Miniature LED device capable of emitting light in two directions

Abstract

The invention provides a bidirectional light-emitting miniature LED device. The bidirectional light-emitting miniature LED device comprises a common bearing plate; the light source group is composed of N micro LED chips, the micro LED chips are inversely arranged on the lower surface of the common bearing plate, and N is a natural number and is larger than or equal to 3; the micro LED chips are connected in pairs through metal connecting wires; and the local reflection layer is arranged on the upper surface of the common bearing plate, and the projection of the local reflection layer on the common bearing plate is not overlapped with the projection of the first micro LED chip and the projection of the Nth micro LED chip on the common bearing plate. According to the scheme, light emitting of the miniature LED in the bottom face direction can be achieved, and the problem of self-absorption caused by multiple times of reflection is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor devices, and in particular to a micro LED device with bidirectional light emission. Background Art

[0002] With the development of LED technology, new technologies such as filament lamp lighting based on omnidirectional LED and transparent micro-LED displays for metaverse augmented reality applications are gradually gaining attention. The common technical demands of these applications for LED chips include: (1) small chip size; (2) light emission from both the front and bottom surfaces. Some LED technologies can now achieve micro-LEDs with chip sizes around 100 microns, but due to the reduction in chip size, it is impossible to set pads for gold wire bonding, and only a flip-chip structure can be used. The flip-chip micro-LED has a pad at the bottom for welding to the packaging substrate. Since the pad occupies most of the bottom surface area, very little light can be emitted from the bottom surface. Most of the light is reflected by the metal pad and emitted from the front and sides of the micro-LED.

[0003] For all-around LED packaging, the light output power of the micro-LED on the front and bottom surfaces must be similar to ensure the all-around light effect of the packaged light. For micro-LED transparent displays for metaverse augmented reality applications, the brightness of the front and back sides of the transparent display must be similar, and the light output power of the micro-LED on the front and bottom surfaces must be similar. Therefore, appropriate technical measures must be adopted to improve the light output of the micro-LED in the bottom direction.

[0004] 202180005001.3 and 202111212826.0 both proposed to use multiple micro LED chips in series to realize micro LED devices. By reinforcing the micro LED chip located in the middle of the micro LED device, it can buffer the needle puncture force during the crystal bonding process and improve the reliability of the micro LED. However, these existing patents still fail to improve the light emission of the micro LED in the bottom direction.

[0005] 202180003070.0 A full-surface reflective layer is set on the top surface of the chip to reflect part of the light emitted from the front side backwards. However, due to the full-surface reflective layer on the top surface, most of the reflected light is reflected again by the metal pad to the front or side, and finally presents the effect of enhanced side light emission. However, most of the reflected light will experience multiple reciprocating reflections between the full-surface reflective layer on the top surface and the metal pad, causing self-absorption, which is not conducive to improving the electro-optical conversion efficiency. Summary of the invention

[0006] In order to solve the above technical problems, a bidirectional light-emitting micro LED device is proposed, comprising:

[0007] Common load bearing plate;

[0008] A light source group, the light source group is composed of N micro LED chips, and the micro LED chips are flip-chip mounted on the lower surface of a common carrier board, where N is a natural number and N ≥ 3; and

[0009] The micro LED chips are connected two by two through metal connecting wires;

[0010] The local reflective layer is disposed on the upper surface of the common carrier plate, and the projection of the local reflective layer on the common carrier plate does not overlap with the projection of the first micro LED chip and the Nth micro LED chip on the common carrier plate.

[0011] Through the above technical solution, the local reflective layer will not reflect the light of the first micro LED chip and the third micro LED chip, so that the light of the micro LED in the bottom direction can be realized without causing multiple reflections and self-absorption problems.

