CN103840045A - Light emitting device with multiple light emitting stacks - Google Patents

Abstract

The invention discloses a light-emitting device, which comprises a first light-emitting element capable of emitting first light with a first dominant wavelength, wherein the first light-emitting element is provided with a first multiple quantum well structure comprising a first number of multiple quantum well pairs; a second multiple quantum well structure comprising a second number of multiple quantum well pairs, located over the first multiple quantum well structure; and a tunneling layer located between the first multiple quantum well structure and the second multiple quantum well structure; and a second light emitting element capable of emitting a third light having a third dominant wavelength, wherein the first number is different from the second number.

Description

Light emitting device with multiple light emitting stacks

technical field

The invention relates to a light-emitting device, in particular to a light-emitting device with multiple light-emitting laminated layers.

Background technique

A light-emitting diode (Light-emitting Diode; LED) is a solid-state semiconductor element that includes at least one p-n junction (p-n junction), which is formed between p-type and n-type semiconductor layers. When a certain degree of bias is applied to the p-n junction, holes in the p-type semiconductor layer and electrons in the n-type semiconductor layer will combine to release light. The region where this light is generated is generally called the light-emitting region.

The main features of LED are small size, high color rendering, high reliability, high luminous efficiency, long life and fast response. At present, it has been widely used in optical display devices, traffic signs, data storage devices, communication devices, lighting devices and medical equipment. With the advent of full-color LEDs, LEDs have gradually replaced traditional lighting equipment such as fluorescent lamps and incandescent bulbs.

In the manufacturing cost of the LED, the price of the substrate occupies a large proportion, so how to reduce the usage of the substrate in the LED is an issue that attracts attention.

Contents of the invention

In order to solve the above problems, the present invention provides a light-emitting device, including a first light-emitting element capable of emitting first light having a first dominant wavelength, wherein the first light-emitting element has a first number of multiple quantum well pairs comprising a first number Multiple quantum well structure; a second multiple quantum well structure including a second number of multiple quantum well pairs, located on the first multiple quantum well structure; and a tunneling layer between the first multiple quantum well structure and between the second multiple quantum well structures; and a second light-emitting element capable of emitting third light with a third dominant wavelength, wherein the first number is different from the second number.

A light-emitting element having a first multiple quantum well structure including a first number of multiple quantum well pairs; a second multiple quantum well structure including a second number of multiple quantum well pairs located in the first multiple quantum well structure; and a first tunneling layer located between the first multiple quantum well structure and the second multiple quantum well structure, wherein the first number is different from the second number

Description of drawings

FIG. 1 shows a schematic cross-sectional view of a light-emitting element according to an embodiment of the present application;

FIG. 2 shows a schematic cross-sectional view of a light-emitting element according to another embodiment of the present application;

FIG. 3 shows a schematic cross-sectional view of a light emitting device according to an embodiment of the present application;

FIG. 4 shows a schematic diagram of a light source generating device according to an embodiment of the present application;

FIG. 5 is a schematic diagram of a backlight module according to an embodiment of the present application.

Symbol Description

1, 2 Light-emitting elements

10 Substrate

11 Contact layer

12 First bonding layer

14, 21 The first light-emitting stack

142 first semiconductor layer

144, 212 The first active layer

146 Second semiconductor layer

16, 22 The first tunneling layer

18, 23 The second light-emitting stack

182 Third semiconductor layer

184, 232 The second active layer

186 Fourth semiconductor layer

24 Second tunneling layer

25 Third light stack

252 The third active layer

3 Second light-emitting element

4 Lighting device

40 carriers

5 light source generating device

51 light source

52 Power supply system

53 control elements

6 backlight module

61 Optics

Detailed ways

Embodiments of the present invention will be described in detail and drawn in the accompanying drawings, and the same or similar parts will appear with the same numbers in the drawings and descriptions.

