WO2018019037A1

WO2018019037A1 - Light-emitting diode provided with full-mirror-surface structure, and preparation method therefor

Info

Publication number: WO2018019037A1
Application number: PCT/CN2017/087715
Authority: WO
Inventors: 郭桓邵; 吴俊毅; 吴超瑜; 王笃祥
Original assignee: 厦门三安光电有限公司
Priority date: 2016-07-29
Filing date: 2017-06-09
Publication date: 2018-02-01
Also published as: CN106129206B; CN106129206A

Abstract

A light-emitting diode provided with a full-mirror-surface structure, and a preparation method therefor. By using a DBR layer (230) that is epitaxially grown in advance, the DBR layer corresponding to an ohmic contact layer (220) is reserved in a chip process, and a full-mirror-surface structure is formed in combination with an ODR mirror surface system (260, 270), so that the area of the reflection mirror surface has no loss. With respect to structure, the light-emitting diode comprises a light-emitting epitaxial superimposed-layer (240) and a mirror surface system located below the light-emitting epitaxial superimposed-layer (240). The mirror surface system comprises a metal reflection layer (270) and a light transmission layer (260) located above the metal reflection layer (270). The light transmission layer comprises a light transmission region (260a) and a ohmic contact region (260b). The light transmission region is made of a light transmission dielectric material, and the light transmission layer and the metal reflection layer form an ODR reflection mirror. The ohmic contact region sequentially comprises the ohmic contact layer and the DBR layer from the bottom to the top, the DBR layer is formed by at least alternately stacking first semiconductor layers and second semiconductor layers, and accordingly an uninterrupted reflection mirror surface system is formed.

Description

Light-emitting diode with full mirror structure and manufacturing method thereof

[0001] The present invention relates to the field of semiconductor optoelectronic devices, and more particularly to a light-emitting diode having a full-mirror structure and a method of fabricating the same.

Background technique

[0002] A light-emitting diode (Light Emitting Diode in English) is a semiconductor solid-state light-emitting device that uses a semiconductor PN junction as a light-emitting material to directly convert electricity into light. As LED applications become more widespread, it is imperative to further increase luminous efficiency.

technical problem

[0003] The luminous efficiency of an LED mainly depends on the internal quantum efficiency and the light extraction efficiency. The former is determined by the epitaxial crystal quality of the luminescent material itself, and the latter is determined by factors such as the structure of the chip, the appearance of the light-emitting interface, and the refractive index of the packaging material. In the existing light-increasing process of the light-emitting diode, a mirror surface is often formed between the epitaxial layer of the chip and the light-absorbing substrate by the bonding process, thereby preventing the light emission in the chip from being absorbed by the light-absorbing substrate and reflecting it to the light-emitting surface to enhance the overall brightness. The mirror material is usually made of a metal material having a high reflectance for the wavelength of the chip, such as an Au/Ag mirror commonly used for red light, and an Al/Ag mirror for blue-green light; in addition, a high reflectivity metal is also commonly combined with Si0 ₂ to form a full The azimuthal mirror ODR structure is shown in Figure 1. In the LED structure shown in FIG. 1, in order to conduct P, N current, the lower portion of the light-emitting epitaxial layer needs to be an ohmic contact electrode 132, which loses the mirror area (~5%) on the one hand, and the other In the aspect, the electrode area of the ohmic contact also absorbs light to cause loss of brightness.

Problem solution

Technical solution

The present invention is directed to the above problems, and the present invention utilizes an extended pre-growth DBR (Distributed Bragg)

Reflector: distributed Bragg mirror) layer, in the chip process, the DBR layer corresponding to the ohmic contact layer is retained, so that the ohmic contact electrode region can form an ohmic contact and a reflective layer effect, and is matched with OD R (Omni Direction Reflection: Omni-directional mirror) The mirror system, which forms a full-mirror structure, achieves a loss of mirror-free area, which in turn increases light extraction efficiency. [0005] The technical solution of the present invention is: a light-emitting diode having a full-mirror structure, comprising a light-emitting epitaxial stack and a mirror system located therebelow, the light-emitting epitaxial layer comprising an N-type semiconductor layer, an active layer and a P-type semiconductor a layer, the mirror system comprising a metal reflective layer and a light transmissive layer thereon, the light transmissive layer comprising a light transmissive region and an ohmic contact region, the light transmissive region being composed of a translucent dielectric material, and a metal reflective The layer constitutes an OD R mirror, and the ohmic contact region includes an ohmic contact layer and a DBR layer in order from bottom to top, the DBR layer being alternately composed of at least a first semiconductor layer and a second semiconductor layer to form an uninterrupted mirror surface system.