[0012] Specifically, the micro LED chip includes: a first semiconductor layer, a second semiconductor layer, a quantum well light-emitting layer, a first electrode, a second electrode and an insulating layer; the first semiconductor layer, the quantum well light-emitting layer and the second semiconductor layer are stacked in sequence from bottom to top; the first electrode is electrically in contact with the first semiconductor layer; the second electrode is electrically in contact with the second semiconductor layer; the insulating layer wraps the side walls of the first semiconductor layer, the quantum well light-emitting layer and the second semiconductor layer.

[0013] Specifically, the second electrode of the micro LED chip is connected to the first electrode of the micro LED chip on its left side through a metal connecting wire.

[0014] Specifically, it also includes a second insulating layer; the second insulating layer covers the metal connecting wire.

[0015] Specifically, it also includes a third electrode and a fourth electrode; the third electrode passes through the second insulating layer to connect to the first electrode of the first micro LED chip; the fourth electrode passes through the second insulating layer to connect to the second electrode of the Nth micro LED chip.

[0016] Specifically, the local reflection layer is a metal reflection layer or a distributed Bragg reflection layer.

[0017] Specifically, the first semiconductor layer includes n-type doped GaN and a buffer layer; the second semiconductor layer includes p-type doped GaN and an electron blocking layer.

[0018] Specifically, the first semiconductor layer includes doped AlGaAs; the second semiconductor layer includes p-type doped GaN and an electron blocking layer.

[0019] Specifically, the first semiconductor layer includes doped AlGaAs; and the second semiconductor layer includes doped AlGaAs.

[0020] Specifically, the quantum well light-emitting layer is formed by alternating stacking of two semiconductor layers with the same chemical formula but different components; the chemical formula is Al x In y Ga z N or Al x Ga y In z Any one of P, where x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1.

[0021] Compared with the prior art, the beneficial results of this application are:

[0022] The local reflective layer reflects all the light emitted by the second micro LED chip to the bottom of the micro LED device, while the first micro LED chip and the Nth micro LED chip pass through the common carrier board and emit from the top of the micro LED device, thereby realizing an all-around micro LED device with light emitting from the front, back and sides. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate the embodiments and are used together with the description to explain the principles of the present application. It will be easy to recognize other embodiments and many expected advantages of the embodiments because they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale with each other. The same reference numerals refer to corresponding similar parts.

[0024] Figure 1 is a schematic structural diagram of a bidirectional light-emitting micro LED device according to the first embodiment of the present application;

[0025] Figure 2 It is a schematic structural diagram of a transmission vibration platform for a micro LED device with bidirectional light output according to the second embodiment of the present application. Description of the drawings:

[0027] 1. Common carrier board; 2. Local reflection layer; 3. Metal connecting wire; 41. First semiconductor layer; 42. Quantum well light-emitting layer; 43. Second semiconductor layer; 44. First electrode; 45. Second electrode; 46. First insulating layer; 51. First micro LED chip; 52. Second micro LED chip; 53. Third micro LED chip; 54. Fourth micro LED chip; 7. Second insulating layer; 81. Third electrode; 82. Fourth electrode. DETAILED DESCRIPTION

[0028] In the following detailed description, reference is made to the accompanying drawings, which form a part of the detailed description and are shown by illustrative specific embodiments in which the present application can be practiced. To this end, directional terms, such as "top", "bottom", "left", "right", "up", "down", etc., are used with reference to the orientation of the figures described. Because the components of the embodiments can be positioned in several different orientations, directional terms are used for the purpose of illustration and are by no means limiting. It should be understood that other embodiments may be utilized or logical changes may be made without departing from the scope of the present application. Therefore, the following detailed description should not be adopted in a limiting sense, and the scope of the present application is defined by the appended claims.

[0029] A micro LED device with bidirectional light output, comprising:

[0030] Common bearing plate 1;

[0031] A light source group, the light source group is composed of N micro LED chips, and the micro LED chips are flip-chip mounted on the lower surface of the common carrier board 1, wherein N is a natural number and N≥3; and

[0032] The micro LED chips are connected in pairs via metal connecting wires 3;

[0033] The partial reflective layer 2 is disposed on the upper surface of the common carrier board 1 , and the projection of the partial reflective layer 2 on the common carrier board 1 does not overlap with the projections of the first micro LED chip 51 and the Nth micro LED chip on the common carrier board 1 .

