Optical element, light-emitting device and display panel

Abstract

The invention discloses an optical element which comprises a first optical transmission layer and a second optical transmission layer, a light-emitting module is arranged on one side of the first optical transmission layer, the second optical transmission layer is arranged on one side, away from the light-emitting module, of the first optical transmission layer, and the refractive index of the first optical transmission layer is smaller than that of the second optical transmission layer. Light emitted by the light-emitting module passes through the first light transmission layer and the second light transmission layer in sequence, and light gathering can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of light-emitting diodes, and particularly to an optical element, a light-emitting device, and a display panel. Background Art

[0002] A micro light-emitting diode (Micro Light Emitting Diode) microdisplay chip is a new type of LED structure obtained by thinning, miniaturizing, and arraying the original LED structure. It integrates arrayed micron-level LED units on an active addressing driving panel to achieve the lighting and individual control of the LED units, thereby outputting the desired display image.

[0003] The core structure of the micro light-emitting diode is a light-emitting mesa, which is actually a PN junction diode composed of a direct bandgap semiconductor material. When a forward bias voltage is applied to the upper and lower electrodes of the micro light-emitting diode to cause current to pass through, electrons and holes recombine in the active region, and at the same time, single-color light photons are emitted. In order to converge and collimate light, existing micro light-emitting diodes usually have a micro lens on the optical path.

[0004] As shown in Figure 1, existing micro lenses 001 are mostly made of SiO 2 material, and its refractive index is 1.45 to 1.5, which is less than that of the light-emitting mesa 002. Therefore, after the light emitted from the light-emitting mesa 002 enters the micro lens 001, it will refract and approach the central axis. After testing, for the micro lens made of SiO 2 material, there is still much room for improvement in the light concentration effect of the outgoing light of the microdisplay chip. Summary of the Invention

[0005] To address some or all of the problems in the prior art, a first aspect of the present invention provides an optical element, including:

[0006] A first light transmission layer, on the first side of which a light-emitting module is provided; and

[0007] A second light transmission layer, which is provided on the second side of the first light transmission layer opposite to its first side, and the refractive index of the second light transmission layer is greater than that of the first light transmission layer.

[0008] Further, the material of the first light transmission layer is one or more of SiO 2 、Ai 2 O 3 、or BN.

[0009] Further, the material of the second light transmission layer is Si 3 N4 , ZrO 2 , TiO 2 , TiO or HfO 2 or one or more of them.

[0010] Further, the second light transmission layer includes an upper curvature portion.

[0011] Further, the radius of curvature at each point of the upper curvature portion is the same or different, and is 1.7 to 2.1 microns.

[0012] Further, the width of the upper curvature portion is greater than the width of the light emitting module.

[0013] Further, the spherical height of the upper curvature portion is 0.5 to 1.5 microns.

[0014] Further, the radius of curvature at each point of the upper curvature portion gradually decreases from bottom to top.

[0015] Further, the thickness of the first light transmission layer is set such that the focus of the upper curvature portion is located in the light emitting module.

[0016] Further, the thickness of the first light transmission layer is 1.1 to 1.7 microns.

[0017] Further, the second light transmission layer further includes a lower spacer portion, and the lower spacer portion is disposed on the surface of the first light transmission layer.

[0018] Further, the sum of the thickness of the lower spacer portion and the first light transmission layer is set such that the focus of the upper curvature portion is located in the light emitting module.

[0019] Further, the thickness of the lower spacer portion is not greater than 1.4 microns, and the thickness of the first light transmission layer is 0.3 to 1.7 microns, and the sum of the thickness of the lower spacer portion and the first light transmission layer is 1.1 to 1.7 microns.

[0020] Further, the refractive index of the light emitting module is greater than the refractive index of the first light transmission layer.

[0021] Based on the optical element as described above, a second aspect of the present invention provides a light emitting device, which includes a plurality of the optical elements arranged in an array as described above.

[0022] Further, the optical element is disposed on the light emitting module, and the optical module is disposed on the driving backplane.

[0023] Further, the light emitting module includes, from bottom to top: a first type semiconductor layer, a light emitting layer, and a second type semiconductor layer, wherein the first type semiconductor layer and the second type semiconductor layer are different.

[0024] Further, the light-emitting layer includes a quantum well layer.

[0025] Further, the area of the first-type semiconductor layer is smaller than the area of the second-type semiconductor layer, where:

[0026] The thickness of the first-type semiconductor layer is 0.1 μm to 0.22 μm; and the second-type semiconductor layer includes:

[0027] A stepped portion, which is electrically connected to the light-emitting layer and has a thickness of 400 nm to 800 nm;; and

[0028] A base portion, which extends from the stepped portion to both sides of the light-emitting mesa and has a thickness of 400 nm to 440 nm.

