greater than 70% (document that sees reference [2]), and ultraviolet (UV) LED being grown on low dislocation GaN substrate shows the η that is approximately 80% recently _i(document that sees reference [3]).These numerical value almost do not have room for improvement.

On the other hand, the space that is significantly improved, light extraction efficiency aspect.Aspect the internal loss of elimination light, can solve a large amount of problems, comprising: high reflection mirror, low reflecting surface (for example coarse surface), high radiator structure etc.

For example, in view of the refractive index of GaN (n ≈ 2.5) (document that sees reference [4]) and air, the critical angle of light escape cone (light escape cone) is approximately 23 °.Suppose that light sends and ignores rear side from sidewall, estimate so to only have to approach 4% interior light (internal light) and can be extracted.The light of described escape cone outside is reflected and enters substrate and by active layer (active layer) or electrode repeated reflection or absorption, escape unless it passes described sidewall.

The structure influence of LED is to sending how much light.LED structure is preferably described by example the impact of light extraction efficiency.Following instance has been described polytype LED structure.

Fig. 1 is the cutaway view of traditional LED structure, and this structure comprises p-type gasket electrode (pad electrode) 10, semitransparent electrode 12, p-type layer 14, active area 16, N-shaped layer 18, N-shaped electrode 20 and substrate 22.Because GaN is grown in dielectric substrate for example on sapphire conventionally, therefore p-type and N-shaped electrode 10,20 are necessary to make in identical plane, thereby and the device architecture of the electrode 10,20 producing introduced transverse current.Due to the high resistivity of p-type GaN, available layer of metal film is as semitransparent electrode 12, to carry out current spread (current spreading) on p-type GaN.The transparency of desirable semitransparent electrode 12 should be 100%; But the transparence value of the thin metal electrode using in GaN base LED is at most 70%.In addition, gasket electrode 10 should form for circuit bonding (wirebonding), but it has covered the light sending from LED inside; Therefore, extraction efficiency is estimated quite low.

Fig. 2 is the cutaway view of upside-down mounting (flip-chip) type LED structure, and it comprises transparent sapphire substrate 24, N-shaped layer 26, N-shaped electrode 28, active area 30, p-type layer 32, p-type electrode 34, scolder 36 and main basal base (host submount) 38.In order to improve external efficiencies (external efficiency), can extract light by the transparent sapphire substrate 24 of described flip chip type LED structure.Compared with traditional LED, the advantage of this method is to use metallic film and gasket electrode to reduce light absorption.But most of light sending from active area reflects the interface between the interface between substrate 24 and N-shaped layer 26 and substrate 24 and air.

A kind of method that GaN film can be peeled off from Sapphire Substrate is called as " laser lift-off " (laser lift off, LLO) technology.By this method being applied to flip chip type GaN base LED, can realize the GaN LED without Sapphire Substrate.Suppose that produced GaN surface is processed to on-plane surface orientation (non-planar orientation), light extraction efficiency expection has significant improvement.

Another approach that increases extraction efficiency is the surface (document that sees reference [5]) of alligatoring LED, and this has suppressed inner reflection of light and has made upwards scattering of light.But coarse surface LED only mentions in the article about phosphatization gallium family (GaP family) material, reason is that GaN is the extraordinary material of durability, and common wet etching is not too effective.Although therefore as far back as 1970, considered the concept of alligatoring semiconductor surface with scattered light, believed that producing this LED structure is difficulty and expensive.

But as mentioned above, typical GaN base LED is made up of the p-GaN/ active layer/n-GaN film on sapphire or carborundum (SiC) substrate.Need certain thickness GaN layer (document that sees reference [6]) although make coarse surface, but due to the relatively high resistivity of p-GaN, do not wish to grow thick p-GaN, if only extracted by p-GaN, on p-GaN surface, just require translucent contact-making surface, and some are for the measure of coarse surface, for example dry etching method (document that sees reference [7]), may cause that electrical property worsens.Do not wish equally by Organometallic Chemistry vapor deposition method (MOCVD) p side (p-side down) structure down of growing, reason is the memory effect (document that sees reference [8]) of magnesium (Mg), and it has damaged active layer.

