CN110970532B - Micro light-emitting diode capable of improving mass transfer yield - Google Patents

Micro light-emitting diode capable of improving mass transfer yield Download PDF

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CN110970532B
CN110970532B CN201811142993.0A CN201811142993A CN110970532B CN 110970532 B CN110970532 B CN 110970532B CN 201811142993 A CN201811142993 A CN 201811142993A CN 110970532 B CN110970532 B CN 110970532B
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CN110970532A (en
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丁肇诚
郭浩中
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Baopu Technology Co ltd
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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
    • H01L33/44—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
    • 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
    • H01L33/04—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 quantum effect structure or superlattice, e.g. tunnel junction
    • H01L33/06—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 quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
    • 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
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/028—Coatings ; Treatment of the laser facets, e.g. etching, passivation layers or reflecting layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
    • H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/3013—AIIIBV compounds

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Abstract

The invention covers a first protective layer and a second protective layer on the surface of a micro light-emitting diode to finish the micro light-emitting diode which can improve the yield of mass transfer. In particular, the micro light emitting diode having the first and second protective layers on the surface thereof can exhibit a high tolerance to external stress. Therefore, when a single micro light emitting diode is transferred to a substrate or a plurality of micro light emitting diodes are transferred in a large amount, the surface layer or other areas of the micro light emitting diodes are not deformed, cracked or broken due to the action of external stress. Meanwhile, in order to avoid the influence of the first protective layer and the second protective layer on the normal light emitting of the micro light emitting diode, the invention particularly makes the refractive index of the first protective layer smaller than that of the second semiconductor material layer, and simultaneously makes the refractive index of the second protective layer smaller than that of the first protective layer.

Description

Micro light-emitting diode capable of improving mass transfer yield
Technical Field
The present invention relates to the field of Light-emitting diode (LED) technology, and more particularly, to a micro LED capable of increasing yield of mass transfer.
Background
A Light-Emitting Diode (LED) is a Light-Emitting element widely used at present, and is widely used in daily life of human beings due to its advantages of small size, long service life, and the like. The diagonal length of the die of the led is typically between 200 microns and 300 microns. On the other hand, a light emitting diode with a die having a diagonal length between 50 and 60 microns is called a sub-millimeter light emitting diode (Mini LED), and a light emitting diode with a die having a diagonal length less than 50 microns is called a Micro LED (μ LED).
Fig. 1 is a schematic diagram illustrating a conventional micro led display panel. The current technology can apply micro-leds to a display panel (or module) as a Sub-pixel (Sub-pixel). For example, in fig. 1, a red micro led RLED ', a green micro led GLED', and a blue micro led BLED 'may form a pixel (pixel) of the micro led display panel 1'. The micro led display panel 1 ' further includes a substrate 10 ', and a plurality of electrical connection pads 101 ' are formed on the surface of the substrate 10 ' for electrically connecting the plurality of red micro leds RLED ', the plurality of green micro leds GLED ' and the plurality of blue micro leds bler '. Generally, the substrate 10' further includes a driving circuit for controlling each sub-pixel or each pixel. It should be noted that the display panel 1' with the resolution of 4K2K has 4096 × 2160 pixels; that is, the display panel 1' with the resolution of 4K2K at least comprises 2,488 thousands of micro leds. Therefore, it can be seen that how to arrange a large number of micro-leds on the substrate 10 'becomes a major problem in the manufacturing of the micro-led display panel 1'.
A huge number of micron-scale LED dies are arranged on a substrate or a circuit board by high-precision equipment, and this process is called Mass transfer (Mass transfer). U.S. patent publication No. 2018/0053742a1 discloses a method for mass transfer of electronic components. Correspondingly, fig. 2A, 2B and 2C are process diagrams illustrating a method for bulk transfer of electronic devices disclosed in U.S. patent publication No. 2018/0053742A 1. According to the disclosure of U.S. patent publication No. 2018/0053742a1, the method of bulk transfer of electronic components includes a plurality of process steps. First, in step 1, a plurality of LED dies 200 '(as shown in fig. 2A) are fabricated on a surface of a substrate 112' in an array arrangement. Next, in step 2, a temporary fixing film 120 'such as Blue tape is attached to the bottom surface of the substrate 112' (as shown in FIG. 2A).