[0029] Further, the light-emitting device further includes:

[0030] A passivation layer, which includes a side portion and an extension portion, where the side portion surrounds the side surface of the light-emitting module or further covers at least a part of the bottom surface of the light-emitting module, and the extension portion extends from the side surface of the light-emitting module to both sides of the light-emitting module;

[0031] A reflective layer, which is disposed on the surface of the passivation layer and is electrically connected to the driving backplane through a conductive post;

[0032] An electrode, which is disposed on the top surface of the base portion of the second-type semiconductor layer and is located between two adjacent light-emitting modules;

[0033] A conductive layer, which is disposed on the bottom surface of the first-type semiconductor layer;

[0034] A dielectric layer, which coats the exposed bottom surface of the passivation layer and the outer surface of the reflective layer;

[0035] A first current spreading layer, which is disposed on the top surface of the base portion of the second-type semiconductor layer, and the electrode is disposed on the first current spreading layer, and / or the surface of the base portion of the second-type semiconductor layer that is not covered by the electrode; and

[0036] A second current spreading layer, which at least covers the top surface of the electrode, or further covers the side surface of the electrode and the top surface of the base portion of the second-type semiconductor layer, or further covers the side surface of the electrode and the surface of the first current spreading layer that is not covered by the electrode

[0037] Further, the conductive layer is a metal layer or a transparent conductive layer; and / or

[0038] The material of the passivation layer is a light-transmissive insulating material, including Al2 O 3 、 SiO 2 、 SiON, SiN or at least one of them; and / or

[0039] The material of the reflective layer is a conductive material with a reflectivity higher than 90%, including at least one of Ag, Au, and Al; and / or

[0040] The reflectivity of the electrode is not less than 39% in the blue light band and not less than 80% in the green light band. The material of the electrode includes at least one of Ag, Au, and Al; and / or

[0041] The material of the conductive column is Cu; and / or

[0042] The material of the dielectric layer is a light-transmissive insulating material, including Al 2 O 3 、 SiO 2 、 SiON, SiN or at least one of them; and / or

[0043] The first current spreading layer and the second current spreading layer are transparent conductive layers.

[0044] Furthermore, the thickness of the passivation layer is 0.15 microns; and / or

[0045] The height of the electrode is 0.7 to 0.9 microns.

[0046] Furthermore, the area of the first type semiconductor layer of the light-emitting module of the optical element is larger than the area of the second type semiconductor layer.

[0047] Furthermore, the light-emitting device further includes:

[0048] A passivation layer that covers the side surface of the light-emitting module or also covers at least part of the top surface of the light-emitting module;

[0049] An electrode that is disposed between two adjacent light-emitting modules;

[0050] A top conductive layer that is disposed on the surface of the passivation layer and contacts and covers the top surface of each light-emitting module.

[0051] Based on the optical element as described above, the third aspect of the present invention provides a display panel, which includes the optical element as described above.

[0052] Furthermore, the display panel includes a microdisplay panel.

[0053] Based on the optical element as described above, the fourth aspect of the present invention provides a display system, which includes the optical element as described above.

[0054] Further, the display panel includes a micro-display system.

[0055] Based on the optical element as described above, a fifth aspect of the present invention provides a near-eye display device, which includes the optical element as described above.

[0056] An optical element provided by the present invention can be applied to modules or devices such as light-emitting devices, display panels, display systems, and near-eye display devices. The optical element includes a stacked lens structure, and the refractive indices of the layers of the stacked lens structure increase sequentially along the light propagation direction, effectively improving the light-gathering effect of the optical element, and further improving the light efficiency and light collection ratio of the optical element. Description of the Drawings

[0057] To further clarify the above and other advantages and features of the embodiments of the present invention, a more specific description of the embodiments of the present invention will be presented with reference to the drawings. It can be understood that these drawings only depict typical embodiments of the present invention and will not be considered as limiting its scope. In the drawings, for clarity, the same or corresponding components will be denoted by the same or similar reference numerals.

[0058] Figure 1 Showing a schematic structural diagram of a light-emitting element in the prior art;

[0059] Figure 2 Showing a schematic structural diagram of an optical element according to an embodiment of the present invention;

[0060] Figure 3 Showing a schematic structural diagram of an optical element according to another embodiment of the present invention;

[0061] Figure 4 Showing a schematic structural diagram of a light-emitting device according to an embodiment of the present invention;

[0062] Figure 5 Showing a schematic structural diagram of a light-emitting device according to another embodiment of the present invention;

[0063] Figure 6 Showing a schematic structural diagram of a light-emitting device according to still another embodiment of the present invention;

[0064] Figure 7 Showing a schematic structural diagram of a light-emitting device according to still another embodiment of the present invention;

[0065] Figure 8 Showing a schematic structural diagram of a light-emitting device according to still another embodiment of the present invention;

[0066] Figure 9 Showing a schematic diagram of the distribution of the light-emitting angle of a light-emitting device according to an embodiment of the present invention; and

[0067] Figure 10Schematic structural diagram of a light-emitting device showing another embodiment of the present invention. Detailed implementation manners

[0068] In the following description, the present invention is described with reference to various embodiments. However, those skilled in the art will recognize that the embodiments can be implemented without one or more specific details or in combination with other alternative and / or additional methods, materials, or components. In other cases, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring the inventive points of the present invention. Similarly, for purposes of explanation, specific quantities, materials, and configurations are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, the present invention is not limited to these specific details. In addition, it should be understood that the embodiments shown in the drawings are illustrative representations and are not necessarily drawn to scale.