1 shows a light-emitting element 1 with a substrate 10; a first adhesive layer 12 formed on the substrate 10; a first light-emitting stack 14 formed on the first adhesive layer 12; a first The tunneling layer 16 is formed on the first light emitting stack 14; a second light emitting stack 18 is formed on the first tunneling layer 16; and a contact layer 11 is formed on the second light emitting stack 18 superior. The first light emitting stack 14 has a first semiconductor layer 142, a first active layer 144 and a second semiconductor layer 146 formed between the substrate 10 and the first tunneling layer 16; the second light emitting stack 18 has a first Three semiconductor layers 182 , a second active layer 184 and a fourth semiconductor layer 186 are formed between the first tunneling layer 16 and the contact layer 11 . The first light-emitting element 1 of this embodiment has two layers of light-emitting laminates on the substrate 10. Compared with a conventional light-emitting element with one layer of light-emitting laminates on the substrate, one of the advantages is that the first light-emitting element 1 produces The lumens are approximately equal to the sum of the lumens of two conventional light-emitting elements each with only one active layer. In addition, compared with two conventional light-emitting elements each having a substrate, because the first light-emitting element 1 only uses one substrate, the usage of the substrate is reduced and the manufacturing cost is reduced. As the lumens increase and the cost decreases, the lumens produced per dollar (lumens/yuan) increase accordingly. The input power of the first light emitting element 1 is also greater than that of conventional light emitting elements. Because the first light-emitting element 1 has two layers of light-emitting stacks and the forward voltage increases, the input power of the first light-emitting element 1 increases under the same input operating current as the conventional light-emitting element, so the lumens generated by the first light-emitting element 1 Increase. Also, since the series resistance is greater than the sheet resistance, current spreading is improved. The area through which current passes through the first light emitting stack 14 is increased, and thus the luminous efficiency is improved.

In addition, the first active layer 144 has a first multiple quantum well structure including a first number of multiple quantum well pairs, wherein the multiple quantum well pairs include a well layer and a barrier layer, and the energy gap of the barrier layer is higher than that of the well Layer gap. The second active layer 184 has a second multiple quantum well structure including a second number of multiple quantum well pairs, the first number being different from the second number. In another embodiment, the first number may be greater than the second number. When the sum of the first number and the second number is fixed, the luminous efficiency of the first light-emitting device 1 of this embodiment is higher than that of another conventional double-junction light-emitting device whose first number is equal to the second number. For example, the sum of the first number and the second number is 10, the first number of this embodiment is 7, the second number is 3, the light produced by the first multiple quantum well structure and the second multiple quantum well structure The lumens are the same as the lumens of the light produced by the conventional double junction light emitting element with both the first number and the second number being 5. However, because the second number of the first light-emitting element is smaller than the first number, fewer multiple quantum well pairs can absorb the light emitted by the first multiple quantum well structure, so the luminous efficiency of the first light-emitting element 1 is greater than that of the traditional double junction Luminous efficiency of light-emitting elements.

The substrate 10 can be used to grow and/or support the light emitting stack on it, and its material can be insulating material or conductive material. The insulating material includes but not limited to sapphire (Sapphire), diamond (Diamond), glass (Glass), quartz (Quartz), acryl (Acryl) or aluminum nitride (AlN). Conductive materials include but are not limited to copper (Cu), aluminum (Al), diamond-like carbon film (Diamond Like Carbon; DLC), silicon carbide (SiC), metal matrix composite (Metal Matrix Composite; MMC), ceramic matrix composite (Ceramic Matrix Composite; CMC), silicon (Si), iodine phosphide (IP), gallium arsenide (GaAs), germanium (Ge), gallium phosphide (GaP), gallium arsenide phosphide (GaAsP), zinc selenide (ZnSe), zinc oxide (ZnO), indium phosphide (InP), lithium gallate (LiGaO ₂ ) or lithium aluminate (LiAlO ₂ ). Materials that can be used to grow light-emitting stacks are, for example, sapphire, gallium arsenide, or silicon carbide. When the substrate 10 is used to grow a light-emitting stack, the first bonding layer 12 can be used as a buffer layer for growing the light-emitting stack instead.