[0034] Through the above technical solution, the local reflective layer 2 will not reflect the light of the first micro LED chip and the third micro LED chip, so that the light of the micro LED can be emitted in the bottom direction without causing multiple reflections and self-absorption problems.

[0035] Specifically, the micro LED chip includes: a first semiconductor layer 41, a second semiconductor layer 43, a quantum well light-emitting layer 42, a first electrode 44, a second electrode 45 and an insulating layer; the first semiconductor layer 41, the quantum well light-emitting layer 42 and the second semiconductor layer 43 are stacked in sequence from bottom to top; the first electrode 44 is in electrical contact with the first semiconductor layer 41; the second electrode 45 is in electrical contact with the second semiconductor layer 43; the insulating layer wraps the side walls of the first semiconductor layer 41, the quantum well light-emitting layer 42 and the second semiconductor layer 43.

[0036] Specifically, the second electrode 45 of the micro LED chip is connected to the first electrode 44 of the micro LED chip on its left side through the metal connection wire 3 .

[0037] Specifically, it also includes a second insulating layer 7 ; the second insulating layer 7 covers the metal connecting wire 3 .

[0038] Specifically, it also includes a third electrode 81 and a fourth electrode; the third electrode 81 passes through the second insulating layer 7 to connect to the first electrode 44 of the first micro LED chip 51; the fourth electrode passes through the second insulating layer 7 to connect to the second electrode 45 of the Nth micro LED chip.

[0039] Specifically, the local reflection layer 2 is a metal reflection layer or a distributed Bragg reflection layer.

[0040] Specifically, the first semiconductor layer 41 includes n-type doped GaN and a buffer layer; the second semiconductor layer 43 includes p-type doped GaN and an electron blocking layer.

[0041] Specifically, the first semiconductor layer 41 includes doped AlGaAs; and the second semiconductor layer 43 includes p-type doped GaN and an electron blocking layer.

[0042] Specifically, the first semiconductor layer 41 includes doped AlGaAs; and the second semiconductor layer 43 includes doped AlGaAs.

[0043] Specifically, the quantum well light emitting layer 42 is formed by alternatingly stacking two semiconductor layers with the same chemical formula but different components; the chemical formula is Al x In y Ga z N or Al x Ga y In z Any one of P, where x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1.

[0044] In order to better understand the present application, four embodiments are taken as examples:

[0045] Embodiment 1:

[0046] Figure 1 is a schematic structural diagram of a bidirectional light-emitting micro LED device according to the first embodiment of the present application, such as Figure 1As shown, in this embodiment, a bidirectional light-emitting micro LED device is provided with a common carrier board 1, a micro LED chip, a local reflective layer 2, and a metal connection 3. The micro LED chip is provided with at least a first semiconductor layer 41, a quantum well light-emitting layer 42, a second semiconductor layer 43, a first electrode 44, a second electrode 45, and a first insulating layer 46. The first insulating layer 46 covers the side wall of the micro LED chip. The first electrode 44 is in electrical contact with the first semiconductor layer 41, and the second electrode 45 is in electrical contact with the second semiconductor layer 43. The quantum well layer 42 can emit light under current injection. The common carrier board 1 has a high light transmittance to the light emitted by the quantum well layer 42. The micro LED chip is provided on the lower surface of the common carrier board 1. There are at least three micro LED chips, namely, a first micro LED chip 51, a second micro LED chip 52, and a third micro LED chip 53. The second micro LED chip 52 is located between the first micro LED chip 51 and the third micro LED chip 53. The local reflective layer 2 is located on the upper surface of the common carrier board 1, and corresponds to the position of the second micro LED chip 52. The projection of the partial reflective layer 2 on the common carrier board 1 does not overlap with the projection of the first electrode of the first micro LED chip 51 on the common carrier board 1 and the projection of the second electrode of the third micro LED chip 53 on the common carrier board 1 .