[0069] In this specification, the reference to "an embodiment" or "the embodiment" means that the specific features, structures, or characteristics described in connection with that embodiment are included in at least one embodiment of the present invention. The phrase "in an embodiment" that appears throughout this specification does not necessarily refer to the same embodiment.

[0070] It should be noted that the embodiments of the present invention describe the process steps in a specific order. However, this is only for the purpose of explaining the specific embodiment and does not limit the sequence of the steps. On the contrary, in different embodiments of the present invention, the sequence of the steps can be adjusted according to the adjustment of the process.

[0071] In the present invention, the term "from bottom to top" means from the side facing away from the light-emitting side of the micro light-emitting diode to the side facing the light-emitting side. Here, the "light-emitting side" refers to the side from which the light emitted by the micro light-emitting diode exits the micro light-emitting diode, for example, the side where the microlens is located. The term "top surface of the light-emitting mesa" refers to the surface of the light-emitting mesa facing the light-emitting side, and the term "bottom surface of the light-emitting mesa" refers to the surface of the light-emitting mesa facing away from the light-emitting side. The term "side surface of the light-emitting mesa" refers to the surface of the light-emitting mesa between the top surface and the bottom surface.

[0072] In the present invention, the term "converge" means that the cross-sectional area of the light beam formed by light becomes smaller during propagation, or the light beam formed by light converges to a certain point (focus) or a certain smaller area.

[0073] Aiming at the problem that the existing lens structures applied to light-emitting elements are usually single-layer and thus have poor light-concentrating effects, the present invention provides a stacked lens structure, which includes multiple layers of lenses with gradually increasing refractive indices, and can improve the light-concentrating effect, light efficiency, and light collection ratio.

[0074] The technical solution of the present invention will be further described below with reference to the accompanying drawings of the embodiments.

[0075] Figure 2 Schematic structural diagram of an optical element showing an embodiment of the present invention. As Figure 2 shown, an optical element includes a stacked lens structure, the stacked lens structure includes a first light transmission layer 202 and a second light transmission layer 203, wherein a first side of the first light transmission layer 202 can be provided with a light emitting module 201, and the second light transmission layer 203 is disposed on a second side opposite to the first side of the first light transmission layer 202, and the refractive index of the second light transmission layer 203 is greater than that of the first light transmission layer 202. It should be understood that in some other embodiments of the present invention, the stacked lens structure may include three or more light transmission layers, and along the light transmission direction, the refractive indices of the light transmission layers increase in sequence.

[0076] In some embodiments, the material of the first light transmission layer 202 is SiO 2 、Ai 2 O 3 、or one or more of BN. The refractive index of SiO 2 is 1.45 to 1.5, the refractive index of Ai 2 O 3 is 1.6 to 1.65, and the refractive index of BN is 1.7. In some embodiments, the first light transmission layer 202 may include multiple layers, and along the light transmission direction, the refractive indices of the layers increase in sequence.

[0077] In some embodiments, the thickness of the first light transmission layer 202 is 0.3 to 1.7 microns.

[0078] As Figure 2 shown, the second light transmission layer 203 includes an upper curvature portion 231 and a lower spacer portion 232, wherein the upper curvature portion 231 is hemispherical or approximately hemispherical, or other shapes, which are not limited herein. In some embodiments, the radius of curvature at each point of the upper curvature portion 231 may be the same or different. In some embodiments, the radius of curvature at each point of the upper curvature portion 231 gradually decreases from bottom to top, and the overall shape is similar to that of a bullet head, thereby improving the light condensing effect. In some embodiments, the radius of curvature at each point of the upper curvature portion 231 should be between 1.7 and 2.1 microns. In some embodiments, the height of the sphere of the upper curvature portion 231 is 0.5 to 1.5 microns. If the height of the sphere is too high, it is easy to cause a change in the original light path, making the light emit almost vertically, and if the height of the sphere is too low, the upper curvature portion 231 is close to a plane, and the light condensing effect is poor. In some embodiments, the width of the upper curvature portion 231 is greater than the width of the light emitting module, so as to ensure that the light emitted by the light emitting module 201 can be effectively emitted through the upper curvature portion 231, and to avoid light emission loss as much as possible.

[0079] The lower spacer 232 has a planar structure, and its thickness is set such that the sum of its thickness and the thickness of the first light transmission layer 202 can make the focus of the upper curvature portion 231 located in the light-emitting module 201. In addition, if the sum of the thickness of the lower spacer 232 and the thickness of the first light transmission layer 202 is too small, the overall volume of a single lens will be small, affecting the light output per unit area. If the sum of the thicknesses is too large, the light may be emitted into the adjacent stacked lens structure, affecting the adjacent stacked lens structure and causing light crosstalk. Based on this, in some embodiments, the thickness of the lower spacer 232 is not greater than 1.4 microns, and thus the sum of its thickness and the thickness of the first light transmission layer 202 is between 1.1 and 1.7 microns.