The first adhesive layer 12 can connect the substrate 10 and the first light emitting stack 14, and includes a plurality of auxiliary layers (not shown). The material of the first adhesive layer 12 can be a conductive material, including but not limited to indium tin oxide (ITO), indium oxide (InO), tin oxide (SnO), cadmium tin oxide (CTO), antimony tin oxide (ATO), Aluminum zinc oxide (AZO), zinc tin oxide (ZTO), gallium zinc oxide (GZO), zinc oxide (ZnO), yttrium zinc oxide (YZO), indium zinc oxide (IZO), diamond-like carbon film, copper (Cu) , aluminum (Al), tin (Sn), gold (Au), platinum (Pt), zinc (Zn), silver (Ag), titanium (Ti), nickel (Ni), lead (Pb), palladium (Pd) , germanium (Ge), chromium (Cr), cadmium (Cd), cobalt (Co), manganese (Mn), antimony (Sb), bismuth (Bi), gallium (Ga), tungsten (W), silver-titanium ( Ag-Ti), copper-tin (Cu-Sn), copper-zinc (Cu-Zn), copper-cadmium (Cu-Cd), tin-lead-antimony (Sn-Pb-Sb), tin-lead-zinc (Sn-Pb-Zn), nickel-tin (Ni-Sn), nickel-cobalt (Ni-Co) or gold alloy (Au alloy), etc. The material of the buffer layer can be a semiconductor material, containing more than one element, which can be selected from gallium (Ga), aluminum (Al), indium (In), phosphorus (P), nitrogen (N), zinc (Zn) , a group consisting of cadmium (Cd) and selenium (Se). The first adhesive layer 12 may further include a reflective layer (not shown) to reflect light generated by the light emitting stack. The material of the reflective layer may include but not limited to copper (Cu), aluminum (Al), tin (Sn), gold (Au), platinum (Pt), zinc (Zn), silver (Ag), titanium (Ti), nickel (Ni), lead (Pb), silver-titanium (Ag-Ti), copper-tin (Cu-Sn), copper-zinc (Cu-Zn), copper-cadmium (Cu-Cd), tin-lead-antimony (Sn-Pb-Sb), tin-lead-zinc (Sn-Pb-Zn), nickel-tin (Ni-Sn), nickel-cobalt (Ni-Co), silver-copper (Ag-Cu) or gold alloys (Au alloy)

The first light emitting stack 14 and/or the second light emitting stack 18 can be directly grown on the substrate 10 , or fixed on the substrate 10 through the first bonding layer 12 . The material of the first light-emitting stack 14 and the second light-emitting stack 18 can be a semiconductor material, including more than one element, which can be selected from gallium (Ga), aluminum (Al), indium (In), phosphorus (P ), nitrogen (N), zinc (Zn), cadmium (Cd) and selenium (Se). The electrical properties of the first semiconductor layer 142 and the second semiconductor layer 146 are different, and the electrical properties of the third semiconductor layer 182 and the second semiconductor layer 186 are different. The first active layer 144 and the second active layer 184 can emit light, wherein the first active layer 144 has a first energy gap and the second active layer 184 has a second energy gap. In this embodiment, the first energy gap is different from the second energy gap. Gap. The energy gap difference between the first energy gap and the second energy gap is between 0.3eV and 0.5eV, the first energy gap can be smaller or larger than the second energy gap, for example, the first energy gap is 1.45eV, and the second energy gap is 1.9eV. In yet another embodiment, the light generated by the first active layer 144 is invisible light that cannot be recognized by human eyes. The wavelength of the invisible light in this embodiment is about less than 400nm or greater than 780nm, preferably between 780nm and 2500nm or between Between 300nm and 400nm, more preferably between 780nm and 900nm. The light generated by the second active layer 184 is visible light that can be recognized by human eyes. The wavelength of visible light in this embodiment is approximately between 400 nm and 780 nm, preferably between 560 nm and 750 nm. In another embodiment, the light generated by the first active layer 144 has a first dominant wavelength, the light generated by the second active layer 184 has a second dominant wavelength, and the wavelength difference between the first dominant wavelength and the second dominant wavelength About 150nm to 220nm, the first dominant wavelength may be greater or smaller than the second dominant wavelength. This embodiment can be applied in the medical field. One of the advantages is that one light-emitting element can have different functions at the same time; for example, the first dominant wavelength is 815nm, which can promote wound healing, and the second dominant wavelength is 633nm, which helps to eliminate fine lines.