Continuously, in step 3, a plurality of notches are formed on the surface of the substrate 112' by using a laser etching apparatus (as shown in fig. 2B); thereafter, the substrate 112 'is turned over so that the bottom surface of the substrate 112' faces upward (as shown in fig. 2B). Next, in step 4, the substrate 112 'is cut along the scribe lines by a dicing saw to obtain a plurality of sub-substrates 113' (as shown in fig. 2C). It is noted that each submount 113 'has a plurality of LED dies 200' on its surface. Continuously, the submount 113 ' is moved onto a carrier substrate BS ' by using a vacuum chuck, so that both electrodes of each LED die 200 ' are electrically connected to the bonding electrode BE ' preset on the surface of the carrier substrate BS '.
Semiconductor device engineers who have actually used the aforementioned bulk electronic device transfer method in their manufacturers should know that some of the LED dies 200 'are damaged by external stress during the flip-chip process of the substrate 112'. In addition, when the sub-substrate 113 'is moved by the vacuum chuck, a part of the LED dies 200' may be damaged by external stress. It should be noted that the carrier substrate BS' is usually a printed circuit board or a flexible circuit board. Therefore, when the LED dies 200 ' are transferred to the flexible circuit board in a large amount, the bending or bending of the flexible circuit board also applies stress to the LED dies 200 ' disposed thereon, thereby causing damage to a portion of the LED dies 200 '.
As can be seen from the above description, although the prior art can arrange huge amount of micron-sized LED dies on a flexible substrate or a printed circuit board by using the blue film and the vacuum suction machine, considerable damage or destruction of the LED dies is caused during the huge amount of transfer. Obviously, such a massive transfer method still shows drawbacks and deficiencies in practical applications; accordingly, the present invention provides a micro light emitting diode capable of improving yield of mass transfer.
Disclosure of Invention
The present invention is directed to a micro light emitting diode capable of increasing yield of mass transfer. In particular, the first protective layer and the second protective layer are coated on the surface of the micro light-emitting diode, so that the micro light-emitting diode with the first protective layer and the second protective layer coated on the surface can show higher tolerance degree of external stress. Therefore, when a single micro light emitting diode is transferred to a substrate or a plurality of micro light emitting diodes are transferred in a large amount, the surface layer or other areas of the micro light emitting diodes are not deformed, cracked or broken due to the action of external stress. Meanwhile, in order to avoid the influence of the first protective layer and the second protective layer on the normal light emitting of the micro light emitting diode, the invention particularly makes the refractive index of the first protective layer smaller than that of the second semiconductor material layer, and simultaneously makes the refractive index of the second protective layer smaller than that of the first protective layer.
To achieve the above objective of the present invention, the present inventors provide an embodiment of the micro led capable of increasing yield of mass transfer, comprising:
a substrate;
a first semiconductor material layer formed on the substrate;
an active layer formed on the first semiconductor material layer;
a second semiconductor material layer formed on the active layer;
a first passivation layer formed on the second semiconductor material layer and having a first opening and a second opening; wherein the first protective layer covers the side surface of the second semiconductor material layer, the side surface of the active layer, and the side surface and part of the surface of the first semiconductor material layer;
a second passivation layer formed on the first passivation layer and having a third opening corresponding to the first opening and a fourth opening corresponding to the second opening;
a first electrode formed on the first semiconductor material layer through the second opening and the fourth opening; and
a second electrode formed on the second semiconductor material layer through the first opening and the third opening;
the refractive index of the first protective layer is smaller than that of the second semiconductor material layer, and the refractive index of the second protective layer is smaller than that of the first protective layer.
To achieve the above objective of the present invention, the present inventors also provide another embodiment of the micro led capable of increasing yield of mass transfer, including:
a substrate;
a first Bragg reflector formed on the substrate;
a first semiconductor material layer formed on the first Bragg reflector;
an active layer formed on the first semiconductor material layer;
a second semiconductor material layer formed on the active layer; and
a second Bragg reflector formed on the second semiconductor material layer;
a first protection layer covering the surface and side of the second Bragg reflector, the surface and side of the second semiconductor material layer, the side of the active layer, the side of the first semiconductor material layer, and the side of the first Bragg reflector, and having a first opening and a second opening;
a second passivation layer formed on the first passivation layer and having a third opening corresponding to the first opening and a fourth opening corresponding to the second opening;
a first electrode formed on the first semiconductor material layer through the second opening and the fourth opening; and
a second electrode formed on the second semiconductor material layer through the first opening and the third opening;
the refractive index of the first protective layer is smaller than that of the second semiconductor material layer, and the refractive index of the second protective layer is smaller than that of the first protective layer.