[0080] In some embodiments, the material of the second light transmission layer 203 is Si 3 N 4 、ZrO 2 、Ti x O y 、or HfO 2 or one or more of them, where the ratio of x to y in Ti x O y is between 0.5 and 1. The refractive index of Si 3 N 4 is 1.8 to 2.0, the refractive index of ZrO 2 is 1.95 to 2.05, the refractive index of Ti x O y is 2.2 to 2.3, and the refractive index of HfO 2 is 2. It can be seen that the refractive indices of the materials of the second light transmission layer 203 are all higher than those of the materials used in the first light transmission layer 202. Similarly, in some embodiments, the second light transmission layer 203 may include multiple layers, and along the direction of light transmission, the refractive indices of the layers increase in sequence.

[0081] Figure 3 FIG. shows a schematic structural diagram of an optical element according to another embodiment of the present invention. The difference from the optical element shown in Figure 2 is that the second light transmission layer 203 only includes the upper curvature portion, that is, the thickness of its lower spacer is 0. At this time, if it is necessary to satisfy that the sum of the thickness of the lower spacer and the thickness of the first light transmission layer 202 can make the focus of the upper curvature portion 231 located in the light-emitting module 201, the thickness of the first light transmission layer 202 should be 1.1 to 1.7 microns. When the thickness of the first light transmission layer 202 is too small, less than 1.1 microns, the overall volume of a single lens may be small, affecting the light output per unit area. If the thickness is too large, greater than 1.7 microns, the light may be emitted into the adjacent stacked lens structure, affecting the adjacent stacked lens structure and causing light crosstalk.

[0082] As Figure 2 and Figure 3As shown, a stacked lens structure is adopted. Since the refractive index of each light transmission layer gradually increases along the light transmission direction, light will refract when entering different light transmission layers, approaching the central axis of the optical element, effectively improving the light concentration effect.

[0083] The aforementioned stacked lens structure can be applied to light-emitting devices such as light-emitting diode chips and micro light-emitting diode chips. In these light-emitting devices, the light-emitting module 201 includes a PN junction diode. Therefore, the refractive index of the light-emitting module 201 is usually greater than that of the first light transmission layer 202.

[0084] Taking a micro light-emitting diode as an example, the application of the stacked lens structure in a light-emitting device will be further described below. In some embodiments, the light-emitting device is a micro light-emitting diode chip with a size not exceeding 1 cm, preferably not exceeding 20 microns. The micro light-emitting diode chip includes a driving backplane (not shown in the figure) and a micro light-emitting diode structure, and the stacked lens structure is arranged on the light-emitting side of the micro light-emitting diode structure. The micro light-emitting diode structure is formed in an array form in the micro light-emitting diode chip, and the resolution ratio is, for example, 720*480, 640*480, 1920*1080, 1280*720, 2K or 4K. The diameter of the micro light-emitting diode structure is in the micron range, for example, 1 micron to 40 microns. Each micro light-emitting diode can form at least a part of the pixel elements on the micro light-emitting diode chip. In some embodiments, the micro light-emitting diode array can include blue micro light-emitting diodes. In some embodiments, the micro light-emitting diode array can include green micro light-emitting diodes. In some embodiments, the micro light-emitting diode array can include red micro light-emitting diodes. In some embodiments, the pitch of the micro light-emitting diode array, that is, the minimum center-to-center distance between micro light-emitting diodes, can be between about 2 microns and about 50 microns. In some embodiments, the number of pixels on the micro light-emitting diode chip can be between several thousand and several million.

[0085] In some embodiments, the driving backplane can be electrically connected to each micro light-emitting diode in the micro light-emitting diode array through separate metal interconnections. In some embodiments, each micro light-emitting diode can be electrically controlled independently by the driving backplane. In some embodiments, the driving backplane can be electrically connected to the electrodes of the micro light-emitting diode chip through metal interconnections.

[0086] In some embodiments, each micro light-emitting diode in the micro light-emitting diode array can include a light-emitting mesa, where the light-emitting mesa is a micron-scale structure. The stacked lens structure is arranged corresponding to the light-emitting mesa, and the horizontal contour of the stacked lens structure is larger than the maximum horizontal contour of the light-emitting mesa, thereby ensuring that the light emitted by the light-emitting mesa is converged through the stacked lens structure, avoiding light loss.

[0087] Figure 4 Schematic structural diagram of a light-emitting device showing an embodiment of the present invention. As Figure 4 shown, a light-emitting device includes a micro light-emitting diode chip as described above.

[0088] As Figure 4 shown, in some embodiments, the light-emitting mesa 401 sequentially includes a first-type semiconductor layer 411, a light-emitting layer 412, and a second-type semiconductor layer 413 from bottom to top. That is to say, in the three-layer structure, the first-type semiconductor layer 411 is closest to the driving backplane, the light-emitting layer 412 is located above the first-type semiconductor layer 211 and is farther from the driving backplane, and the second-type semiconductor layer 413 is located above the light-emitting layer 412 and is the farthest from the driving backplane.

