WO2013139251A1 - 具有反射镜的发光二极管及其制作方法 - Google Patents

具有反射镜的发光二极管及其制作方法 Download PDF

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WO2013139251A1
WO2013139251A1 PCT/CN2013/072853 CN2013072853W WO2013139251A1 WO 2013139251 A1 WO2013139251 A1 WO 2013139251A1 CN 2013072853 W CN2013072853 W CN 2013072853W WO 2013139251 A1 WO2013139251 A1 WO 2013139251A1
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layer
gallium nitride
emitting diode
silver
plated
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PCT/CN2013/072853
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English (en)
French (fr)
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潘群峰
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厦门市三安光电科技有限公司
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Priority claimed from CN201210074485.XA external-priority patent/CN102610720B/zh
Priority claimed from CN201210074327.4A external-priority patent/CN102610728B/zh
Application filed by 厦门市三安光电科技有限公司 filed Critical 厦门市三安光电科技有限公司
Publication of WO2013139251A1 publication Critical patent/WO2013139251A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/10—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a light reflecting structure, e.g. semiconductor Bragg reflector
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/44—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating
    • H01L33/46—Reflective coating, e.g. dielectric Bragg reflector

Definitions

  • the present invention relates to a light emitting diode and a method of fabricating the same, and more particularly to a gallium nitride based light emitting diode having a mirror and a method of fabricating the same.
  • Gallium nitride based light emitting diode devices have been widely used in various fields such as display, indication, backlight and illumination.
  • mainstream GaN-based LED chips can be divided into three types: formal, flip-chip and vertical.
  • formal, flip-chip and vertical the formal structure with insulating sapphire as the substrate is the most common and widely used in the industry.
  • the present invention provides a light emitting diode having a back-plated silver reflective layer and a method of fabricating the same, by inserting a layer of gallium nitride-based material between the sapphire substrate and the reflective layer to solve the problem of adhesion between the two.
  • a layer of gallium nitride-based material between the sapphire substrate and the reflective layer to solve the problem of adhesion between the two.
  • the gallium nitride-based material layer and the silver layer can form a close adhesion after annealing, and the gallium nitride-based material is completely transparent to the blue and green light bands, the gallium nitride-based material layer is used as the adhesion layer as compared with The thin metal layer can increase the overall reflectivity of the back-plated reflective layer.
  • a technical solution for achieving the above object is: a light emitting diode having a back plating reflective layer, the structure comprising: a transparent substrate; a semiconductor layer formed on a first surface of the transparent substrate, the semiconductor layer comprising a first conductive semiconductor layer, a second conductive semiconductor layer and a light emitting layer interposed therebetween; a back-plated reflective layer is formed on a second surface of the transparent substrate relative to the first surface, and the back-plated silver reflective layer comprises an adhesion layer and a metal reflective layer in sequence from the second surface, and
  • the adhesive layer is made of a gallium nitride-based material, and the first layer of the metal reflective layer is silver.
  • the method for fabricating a light-emitting diode having a back-plated reflective layer includes the steps of: providing a transparent substrate; epitaxially growing a semiconductor stack on the first surface of the transparent substrate, the semiconductor stack comprising a first conductive semiconductor layer, a second conductive semiconductor layer and a light emitting layer interposed therebetween; thinning and grinding the transparent substrate from the second surface of the transparent substrate relative to the first surface; transparent substrate after grinding a second surface epitaxially growing a gallium nitride based material layer as an adhesion layer; a metal reflective layer is plated on the gallium nitride based material layer, wherein the first layer material is silver; annealing to form a silver and gallium nitride based material layer Tightly bonded.
  • the transparent substrate is made of sapphire; the semiconductor laminate is made of a gallium nitride-based material; and the adhesion layer can be formed by epitaxial growth, including metal organic chemical vapor deposition (MOCVD). ), molecular beam epitaxy (MBE) and hydride vapor phase epitaxy (HVPE); GaN is an ideal adhesion layer material for comprehensive transmittance and adhesion; the thickness of the adhesion layer should not be too thick.
  • MOCVD metal organic chemical vapor deposition
  • MBE molecular beam epitaxy
  • HVPE hydride vapor phase epitaxy
  • GaN is an ideal adhesion layer material for comprehensive transmittance and adhesion
  • the thickness of the adhesion layer should not be too thick.
  • the annealing for the back plating reflective layer can be carried out in an atmosphere containing nitrogen and oxygen, and the annealing temperature is preferably between 300 ° C and 800 ° C.