Drawings
FIG. 1 is a schematic diagram showing a conventional micro-LED display panel;
FIGS. 2A, 2B and 2C are schematic process diagrams illustrating a method for bulk transfer of electronic components disclosed in U.S. Pat. No. 2018/0053742A 1;
FIG. 3 is a schematic perspective view of a micro LED capable of improving yield of mass transfer according to a first embodiment of the present invention;
FIG. 4 is a first cross-sectional view of a micro LED for improving yield of mass transfer according to the present invention;
FIG. 5 is a second cross-sectional view of a micro LED for improving yield of mass transfer according to the present invention;
FIG. 6 is a first cross-sectional view of a second embodiment of a micro LED for improving yield of mass transfer according to the present invention;
FIG. 7 is a second cross-sectional view of a second embodiment of a micro LED for improving yield of mass transfer according to the present invention; and
FIG. 8 is a third cross-sectional view of a second embodiment of a micro LED for improving the yield of mass transfer according to the present invention.
Wherein the reference numerals are:
1 micro light emitting diode capable of improving mass transfer yield
10 base plate
11 first layer of semiconductor material
12 active layer
13 second semiconductor material layer
14 first protective layer
15 second protective layer
16 first electrode
17 second electrode
BF buffer layer
20 base plate
21 first bragg reflector
22 first layer of semiconductor material
23 active layer
24 layer of a second semiconductor material
25 second bragg mirror
26 first protective layer
27 second protective layer
28 first electrode
29 second electrode
ACO oxide layer
24a intermediate semiconductor material layer
TJ tunnel junction
22a first bonding layer
24b second bonding layer
112' substrate
200' LED die
120' temporary fixation film
113' submount
BS' bearing substrate
BE' junction electrode
RLED' Red light micro-LED
GLED' Green micro-LED
BLED' blue light micro-LED
1' display panel
101' electrical connection pad
10' substrate
Detailed Description
In order to more clearly describe the micro led capable of increasing yield of mass transfer, the preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.
First embodiment
Fig. 3 is a schematic perspective view showing a micro light emitting diode capable of increasing yield of mass transfer according to a first embodiment of the present invention, and fig. 4 is a first cross-sectional view showing the micro light emitting diode capable of increasing yield of mass transfer according to the present invention. As will be understood by engineers familiar with the basic component design and fabrication of leds from fig. 3 and 4, the first embodiment of the micro-leds 1 (hereinafter referred to as "micro-leds") of the present invention that can improve yield of mass transfer includes a standard led base structure. As shown in fig. 3 and 4, the novel micro light emitting diode 1 structurally includes: a substrate 10, a first semiconductor material layer 11 formed on the substrate 10, an active layer 12 formed on the first semiconductor material layer 11, a second semiconductor material layer 13 formed on the active layer 12, a first passivation layer 14, a second passivation layer 15, a first electrode 16, and a second electrode 17.
In particularThe first passivation layer 14 is formed on the second semiconductor material layer 13 and has a first opening and a second opening. Fig. 4 shows that the first passivation layer 14 covers the side surfaces of the second semiconductor material layer 13, the active layer 12, and the first semiconductor material layer 11. It should be noted that fig. 3 only shows that the first passivation layer 14 only covers the surface of the second semiconductor material layer 13, and the main purpose is to expose each material layer of the micro light emitting diode 1. On the other hand, the second passivation layer 15 is formed on the first passivation layer 14 and has a third opening corresponding to the first opening and a fourth opening corresponding to the second opening. As shown in fig. 3 and 4, a first electrode 16 is formed on the first semiconductor material layer 11 through the second opening and the fourth opening, and a second electrode 17 is formed on the second semiconductor material layer 13 through the first opening and the third opening. Of course, the process materials of the first semiconductor material layer 11, the active layer 12 and the second semiconductor material layer 13 may be selected according to different colors of light emission. Conventionally, GaP, GaAsP, and AlGaAs are the main materials of the active layer 12, so that the active layer 12 can emit visible light with a wavelength ranging from 580nm to 740 nm. However, as metal-organic chemical vapor deposition (MOCVD) process technology advances, gallium nitride (GaN) and aluminum gallium nitride (Al) are increasingly usedxGa1-xN), or indium gallium nitride (In)xGa1-xN) then becomes the main material of the active layer 12.