[0089] In some embodiments, the area of the first-type semiconductor layer 411 is smaller than the area of the second-type semiconductor layer 413, and thus the cross-section of the light-emitting mesa 401 is an inverted trapezoid or approximately an inverted trapezoid.

[0090] In some embodiments, the thickness of the first-type semiconductor layer 411 is 0.1 μm to 0.22 μm. The second-type semiconductor layer 413 includes a stepped portion 4131 and a base portion 4132, wherein the stepped portion 4131 is electrically connected to the light-emitting layer 412, and the base portion 4132 extends from the stepped portion 4131 to both sides of the light-emitting mesa 401. In the actual manufacturing process, a relatively thick second-type semiconductor material can be deposited first, and the light-emitting layer 412 and the first-type semiconductor layer 411 are sequentially deposited thereon. Subsequently, etching of each light-emitting mesa is performed, and a certain thickness of the second-type semiconductor material at the bottom is reserved without being etched through, thereby obtaining the base portion 4132. In some embodiments, the thickness of the stepped portion 4131 is 400 nm to 800 nm, and the thickness of the base portion 4132 is 400 nm to 440 nm. In some embodiments, the thickness of the first-type semiconductor layer 411 is less than that of the second-type semiconductor layer 413.

[0091] In some embodiments, the first-type semiconductor layer 411 has a semiconductor material of a first conductivity type and includes a plurality of semiconductor layers. The main matrix material of the first-type semiconductor layer 411 includes, but is not limited to, Ga, N, As, P, In, or Al. In addition, the first-type semiconductor layer 411 may include, from top to bottom, but is not limited to, a waveguide layer, a confinement layer, a transition layer, and a window layer; in addition, an ohmic contact layer may be formed below the window layer. In some embodiments, the second-type semiconductor layer 413 has a semiconductor material of a second conductivity type and includes a plurality of semiconductor layers. The main matrix material of the second-type semiconductor layer 413 may be, but is not limited to, composed of materials such as Ga, N, As, P, In, or Al. In addition, the second-type semiconductor layer 413 may include, from top to bottom, but is not limited to, a confinement layer and a waveguide layer; in addition, in some embodiments, an ohmic contact layer may be formed on the confinement layer. In one embodiment, the first conductivity type is different from the second conductivity type. For example, in some embodiments, if the light-emitting mesa 401 emits blue-green light, the first-type semiconductor layer 411 is an N-type GaN layer, an N-type AlGaN layer, or an N-type InGaN layer, and the second-type semiconductor layer 413 is a P-type GaN layer, a P-type AlGaN layer, or a P-type InGaN layer. If the light-emitting mesa 401 emits red light, the first-type semiconductor layer 411 is an N-type GaInP layer, or an N-type AlGaInP layer, and the second-type semiconductor layer 413 is a P-type GaInP layer, or a P-type AlGaInP layer.

[0092] In some embodiments, one of the first-type semiconductor layer 411 and the second-type semiconductor layer 413 is an N-type semiconductor layer and the other is a P-type semiconductor layer. In some embodiments, the N-type semiconductor layer further includes a doped N-type contact layer and an N-type cladding layer. The doped N-type contact layer is configured to bond with the bonding layer, and the N-type cladding layer is formed on the doped N-type contact layer. The material of the N-type cladding layer is Al x In 1-x P, where the range of x is from 0.1 to 0.5, for example, x is 0.5. In addition, in these embodiments, the thickness of the N-type cladding layer is not greater than 350 nm. For example, the thickness of the N-type cladding layer is 320 nm. The doping concentration of the N-type cladding layer is 5e 17 cm -3 to 1e 18 cm -3 . In some embodiments, the N-type semiconductor layer further includes a doped N-type contact layer and an N-type cladding layer formed on the doped N-type contact layer. The doped N-type contact layer is configured to bond with the bonding layer. The material of the doped N-type contact layer is GaAs. In some embodiments, the thickness of the doped N-type contact layer is from 10 nm to 30 nm. In some embodiments, the doping concentration of the doped N-type contact layer is 2e 18 cm -3 to 1e19 cm -3 。In some embodiments, the N-type semiconductor layer further includes an N-type spacer layer formed on the N-type cladding layer. The material of the N-type spacer layer is (Al x Ga 1-x ) y In 1-y P, where the range of x is 0.5 to 0.9, and the range of y is 0.1 to 0.5. For example, x is 0.8 and y is 0.5. In some embodiments, the relationship between x and y is that x is 1 to 2 times y. The thickness of the N-type spacer layer is 50 nm to 75 nm, for example, 65 nm. In some embodiments, the P-type semiconductor layer includes a P-type cladding layer and a doped P-type contact layer. The P-type cladding layer is formed on the light-emitting layer, and the doped P-type contact layer is formed on the P-type cladding layer.

[0093] In some embodiments, the material of the P-type cladding layer is Al x In 1-x P, where x is 0.3 to 0.5, for example, x is 0.5. In such embodiments, the thickness of the P-type cladding layer is not greater than 380 nm. For example, the thickness of the P-type cladding layer is 360 nm.