Recently the GaN film that, a kind of laser lift-off (LLO) method has been used to from being grown in substrate separates Sapphire Substrate (document that sees reference [9-11]).Further, LLO has been used to make GaN base LED (document that sees reference [12,13]).But, relate to this technology in the effect aspect configuration of surface (surface morphology) or extraction efficiency without any list of references.

On the other hand, in the present invention, use flip chip technology (document that sees reference [14]) and LLO method, can make nitrogen of the linerless end (N) side GaN based LED construction upward.Afterwards, can take anisotropic etching processing to come the alligatoring N side surface of GaN base LED upward.This causes hexagon " class cone (the cone-like) " surface that contributes to light to extract.LED before contrast alligatoring, surface increases and exceedes 100% through the extraction efficiency of the LED of best alligatoring.

Note that for a period of time, GaN has been considered to be difficult to by anisotropic etching.This is correct, because compare with other semi-conducting material, GaN is the material of stable chemical nature.It is possible adopting dry etching method to make rough surface, but needs additional treatments, for example photoengraving, thereby adopt dry etching method can not on GaN, produce good class poppet surface.

In the time strengthening chemistry (photo-enhancedchemical, PEC) etching method at the upper utilization of gallium face (Ga face) GaN light, on described surface, form small rut.This forms contrast with the PEC etching of nitrogen face (N face) GaN that causes completely different class cone feature.Adopt LLO fabrication techniques GaN base LED although there are some reports to relate to, the present invention adopts anisotropic etch process to make the lip-deep class wimble structure of N face GaN of GaN base LED.

Summary of the invention

The invention describes the light-emitting diode (LED) of gallium nitride (GaN) base, wherein, be only roughened and form one or more hexagon conical surfaces by nitrogen face (N face) surface that be extracted and described N face of LED.Described coarse surface has reduced light and has repeated the reflection occurring in LED inside, and therefore extracts more light outward at described LED.

The surface of described N face is roughened by anisotropic etch process.Described anisotropic etch process comprises that dry etching method or light strengthen chemistry (PEC) etching method.

In one embodiment, N face GaN is prepared by laser lift-off (LLO) technology.In another embodiment, LED grows on c plane GaN wafer, and the surface of p-type layer is gallium face (Ga face), and the surface of N-shaped layer is nitrogen face (N face).

Brief description of the drawings

With reference now to accompanying drawing,, run through institute's drawings attached, wherein identical Ref. No. represents identical parts.

Fig. 1 is the cutaway view of traditional LED structure.

Fig. 2 is the cutaway view of flip chip type LED structure.

Fig. 3 is the schematic diagram of surface coarsening LED.

Fig. 4 is the flow chart of describing the operating procedure adopting in the preferred embodiments of the present invention.

Fig. 5 (a) further illustrates the making step that LED is carried out to surface coarsening to (f).

Fig. 6 (a) shows the LED with electric current barrier layer (current-blocking layer), and Fig. 6 (b) shows the LED with restriction of current framework (current-confining frame).

Fig. 7. (a) He 7. (b) are the micrographs of overlooking with the LLO-LED of cross n electrode.

Fig. 8 (a) and 8 (b) are after different etching periods are carried out PEC etching, scanning electron micrograph (SEM) image of the N face of GaN.

Fig. 9 (a) and 9 (b) show electroluminescence (EL) spectrum from flat surfaces LED and coarse surface LED respectively; And

Figure 10 is the curve chart of EL power output contrast DC Injection Current (L-I) characteristic that rises, its corresponding under room temperature through different etching periods and LED.

Embodiment

In the description of following preferred embodiment, with reference to the accompanying drawing that forms this specification part, and accompanying drawing schematically shows one of them and can implement specific embodiment of the present invention.Will be appreciated that and do not departing under the prerequisite of scope of the present invention, can adopt other embodiment and can carry out structure of modification.

General introduction

The invention provides a kind of device, this device has improved extraction efficiency by the surface of alligatoring GaN base LED.Specifically, N face c plane GaN surface applied anisotropy PEC engraving method is caused forming conical surface feature.The surface of this alligatoring has been reduced LED inside and has been repeated the light reflection occurring, and therefore extracts more light outward at described LED.And, contrasting other and may jeopardize the method for coarsening surface of quality of materials, method of the present invention is simple, can repeat and should be unable to damage material, and all these advantages make the present invention be more suitable for making LED.