  • the present invention provides a gallium nitride-based light emitting diode having an omnidirectional mirror and a method of fabricating the same, by inserting a gallium oxide layer between a layer of silver and an oxide transparent dielectric material to solve two Poor adhesion between people. Since gallium oxide and silver can be tightly bonded by interdiffusion alloy after annealing, and gallium oxide is completely transparent to the blue light band, a gallium oxide layer can be used as an intermediate adhesion layer to construct a back-plated omnidirectional mirror containing silver, thereby Further improve the reflectivity of the omnidirectional mirror.
  • a technical solution for achieving the above object is: a gallium nitride-based light emitting diode having an omnidirectional mirror, the structure comprising: a sapphire substrate; a gallium nitride-based epitaxial stack formed on the first surface of the sapphire substrate, The gallium nitride based epitaxial stack comprises N-type gallium nitride based epitaxial layer, P a type gallium nitride based epitaxial layer and a light emitting layer interposed therebetween; an omnidirectional mirror is formed on the second surface of the sapphire substrate relative to the first surface, and from the second surface
  • the omnidirectional mirror sequentially comprises a plurality of transparent dielectric layer stacks, a gallium oxide layer and a silver reflective layer having alternating refractive indices at high and low periodicities.
  • the method for fabricating a gallium nitride-based light-emitting diode having an omnidirectional mirror comprises the steps of: providing a sapphire substrate; epitaxially growing a gallium nitride-based epitaxial layer on the first surface of the sapphire substrate, the gallium nitride-based epitaxial layer Stack contains N Type gallium nitride based epitaxial layer, P a gallium nitride-based epitaxial layer and a light-emitting layer are interposed therebetween; an omnidirectional mirror is formed on the second surface of the sapphire substrate, and the omnidirectional mirror sequentially includes a refractive index from the second surface a plurality of periodically alternating dielectric layer stacks, a gallium oxide layer and a silver reflective layer; the annealing is such that the interface between the silver and the gallium oxide layer mutually diffuses and forms an alloy.
  • gallium oxide as an intermediate adhesion layer of a layer of silver and oxide light transmissive dielectric material.
  • the adhesion between gallium oxide and the oxide transparent dielectric material layer is good and reliable.
  • Gallium oxide and silver must pass through the annealing alloy to form a close bond. After high temperature annealing, the silver will diffuse and melt into the gallium oxide layer to form gallium.
  • the silver oxide interface layer and the formation of the gallium-silver oxide interface layer greatly enhance the adhesion of silver to gallium oxide.
  • the annealing may be performed in an atmosphere containing nitrogen and oxygen, and the annealing temperature is selected. It is suitable between 300 °C and 800 °C.
  • FIG. 1 is a schematic view showing the structure of a light-emitting diode chip having a back-plated reflective layer in the prior art.
  • FIG. 2 is a schematic view showing the structure of a light emitting diode chip having a back plating reflective layer according to an embodiment of the present invention.
  • FIG. 3 is a schematic view showing the structure of a gallium nitride based light emitting diode having a back plated omnidirectional mirror according to an embodiment of the present invention.
  • 100 sapphire substrate; 101: n-type gallium nitride-based epitaxial layer; 102: light-emitting layer; 103: p Type gallium nitride based epitaxial layer; 110: thin chromium layer; 120: silver reflective layer; 200: sapphire substrate; 201: buffer layer; 202: n-GaN layer; 203: multiple quantum well layer; 204: p-GaN layer; 210: ITO transparent conductive layer; 211: P electrode; 212: N electrode; 220: GaN adhesion layer; Silver mirror; 300: sapphire substrate; 301: buffer layer; 302: n-GaN layer; 303: multiple quantum well layer; 304: p-GaN layer; ITO transparent conductive layer; 311: P electrode; 312: N electrode; 320: TiO2/SiO2 DBR; 330: gallium oxide layer; 340: gallium silver oxide layer; 350: Silver mirror.
  • a highly reflective metal layer is usually plated on the back of the thinned sapphire substrate to reduce light loss.
  • the structure of the mirror may be selected from a highly reflective metal layer such as a high reflectivity metal such as silver or aluminum; or a transparent dielectric layer stack in which the refractive index is periodically changed in high or low, such as multiple layers.
  • Distributed Bragg reflector consisting of SiO2/TiO2 (Distributed Bragg reflector, DBR) ).
  • DBR distributed Bragg reflector
  • Silver has a very high reflectance in the blue-green light band and is an ideal reflective layer material, but silver and sapphire have poor adhesion and cannot be directly used as a back-reflecting layer.