In another embodiment, the first active layer 144 is formed by alternately stacking a first quantum well and a second quantum well, wherein the first quantum well has a first quantum well energy gap, and the second quantum well has a second quantum well Well energy gap, the energy gap of the first quantum well is different from the energy gap of the second quantum well, the energy gap difference between the energy gap of the first quantum well and the energy gap of the second quantum well is about 0.06eV to 0.1eV, the energy gap of the first quantum well The gap can be smaller or larger than the second quantum well energy gap. The second active layer 184 is formed by alternating stacking of a third quantum well and a fourth quantum well, wherein the third quantum well has a third quantum well energy gap, the fourth quantum well has a fourth quantum well energy gap, and the third quantum well has an energy gap of a fourth quantum well. The quantum well energy gap is different from the fourth quantum well energy gap. The energy gap difference between the third quantum well energy gap and the fourth quantum well energy gap is about 0.06eV to 0.1eV. The first quantum well energy gap can be smaller or larger than the second quantum well energy gap. Two quantum well energy gap.

The first tunneling layer 16 is grown on the first light-emitting stack 14 , and its doping concentration is greater than 8×10 ¹⁸ /cm ³ , so electrons can pass through the first tunneling layer 16 by utilizing the tunneling effect. The material of the first tunneling layer 16 can be a semiconductor material, including more than one element, which can be selected from gallium (Ga), aluminum (Al), indium (In), phosphorus (P), nitrogen (N), A group consisting of zinc (Zn), cadmium (Cd) and selenium (Se). In another embodiment, the first tunneling layer 16 can be replaced by a second adhesive layer to bond the first light emitting stack 14 and the second light emitting stack 18 . The material of the second bonding layer includes transparent conductive materials, such as indium tin oxide (ITO), indium oxide (InO), tin oxide (SnO), cadmium tin oxide (CTO), antimony tin oxide (ATO), zinc oxide (ZnO ), magnesium oxide (MgO), aluminum gallium arsenide (AlGaAs), gallium nitride (GaN), gallium phosphide (GaP), aluminum zinc oxide (AZO), zinc tin oxide (ZTO), gallium zinc oxide (GZO) , indium zinc oxide (IZO) or tantalum oxide (Ta ₂ O ₅ ); or insulating materials such as Su8, benzocyclobutene (BCB), perfluorocyclobutane (PFCB), epoxy resin (Epoxy), Acrylic resin (Acrylic Resin), cycloolefin polymer (COC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyimide (PI), polycarbonate (PC) , Polyetherimide (Polyetherimide), Fluorocarbon Polymer (FluorocarbonPolymer), Glass (Glass), Aluminum Oxide (Al ₂ O ₃ ), Silicon Oxide (SiO ₂ ), Titanium Oxide (TiO ₂ ), Silicon Nitride ( SiN _x ), spin-on-glass (SOG) or tetraethoxysilane (TEOS). The contact layer 11 is used to conduct current, and its material includes GaP, Al _x Ga _1-x As (0≤x≤1) or Al _a Ga _b In _1-ab P (0≤a≤1, 0≤b≤1, 0≤a+b≤1).

2 shows a first light-emitting element 2 with a substrate 10; a first adhesive layer 12 formed on the substrate 10; a first light-emitting stack 21 formed on the first adhesive layer 12; A first tunneling layer 22 is formed on the first light emitting stack 21; a second light emitting stack 23 is formed on the first tunneling layer 22; a second tunneling layer 24 is formed on the second light emitting on the stack 23 ; a third light emitting stack 25 formed on the second tunneling layer 24 ; and a contact layer 11 formed on the third light emitting stack 25 . The first light emitting stack 21 has a first active layer 212 ; the second light emitting stack 23 has a second active layer 232 ; and the third light emitting stack 25 has a third active layer 252 . The first light-emitting element 2 of this embodiment has three layers of light-emitting stacks on the substrate 10 . One of the advantages is that the lumens generated by the first light-emitting element 2 are approximately equal to the sum of the lumens of three conventional light-emitting elements. In addition, compared with three conventional light-emitting elements using three substrates, because the first light-emitting element 2 only uses one substrate, the amount of substrates used is reduced and the manufacturing cost is reduced. As the lumens increase and the cost decreases, the lumens per dollar (lumen/yuan) also increases. The input power of the first light emitting element 2 is also greater than that of conventional light emitting elements. Because the first light-emitting element 2 has a three-layer light-emitting stack and the forward voltage increases, the input power of the first light-emitting element 2 increases under the same input operating current as the conventional light-emitting element, so the lumens generated by the first light-emitting element 2 Increase. Also, since the series resistance is greater than the sheet resistance, current spreading is improved. The area through which current passes through the first light emitting stack 21 is increased, and thus the luminous efficiency is improved.