[0094] In some embodiments, the material of the doped P-type contact layer is GaAs. The thickness of the doped P-type contact layer is 10 nm to 30 nm, for example, 20 nm.

[0095] In some embodiments, the P-type semiconductor layer further includes a P-type spacer layer formed under the P-type cladding layer, a first doped P-type transition layer formed on the P-type cladding layer, and a second doped P-type transition layer formed on the first doped P-type transition layer. In some embodiments, the material of the P-type spacer layer is (Al x Ga 1-x ) y In 1-y P, where the range of x is 0.5 to 0.9, and the range of y is 0.3 to 0.5. For example, x is 0.8 and y is 0.5. In some embodiments, the relationship between x and y is that x is 1 to 2 times y. In some embodiments, the thickness of the P-type spacer layer is 50 nm to 70 nm, for example, 65 nm.

[0096] In some embodiments, the material of the first doped P-type transition layer is (Al x Ga 1-x ) y In 1-yP, where the range of x is from 0.1 to 0.3 and the range of y is from 0.3 to 0.5. For example, x is 0.17 and y is 0.5. In some embodiments, the relationship between x and y is that y is 1 to 5 times of x. In some embodiments, the thickness of the first doped P-type transition layer is from 20 nm to 40 nm, for example 30 nm.

[0097] In some embodiments, the material of the second doped P-type transition layer is Al x Ga 1-x As, where the range of x is from 0.5 to 0.9, for example x is 0.6. In some embodiments, the thickness of the second doped P-type transition layer is from 10 nm to 30 nm, for example 20 nm.

[0098] In some embodiments, the doping concentration of the second doped P-type transition layer is greater than the doping density of the first doped P-type transition layer. The doping concentration of the doped P-type contact layer is 1 to 10 times that of the second doped P-type transition layer.

[0099] In some embodiments, the doping concentration of the doped P-type contact layer is greater than that of the second doped P-type transition layer. In addition, in some embodiments, the doping concentration of the second doped P-type transition layer is 2 to 4 times that of the first doped P-type transition layer.

[0100] For example, the doping concentration of the first doped P-type transition layer is greater than 1e 18 cm -3 , the doping density of the second doped P-type transition layer is in the range of 2e 18 cm -3 -4e 18 cm -3 , and the doping density of the doped P-type contact layer is greater than 5e 18 cm -3 .

[0101] In some embodiments, the light-emitting layer 412 is formed by a plurality of stacked quantum well layers, particularly superlattice-stacked quantum well layers. Preferably, the superlattice-stacked quantum well layers include multiple pairs of quantum well layers stacked with quantum barrier layers. In some embodiments, the light-emitting layer 412 includes at least one quantum well layer. The thickness of the quantum well layer is between 20 nm and 40 nm, for example, the thickness is 30 nm.

[0102] In some embodiments, the light-emitting layer is a multi-quantum well (MQW). For blue-green light-emitting diodes, the multi-quantum well layer is an InGaN / GaN multi-quantum well layer, or an InGaN / AlGaN multi-quantum well layer, or an InGaAs / AlGaAs multi-quantum well layer. For red light-emitting diodes, the multi-quantum well layer is an InGaN, AlInP, or GaInP multi-quantum well layer. In some embodiments, the light-emitting layer 412 further includes an electron blocking layer disposed on the first side of the quantum well layer, where the first side refers to the side along which electrons migrate out of the light-emitting layer.

[0103] As Figure 4 shown, in some embodiments, the micro light-emitting diode chip further includes a conductive layer 404 disposed on the bottom surface of the light-emitting mesa 401. In some embodiments, the conductive layer 404 can be a metal layer or a conductive transparent layer, such as ITO, FTO, or a copper layer, which is formed to improve conductivity and transparency. In some embodiments, the conductive layer 404 is a transparent conductive layer with a light transmittance of 85% to 95% and a resistivity as low as 10-4 to 10-3 Ω·cm.

[0104] As Figure 4 shown, the micro light-emitting diode chip further includes a passivation layer 402, which includes a side surface portion 421 and an extension portion 422. The side surface portion 421 surrounds the side surface of the light-emitting mesa 401, i.e., the side surfaces of the first-type semiconductor layer 411, the light-emitting layer 412, and the second-type semiconductor layer 413. The extension portion 422 extends from the side surface of the light-emitting mesa 401 to both sides of the light-emitting mesa 401 to cover the bottom surface of the base portion 4132 of the second-type semiconductor layer 413. In some embodiments, the passivation layer 402 also covers a part of the bottom surface of the first-type semiconductor layer 411. Specifically, it is the edge portion of the bottom surface of the first-type semiconductor layer 411, i.e., there is an opening in the passivation layer 402 on the bottom surface of the first-type semiconductor layer 411, and the conductive layer 404 is formed in the opening. In some embodiments, the passivation layer 402 mainly functions as an electrical isolation layer, and it can be, for example, an aluminum oxide (Al 2 O 3 ) thin film layer, a SiO 2 thin film layer, a SiON thin film layer, a SiN thin film layer, etc., which are insulating material layers with good light transmittance, formed by atomic layer deposition process, chemical deposition process, etc. The passivation layer 402 is used for electrical isolation between the conductive layer 404 and the first-type semiconductor layer 411, the light-emitting layer 412, and the second-type semiconductor layer 413. In some embodiments, the thickness of the passivation layer 402 is 0.15 micrometers.