[0006] Preferably, the metal reflective layer, the light transmissive layer and the DBR layer of the ohmic contact region constitute a three-dimensional mirror system.

[0007] Preferably, the DBR layer has inclined side walls with an inclination angle of 45 to 60 degrees.

[0008] Preferably, there is no gap between the light transmissive area and the ohmic contact area of the light transmissive layer.

[0009] Preferably, a flatness RMS of the light transmissive layer away from a side surface of the light emitting epitaxial laminate is within 1 nm.

[0010] Preferably, the thickness of the light transmissive layer is η χ λ / 4.

[0011] Preferably, the lattice constant of the DBR layer matches the lattice constant of the luminescent epitaxial stack.

[0012] The present invention also provides a method for fabricating a light emitting diode having a full mirror structure, comprising the steps of: (1) providing an epitaxial structure comprising a light emitting epitaxial layer, a DBR layer and an ohmic contact layer in sequence, the light emitting The epitaxial layer comprises a germanium-type semiconductor layer, an active layer and a germanium-type semiconductor layer, the DBR layer being alternately composed of at least a first semiconductor layer and a second semiconductor layer; (2) defining a surface on the surface of the ohmic contact layer a light region and an ohmic contact region, removing an ohmic contact layer and a DBR layer of the light transmitting region to expose a surface of the light emitting epitaxial layer; (3) depositing a light transmissive layer on the surface of the exposed light emitting epitaxial layer An electric material is used as the light transmissive layer; (4) forming a metal reflective layer over the light transmissive layer and the ohmic contact layer, the light transmissive layer and the metal reflective layer forming an ODR mirror, and the DBR of the ohmic contact region Form an uninterrupted mirror system.

[0013] Preferably, the step (2) is specifically: defining a light transmitting region and an ohmic contact region on a surface of the ohmic contact layer; forming a metal electrode layer on the ohmic contact region; The layer is a mask layer, and the ohmic contact layer and the DBR layer of the light transmissive region are etched away.

[0014] Preferably, after depositing the light transmissive layer in the step (3), the surface thereof is polished by CMP, and the metal electrode layer is exposed to conduct current as a current. After polishing, there is no between the light transmissive layer and the metal electrode layer The slit and the flatness RMS of the surface of the light transmissive layer are within 5 nm, and have better flatness and step coverage for subsequent metal mirror vapor deposition.

Advantageous effects of the invention

Beneficial effect

[0015] The present invention has at least the following beneficial effects: (1) The ohmic contact region under the light-emitting epitaxial layer forms both an ohmic contact and a reflective layer; (2) an uninterrupted reflection of ODR and DBR under the light-emitting epitaxial stack Mirror structure, and ODR and ohmic contact electrode have no gap, mirror surface system does not have any loss of reflection area; (3) There is no gap between ODR mirror and DBR structure of ohmic contact area, DBR structure with inclined 45~60° combined with ODR mirror The system forms a three-dimensional mirror surface system, so that the mirror surface area is further increased. (4) In the manufacturing method, the ohmic contact layer metal is directly evaporated on the epitaxy, and is used as a mask layer, and no yellow light alignment is required. Streamline processes and increase yield.

Other features and advantages of the invention will be set forth in the description which follows, The objectives and other advantages of the invention will be realized and attained by the <RTI

Brief description of the drawing

DRAWINGS

The drawings are intended to provide a further understanding of the invention, and are intended to be a part of the description of the invention. In addition, the drawing figures are a summary of the description and are not drawn to scale.

1 is a side cross-sectional view of a conventional vertical structure light emitting diode chip.

2 is a side cross-sectional view of an LED chip in accordance with an embodiment of the present invention.

3 is a view showing a distribution of a light-transmitting layer of the light-emitting diode chip shown in FIG. 2, which is divided into a light-transmitting region and an ohmic contact region.

4 to 12 are schematic diagrams showing a manufacturing process of an LED chip according to an embodiment of the present invention.

[0022] FIG. 13 is a cross-sectional view showing another structure of an LED chip in accordance with an embodiment of the present invention.

14 is a cross-sectional view showing an epitaxial structure of still another light emitting diode according to an embodiment of the present invention.