  • the current practice is to add a thin layer of metal between the silver and the sapphire as an adhesion layer, such as Cr, Ni, etc., the thickness is generally controlled to a few angstroms, so as to avoid a significant decrease in reflectance.
  • FIG. 1 is a schematic diagram of a typical LED structure using a conventional back plating technique, including a sapphire substrate 100, a n A gallium nitride based epitaxial layer 101, a light emitting layer 102, a p-type gallium nitride based epitaxial layer 103, a thin chromium layer (thickness 10 angstroms) 110 and a silver reflective layer 120.
  • Thin chrome layer 110 The presence of the silver reflective layer 120 enables the sapphire substrate 100
  • the back is plated with a reflective layer and, because of its thickness of only a few atomic layers, does not cause a significant reduction in reflectivity.
  • the thin metal layer can solve the problem of poor adhesion between silver and sapphire, the overall reflectivity is not as good as that of the pure silver reflective layer, and there are disadvantages such as difficulty in control and poor repeatability in production and production.
  • the following embodiments provide a completely new back-plated reflective layer solution to address the limitations of the prior art described above.
  • a gallium nitride based light emitting diode chip structure having a back plating reflective layer including a sapphire substrate 200 and a buffer layer 201 , n-GaN layer 202 , multiple quantum well active layer 203 , p-GaN layer 204 , ITO transparent conductive layer 210 , P electrode 211 , N electrode 212 , GaN adhesion layer 220, silver mirror 230.
  • the sapphire substrate 200 has two main surfaces, a front surface and a back surface; and the buffer layer 201 is formed on the sapphire substrate 200.
  • an n-GaN layer 202 is formed over the buffer layer 201;
  • a multiple quantum well active layer 203 is formed over the n-GaN layer 202; and
  • a p-GaN layer 204 Formed on the multiple quantum well active layer 203;
  • an ITO layer 210 is formed over the p-GaN layer 204;
  • a P electrode 211 is formed over the ITO layer 210;
  • An electrode 212 is formed over the n-GaN layer 202;
  • a GaN adhesion layer 220 is formed on the back surface of the sapphire substrate 200 to a thickness of 200 angstroms;
  • a silver mirror 230 Formed on the GaN adhesion layer 220, the material is Ag/Ti/Pt/Au, and the first layer material is Ag.
  • the manufacturing method of the light emitting diode of the above structure comprises the steps of: first step, on the sapphire substrate 200 Epitaxially growing a gallium nitride based epitaxial layer on the front surface, including: a buffer layer 201, an n-GaN layer 202, a multiple quantum well active layer 203, and a p-GaN layer 204 .
  • the second step fabricating an electrode comprising partially etching a gallium nitride based epitaxial layer to expose the n-GaN layer 202, and forming an ITO transparent conductive layer 210 on the p-GaN layer 204, A P electrode 211 is formed on the ITO layer 210 and an N electrode 212 is formed on the n-GaN layer 202.
  • the third step grinding the sapphire substrate 200 The back surface to achieve a thinning and polishing effect.
  • Step 4 Epitaxially growing a GaN layer having a thickness of 200 ⁇ on the back surface of the ground sapphire transparent substrate 200 by HVPE 220 .
  • Step 5 A silver mirror 230 is plated on the GaN layer 220, the material is Ag/Ti/Pt/Au, and the first layer material is Ag.
  • Step 6 In a mixed atmosphere of nitrogen and oxygen, the temperature Rapid thermal annealing is performed at 480 °C so that the silver in the silver mirror layer 230 and the GaN layer 220 diffuse and form a close bond.
  • the light-emitting diode fabricated by the above manufacturing method has 'sapphire/gallium nitride/ Silver's back-plated reflective layer structure, which has higher reflectivity than the 'sapphire/thin metal/silver' structure, and therefore is superior in improving the light extraction efficiency of the light emitting diode.
  • a highly reflective metal layer and a distributed Bragg reflector can be combined to form a so-called omnidirectional mirror ( Omni-Direction Reflector, ODR).
  • ODR Omni-Direction Reflector
  • a small angle of axial light is reflected by the DBR portion, while a non-axial light is reflected by the high anti-metal layer, so that the average reflectance obtained can exceed 90%.
  • the common transparent dielectric layer stack combination can be an oxide such as SiO2/TiO2.
  • high anti-metal layers generally choose aluminum.
  • a gallium nitride-based light emitting diode structure having an omnidirectional mirror includes a sapphire substrate 300, a buffer layer 301, an n-GaN layer 302, a multiple quantum well active layer 303, and a p-GaN layer. 304, ITO transparent conductive layer 310, P electrode 311, N electrode 312, 6 pairs of TiO 2 /SiO 2 DBR 320 , gallium oxide layer 330 , gallium silver oxide layer 340 , and silver mirror 350 .