[0105] As Figure 4As shown, the micro light-emitting diode chip further includes a reflective layer 403. The reflective layer 403 is disposed on the surface of the passivation layer 402 and the bottom surface of the conductive layer 404. The reflective layer 403 is electrically connected to the driving backplane through conductive posts 409. In some embodiments, the reflective layer 403 may be a conductive material layer having one or more layers with a high refractive index, which can reflect the light emitted from the light-emitting region, improving the brightness and light efficiency of the micro light-emitting diode chip. For example, the reflective layer 403 may include one or more metal layers, such as Pt, Rh, Al, Au, and Ag, etc., or a stacked DBR layer of TiO2 / SiO 2 layers, or any other layer having a total reflection characteristic, such as a multi-layer omnidirectional reflector ODR, or a combination thereof. In some embodiments, the reflectivity of the reflective layer material with respect to light in the visible light range should be not less than 90%. In addition, in some embodiments, the root mean square roughness of the inner surface of the reflective layer 403 is between 1 and 10 nanometers.

[0106] As Figure 4 shown, in some embodiments, the micro light-emitting diode chip further includes a dielectric layer 405. The dielectric layer 405 is disposed between two adjacent light-emitting mesa surfaces, covering the bottom surface of the exposed passivation layer 402 and the outer surface of the reflective layer 403, but exposing the ends of the conductive posts 409. In some embodiments, the dielectric layer 405 is made of a light-transmissive insulating material, such as Al 2 O 3 , SiO 2 , SiON, SiN, or at least one material of the like.

[0107] As Figure 4 shown, in some embodiments, the micro light-emitting diode chip further includes an electrode 406. The electrode 406 is disposed on the top surface of the base of the second-type semiconductor layer 413, between two adjacent light-emitting mesa surfaces. In some embodiments, the cross-section of the electrode 406 is trapezoidal, and its height is 0.7 to 0.9 micrometers. In order to further improve the light efficiency, in some embodiments, the electrode 406 is made of a conductive material with a high reflectivity, such as Ag, or Au, or Al, etc., and the reflectivity of the conductive material with respect to light in the visible light range should be not less than 40%.

[0108] To achieve current spreading and simultaneously connect the second-type semiconductor layers 413 of each semiconductor light-emitting mesa in series, as Figure 4As shown, the micro light-emitting diode chip further includes a first current spreading layer 471 and / or a second current spreading layer 472. The first current spreading layer 471 is disposed at the bottom of the electrode 406, and the second current spreading layer 472 is disposed on the outer surface of the electrode 406. It should be understood that at least one of the first current spreading layer 471 and the second current spreading layer 472 also covers the top surface of the base 4132 where no electrode is provided, so that the electrodes are connected in series and shared.

[0109] Specifically, in the embodiment as Figure 4 shown, the first current spreading layer 471 covers the top surface of the entire base layer 4132. The electrode 406 is disposed on the first current spreading layer 471 and is located between two light-emitting mesa 401. At the same time, the second current spreading layer 472 covers the top surface and the side surface of the electrode 406, and also covers the surface of the first current spreading layer 471 where no electrode is provided.

[0110] In the embodiment as Figure 5 shown, the micro light-emitting diode chip only includes the first current spreading layer 471. The first current spreading layer 471 covers the top surface of the entire base, and the electrode 406 is disposed on the first current spreading layer 471 and is located between two light-emitting mesa 401.

[0111] In the embodiment as Figure 6 shown, the first current spreading layer 471 covers the top surface of the entire base, the electrode 406 is disposed on the first current spreading layer 471 and is located between two light-emitting mesa 401. At the same time, the second current spreading layer 472 covers the top surface and the side surface of the electrode 406.

[0112] In the embodiment as Figure 7 shown, the first current spreading layer 471 is only disposed at the bottom of the electrode 406. At the same time, the second current spreading layer 472 covers the top surface and the side surface of the electrode 406, and the top surface of the base 4132 where no electrode is provided.

[0113] In the embodiment as Figure 8 shown, the micro light-emitting diode chip only includes the second current spreading layer 472. The second current spreading layer 472 covers the top surface and the side surface of the electrode 406, and the top surface of the base 4132 where no electrode is provided.

[0114] In some embodiments, the first and second current spreading layers 471 and 472 are transparent conductive layers ITO.