[0024] In the figure:

[0025] 100: a conductive substrate; 110: a metal bonding layer; 120: a metal reflective layer; 130: a light transmitting layer; : metal electrode layer; 132: ohmic contact layer; 140: light emitting epitaxial layer; 141: N type semiconductor layer; 1 42: active layer; 143: P type semiconductor layer; 150: P type electrode; 200: growth substrate 201: Linyi substrate; 202: Conductive substrate; 210: Etch cut-off layer; 220: N-type ohmic contact layer; 230: DBR layer; 240: Luminescent epitaxial stack; 241: N-type semiconductor layer; 242: Active layer 243: P-type semiconductor layer; 250: metal electrode layer; 260: light-transmitting layer; 270: metal reflective layer; 280: metal bonding layer; 290: P-type electrode.

Embodiments of the invention

[0026] The core point of the present invention is to provide an LED structure having a full mirror structure, which utilizes an epitaxially grown DBR layer to remove the DBR layer of the light transmissive region in the chip process, and only retains the DBR of the ohmic contact electrode region to make ohms. The contact electrode region can both form an ohmic contact and a reflective layer. The invention will now be further described with reference to the drawings and preferred embodiments.

2, a light emitting diode having a total reflection structure according to an embodiment of the present invention includes, in order from bottom to top, a conductive substrate 202, a metal bonding layer 280, a metal reflective layer 270, a light transmissive layer 260, The epitaxial stack 240 and the P-type electrode 290 are illuminated.

[0028] Specifically, the conductive substrate 202 may be a Si substrate, a metal substrate or a semiconductor material or the like; the metal bonding layer 280 is used to bond the light emitting epitaxial layer 240 and the conductive substrate 202; and the metal reflective layer 270 is made of a high reflectivity metal material. And the light transmissive layer 260 above it constitutes an ODR mirror; the light transmissive layer 260 is divided into a transparent region 260a and an ohmic contact region 260b, and the transparent region 260a and the ohmic contact region 260b are connected without a gap, wherein the transparent region 260a It is composed of a translucent dielectric material having a thickness of η χ λ / 4 (λ is the illuminating wavelength of the luminescent epitaxial stack), and the ohmic contact region 260 b is used for current conduction, including a metal electrode layer 250, ohms in order from bottom to top. The contact layer 220 and the DBR layer 230, the DBR layer 230 is a semiconductor material, and the lattice constant is often matched with the lattice of the light-emitting epitaxial layer 240, and at least a first semiconductor layer and a second semiconductor layer are alternately stacked. Having an electrically conductive function, and on the other hand, for reflecting the light emitted from the luminescent epitaxial layer toward the ohmic contact layer 220, avoiding the ohmic contact layer 220 and the metal electrode therebelow Absorbance 250; 240 emission epitaxial layer stack comprising at least an N-type semiconductor layer 241, the active layer 242 and a P-type semiconductor layer 243.

[0029] In a specific embodiment, the light-emitting epitaxial layer stack 240 is made of an AlGalnP-based material, and a buffer layer may be added between the N-type semiconductor layer and the active layer, and the P-type semiconductor layer and the active layer may be respectively added to the P-type semiconductor. Above the layer Forming a current spreading layer, a window layer, etc., the material of the light transmitting region 260b of the light transmitting layer 260 may be selected from silicon dioxide (SiO 2 ), lanthanum fluoride (LaF 3 ), magnesium fluoride (MgF 2 ), sodium fluoride (NaF). A group consisting of sodium aluminum fluoride (Na3AlF6), calcium fluoride (CaF2) and a combination of the above materials, and the DBR layer 230 is an AlGaAs/AlAs alternating structure.

[0030] In the above light emitting diode structure, the light transmissive region of the light transmissive layer directly forms an ODR mirror with the metal reflective layer, and forms an uninterrupted full specular reflection structure with the DBR layer of the ohmic contact region to achieve a non-reflective mirror surface. Area loss, which in turn increases light extraction efficiency.

[0031] The above LEDs will be described in detail below with reference to FIGS. 4 to 11 and a manufacturing method.