  • the sapphire substrate 300 has two main surfaces, a front surface and a back surface; a buffer layer 301 is formed on the front surface of the sapphire substrate 300; an n-GaN layer 302 is formed on the buffer layer 301; and a multi-quantum well active layer 303 Formed on the n-GaN layer 302; a p-GaN layer 304 is formed over the multiple quantum well active layer 303; an ITO layer 310 is formed over the p-GaN layer 304; and a P electrode 311 is formed over the ITO layer 310
  • the N electrode 312 is formed on the n-GaN layer 303; 6 pairs of TiO 2 /SiO 2 DBR 320 are formed on the back surface of the sapphire substrate 300, and the gallium oxide layer 330 is formed on the TiO 2 /SiO 2 DBR 320.
  • gallium silver oxide layer 340 is formed on gallium oxide layer 330, the thickness of which is less than 500 angstroms, no fixed component; silver mirror 350 is formed on gallium silver oxide layer 340, the material is Ag/Ti /Pt/Au, the first layer of material is Ag.
  • the manufacturing method of the above light emitting diode comprises the steps of:
  • First step epitaxially growing a gallium nitride based epitaxial layer on the front side of the sapphire substrate 100, including: a buffer layer 101, an n-GaN layer 102, multiple quantum well active layer 103 and p-GaN layer 104;
  • Second step fabricating an electrode comprising partially etching a gallium nitride based epitaxial layer to expose the n-GaN layer 102 and the p-GaN layer
  • An ITO transparent conductive layer 110 is formed on the 104, a P electrode 111 is formed on the ITO layer 110, and an N electrode is formed on the n-GaN layer 102. ;
  • the third step grinding the back surface of the sapphire substrate 100 to achieve a thinning and polishing effect
  • the fourth step firstly deposit a 6 pairs of TiO2/SiO2 DBR on the back side of the polished sapphire transparent substrate 100 by electron beam evaporation. Combining 120, corresponding to a central wavelength of 460 nm; then continuing to deposit a gallium oxide layer 130 having a thickness of 200 angstroms in the same cavity;
