Micro LED, Micro LED Panel and Micro LED Chip

Abstract

The micro LED includes a light emitting structure, a passivation layer formed on the light emitting structure, a reflective layer formed on the passivation layer, and a conductive layer formed on a top surface of the passivation layer and on the top surface of the reflective layer.

Description

[Technical field]

[0001] The present disclosure relates generally to the field of light emitting diode technology, and more particularly to micro light emitting diodes (LEDs), micro LED panels, and micro LED chips. [Background technology]

[0002] Inorganic micropixel light-emitting diodes, also known as micro light-emitting diodes, micro LEDs or μ-LEDs, are becoming increasingly important due to their use in various areas including self-emitting microdisplays, visible light communication, and optogenetics. Micro LEDs have higher output performance than conventional LEDs due to better strain relief, improved light extraction efficiency, and uniform current spreading. Compared with conventional LEDs, micro LEDs also exhibit several advantages such as improved thermal effect, fast response speed, larger working temperature range, higher resolution, wider color gamut, higher contrast, lower power consumption, and operability at higher current density.

[0003] Conventionally, inorganic microLEDs are fabricated by etching III-V epitaxial layers to form multiple mesas. Most of the light emitting from the sidewalls of the mesas has a large emission angle perpendicular to the microdisplay. However, in an augmented reality (AR) device, the emitted light with a large emission angle is blocked and lost, so that the emitted light cannot reach the user's eye. This results in a decrease in luminous efficiency. Therefore, it is necessary to reduce the loss of emitted light from the sidewalls of the mesas.

[0004] The above description is only provided to facilitate understanding of the technical solutions of the present disclosure, and does not constitute an admission that the above is prior art. Summary of the Invention

[0005] To overcome the above drawbacks, the present disclosure provides a micro-LED to recycle light emitting from the sidewalls of the mesa.

[0006] An embodiment of the present disclosure provides a micro-LED, which includes a light emitting structure, a passivation layer formed on the light emitting structure, a reflective layer formed on the passivation layer, and a conductive layer formed on a top surface of the passivation layer and on a top surface of the reflective layer.

[0007] An embodiment of the present disclosure provides a micro LED panel, which includes two or more of the above-mentioned micro LEDs, and a reflective layer is formed between adjacent light emitting structures of the two or more micro LEDs.

[0008] An embodiment of the present disclosure provides a micro LED chip. A micro LED panel includes one or more of the micro LED panels described above.

[0009] Further advantages and features of the present disclosure will be better understood from the following detailed description and the accompanying drawings.

[0010] Embodiments and various aspects of the present disclosure are set forth in the following detailed description and in the accompanying drawings, in which various features are not drawn to scale. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a structural diagram of an exemplary micro LED according to some embodiments of the present disclosure. [Diagram 2] FIG. 1 is a structural diagram of an exemplary micro LED panel according to some embodiments of the present disclosure. [Diagram 3] FIG. 1 is a structural diagram illustrating adjacent micro LEDs according to some embodiments of the present disclosure. [Figure 4] FIG. 1 is a structural diagram of an exemplary micro LED chip according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which the same numbers represent the same or similar elements in different drawings, unless otherwise indicated. The embodiments described in the following description of exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of apparatus and methods consistent with aspects related to the present invention as set forth in the appended claims. Certain aspects of the present disclosure are described in more detail below. The terms and definitions provided herein control in the event of a conflict with terms and / or definitions incorporated by reference.

[0013] 1 is a structural diagram of an exemplary micro LED 100 according to some embodiments of the present disclosure. Referring to FIG. 1, the micro LED 100 includes a light emitting structure 110, a passivation layer 120, a conductive layer 130, a reflective layer 140, and a conductive substrate 150.

[0014] The light emitting structure 110 is formed on a conductive substrate 150. In some embodiments, the light emitting structure 110 includes a PN junction and a quantum well. For example, the light emitting structure 110 includes a PN junction formed by an n-doped semiconductor layer and a p-doped semiconductor layer. The quantum well is formed between the n-doped semiconductor layer and the p-doped semiconductor layer. The light emitting structure 110 is a mesa structure having a flat top surface. In some embodiments, the light emitting structure 110 is a cone structure without a pointed top. The conductive substrate 150 is a circuit board such as an IC (Integrated Circuit) board. The light emitting structure 110 is bonded onto the conductive substrate 150 via a metal bonding process. A metal bonding layer 170 is formed between the light emitting structure 110 and the conductive substrate 150. The material of the metal bonding layer 170 may include one or more reflective metal materials to reflect light from the bottom of the light emitting structure 110 to the top of the light emitting structure 110. The metal bonding layer 170 ensures that virtually no light emission is lost through the bottom, improving light emission efficiency.