In general, the active layer 12 including GaN may emit blue light. Additionally, it should be known to component engineers familiar with the design and manufacture of LED dies (die) by increasing the value of x (x)<1) May contain InxGa1-xThe N active layer 12 emits light of a long wavelength. Correspondingly, by increasing the value of x (x)<1) May contain AlxGa1-xThe N active layer 12 emits light of a short wavelength. Here, it should be noted that GaN and Al are usedxGa1-xN or InxGa1-xAn active layer 12 of N is formed on the first semiconductor material layer 11 and the second semiconductorA single quantum well structure is formed between the material layers 13. Therefore, the first semiconductor material layer 11 and the second semiconductor material layer 13 can be regarded as a Lower cladding layer (Lower cladding layer) and an Upper cladding layer (Upper cladding layer) of the active layer 12; the first semiconductor material layer 11 is made of N-type gallium nitride (N-GaN), such as silicon (Si) doped GaN. In contrast, the second semiconductor material layer 13 is made of P-type gallium nitride (P-GaN), such as gallium nitride doped with magnesium (Mg). Further, the active layer 12 may be designed as a multiple quantum well structure, thereby increasing the recombination efficiency of electron holes in the active layer 12. The multiple quantum well structure may be any of the following: gallium nitride and indium gallium nitride (In)xGa1-xN), gallium nitride and aluminum gallium nitride (Al)xGa1-xN) multiple stacked structure, or aluminum gallium nitride (Al)xGa1-xN) and indium gallium nitride (In)xGa1-xN) of the stack.
Furthermore, the first electrode 16 and the second electrode 17 can be made of any one of the following materials: aluminum (Al), silver (Ag), titanium (Ti), nickel (Ni), gold (Au), copper (Cu), chromium (Cr), platinum (Pt), a combination of any two of the foregoing, or a combination of any two or more of the foregoing. It is particularly emphasized that the technical feature of the present invention is that, due to the protection effect provided by the first protection layer 14 and the second protection layer 15, when a single micro-led 1 is subjected to substrate transfer or a plurality of micro-leds 1 are subjected to mass transfer, the surface layer or other regions thereof will not be deformed, cracked or collapsed due to the external stress. In particular, in order to prevent the first protective layer 14 and the second protective layer 15 from affecting the normal light output of the light emitted from the active layer 12, the refractive index of the first protective layer 14 is smaller than that of the second semiconductor material layer 13, and the refractive index of the second protective layer 15 is smaller than that of the first protective layer 14.
As can be seen from the above description, the micro light emitting diode 1 having the first protective layer 14 and the second protective layer 15 coated thereon can exhibit a high tolerance to external stress. Therefore, when a single micro-led 1 is transferred to a substrate or a plurality of micro-leds 1 are transferred in a large amount, the surface layer or other regions of the micro-leds 1 are not deformed, cracked or broken due to external stress. Of course, the substrate of the micro light emitting diode 1 is usually a Sapphire (Sapphire) substrate or a spinel (spinel) substrate before the substrate transfer is completed. It is noted that after the substrate transfer is completed, the substrate of the micro light emitting diode 1 may be replaced by a spinel (spinel) substrate, a silicon carbide (SiC) substrate, a ceramic substrate, a Polyimide (Polyimide) substrate, a hard printed circuit board, or a flexible printed circuit board. It should be noted that the main material of the first semiconductor material layer 11 and the second semiconductor material layer 13 is gallium nitride (GaN), and the refractive index and the lattice constant thereof are summarized in the following table (1).
Watch (1)
Figure BDA0001816218210000081
It is conceivable that the process material of the first protective layer 14 must be selected in consideration of both the refractive index and the lattice constant of the material. In particular, the process material of the first protective layer 14 must have a refractive index less than GaN, and it must be made of a single crystal material with a lattice constant matching GaN, such as: aluminum nitride (AlN), undoped gallium nitride (undoped GaN), or zinc oxide (ZnO), the refractive indices and lattice constants of which are collated in table (2) below.