LED structure

Fig. 3 is the schematic diagram of coarse surface LED, it comprises N-shaped electrode 40, N-shaped layer 42, active area 44, p-type layer 46 and p-type electrode 48, this p-type electrode 48 is adhered to silicon (Si) base station 52 by weld layer 50 upside-down mountings, and this silicon submount 52 comprises N-shaped electrode 54.Described N-shaped layer 42, active area 44 and p-type layer 46 are made up of (B, Al, Ga, In) N alloy.Adopt dry type or PEC engraving method to come the surface of alligatoring N-shaped layer 42.In order to obtain required surface, be necessary to set suitable condition, for example for dry-etching, set suitable plasma chemistry composition and plasma power, and for PEC etching, set suitable electrolyte and lamp power.Importantly, this GaN base LED should should be N face along its c-axis growth and this N-shaped GaN surface, and reason is to observe anisotropic etching on N face GaN than much easier on Ga face GaN.

Notice that c plane GaN has following structure: the plane that only includes Ga atom is stack up with the plane that only includes N atom, or alternately gather into folds.If a surface is Ga face, relative surface is N face.From the viewpoint of crystal growth and device performance, Ga face c plane GaN is generally preferred, and based on this fact, N face GaN need to be prepared by LLO technology, or can be selectively, and LED structure can be grown on c plane bulk GaN wafer.

Light penetrates from active region 44, the N-shaped GaN of directive alligatoring surface 42 by this surface scattering, and this surface is not reflected back described active region by described light.Desirable, described p-type electrode 48 has highly reflective to reduce light absorption, thereby and makes to increase towards the light of described N-shaped GaN surface 42 reflections.In experimental result, it has been determined that: contrast is with the LED of flat surfaces, the upper of the LED with coarse surface that the present invention adopts is increased to twice or three times to light (upward light) power output.

Operating procedure

Fig. 4 is the flow chart of describing the operating procedure that adopted in a preferred embodiment of the invention.

Square frame 56 is expressed as follows step: by MOCVD at c plane sapphire Grown Ga face epitaxial loayer, thereby produce sample.

Square frame 58 is expressed as follows step: after MOCVD, make described sample anneal to carry out p-type activation (p-type activation).

Square frame 60 is expressed as follows step: on described sample, carry out p-type metallization operations, it is including, but not limited to silver (Ag) or aluminium (Al), to form high reflection p-GaN contact.

Square frame 62 is expressed as follows step: deposition of thick gold (Au) layer on described sample then evaporates to deposit tin (Sn) layer as weld metal by Sn in hot vaporizer (thermal evaporator).

Square frame 64 is expressed as follows step: the temperature more than 280 DEG C, and the described sample being sticked on the Si substrate/base station of Au coating of overturning, wherein forms Au/Sn alloy, and this contributes to described sample to be adhered on Si substrate.

Square frame 66 is expressed as follows step: carry out LLO operation,, use KrF (KrF) excimer laser (eximer laser light) (248nm), by the transparent sapphire substrate of sample described in the back side illuminaton of Sapphire Substrate, thereby cause the GaN exploded in GaN/ Sapphire Substrate interface.Specifically, carry out raster manipulation by the KrF excimer laser hot spot on described sample, GaN base LED film is just transformed into Si substrate/base station.

Square frame 68 is expressed as follows step: described sample is carried out, after the operation of KrF laser grating, Sapphire Substrate being peeled off from described sample.

Square frame 70 is expressed as follows step: on the GaN surface of the separation of described sample, with any residual Ga droplet (droplet) of hydrogen chloride (HCl) solution removal.

Square frame 72 is expressed as follows step: make the GaN attenuation of transformation, be exposed on described sample until mix the N face GaN of Si.

Square frame 74 is expressed as follows step: on the N face GaN of the exposure of described sample, titanium deposition/aluminium/titanium/gold (Ti/Al/Ti/Au) electrode, as N-shaped contact electrode in other words.