[0015] The light emitting structure 110 is covered by a passivation layer 120 having an exposed region A on the top. That is, the passivation layer 120 is formed on the top and sidewalls of the light emitting structure 110 except for the exposed region A. The passivation layer 120 is also formed on the conductive substrate 150. In this embodiment, as shown in FIG. 1, the passivation layer 120 is further formed on the surface of the metal bonding layer 170. The material of the passivation layer 120 can be a dielectric material. In some embodiments, the material of the passivation layer 120 is selected from SiO2, Si3N4, etc. The conductive layer 130 is formed on the passivation layer 120 and fills the exposed region A. Thereby, a contact hole is formed.

[0016] The reflective layer 140 is formed on the conductive layer 130. The top surface of the reflective layer 140 is higher than the top surface of the light emitting structure 110 and lower than the top surface of the conductive layer 130. In some embodiments, the top surface of the passivation layer 120 is higher than or equal to the top surface of the reflective layer 140. Preferably, the reflective layer 140 completely fills the space between the adjacent light emitting structures 110. In some embodiments, the material of the reflective layer 140 can be a metal or oxide material. In some embodiments, the reflective layer 140 is formed by lamination. In some embodiments, the reflective layer 140 is laminated by at least one of Ni, Ag and Au layers. In some embodiments, the thickness of the reflective layer 140 is thicker than half the thickness of the light emitting structure 110, for example, H1>1 / 2H2, where H1 and H2 are the thicknesses shown in FIG. 1.

[0017] The micro-LED 100 further includes a microlens 160 and a conductive layer 130. The conductive layer 130 is formed between the bottom surface of the microlens 160 and the passivation layer 120 and the reflective layer 140, and fills the exposed area A. As shown in FIG. 1, the conductive layer 130 covers the entire surface of the micro-LED, including the surface of the passivation layer 120 and the surface of the reflective layer 140, and is deposited on the exposed area A. In some embodiments, when the top surface of the passivation layer 120 is higher than the top surface of the reflective layer 140, for example as shown in FIG. 1, the conductive layer 130 is further formed on the upper sidewall of the passivation layer 120. Thus, the conductive layer 130 covers the entire surface of the micro-LED 100. The material of the conductive layer 130 can be a transparent conductive material. In some embodiments, the material of the conductive layer 130 is ITO(IN) (tin-doped indium oxide), FTO (fluorine-doped tin oxide), etc.

[0018] In some embodiments, the microlens 160 only covers the top surface of the conductive layer 130, i.e., the bottom surface of the microlens 160 is the same as the top surface of the conductive layer 130. The material of the microlens 160 is selected from silicon oxide, photoresist, etc.

[0019] 1, in some embodiments, the sidewalls of the light emitting structure 110 have a slope angle α of less than 90°. In some embodiments, the sidewalls of the light emitting structure 110 have a slope angle α of less than 90° and greater than 60°. The top surface of the conductive layer 130 is higher than the top surface of the reflective layer 140.

[0020] The micro LED 100 provided in the present disclosure improves the light emission efficiency at small angles through the reflective layer 140. The light emitting from the sidewall of the light emitting structure 110 is first reflected one or more times by the reflective layer 140 and then emitted from the top surface of the light emitting structure 110. Thus, the loss of the light emitting from the sidewall is reduced and the light emission efficiency from the top surface of the light emitting structure 110 is improved. As a result, substantially all the light can be emitted from the top surface of the light emitting structure 110 without being blocked in the device (e.g., an AR device).

[0021] FIG. 2 is a structural diagram showing a plan view of an exemplary micro LED panel 200 according to some embodiments of the present disclosure. As shown in FIG. 2, the micro LED panel 200 includes one or more of the micro LEDs 100 described above. The one or more micro LEDs 100 are arranged in an array on the micro LED panel 200. FIG. 3 is a structural diagram showing a side cross-sectional view of the micro LED 100 as exemplary adjacent micro LEDs 300a and 300b included in the micro LED panel 200 according to some embodiments of the present disclosure. Referring to FIG. 2 and FIG. 3, a conductive layer 330 is formed on the micro LED panel 200 and covers the entirety thereof. A reflective layer 340 is formed between adjacent light emitting structures 310a, 310b of the micro LEDs 300a, 300b and covers the entirety of the micro LED panel 200. The structure of the reflective layer 340 is a net having an array of holes respectively corresponding to the array of the micro LEDs 100 on the micro LED panel 200.

[0022] In some embodiments, in the micro LED panel 200, the micro LED 100 array can be 640*480, 1280*720 or 1920*1080, etc.