In addition, the first active layer 212 has a first multiple quantum well structure including a first number of multiple quantum well pairs, wherein the multiple quantum well pairs include a well layer and a barrier layer, and the energy gap of the barrier layer is higher than that of the well Layer gap. The second active layer 232 has a second multiple quantum well structure including a second number of multiple quantum well pairs. The third active layer 252 has a third multiple quantum well structure, wherein the third multiple quantum well structure can emit a fourth light with a fourth dominant wavelength, and has a third number of multiple quantum well pairs, the first The quantity, the second quantity and the third quantity are all different. In another embodiment, the first quantity may be greater than the second quantity and the second quantity may be greater than the third quantity. When the sum of the first quantity, the second quantity and the third quantity is fixed, the luminous efficiency of the first light-emitting element 2 of this embodiment will be higher than that of another traditional three-dimensional light-emitting element in which the first quantity, the second quantity and the third quantity are all equal. The luminous efficiency of the junction light-emitting element. For example, the sum of the first number, the second number and the third number is 15, the first number of this embodiment is 7, the second number is 5, and the third number is 3. The first multiple quantum well structure, the second The lumens of the light generated by the multiple quantum well structure and the third multiple quantum well structure are the same as the lumens of the light generated by the traditional double junction light emitting element with the first quantity, the second quantity and the third quantity all being 5. However, because the second number or the third number of the first light-emitting element 2 is smaller than the first number, fewer multiple quantum well pairs can absorb the light emitted by the first multiple quantum well structure, so the luminous efficiency of the first light-emitting element 2 It is greater than the luminous efficiency of the traditional three-junction light-emitting element.

As shown in FIG. 3 , a light emitting device 4 includes a carrier 40 ; the first light emitting device 1 is formed on a part of the carrier 40 ; and a second light emitting device 3 is formed on another part of the carrier 40 . The first light-emitting element 1 has a first light-emitting stack 14 capable of emitting first light having a first dominant wavelength, and a second light-emitting stack 18 capable of emitting second light having a second dominant wavelength, wherein the first dominant wavelength different from the second dominant wavelength. The second light emitting element 3 has a third light emitting stack (not shown) capable of emitting a third light having a third dominant wavelength, wherein the third dominant wavelength may be different from the first dominant wavelength and the second dominant wavelength. Because the first light, the second light and the third light have different dominant wavelengths and can display different colors, the mixed light produced by mixing the first light, the second light and the third light has a better color rendering index (CRI) ). For example, the mixed light is white light, and the white light has the first light being red light; the second light being green light; and the third light being blue light. In another embodiment, a wavelength conversion layer (not shown) may be located on the second light emitting element 3 so that the generated third light is cool white light with a color temperature between about 5700K and 6500K. The first light-emitting element 1 can emit first light and second light with different dominant wavelengths. The first light, second light and third light can be mixed to generate warm white light with a color temperature between 2700K and 3700K. Therefore, the light-emitting device 4 The color rendering index is better than that of the traditional light-emitting device in which the first light-emitting element has only one dominant wavelength. The color rendering index of the light emitting device 4 is at least 80, more preferably 90, and the red index R9 is at least 50. The first light and the second light can display the same color, such as red. In one embodiment, the first active layer 144 has a multiple quantum well structure, and the multiple quantum well structure is formed by alternately stacking multiple first well layers and multiple first barrier layers, and the second active layer 184 has another multiple quantum well structure. Quantum well structure, another multiple quantum well structure is formed by alternately stacking multiple second well layers and multiple second barrier layers. The materials of the first well layer and the second well layer can be represented by the chemical formula In _x Ga _1-x P or In _x Ga _1-x As, and 0<x<1, wherein the proportion of indium shown by x in the first well layer is greater than second well layer. The difference between the ratio of indium in the first well layer and the ratio of indium in the second well layer is about 1% and 6%, preferably about 2% and 5%. The difference between the first dominant wavelength and the second dominant wavelength may be about 5 nm to 30 nm, preferably about 10 nm to 25 nm. In this embodiment, the first dominant wavelength is, for example, 615 nm to 635 nm, and the second dominant wavelength is, for example, 605 nm to 625 nm.