Square frame 76 is expressed as follows PEC etching step: described sample is immersed in potassium hydroxide (KOH) electrolyte solution, and with xenon/mercury (Xe/Hg) light irradiation N face GaN surface, makes in this way upper surface be roughened.The etched details of PEC is described in list of references [15].

Square frame 78 is expressed as follows step: adopt dry-etching, cutting (dicing) or split each device on the Si substrate that (cleaving) method of cutting separates described sample.

Fig. 5 (a) further illustrates the making step of the LED to having coarse surface to (f), wherein said LED structure comprises p-type electrode 80, GaN base LED film 82, Sapphire Substrate 84, weld metal 86, base station (carrier) 88 and N-shaped electrode 90.Specifically, Fig. 5 (a) shows the post-depositional result of p-type electrode 80, Fig. 5 (b) shows the result of described LED after being adhered on main base station 88, Fig. 5 (c) shows the result after Sapphire Substrate being separated with LLO, Fig. 5 (d) shows the post-depositional result of N-shaped electrode 90, Fig. 5 (e) shows the result after GaN surface 82 alligatoring, and Fig. 5 (f) shows the result after device isolation.

Possible amendment

Although described basic structure above, also had a large amount of possible modifications and variations schemes.

Fig. 6 (a) shows the LED with electric current barrier layer, and Fig. 6 (b) shows the LED with restriction of current framework, wherein said LED comprises N-shaped electrode 92, N-shaped layer 94, active layer 96, p-type layer 98, p-type electrode 100, electric current barrier layer 102 and restriction of current framework 104.

In Fig. 6 (a), described LED has electric current barrier layer 102, and its aligning is placed in N-shaped electrode 92 belows.This electric current barrier layer 102 prevents that electric current from concentrating under N-shaped electrode 92, thereby has avoided the light sending under N-shaped electrode 92 to be absorbed, thereby has improved extraction efficiency.SiO ₂and so on insulant be suitable for being placed on p-GaN layer 98, this is because generation current diffusion hardly in ohmic p-GaN layer 98.

In Fig. 6 (b), described LED has the restriction of current framework 104 that insulator is made.If carry out discrete device with dry etching method or patterning method, if surface suffers damage, the sidewall of device may produce leakage current.This leakage current has reduced efficiency and the useful life of LED.Restriction of current framework 104 contributes to suppress the leakage current by the sidewall of LED, and if the width of this framework is selected suitably, can obviously not reduce light-emitting area.

Although Si substrate has been described as the main base station in LLO operation, also can use other alternative backing material but will put into practice the present invention.Although Si is more cheap and have higher pyroconductivity than sapphire, other substrate, for example SiC, diamond, AlN or various metals as CuW, from heat conducting viewpoint, also can be applicable to use.

At present, GaN device can also be directly at SiC and Si Grown.If GaN base LED grows on SiC or Si, traditional dry-etching or Wet-type etching can separate substrate.By using bulk GaN substrate, can omit LLO operation.

Make for LED, sample size is also a key point.Now, large-sized LED is paid close attention to because meeting the demand of great power LED.Even if the resistivity of N-shaped GaN is less than p-type GaN's, for current spread object, its size has also affected arranging for how much of N-shaped electrode.

Experimental result

In the experiment of carrying out inventor, Ga face epitaxial loayer by MOCVD at c plane sapphire Grown.Its structure comprises 4 micron thick undope and adulterate the GaN layer of Si, the Multiple Quantum Well (MQW) of the GaN/InGaN in 5 cycles, the Al of 20 nanometer thickness doped with Mg _0.2ga _0.8the GaN of N layer and 0.3 micron thick doped with Mg.After MOCVD operation, described sample is annealed to carry out p-type activation, and carries out subsequently p-type metallization operations.Adopt Ag base electrode as height reflection p-GaN contact.On sample, thick Au deposition is then carried out Sn evaporation in hot vaporizer.280 DEG C of temperature, the described wafer adhered to the Si base station of Au coating of overturning, thus forming the alloy of Au and Si, this contributes to strengthen the bonding of described wafer and base station.Adopt KrF laser (248nm) to carry out LLO operation, in this operation, institute's Emission Lasers is by transparent Sapphire Substrate, caused the exploded of GaN at GaN and sapphire intersection.On described sample, carry out after the rasterisation operation of KrF laser, Sapphire Substrate is stripped from.At the Ga droplet of the lip-deep remnants of GaN changing by HCl solution removal.Then, make the GaN attenuation of transformation, until the GaN of doping Si comes out.On the N face n-GaN exposing, form n contact, and make each device and its close on part to separate by active-ion-etch (reactive ion etching, RIE).Finally, adopt PEC etching so that coarse surface top layer.Adopt KOH solution and Xe/Hg lamp respectively as electrolyte and light source.The power output of described LED is used the Si detector means that is positioned at 7 millimeters of places of LED sheet height to measure.