[0023] 4 is a structural diagram illustrating a plan view of an exemplary micro LED chip 400 according to some embodiments of the present disclosure. As shown in FIG. 4, the micro LED chip 400 includes one or more micro LED display panels 410, each having the structure of a micro LED panel described above with reference to FIG. 2 and FIG. 3. Referring to FIG. 3 and FIG. 4, a conductive layer 330 is formed on and entirely covers the micro LED chip 400. A reflective layer 340 is formed between adjacent light emitting structures 310a and 310b and entirely covers the micro LED chip 400. The structure of the reflective layer 340 can be a net having an array of holes corresponding to the micro LEDs 100, respectively.

[0024] It should be noted that the number of micro LEDs 100 in the micro LED panel 200 of Figure 2 and the number of micro LED panels 410 shown in Figure 4 are for illustrative purposes only. The number of micro LEDs in a micro LED panel and the number of micro LED panels in a micro LED chip may vary in practice.

[0025] It should be noted that relational terms such as "first" and "second" are used herein only to distinguish one entity or operation from another and do not require or imply an actual relationship or order between those entities or operations. Additionally, the words "comprising," "having," "containing," and "including," as well as other similar forms, are intended to be equivalent in meaning and open-ended in that the item or items following any one of these words are not intended to be an exhaustive enumeration of such item or items, nor are they intended to be limited to only the item or items listed.

[0026] As used herein, unless otherwise stated, the term "or" encompasses all possible combinations unless impracticable. For example, if it is stated that a database can include A or B, the database can include A, or B, or A and B, unless otherwise stated or impracticable. As a second example, if it is stated that a database can include A, B, or C, the database can include A, or B, or C, or A and B, or A and C, or A and B and C, unless otherwise stated or impracticable.

[0027] In the foregoing specification, the embodiments have been described with reference to numerous specific details that may vary from implementation to implementation. Certain adaptations and modifications of the described embodiments may be made. Other embodiments may be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims. It is also intended that the sequence of steps depicted in the figures is for illustrative purposes only, and is not intended to be limited to the particular sequence of steps. Thus, one skilled in the art can appreciate that these steps may be performed in different orders while implementing the same method.

[0028] In the drawings and specification, illustrative embodiments have been disclosed. However, many variations and modifications to these embodiments may be made. Thus, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A micro LED, A light emitting structure; a passivation layer formed on the light emitting structure; a reflective layer formed on the passivation layer; a conductive layer formed on a top surface of the passivation layer and on a top surface of the reflective layer; A micro LED comprising:

2. 2. The micro LED of claim 1, wherein the top surface of the reflective layer is equal to or lower than the top surface of the passivation layer, and the conductive layer is further formed on an upper sidewall of the passivation layer that is higher than the top surface of the reflective layer.

3. 3. The micro-LED of claim 1 or 2, wherein the reflective layer completely fills the space between adjacent light emitting structures.

4. The microLED according to any one of claims 1 to 3, wherein the top surface of the reflective layer is higher than a top surface of the light emitting structure.

5. The micro-LED according to any one of the preceding claims, wherein the material of the reflective layer is a metal or an oxide material.

6. The microLED according to any one of the preceding claims, wherein the reflective layer is formed by lamination.

7. 7. The micro-LED of claim 6, wherein the reflective layer comprises a stack of Ni, Ag, or Au.

8. 8. The microLED according to any one of the preceding claims, wherein the inclination angle of the sidewalls of the light emitting structure is less than 90°.

9. The microLED according to any one of the preceding claims, wherein the thickness of the reflective layer is greater than half the thickness of the light emitting structure.

10. 10. The micro-LED according to any one of claims 1 to 9, wherein the light emitting structure is a mesa structure having a flat top surface.

11. 11. The micro-LED of claim 10, wherein the light emitting structure is a conical structure without a pointed apex.

12. 12. The micro-LED of claim 1, further comprising a microlens formed on the conductive layer and the reflective layer.

13. 13. The microLED of claim 1, further comprising a conductive substrate formed below said light emitting structure and electrically connected to said light emitting structure.

14. 14. The micro-LED of claim 13, wherein the conductive substrate is an integrated circuit (IC) substrate.

15. 15. The micro-LED of claim 13 or 14, wherein the conductive substrate is bonded to the light emitting structure.

16. 16. A micro LED panel comprising two or more micro LEDs according to any one of claims 1 to 15, wherein the reflective layer is formed between adjacent light emitting structures of two or more of the micro LEDs.

17. 17. A micro LED panel comprising one or more micro LED chips according to claim 16.

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