  • the fifth step a silver mirror 150 is plated on the gallium oxide layer 130, and the material thereof is Ag/Ti/Pt/Au;
  • Step 6 Rapid thermal annealing at a temperature of 480 ° C in an atmosphere containing a mixed gas of nitrogen and oxygen to make the silver mirror layer 150
  • the silver and gallium oxide layers 130 are mutually diffused and fused to form a gallium-silver oxide interface layer 140, so that the first two are closely bonded.
  • the light-emitting diode fabricated by the above manufacturing method has 'sapphire/DBR/gallium oxide/ Silver's back-plated omnidirectional mirror structure, which combines a highly reflective silver layer, can greatly improve the overall reflectivity of the omnidirectional mirror.

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Abstract

一种具有反射镜的氮化镓基发光二极管及其制作方法。反射镜形成于发光二极管衬底（200）的背面，其可用金属反射镜或全方位反射镜，至少包括银反射层（230）和氮化镓层（220），通过所述氮化镓层（220）实现银反射层（230）与衬底（200）或氧化物透光介电材料层的紧密黏合。

Description

具有反射镜的发光二极管及其制作方法 相关申请
本申请主张如下优先权：中国发明专利申请号 201210074327.4 ，题为 ' 具有背镀反射层的发光二极管及其制作方法 ' ，于 2012 年 3 月 21 日 提交；中国发明专利申请号 201210074485.X ，题为 ' 具有全方位反射镜的发光二极管及其制作方法 ' ，于 2012 年 3 月 21 日 提交。上述申请的全部内容通过引用结合在本申请中。
技术领域
本发明涉及一种发光二极管及其制作方法，更为具体地，涉及一种具有反射镜的氮化镓基发光二极管及其制作方法。
背景技术
近年来，以氮化镓基宽带隙半导体材料为代表的半导体照明技术得到飞速发展。氮化镓基发光二极管器件已经广泛应用在显示、指示、背光源和照明等多种领域。当前，主流的氮化镓基发光二极管芯片按结构可以分为正装、倒装和垂直三种类型，其中以绝缘蓝宝石为衬底的正装结构最为普遍，被业界所广泛采用。
发明内容
在一方面，本发明提供一种具有背镀银反射层的发光二极管及其制作方法，通过在蓝宝石衬底与反射层之间插入一氮化镓基材料层，以解决两者之间黏附不佳的问题。因氮化镓基材料层与银层在退火后可以形成紧密粘合，同时氮化镓基材料对于蓝、绿光波段是完全透明的，所以采用氮化镓基材料层作为黏附层相比于薄金属层可以提高背镀反射层的整体反射率。
实现上述目的的技术方案为：一种具有背镀反射层的发光二极管，其结构包括：一透明衬底； 一半导体叠层，形成于该透明衬底的一第一表面，该半导体叠层包含一第一导电性半导体层、一第二导电性半导体层以及一发光层介于前述两者之间；一背镀反射层形成于相对于所述第一表面的所述透明衬底的一第二表面，自该第二表面起，该背镀银反射层依次包含一黏附层和一金属反射层，并且所述黏附层材质为氮化镓基材料，以及所述金属反射层的首层材料为银。
前述具有背镀反射层的发光二极管的制作方法，包括步骤：提供一透明衬底；在该透明衬底的第一表面外延生长半导体叠层，该半导体叠层包含一第一导电性半导体层、一第二导电性半导体层以及一发光层介于前述两者之间；从相对于第一表面的该透明衬底的第二表面减薄并研磨该透明衬底；在研磨后的透明衬底的第二表面外延生长一氮化镓基材料层作为黏附层；在氮化镓基材料层上镀一金属反射层，其中首层材料为银；退火以使得银与氮化镓基材料层形成紧密黏合。
在一些实施例中，所述透明衬底的材质主要是蓝宝石；半导体叠层的材料为氮化镓基材料；黏附层的形成方式可以采用外延生长，包括金属有机化学气相沉积（ MOCVD ）、分子束外延（ MBE ）和氢化物气相外延（ HVPE ）等；综合透光率和黏附性考虑，氮化镓（ GaN ）是较为理想的黏附层材料；黏附层的厚度不宜太厚， 500 埃以内即可；在制作方法中，针对背镀反射层的退火可以在包含氮气和氧气的氛围中进行，并且退火的温度介于 300 ℃ ~800 ℃之间为宜。