Watch (2)
Figure BDA0001816218210000082
It should be noted that the material for manufacturing the first protective layer 14 may also be a single crystal material with a lattice constant close to an integer multiple of GaN, such as: zinc sulfide (ZnS) of group II-VI semiconductor compounds and zinc selenide (ZnSe) of group II-VI semiconductor compounds. The refractive indices and lattice constants of the foregoing materials are collated in the following Table (3).
Watch (3)
Figure BDA0001816218210000083
Figure BDA0001816218210000091
On the other hand, the second passivation layer 15 can be made of any one of the following materials: alumina (Al)2O3) Hafnium oxide (HfO)2) Magnesium oxide (MgO), zinc oxide (ZnO), or yttrium oxide (Y)2O3). The refractive indices of the foregoing materials are collated in Table (4) below.
Watch (4)
Figure BDA0001816218210000092
Continuing to refer to fig. 5, a second cross-sectional view of the micro led capable of increasing yield of mass transfer according to the present invention is shown, and it can be seen from a comparison of fig. 4 that the micro led 1 shown in fig. 5 further includes: a buffer layer BF formed on the second passivation layer 15 and the first passivation layer 14. In order to further increase the tolerance of the micro led 1 to external stress, a buffer layer BF is inserted between the second passivation layer 15 and the first passivation layer 14. It should be noted that if the second passivation layer 15 is a first metal oxide layer, the buffer layer BF can be defined as a second metal oxide layer; moreover, the size of the atom of a second metal element constituting the buffer layer BF is smaller than the size of the atom of a first metal element constituting the second protective layer 15. Exemplary materials of the first metal oxide layer and the second metal oxide layer are summarized in table (5) below.
Watch (5)
Figure BDA0001816218210000093
Figure BDA0001816218210000101
Second embodiment
Fig. 6 is a first cross-sectional view of a micro led capable of increasing yield of mass transfer according to a second embodiment of the present invention. As will be understood by engineers familiar with basic device design and fabrication of leds from fig. 6, a second embodiment of a micro-led 1 (hereinafter referred to as "micro-led") capable of increasing yield of mass transfer according to the present invention includes a Vertical Cavity Surface Emitting Laser (VCSEL) basic structure. As shown in fig. 6, the novel micro light emitting diode 1 structurally includes: a substrate 20, a first bragg reflector 21 formed on the substrate 20, a first semiconductor material layer 22 formed on the first bragg reflector 21, an active layer 23 formed on the first semiconductor material layer 22, a second semiconductor material layer 24 formed on the active layer 23, a second bragg reflector 25 formed on the second semiconductor material layer 24, a first protection layer 26, a second protection layer 27, a first electrode 28, and a second electrode 29.
Generally, the first Bragg reflector (DBR) 21 is typically an n-type DBR formed from AlXGa1-XAs/Al1-YGaYAs is repeatedly stacked, wherein the n-type DBR may be obtained after silicon (Si) doping of the undoped DBR. Conversely, the second Bragg reflector 25 is a p-type DBR, also made of AlXGa1-XAs/Al1-YGaYAs is repeatedly stacked, wherein the p-type DBR may be obtained after carbon (C) doping the undoped DBR. On the other hand, the first semiconductor material layer 22 and the second semiconductor material layer 24 are used as a Lower cladding layer (Lower cladding layer) and an Upper cladding layer (Upper cladding layer) of the active layer 23 (i.e., multi-quantum well), respectively, and are made of n-type III-V semiconductor compound and p-type III-V semiconductor compound, respectively.
Continuing to refer to fig. 7 and 8, a second cross-sectional view and a third cross-sectional view of a second embodiment of a micro led capable of increasing yield of mass transfer according to the present invention are respectively shown. The present invention is characterized in that a first passivation layer 26 and a second passivation layer 27 are sequentially formed on the surface of a Vertical Cavity Surface Emitting Laser (VCSEL), and particularly, the refractive index of the first passivation layer 26 is smaller than that of the second semiconductor material layer 24, and the refractive index of the second passivation layer 27 is smaller than that of the first passivation layer 26. It is obvious that the present invention is not limited to the second embodiment of the micro-led 1 (i.e. VCSEL) which is identical to the structure shown in fig. 6. For example, fig. 7 shows that a (ring) oxide layer ACO is formed between the second semiconductor material layer 24 and the active layer 23, and the oxide layer ACO is used to define a light emitting opening (light emitting aperture).