[0032] First, an epitaxial wafer is provided, the structure of which is shown in FIG. 4. The epitaxial wafer may include: a growth substrate 200, an etch stop layer 210, an ohmic contact layer 220, a DBR layer 230, an N-type semiconductor from bottom to top. A layer 241, an active layer 242, and a P-type semiconductor layer 243. In the present embodiment, the N-type semiconductor layer 241 is a Si-doped AlGalnP material layer having a Si concentration of 7x10 ¹⁷ ~ lxl0 ¹⁸ , and the P-type semiconductor layer 243 is a poor Mg GaP material layer, and the impurity concentration is 1.5× ¹⁰ ^{18 .}

Above, the ohmic contact layer 220 is a highly turbid N-GaAs material layer, and the DBR layer is an AlGaAs/AlAs material layer, each layer being 5-20 nm, and having 20 to 100 pairs in total.

Next, a P-type electrode 290 is formed on the surface of the P-type semiconductor layer, annealed, and bonded to a substrate 201 as shown in FIG.

[0034] Next, the growth substrate 200 is removed, and the surface of the ohmic contact layer 220 is exposed, as shown in FIG. 6. In the present embodiment, the growth substrate 200 and the etch stop layer 210 are removed by wet etching using a layer of NH ₄ OH: H ₂ 0 ₂ and HCl: H ₃ PO _{3 , respectively} .

[0035] Next, the surface of the exposed ohmic contact layer 220 is divided into an ohmic contact region and a light transmitting region, and a metal electrode layer 250 is formed on the ohmic contact region as shown in FIG. The metal electrode layer 250 and the ohmic contact layer 22

0 forms an ohmic contact after high temperature fusion.

[0036] Next, using the metal electrode layer 250 as a mask layer, the ohmic contact layer 220 and the DBR layer 230 of the light-transmitting region are etched away to expose the surface of the light-emitting epitaxial laminate, as shown in FIG.

[0037] Next, a light-transmitting dielectric material is deposited as a light-transmitting layer 260 on the surface of the exposed light-emitting epitaxial laminate, which has no gap with the metal electrode layer 250 and the DBR layer of the ohmic contact region. In the embodiment, the transparent dielectric material is made of SiO _x , and a certain thickness of SiO jl260 is first deposited, which is at least on the upper surface of the light transmitting region. The upper surface of the metal electrode layer 250 and the ohmic contact region flush, specifically deposited by CVD 400 ~ 1000 nm of _SiO Χ 260, 9, and then polished using CMP to meet SiO J1260 ηλ / 4 thickness, and The metal electrode layer 250 is exposed to conduct current as shown in FIG. The flatness RMS of the surface of the CMP-polished light transmissive layer is within 1 nm, preferably ~1, so that it has better flatness and step coverage for subsequent metal mirror evaporation.

[0038] Next, a metal reflective layer 270 is deposited on the light transmissive layer 260, as shown in FIG. 11, thereby forming a full specular reflection structure on the non-light-emitting surface of the light-emitting epitaxial structure, wherein the light-transmitting region has a light-transmissive dielectric material. 260 and the metal reflective layer 270 form an ODR mirror, and the ohmic contact region has a DBR layer 230 to form a complete, continuous, uninterrupted mirror structure. In the present embodiment, the metal reflective layer 270 may be Au Ag A1 or the like having a thickness of 0.2 μm or more, preferably 0.25 μm.

[0039] Next, a conductive substrate 202 is provided, and a metal bonding layer 280 is formed on the surface of the conductive substrate 202 and the metal reflective layer 260 to perform high temperature bonding, thereby bonding the conductive substrate 202 to the light emitting epitaxial layer 240, such as Figure 12 shows.

[0040] Finally, the copy substrate 201 is removed to form a light-emitting diode having a full mirror structure as shown in FIG. 2.

[0041] In the above fabrication method, a DBR layer is formed between the luminescent epitaxial stack of the epitaxial wafer and the ohmic contact layer by an epitaxial growth process in advance, and then a metal electrode is formed on the ohmic contact region of the ohmic contact layer in the chip fabrication process. a layer, using the metal electrode layer as a mask layer, etching and removing the ohmic contact layer and the DBR layer except the ohmic contact region (in this embodiment, the light transmitting region), in which no yellow light alignment is required, thereby avoiding The LED structure shown in Figure 1 needs to be aligned during the ODR process, which simplifies the chip process and greatly improves the yield.

[0042] FIG. 13 shows another LED structure in accordance with the practice of the present invention, which differs from the LED of FIG. 2 in that the DBR layer has sloped sidewalls with an angle of inclination of 45-60°. In the present embodiment, the inclined DBR layer 230 and the ODR mirror of the light transmitting region form a three-dimensional mirror system, so that the mirror surface area is further increased.