在另一方面，本发明提供一种具有全方位反射镜的氮化镓基发光二极管及其制作方法，通过在银与氧化物透光介电材料层之间插入一氧化镓层，以解决两者之间黏附不佳的问题。因氧化镓与银在退火后可以通过相互扩散合金形成紧密结合，同时氧化镓对于蓝光波段是完全透明的，所以可以采用氧化镓层作为中间黏附层构造包含银的背镀全方位反射镜，从而更进一步地提高全方位反射镜的反射率。
实现上述目的的技术方案为：一种具有全方位反射镜的氮化镓基发光二极管，其结构包括：蓝宝石衬底；氮化镓基外延叠层，形成于该蓝宝石衬底的第一表面，该氮化镓基外延叠层包含 N 型氮化镓基外延层、 P 型氮化镓基外延层以及发光层介于前述两者之间；全方位反射镜形成于相对于所述第一表面的所述蓝宝石衬底的第二表面，并且自该第二表面起，该全方位反射镜依次包含折射率呈高低周期性交替变化的复数层透光介电层堆、氧化镓层和银反射层。
前述具有全方位反射镜的氮化镓基发光二极管的制作方法，包括步骤：提供蓝宝石衬底；在该蓝宝石衬底的第一表面外延生长氮化镓基外延叠层，该氮化镓基外延叠层包含 N 型氮化镓基外延层、 P 型氮化镓基外延层以及发光层介于前述两者之间；在该蓝宝石衬底的第二表面制作全方位反射镜，从第二表面起，该全方位反射镜依次包含折射率呈高低周期性交替变化的复数层透光介电层堆、氧化镓层和银反射层；退火以使得银与氧化镓层二者界面相互扩散并形成合金。
前述技术方案的创新之处于：采用氧化镓作为银与氧化物透光介电材料层的中间黏附层。氧化镓与氧化物透光介电材料层的黏附性良好可靠，氧化镓与银则必须通过退火合金以形成紧密粘合，经过高温退火后，银会扩散并熔入氧化镓层中，形成镓银氧化界面层，镓银氧化界面层的形成则大大增强了银与氧化镓的黏附力。在一些实施例的具体的制作方法中，退火可以在包含氮气和氧气的氛围中进行，退火温度选择介于 300 ℃ ~800 ℃之间为宜。
附图说明
附图用来提供对本发明的进一步理解，并且构成说明书的一部分，与本发明的实施例一起用于解释本发明，并不构成对本发明的限制。此外，附图数据是描述概要，不是按比例绘制。
图 1 是现有技术的具有背镀反射层发光二极管芯片结构示意图。
图 2 是根据本发明实施的一种具有背镀反射层的发光二极管芯片结构示意图。
图 3 是根据本发明实施的具有背镀全方位反射镜的氮化镓基发光二极管结构示意图。
图中部件符号说明：
100 ：蓝宝石衬底； 101 ： n 型氮化镓基外延层； 102 ：发光层； 103 ： p 型氮化镓基外延层； 110 ：薄铬层； 120 ：银反射层； 200 ：蓝宝石衬底； 201 ：缓冲层； 202 ： n-GaN 层； 203 ：多量子阱层； 204 ： p-GaN 层； 210 ： ITO 透明导电层； 211 ： P 电极； 212 ： N 电极； 220 ： GaN 黏附层； 230 ：银反射镜； 300 ：蓝宝石衬底； 301 ：缓冲层； 302 ： n-GaN 层； 303 ：多量子阱层； 304 ： p-GaN 层； 310 ： ITO 透明导电层； 311 ： P 电极； 312 ： N 电极； 320 ： TiO2/SiO2 DBR ； 330 ：氧化镓层； 340 ：镓银氧化层； 350 ：银反射镜。
具体实施方式
以下将结合附图及实施例来详细说明本发明的实施方式，借此对本发明如何应用技术手段来解决技术问题，并达成技术效果的实现过程能充分理解并据以实施。需要说明的是，只要不构成冲突，本发明中的各个实施例以及各实施例中的各个特征可以相互结合，所形成的技术方案均在本发明的保护范围之内。
对于正装结构 LED ，为了减少封装环节中基板反射率不佳引起的取光效率降低，通常在减薄后的蓝宝石衬底背面镀上一高反射金属层以减少光损失。反射镜的结构，可以选择高反射金属层，诸如银、铝等高反射率金属；或者是折射率呈高低周期性交替变化的透光介电层堆，如多层 SiO2/TiO2 组成的分布式布拉格反射器（ Distributed Bragg reflector, DBR ）。银在蓝绿光波段具有极高的反射率，是理想的反射层材料，但银与蓝宝石的黏附很差，不能直接用作背镀反射层。现有的做法是在银与蓝宝石之间加一薄层金属作为黏附层，诸如 Cr 、 Ni 等，其厚度一般控制在几个埃左右，以免造成反射率大幅降低。
实施例 1
如附图 1 为一典型的采用现有背镀层技术的发光二极管结构示意图，其包括一蓝宝石衬底 100 、一 n 型氮化镓基外延层 101 、一发光层 102 、一 p 型氮化镓基外延层 103 、一薄铬层（厚度 10 埃） 110 和一银反射层 120 。薄铬层 110 的存在，使得银反射层 120 能够用于蓝宝石衬底 100 的背镀反射层，而且由于其厚度只有几个原子层，不会造成反射率明显降低。采用薄层金属层虽然可以解决银与蓝宝石的黏附差的问题，但其整体的反射率还是不如较纯银反射层，而且在生产制作上存在不易控制，重复性不佳等缺点。