Fig. 7 (a) and 7 (b) are the microphotos of overlooking with the LLO-LED of cross n electrode, and wherein said LED sticks on Si substrate.Fig. 7 (a) shows surface before alligatoring and Fig. 7 (b) shows the surface after alligatoring.Because stopped UV light at PEC during etching n electrode, the GaN under it does not have etched, thereby after alligatoring, described electrode is retained on GaN.Available indium tin oxide (ITO) and so on transparency electrode is as current spread electrode.

Fig. 8 (a) and 8 (b) are after the PEC of different etching periods etching, scanning electron micrograph (SEM) image of the N face of GaN.Note comprising multiple hexagon conical surfaces through the etched N face GaN of PEC surface, this PEC etching GaN reporting with the people (document that sees reference [16]) such as Youtsey is surperficial different.This difference is considered to the surface polarity (surface polarity) because of GaN.By 10 minutes etched surfaces in 2 minutes (min) etched surfaces and Fig. 8 (b) in comparison diagram 8 (a), the latter's characteristic size increases and the faceted pebble of hexagonal cone seems more clear.

Carry out light extraction from LED aspect, it is very effective that conical surface seems.And experimental result shows that taper can extract more light.For example, in GaN crystal, the wavelength of blue-ray LED is about 200nm.If the size of taper is more much smaller than this value, light may not be subject to the impact of this roughness so.On the other hand, if the size of taper approaches this value, may there is scattering or diffraction in light.

In experimental result, it has been determined that described coarse surface comprises many hexagon conical surfaces, its angle having is equal to or less than: 2sin ^-1(n _air/ n _s) 47.2 ° of ≈ are for GaN, wherein n _airthe refractive index of air, and n _sit is the refractive index of GaN.Similarly, it has been determined that coarse surface comprises many hexagon conical surfaces, its angle having is equal to or less than: 2sin ^-1(n _enc/ n _s) for epoxy, wherein n _encthe refractive index of epoxy, and n _sit is the refractive index of GaN.

It is taper that described surface may there is no need, and should consider grating texture (grating structure) and photonic crystal (photonic crystal).Extract for light, these may be better structures.But the making of photonic crystal needs accurate design and operation, this more takes cost than making taper rough surface.

" eka-ytterbium (mirror-like) " surface before PEC etching appears and fades along with the increase of etching period.If high reflecting metal is deposited on to the opposite side of GaN film, described surperficial whitening look; Otherwise it is darker.This it is believed that it is because at air/GaN interface, and light reflection is suppressed, and if have highly reflective metal at the GaN back side, the light of injecting GaN will be again out, in described coarse surface scattering.

Fig. 9 (a) and 9 (b) show respectively electroluminescence (EL) spectrum from flat surfaces LED and coarse surface LED.Under room temperature (RT), with 25A/cm ²the forward current density of DC is measured.As shown in Fig. 9 (a), the spectrum of flat surfaces LED presents multimodal transmitting (multi-peaked emission), show that the light sending from active area, vertical GaN chamber, interference has occurred, this chamber is clipped between the minute surface of GaN/ metal formation and the minute surface of GaN/ air formation.On the contrary, as shown in Fig. 9 (b), on coarse surface LED, do not observe longitudinal mode.This means, the GaN/ air interface scattering of alligatoring light, cause resonance suppressed.