[0047] The second electrode of the first micro LED chip 51 is connected to the first electrode of the second micro LED chip through the metal wire 3, and the second electrode of the second micro LED chip 52 is connected to the first electrode of the third micro LED chip through the metal wire 3, thereby realizing the series connection between the micro LED chips.

[0048] The metal connection line 3 is covered with a second insulating layer 7 .

[0049] A third electrode 81 and a fourth electrode 82 are provided. The third electrode 81 passes through the second insulating layer 7 to be connected to the first electrode of the first micro LED chip 51, and the fourth electrode 82 passes through the second insulating layer 7 to be connected to the second electrode of the third micro LED chip 53, so that the first electrode of the first micro LED chip 51 is connected to the external circuit, and the second electrode of the third micro LED chip 53 is connected to the external circuit.

[0050] The local reflection layer 2 is a metal reflection layer or a distributed Bragg reflection layer.

[0051] The first semiconductor layer 41 includes a layer of n-type doped GaN. The first semiconductor layer also includes a buffer layer. The quantum well light emitting layer is composed of a chemical formula of Al x In y Ga zN (wherein, x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1) is formed by alternatingly stacking two semiconductor layers with different components and nanometer thickness, the second semiconductor layer includes a layer of p-type doped GaN, and the second semiconductor layer includes an electron blocking layer.

[0052] Embodiment 2:

[0053] Figure 2 FIG. 1 is a schematic structural diagram of a transmission vibration platform for a micro LED device with bidirectional light emission according to a second embodiment of the present application. Figure 2 As shown, this embodiment has the following differences compared with the first embodiment: at least four micro LED chips are provided, namely, a first micro LED chip 51, a second micro LED chip 52, a third micro LED chip 53, and a fourth micro LED chip 54, and the partial reflection layer 2 is located on the upper surface of the common carrier board 1, and corresponds to the positions of the second micro LED chip 52 and the third micro LED chip 53. The projection of the partial reflection layer 2 on the common carrier board 1 does not overlap with the projection of the first electrode of the first micro LED chip 51 on the common carrier board 1, and the projection of the second electrode of the fourth micro LED chip 54 on the common carrier board 1.

[0054] The second electrode of the first micro LED chip 51 is connected to the first electrode of the second micro LED chip 52 through the metal wire 3, the second electrode of the second micro LED chip 52 is connected to the first electrode of the third micro LED chip 53 through the metal wire 3, and the second electrode of the third micro LED chip 53 is connected to the first electrode of the fourth micro LED chip 54 through the metal wire 3, thereby realizing the series connection between the micro LED chips.

[0055] A third electrode 81 and a fourth electrode 82 are provided. The third electrode 81 passes through the second insulating layer 7 to be connected to the first electrode of the first micro LED chip 51, and the fourth electrode 82 passes through the second insulating layer 7 to be connected to the second electrode of the fourth micro LED chip 54, so that the first electrode of the first micro LED chip 51 is connected to the external circuit, and the second electrode of the fourth micro LED chip 54 is connected to the external circuit.

[0056] Embodiment three:

[0057] This embodiment is different from the first embodiment in the following ways: the first semiconductor layer 41 contains at least one layer of doped AlGaAs, and the quantum well light emitting layer 42 is composed of a chemical formula of Al x Ga y In zP (wherein, x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1) is formed by alternatingly stacking two semiconductor layers with different components and nanometer thickness, and the second semiconductor layer 43 contains at least one layer of doped AlGaAs.

[0058] Embodiment 4:

[0059] This embodiment is different from the second embodiment in that the first semiconductor layer 41 of the first micro LED chip and the second micro LED chip contains at least one layer of doped AlGaAs, and the quantum well light emitting layer 42 is composed of a chemical formula of Al x Ga y In z P (wherein, x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1) is formed by alternatingly stacking two semiconductor layers with different components and nanometer thickness, and the second semiconductor layer 43 contains at least one layer of doped AlGaAs.