[0043] Compared to the light-emitting diode shown in FIG. 1, the brightness of the light-emitting diode using the mirror system can be improved by 8~1 0<3⁄4

[0044] Although the above embodiments are all examples of light-emitting diodes emitting light on the P side, it should be clear that the present invention is equally applicable to light-emitting diodes emitting light on the N side. When the N side is used as the light exit surface, the method shown in FIG. 14 can be used. The epitaxial wafer structure is prepared.

Although the exemplary embodiments of the present invention have been described, it is understood that the invention is not to be construed as being limited to the exemplary embodiments. Make various changes and modifications.

Claims

Claim

A light emitting diode having a full mirror structure, comprising a light emitting epitaxial stack and a mirror system thereunder, the light emitting epitaxial layer comprising an N-type semiconductor layer, an active layer and a P-type semiconductor layer, the mirror system comprising a metal reflective layer And a light transmissive layer disposed thereon, wherein: the light transmissive layer comprises a light transmissive region and an ohmic contact region, wherein the light transmissive region is composed of a translucent dielectric material, and the metal reflective layer constitutes an ODR mirror. The ohmic contact region includes an ohmic contact layer and a DBR layer in order from bottom to top, and the DBR layer is alternately composed of at least a first semiconductor layer and a second semiconductor layer to form an uninterrupted mirror system.

The light emitting diode having a full mirror structure according to claim 1, wherein the metal reflective layer, the light transmissive layer and the DBR layer of the ohmic contact region constitute a three-dimensional mirror system. A light emitting diode having a full mirror structure according to claim 2, wherein: said DBR layer has inclined side walls.

The light emitting diode with a full mirror structure according to claim 1, wherein: there is no gap between the light transmitting region and the ohmic contact region of the light transmitting layer.

The light emitting diode having a full mirror structure according to claim 1, wherein: a flatness RMS of the light transmitting layer away from a side surface of the light emitting epitaxial layer is within 10 nm.

A light emitting diode having a full mirror structure according to claim 1, wherein: said light transmitting layer has a thickness of η χ λ / 4.

A light emitting diode having a full mirror structure according to claim 1, wherein: a lattice constant of said DBR layer matches a lattice constant of said light emitting epitaxial layer.

A method for fabricating a light-emitting diode having a full mirror structure, comprising the steps of:

(1) Providing an epitaxial structure comprising, in order, a light-emitting epitaxial laminate, a DBR layer, and an ohmic contact layer, the light-emitting epitaxial layer comprising a germanium-type semiconductor layer, an active layer, and a germanium-type semiconductor layer

The DBR layer is alternately composed of at least a first semiconductor layer and a second semiconductor layer;

(2) defining a light transmitting region and an ohmic contact region on a surface of the ohmic contact layer, removing an ohmic contact layer and a DBR layer of the light transmitting region, exposing a surface of the light emitting epitaxial laminate;

(3) depositing a light transmissive dielectric material on the exposed surface of the exposed epitaxial laminate as a light transmissive Floor;

(4) forming a metal reflective layer over the light transmissive layer and the ohmic contact layer, the light transmissive layer and the metal reflective layer forming an ODR mirror, and forming an uninterrupted mirror system with the DBR of the ohmic contact region .

[Claim 9] The method for fabricating a light-emitting diode having a full-mirror structure according to claim 8, wherein: the step (2) is specifically:

Defining a light transmitting region and an ohmic contact region on a surface of the ohmic contact layer;

Forming a metal electrode layer on the ohmic contact region;

The ohmic contact layer and the DBR layer of the light transmissive region are etched away by using the metal electrode layer as a mask layer.

[Claim 10] The method for fabricating a light-emitting diode having a full-mirror structure according to claim 9, wherein: after the light-transmitting layer is deposited in the step (3), the surface is polished by CMP, and exposed. The metal electrode layer is turned on as a current.

[Claim 11] The method for fabricating a light-emitting diode having a full-mirror structure according to claim 9, wherein: after polishing, the surface of the light-transmitting layer has a flatness RMS of 5 nm or less.

[Claim 12] The method for fabricating a light-emitting diode having a full-mirror structure according to claim 9, wherein after the polishing, there is no gap between the light-transmitting layer and the metal electrode layer.