The carrier 40 can be used to grow and/or support the light-emitting device on it, and its material can be an insulating material or a conductive material. The insulating material includes but not limited to sapphire (Sapphire), diamond (Diamond), glass (Glass), quartz (Quartz), acryl (Acryl), zinc oxide (ZnO) or aluminum nitride (AlN). Conductive materials include but are not limited to copper (Cu), aluminum (Al), diamond-like carbon film (Diamond Like Carbon; DLC), silicon carbide (SiC), metal matrix composite (Metal Matrix Composite; MMC), ceramic matrix composite (Ceramic Matrix Composite; CMC), silicon (Si), iodine phosphide (IP), gallium arsenide (GaAs), germanium (Ge), gallium phosphide (GaP), gallium arsenide phosphide (GaAsP), zinc selenide (ZnSe), zinc oxide (ZnO), indium phosphide (InP), lithium gallate (LiGaO ₂ ) or lithium aluminate (LiAlO ₂ ). Materials that can be used to grow light-emitting stacks are, for example, sapphire, gallium arsenide, or silicon carbide.

FIG. 4 is a schematic diagram of a light source generating device. A light source generating device 5 includes the light emitting element or light emitting device in any embodiment of the present invention. The light source generating device 5 can be a lighting device, such as a street lamp, a car lamp or an indoor lighting source, and can also be a traffic signal or a backlight source of a backlight module in a flat panel display. The light source generating device 5 has a light source 51 composed of the aforementioned light emitting devices, a power supply system 52 for supplying a current to the light source 51 , and a control element 53 for controlling the power supply system 52 .

FIG. 5 is a schematic cross-sectional view of a backlight module. A backlight module 6 includes the light source generating device 5 and an optical element 61 in the foregoing embodiment. The optical element 61 can process the light emitted by the light source generating device 5 to be applied to a flat panel display, for example, diffuse the light emitted by the light source generating device 5 .

The above-mentioned embodiments are only illustrative to illustrate the principles and effects of the present application, but are not intended to limit the present application. Anyone with ordinary knowledge in the technical field to which this application belongs can modify and change the above embodiments without violating the technical principle and spirit of this application. Therefore, the scope of protection of the rights of this application is listed in the scope of patent application mentioned above.

Claims (10)

1. A lighting device, comprising: A first light emitting element, comprising: The first multiple quantum well structure emits first light with a first dominant wavelength; and a second multiple quantum well structure, located on the first multiple quantum well structure, emitting a second light having a second dominant wavelength; and a carrier, carrying the first light-emitting element; Wherein the difference between the first dominant wavelength and the second dominant wavelength is 5 nm to 30 nm. 2. The light emitting device as claimed in claim 1, wherein the first multiple quantum well structure is located between the second multiple quantum well structure and the carrier, and the first dominant wavelength is greater than the second dominant wavelength. 3. The light-emitting device according to claim 1, wherein the first multiple quantum well structure comprises a first number of multiple quantum well pairs, the second multiple quantum well structure comprises a second number of multiple quantum well pairs, the The first quantity is different from the second quantity. 4. The light-emitting device according to claim 3, wherein the first light-emitting element comprises a third multiple quantum well structure, the third multiple quantum well structure comprises a third number of multiple quantum well pairs, and the third number is different from in the second quantity. 5. The light-emitting device according to claim 4, wherein the third multiple quantum well structure emits a third light including a third main wavelength, the first main wavelength, the second main wavelength and the third main wavelength all different. 6. The light-emitting device as claimed in claim 1, further comprising a second light-emitting element located on the carrier and emitting third light including a third dominant wavelength. 7. The light emitting device according to claim 6, wherein the first light, the second light and the third light are mixed to generate a mixed light, and the color rendering index of the mixed light is above 90. 8. The light emitting device as claimed in claim 6, wherein the red index R9 of the mixed light is above 50. 9. The light emitting device as claimed in claim 6, wherein the second dominant wavelength is greater than the third dominant wavelength. 10. The light emitting device as claimed in claim 6, further comprising a wavelength conversion layer on the second light emitting element.

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