On the other hand, as can be seen from comparing fig. 6 and 8, fig. 8 shows that an intermediate semiconductor material layer 24a having the same material as the first semiconductor material layer 22 is formed between the second semiconductor material layer 24 and the active layer 23. This is designed such that a tunnel junction TJ is formed at the junction of the intermediate semiconductor material layer 24a and the second semiconductor material layer 24 and extends from the junction into the second semiconductor material layer 24. It is noted that in fig. 8, a first bonding layer (bonding layer)22a is further interposed between the first bragg reflector 21 and the first semiconductor material layer 22, and a second bonding layer 24b is also interposed between the second bragg reflector 25 and the second semiconductor material layer 24.
Similarly, the vcsel (or micro-led 1) with the first and second passivation layers 26 and 27 on the surface thereof can exhibit a high tolerance to external stress. Therefore, when a single micro-led 1 is transferred to a substrate or a plurality of micro-leds 1 are transferred in a large amount, the surface layer or other regions of the micro-leds 1 are not deformed, cracked or broken due to external stress. Of course, the substrate of the micro light emitting diode 1 is usually a Sapphire (Sapphire) substrate or a spinel (spinel) substrate before the substrate transfer is completed. It is noted that after the substrate transfer is completed, the substrate of the micro light emitting diode 1 may be replaced by a spinel (spinel) substrate, a silicon carbide (SiC) substrate, a ceramic substrate, a Polyimide (Polyimide) substrate, a hard printed circuit board, or a flexible printed circuit board.
It should be emphasized that the above detailed description is specific to possible embodiments of the invention, but this is not to be taken as limiting the scope of the invention, and all equivalent implementations or modifications that do not depart from the technical spirit of the invention are intended to be included within the scope of the invention.

Claims (16)

1. A micro light emitting diode, comprising:
a substrate;
a first semiconductor material layer formed on the substrate;
an active layer formed on the first semiconductor material layer;
a second semiconductor material layer formed on the active layer;
a first passivation layer formed on the second semiconductor material layer and having a first opening and a second opening; the first protective layer covers the side surface of the second semiconductor material layer, the side surface of the active layer, the side surface of the first semiconductor material layer and part of the surface, the refractive index of the first protective layer is smaller than that of the second semiconductor material layer, and the lattice constant of the first protective layer is matched with that of the second semiconductor material layer;
a second passivation layer formed on the first passivation layer and having a third opening corresponding to the first opening and a fourth opening corresponding to the second opening;
a first electrode formed on the first semiconductor material layer through the second opening and the fourth opening; and
a second electrode formed on the second semiconductor material layer through the first opening and the third opening;
wherein the refractive index of the first protective layer is smaller than that of the second semiconductor material layer, and the manufacturing material is any one of the following materials: undoped gallium nitride (undoped GaN) or zinc selenide (ZnSe);
wherein the refractive index of the second protective layer is smaller than that of the first protective layer, and the second protective layer is any one of the following first metal oxide layers: hafnium oxide (HfO)2) Magnesium oxide (MgO) or yttrium oxide (Y)2O3)；
The buffer layer is a second metal oxide layer, and the size of atoms of a second metal element forming the buffer layer is smaller than that of atoms of a first metal element forming the second protective layer.
2. The micro-led of claim 1, wherein the substrate is any one of: a spinel (spinel) substrate, a silicon carbide (SiC) substrate, a Sapphire (Sapphire) substrate, a ceramic substrate, a Polyimide (Polyimide) substrate, or a printed circuit board.
3. The micro led of claim 1, wherein the first semiconductor material layer is N-type gallium nitride (N-GaN) and the second semiconductor material layer is P-type gallium nitride (P-GaN).
4. The micro-led of claim 1, wherein the active layer is a single quantum well structure formed between the first semiconductor material layer and the second semiconductor material layer, and the active layer is made of any one of the following materials: gallium nitride (GaN), aluminum gallium nitride (Al)xGa1-xN), or indium gallium nitride (In)xGa1-xN)。
5. The micro-led of claim 1, wherein the active layer is a multiple quantum well structure formed between the first semiconductor material layer and the second semiconductor material layer, and the multiple quantum well structure is any one of: gallium nitride and indium gallium nitride (In)xGa1-xN), gallium nitride and aluminum gallium nitride (A)lxGa1-xN) multiple stacked structure, or aluminum gallium nitride (Al)xGa1-xN) and indium gallium nitride (In)xGa1-xN) of the stack.