因此，下面实施例提供一全新的背镀反射层方案，以解决上述现有技术的局限。
请参考附图 2 ，一种具有背镀反射层的氮化镓基发光二极管芯片结构，包括蓝宝石衬底 200 、缓冲层 201 、 n-GaN 层 202 、多量子阱有源层 203 、 p-GaN 层 204 、 ITO 透明导电层 210 、 P 电极 211 、 N 电极 212 、 GaN 黏附层 220 、银反射镜 230 。
其中，蓝宝石衬底 200 具有两个主表面，正表面和背表面；缓冲层 201 形成于蓝宝石衬底 200 的正表面之上； n-GaN 层 202 形成于缓冲层 201 之上；多量子阱有源层 203 形成于 n-GaN 层 202 之上； p-GaN 层 204 形成于多量子阱有源层 203 之上； ITO 层 210 形成于 p-GaN 层 204 之上； P 电极 211 形成于 ITO 层 210 之上； N 电极 212 形成于 n-GaN 层 202 之上； GaN 黏附层 220 形成于蓝宝石衬底 200 的背表面，其厚度为 200 埃；银反射镜 230 形成于 GaN 黏附层 220 之上，其材料为 Ag/Ti/Pt/Au ，首层材料为 Ag 。
上述结构的发光二极管之制作方法包括步骤：第一步，在蓝宝石衬底 200 的正表面上外延生长氮化镓基外延层，包括；缓冲层 201 、 n-GaN 层 202 、多量子阱有源层 203 和 p-GaN 层 204 。第二步：制作电极，包括部分地蚀刻氮化镓基外延层以暴露出 n-GaN 层 202 ，以及在 p-GaN 层 204 上制作 ITO 透明导电层 210 ，在 ITO 层 210 之上制作 P 电极 211 和在 n-GaN 层 202 制作 N 电极 212 。第三步：研磨蓝宝石衬底 200 的背表面，以达到减薄和抛光效果。第四步：在研磨后的蓝宝石透明衬底 200 的背表面采用 HVPE 外延生长一厚度为 200 埃的 GaN 层 220 。第五步：在 GaN 层 220 上镀银反射镜 230 ，材料为 Ag/Ti/Pt/Au ，首层材料为 Ag 。第六步：在氮气和氧气混合气体氛围中，温度 480 ℃中进行快速热退火，以使得银反射镜层 230 中的银与 GaN 层 220 相互扩散并形成紧密黏合。
采用上述制作方法制作而成的发光二极管具有'蓝宝石 / 氮化镓 / 银'的背镀反射层结构，该结构相比于'蓝宝石 / 薄金属 / 银'结构具有更高的反射率，因此在提高发光二极管的取光效率上更为优越。
实施例 2
在反射镜中，可将高反射金属层和分布式布拉格反射器结合起来，组成所谓的全方位反射镜（ Omni-Direction Reflector, ODR ）。由 DBR 部分反射小角度轴向光，而非轴向光则由高反金属层反射，这样可以获得的平均反射率超过 90% 。对于蓝光波段， ODR 结构中，常见的透光介电层堆组合可以是 SiO2/TiO2 等氧化物 DBR ，而高反金属层则一般会选择铝。银虽然在蓝光波段具有极高的反射率，但银与氧化硅、氧化钛等常见透光介电材料的黏附极差，所以在现有的技术中，银一直无法用于背镀全方位反射镜结构。
因此，需要改进背镀全方位反射镜结构设计，以解决上述现有技术的局限。 请参考附图 3 ，一种具有全方位反射镜的氮化镓基发光二极管结构，包括蓝宝石衬底 300 、缓冲层 301 、 n-GaN 层 302 、多量子阱有源层 303 、 p-GaN 层 304 、 ITO 透明导电层 310 、 P 电极 311 、 N 电极 312 、 6 对 TiO2/SiO2 DBR 320 、氧化镓层 330 、镓银氧化层 340 、和银反射镜 350 。
其中，蓝宝石衬底 300 具有两个主表面，正面和背面；缓冲层 301 形成于蓝宝石衬底 300 的正面之上； n-GaN 层 302 形成于缓冲层 301 之上；多量子阱有源层 303 形成于 n-GaN 层 302 之上； p-GaN 层 304 形成于多量子阱有源层 303 之上； ITO 层 310 形成于 p-GaN 层 304 之上； P 电极 311 形成于 ITO 层 310 之上； N 电极 312 形成于 n-GaN 层 303 之上； 6 对 TiO2/SiO2 DBR 320 形成于蓝宝石衬底 300 的背面，氧化镓层 330 形成于 TiO2/SiO2 DBR 320 之上，其厚度为 200 埃；镓银氧化层 340 形成于氧化镓层 330 之上，其厚度在 500 埃以内，无固定组分；银反射镜 350 形成于镓银氧化层 340 之上，其材料为 Ag/Ti/Pt/Au ，首层材料为 Ag 。
上述发光二极管的制作方法包括步骤：