[0060] The first semiconductor layer 41 of the third micro LED chip and the fourth micro LED chip includes a layer of n-type doped GaN, the first semiconductor layer 41 also includes a buffer layer, and the quantum well light emitting layer 42 is composed of a chemical formula of Al x In y Ga z N (wherein, x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1) is formed by alternating semiconductor layers of different components and nanometer thickness, the second semiconductor layer 43 includes a layer of p-type doped GaN, and the second semiconductor layer 43 includes an electron blocking layer.

[0061] Obviously, those skilled in the art can make various modifications and changes to the embodiments of the present application without departing from the spirit and scope of the present application. In this way, if these modifications and changes are within the scope of the claims of the present application and their equivalents, the present application is also intended to cover these modifications and changes. The word "comprising" does not exclude the presence of other elements or steps not listed in the claims. The simple fact that certain measures are recorded in mutually different dependent claims does not indicate that the combination of these measures cannot be used to profit. Any figure mark in the claims should not be considered to limit the scope.

Claims

1. A micro LED device with bidirectional light output, characterized in that: include: Common load bearing plate; A light source group, the light source group is composed of N micro LED chips, and the micro LED chips are flip-chip mounted on the lower surface of the common carrier board, wherein N is a natural number and N≥3; and The micro LED chips are connected in pairs via metal connecting wires; A partial reflection layer is disposed on the upper surface of the common carrier plate, and a projection of the partial reflection layer on the common carrier plate does not overlap with a projection of the first micro LED chip and the Nth micro LED chip on the common carrier plate.

2. A bidirectional light emitting micro LED device according to claim 1, characterized in that: The micro LED chip includes: a first semiconductor layer, a second semiconductor layer, a quantum well light-emitting layer, a first electrode, a second electrode and an insulating layer; the first semiconductor layer, the quantum well light-emitting layer and the second semiconductor layer are stacked in sequence from bottom to top; the first electrode is electrically in contact with the first semiconductor layer; the second electrode is electrically in contact with the second semiconductor layer; the insulating layer wraps the side walls of the first semiconductor layer, the quantum well light-emitting layer and the second semiconductor layer.

3. A bidirectional light emitting micro LED device according to claim 2, characterized in that: The second electrode of the micro LED chip is connected to the first electrode of the micro LED chip on the left side thereof through the metal connecting wire.

4. The bidirectional light emitting micro LED device according to claim 3, characterized in that: It also includes a second insulating layer; the second insulating layer covers the metal connecting line.

5. The bidirectional light emitting micro LED device according to claim 4, characterized in that: It also includes a third electrode and a fourth electrode; the third electrode passes through the second insulating layer to connect to the first electrode of the first micro LED chip; the fourth electrode passes through the second insulating layer to connect to the second electrode of the Nth micro LED chip.

6. The bidirectional light emitting micro LED device according to claim 1, characterized in that: The local reflection layer is a metal reflection layer or a distributed Bragg reflection layer.

7. The bidirectional light emitting micro LED device according to claim 2, characterized in that: The first semiconductor layer includes n-type doped GaN and a buffer layer; the second semiconductor layer includes p-type doped GaN and an electron blocking layer.

8. The bidirectional light emitting micro LED device according to claim 2, characterized in that: The first semiconductor layer includes doped AlGaAs; the second semiconductor layer includes p-type doped GaN and an electron blocking layer.

9. The bidirectional light emitting micro LED device according to claim 2, characterized in that: The first semiconductor layer includes doped AlGaAs; the second semiconductor layer includes doped AlGaAs.

10. The bidirectional light emitting micro LED device according to claim 9, characterized in that: The quantum well light-emitting layer is formed by alternating stacking of two semiconductor layers with the same chemical formula but different components; the chemical formula is Al x In y Ga z N or Al x Ga y In z Any one of P, where x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1.

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