6. The micro led of claim 1, wherein the first electrode and the second electrode are made of any one of the following materials: aluminum (Al), silver (Ag), titanium (Ti), nickel (Ni), gold (Au), copper (Cu), chromium (Cr), platinum (Pt).
7. The micro led of claim 1, wherein the first electrode and the second electrode are made of any two or a combination of two or more of the following materials: aluminum (Al), silver (Ag), titanium (Ti), nickel (Ni), gold (Au), copper (Cu), chromium (Cr), platinum (Pt).
8. The micro led of claim 1, wherein the first passivation layer and the second passivation layer have a thickness of 1 nm to 50 nm.
9. A micro light emitting diode, comprising:
a substrate;
a first Bragg reflector formed on the substrate;
a first semiconductor material layer formed on the first Bragg reflector;
an active layer formed on the first semiconductor material layer;
a second semiconductor material layer formed on the active layer; and
a second Bragg reflector formed on the second semiconductor material layer;
a first protection layer covering the surface and side of the second Bragg reflector, the surface and side of the second semiconductor material layer, the side of the active layer, the side of the first semiconductor material layer, and the side of the first Bragg reflector, and having a first opening and a second opening;
a second passivation layer formed on the first passivation layer and having a third opening corresponding to the first opening and a fourth opening corresponding to the second opening;
a first electrode formed on the first semiconductor material layer through the second opening and the fourth opening; and
a second electrode formed on the second semiconductor material layer through the first opening and the third opening;
wherein the refractive index of the first protective layer is smaller than that of the second semiconductor material layer, the lattice constant of the first protective layer is matched with that of the second semiconductor material layer, and the manufacturing material is any one of the following materials: undoped gallium nitride (undoped GaN) or zinc selenide (ZnSe);
wherein, the refractive index of the second protective layer is smaller than that of the first protective layer, and the second protective layer is any one of the following first metal oxide layers: hafnium oxide (HfO)2) Magnesium oxide (MgO) or yttrium oxide (Y)2O3)；
The buffer layer is a second metal oxide layer, and the size of atoms of a second metal element forming the buffer layer is smaller than that of atoms of a first metal element forming the second protective layer.
10. The micro-led of claim 9, wherein the substrate is any one of: a spinel (spinel) substrate, a silicon carbide (SiC) substrate, a Sapphire (Sapphire) substrate, a ceramic substrate, a Polyimide (Polyimide) substrate, or a printed circuit board.
11. The micro light-emitting diode of claim 9, being a Vertical cavity surface emitting laser device (VCSEL device).
12. The micro led of claim 9, wherein the first semiconductor material layer is made of an N-type III-V semiconductor compound, and the second semiconductor material layer is made of a P-type III-V semiconductor compound.
13. The micro led of claim 9, wherein the active layer is a single quantum well structure or a multiple quantum well structure formed between the first and second layers of semiconductor material.
14. The micro-led of claim 9, wherein the first electrode and the second electrode are made of any one of the following materials: aluminum (Al), silver (Ag), titanium (Ti), nickel (Ni), gold (Au), copper (Cu), chromium (Cr), platinum (Pt).
15. The micro-led of claim 9, wherein the first electrode and the second electrode are made of any two or a combination of two or more of the following materials: aluminum (Al), silver (Ag), titanium (Ti), nickel (Ni), gold (Au), copper (Cu), chromium (Cr), platinum (Pt).
16. The micro led of claim 9, wherein the first passivation layer and the second passivation layer have a thickness of 1 nm to 50 nm.
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CN104518064A (en) * 2013-10-02 2015-04-15 Lg伊诺特有限公司 Light emitting diode and light emitting diode packaging having same light emitting diode
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JP2002344015A (en) * 2001-05-17 2002-11-29 Nichia Chem Ind Ltd Nitride semiconductor light-emitting element
CN102047445A (en) * 2008-04-05 2011-05-04 宋俊午 Light-emitting element
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