第一步：在蓝宝石衬底 100 的正面外延生长氮化镓基发光外延层，包括；缓冲层 101 、 n-GaN 层 102 、多量子阱有源层 103 和 p-GaN 层 104 ；
第二步：制作电极，包括部分地蚀刻氮化镓基外延层以暴露出 n-GaN 层 102 ，以及在 p-GaN 层 104 上制作 ITO 透明导电层 110 ，在 ITO 层 110 之上制作 P 电极 111 和在 n-GaN 层 102 制作 N 电极 112 ；
第三步：研磨蓝宝石衬底 100 的背面，以达到减薄和抛光效果；
第四步：在研磨后的蓝宝石透明衬底 100 的背面采用电子束蒸发先沉积一 6 对 TiO2/SiO2 DBR 组合 120 ，对应中心波长 460nm ；接着继续同腔沉积一厚度为 200 埃的氧化镓层 130 ；
第五步：在氧化镓层 130 上镀银反射镜 150 ，其材料为 Ag/Ti/Pt/Au ；
第六步：在含有氮气和氧气混合气体的氛围中，温度 480 ℃条件下进行快速热退火，以使得银反射镜层 150 中的银与氧化镓层 130 相互扩散熔合形成镓银氧化界面层 140 ，从而使得前二者紧密黏合。
采用上述制作方法制作而成的发光二极管具有'蓝宝石 /DBR/ 氧化镓 / 银'的背镀全方位反射镜结构，该结构结合了高反射银层，可以大大提高全方位反射镜的整体反射率。

Claims (15)

  1. 具有背镀反射层的发光二极管，包括：
    透明衬底；
    半导体叠层，形成于该透明衬底的一第一表面，该半导体叠层包含一第一导电性半导体层、一第二导电性半导体层以及一发光层介于前述两者之间；
    背镀反射层，形成于相对于所述第一表面的所述透明衬底的一第二表面，自该第二表面起，该背镀银反射层依次包含一黏附层和一金属反射层，并且所述黏附层材质为氮化镓基材料，以及所述金属反射层的首层材料为银。
  2. 根据权利要求 1 所述的具有背镀银反射层的发光二极管，其透明衬底为蓝宝石。
  3. 根据权利要求 1 所述的具有背镀银反射层的发光二极管，其半导体叠层为氮化镓基材料。
  4. 根据权利要求 1 所述的具有背镀银反射层的发光二极管，其黏附层材料为氮化镓。
  5. 根据权利要求 1 所述的具有背镀银反射层的发光二极管，其黏附层厚度小于 500 埃。
  6. 具有背镀反射层的发光二极管的制作方法，包括步骤
    提供一透明衬底；
    在该透明衬底的第一表面外延生长半导体叠层，该半导体叠层包含一第一导电性半导体层、一第二导电性半导体层以及一发光层介于前述两者之间；
    从相对于第一表面的该透明衬底的第二表面减薄并研磨该透明衬底；
    在研磨后的透明衬底的第二表面外延生长一氮化镓基材料层作为黏附层；
    在氮化镓基材料层上镀一金属反射层，其中首层材料为银；
    退火，使得银与氮化镓基材料层形成紧密粘合。
  7. 根据权利要求 6 所述的具有背镀银反射层的发光二极管的制作方法，其透明衬底为蓝宝石。
  8. 根据权利要求 6 所述的具有背镀银反射层的发光二极管的制作方法，其半导体叠层为氮化镓基材料。
  9. 根据权利要求 6 所述的具有背镀银反射层的发光二极管的制作方法，其退火的氛围包含氮气和氧气。
  10. 根据权利要求 6 所述的具有背镀银反射层的发光二极管的制作方法，其退火的温度介于 300 ℃ ~800 ℃之间。
  11. 具有全方位反射镜的氮化镓基发光二极管，包括：
    蓝宝石衬底；
    氮化镓基外延叠层，形成于该蓝宝石衬底的一第一表面，该氮化镓基外延叠层包含 N 型氮化镓基外延层、 P 型氮化镓基外延层以及发光层介于前述两者之间；
    全方位反射镜形成于相对于所述第一表面的所述蓝宝石衬底的一第二表面，并且自该第二表面起，该背镀全方位反射镜依次包含折射率呈高低周期性交替变化的复数层透光介电层堆、氧化镓层和银反射层。
  12. 根据权利要求 11 所述的具有全方位反射镜的氮化镓基发光二极管，其还包括镓银氧化界面层形成于所述氧化镓层和银反射层之间。
  13. 具有全方位反射镜的氮化镓基发光二极管的制作方法，包括步骤：
    提供蓝宝石衬底；
    在该蓝宝石衬底的第一表面外延生长氮化镓基外延叠层，该氮化镓基外延叠层包含 N 型氮化镓基外延层、 P 型氮化镓基外延层以及发光层介于前述两者之间；
    在该蓝宝石衬底的第二表面制作背镀全方位反射镜，从第二表面起，该背镀全方位反射镜依次包含折射率呈高低周期性交替变化的复数层透光介电层堆、氧化镓层和银反射层；
    退火，使得银与氧化镓层二者界面相互扩散并形成合金。
  14. 根据权利要求 13 所述的具有全方位反射镜的氮化镓基发光二极管的制作方法，其退火的氛围包含氮气和氧气。
  15. 根据权利要求 13 所述的具有全方位反射镜的氮化镓基发光二极管的制作方法，其退火的温度介于 300 ℃ ~800 ℃之间。
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