Figure 10 be one in room temperature through different etching periods and curve chart to DC Injection Current (L-I) characteristic of the rising EL power output of LED.These data are from identical equipment, to obtain before PEC etching and afterwards, therefore can ignore and except configuration of surface, cause this different any factor.Arbitrary L-I curve all shows until the linear characteristic of 50mA.Because contrast sapphire, Si has relatively high pyroconductivity, and therefore these devices have advantage aspect high power operation.Along with PEC etching period increases, the power output of given electric current increases.Relatively, corresponding to the power output of flat surfaces LED and 10 minutes etched surfaces LED, this roughening treatment causes power output to increase to 2.3 times.Measure according to other carrying out on distinct device, after roughening treatment, power also demonstrates the growth of two to three times.Because, compared with coarse surface LED, due to the horizontal transmission (lateral propagation) of light, flat surfaces LED often sends more light from the sidewall of LED sheet, if so gross power is to measure with integrating sphere (integrating sphere), the difference of power output is by smaller so.But by means of anisotropic etch techniques, this raising of extraction efficiency has still demonstrated major progress.

In a word, for the object that increases extraction efficiency, anisotropic etch process has been applied to GaN base LED.Outputing test result of LED shows: can suppose because light in GaN film is propagated minimizing, between alligatoring appearance (roughened appearance) and extraction efficiency, have certain relation.Although also do not measure total integral light power, but maximum aspect extraction efficiency increases and has exceeded 100%.It should be noted that technology is simple described in this specification, and do not need complicated operation, this shows to take surface coarsening will be suitable for making GaN base LED.

List of references

This specification is in conjunction with quoting below with reference to document: 1.http: //www.cree.com/News/news 175.asp2.Y.Kawakami, Y.Narukawa, K.Omae, S.Fujita, and S.Nakamura, Phys.Stat.Sol. (a) 178, 331 (2000) .3.T.Nishida, H.Saito, and N.Kobayashi, Appl.Phys.Lett.79, 711 (2001) .4.A.Billeb, W.Grieshaber, D.Stocker, E.F.Schubert, R.F.Karlicek, Jr., Appl.Phys.Lett.70, 2790 (1997) .5.A.A.Bergh, M.Hill, R.H.Saul, and S.Plains, U.S.Patent No.3, 739, 217 (1973), entitled " Surface Roughening Of ElectroluminescentDiodes. " 6.Chul Huh et al., Appl.Phys.Lett.93, 9383 (2003) .7.X.A.Cao, S.J.Pearton, A.P.Zhang, G.T.Dang, F.Ren, R.J. Shul, L.Zhang, R.Hickman, and J.M.Van Hove, Appl.Phys.Lett.75, 2569 (1999) .8.Y.Ohba and A.Hatano, J.Crystal.Growth 145, 214 (1994) .9.W.S.Wong, T.Sands, N.W.Cheung, M.Kneissl, D.P.Bour, P.Mei, L.T.Romano, and N.M.Johnson, Appl.Phys.Lett.72, 1999 (1998) .10.P.R.Tavernier and D.R.Clarke, J.Appl.Phys.89, 1527 (2001) 11.C.F.Chu, C.C.Yu, H.C.Cheng, C.F.Lin, and S.C.Wang, Jpn.J.Appl.Phys.42, L147 (2003) .12.W.S.Wong, T.Sands, N.W.Cheung, M.Kneissl, D.P.Bour, P.Mei, L.T.Romano, N.M.Johnson, " Fabrication of thin-film InGaNlight-emitting diode membranes by laser lift off, " Appl.Phys.Lett., 75 (10) 1360 (1999) .13.W.S.Wong, T.Sands, N.W.Cheung, M.Kneissl, D.P.Bour, P.Mei, L.T.Romano, N.M.Johnson, " light emitting diodes on Si substratesfabricated by Pd-In metal bonding and laser lift-off, " Appl.Phys.Lett., 77 (18) 2822 (2000) .14.J.J.Wierer, D.A.Steigerwald, M.R.Krames, J.J.O ' Shea, M.J.Ludowise, N.F.Gardner, R.S.Kern, and S.A.Stockman, Appl.Phys.Lett.78, 3379 (2001) .15.M.S.Minsky, M.White, and E.L.Hu, Appl.Phys.Lett.68, 1531 (1996) .16.C.Youtsey, L.T.Romano, and I.Adesida, Appl.Phys.Lett.73, 797 (1998).

Conclusion

The description of summing up the preferred embodiment of the present invention at this.Some are below described for implementing optional embodiment of the present invention.

In the present invention, except MOCVD, can also use many different growing methods.

In addition, can adopt other substrate outside sapphire or carborundum.

Further, can construct different LED structures.For example, also can construct resonant cavity LED (RCLED) or microcavity LED (MCLED).

For the object of explaining and illustrating, provide the description to one or more embodiment of the present invention before.Not milli is exhaustively nor be to be meant to limit the invention to disclosed precise forms for this.In the operating aspect of the above light of lecturing, may there is many modifications and variations scheme.Scope of the present invention should not limited by this detailed description, and should be limited to claims.

Claims

1. a c planar I II group-III nitride based light-emitting diode, wherein nitrogen face surface extraction by described light-emitting diode only, and described nitrogen face surface is structured to form taper, described taper has the size of the light wavelength of the approaching described nitrogen face surface extraction from described light-emitting diode, so that the light in described light-emitting diode is scattered or diffraction repeats to reduce the light reflection that occurs in described light-emitting diode, strengthen thus from described nitrogen face surface extraction light.

2. c planar I II group-III nitride light-emitting diode according to claim 1, wherein said nitrogen face surface is structured by alligatoring.

3. c planar I II group-III nitride light-emitting diode according to claim 1, wherein said nitrogen face surface is structured by patterning.

4. c planar I II group-III nitride light-emitting diode according to claim 1, wherein said nitrogen face surface is the surface of the N-shaped layer of described light-emitting diode.

5. c planar I II group-III nitride light-emitting diode according to claim 1, wherein said nitrogen face surface is structured by anisotropic etching.

6. c planar I II group-III nitride light-emitting diode according to claim 5, wherein said anisotropic etching is dry etching.

7. c planar I II group-III nitride light-emitting diode according to claim 5, wherein said anisotropic etching is wet etching.

8. c planar I II group-III nitride light-emitting diode according to claim 7, wherein said wet etching is that light strengthens chemical etching.

9. c planar I II group-III nitride light-emitting diode according to claim 1, prepare by substrate removal technology on wherein said nitrogen face surface.

10. c planar I II group-III nitride light-emitting diode according to claim 1, this c planar I II group-III nitride light-emitting diode further comprises the metal on the gallium face epitaxial loayer that is deposited on described light-emitting diode.

11. c planar I II group-III nitride light-emitting diodes according to claim 10, wherein said metal is p-type electrode, described p-type electrode has high reflection characteristic to reduce light absorption, and increases the surperficial light reflection towards N-shaped layer.

12. c planar I II group-III nitride light-emitting diodes according to claim 10, wherein said metal is silver or aluminium.

13. 1 kinds generate the method for c planar I II group-III nitride based light-emitting diode, wherein nitrogen face surface extraction by described light-emitting diode only, and described nitrogen face surface is structured so that described light is extracted from described light-emitting diode, and described method comprises:

On substrate, make one or more layers of described c planar I II group-III nitride light-emitting diode;

By described substrate is removed to the described nitrogen face surface that exposes described light-emitting diode from described layer; And

After being removed, described substrate constructs described nitrogen face surface to form taper, described taper has the size approaching from the light wavelength of described nitrogen face surface extraction, so that the light in described light-emitting diode is scattered or diffraction repeats to reduce the light reflection that occurs in described light-emitting diode, strengthen thus from described nitrogen face surface extraction light.

14. 1 kinds of c planar I II group-III nitride based light-emitting diodes, it at least comprises N-shaped electrode, N-shaped layer, active area, p-type layer and p-type electrode, wherein from the light of described active area by the nitrogen face surface extraction of described light-emitting diode, and described nitrogen face surface is structured to form taper, described taper has the size of the light wavelength of the approaching described nitrogen face surface extraction from described light-emitting diode, so that the light in described light-emitting diode is scattered or diffraction repeats to reduce the light reflection that occurs in described light-emitting diode, strengthen thus from described nitrogen face surface extraction light.