[0115] Verified, as Figure 9 shown, in the embodiment as Figure 4In the micro light-emitting diode chip shown, a stacked lens structure is adopted, which can increase the proportion of the light rays in the emitted light of the microdisplay chip with an angle not greater than ±20° with respect to the central axis, that is, the light collection ratio within ±20°. After testing, if a single-layer lens is used, the light collection ratio within ±20° in the emitted light of the microdisplay chip is about 25%. However, if the stacked lens structure is adopted, the light collection ratio within ±20° can be increased from 25% to 30% to 40%. Since the light extraction efficiency within ±20° is higher than that of other large-angle light rays, therefore, when its light collection ratio increases, the directivity of the light can also be improved.

[0116] Figure 10 FIG. shows a schematic structural diagram of a light-emitting device according to another embodiment of the present invention. As Figure 10 shown, the light-emitting device includes the micro light-emitting diode chip as described above, but there are certain differences from the Figure 4 light-emitting device shown.

[0117] As Figure 10 shown, in some embodiments, the micro light-emitting diode structure includes a driving backplane 110, a lower electrode layer 120, a conductive layer 130, a light-emitting mesa 140, an upper electrode layer 150, a passivation layer 160, a microlens 170, and an electrode 180.

[0118] In some embodiments, the lower electrode layer 120 may be a metal bonding composite layer. The light-emitting mesa 140 of the micro light-emitting diode may be bonded to the surface of the driving backplane 110 through the lower electrode layer 120, and the bonding may be completed by means such as eutectic bonding, thermocompression bonding, and transient liquid phase (TLP) bonding. In some embodiments, the lower electrode layer 120 may be disposed on the driving backplane 110. In another embodiment, the lower electrode layer 120 grows on the driving backplane 110. In some embodiments, the thickness of the lower electrode layer 120 is from 0.1 micrometer to 3 micrometers. In a preferred embodiment, the thickness of the lower electrode layer 120 is 0.3 μm. In some embodiments, the material of the lower electrode layer 120 is an alloy of one or more of the following metals: Cr, Al, Ti, Ni, Pt, Au, Ag, and Sn. The lower electrode layer 120 may include an ohmic contact layer and a metal bonding layer. In some cases, the lower electrode layer 120 includes two metal layers. One of the two metal layers is deposited on a layer above the metal bonding layer within the LED. The corresponding bonding metal layer is deposited on the driving backplane 110. For example, the lower electrode layer 120 may be an Au-Au bonding, Au-Sn bonding, Au-In bonding, Ti-Ti bonding, Cu-Cu bonding, or a combination of the above. For example, if Au-Au bonding is selected, two Au layers respectively require a Cr layer as an adhesion layer and a Pt layer as an anti-diffusion layer. The Pt layer is located between the Au layer and the Cr layer. The Cr and Pt layers are located on the top and bottom of the two bonded Au layers. In some embodiments, when the thicknesses of the two Au layers are substantially the same, at high pressure and high temperature, the Au on the two layers diffuses into each other to bond the two layers together.

[0119] In some embodiments, the lower electrode layer 120 may also be used as a mirror to reflect the light emitted from the light-emitting mesa 140 above.

[0120] In some embodiments, the conductive layer 130 is formed on the bottom surface of the light-emitting mesa 140 for forming an electrical connection between the light-emitting mesa 140 and the lower electrode layer 120. In some embodiments, the conductive layer 130 may be a conductive transparent layer transparent to the light emitted from the light-emitting mesa 140 to improve conductivity and light transmittance. In some embodiments, the upper electrode layer 150 is formed on the top surface of the light-emitting mesa 140, and the upper electrode layer 150 is electrically connected to a current spreading structure or a top electrode (not shown).

[0121] In some embodiments, the conductive layer 130, the upper electrode layer 150, and their connecting components can be one or more combinations of, for example, graphene, indium tin oxide (ITO), antimony doped zinc oxide (AZO), fluorine doped tin oxide (FTO), or other transparent conductive oxides (TCO).

[0122] The light-emitting mesa 140 includes a first-type semiconductor layer 141, a second-type semiconductor layer 143, and a light-emitting layer 142 located therebetween. The first-type semiconductor layer 141 is electrically connected to the conductive layer 130. The second-type semiconductor layer 143 is electrically connected to the upper electrode layer 150. The difference between the light-emitting mesa and the light-emitting mesa in the embodiment shown in Figure 4 is that the area of the first-type semiconductor layer 141 is larger than the area of the second-type semiconductor layer 143, and thus the cross-section of the light-emitting mesa 140 is approximately a right trapezoid. That is, there is an inclination angle between the side wall of the light-emitting mesa 140 and the bottom of the light-emitting mesa, and the inclination angle is less than or equal to 90°. In some embodiments, the range of the inclination angle of the side wall of the light-emitting mesa is: 45° to 90°. In some embodiments, the bottom lateral dimension of the light-emitting mesa 140 exceeds 2 microns. In some embodiments, the top lateral dimension of the light-emitting mesa 140 does not exceed 1.5 microns. In some embodiments, the lateral dimension of the lower electrode layer 120 is larger than the bottom lateral dimension of the light-emitting mesa 140.

[0123] In some embodiments, the electrode polarity of the conductive layer 130 is determined by the first-type semiconductor layer 141, and the electrode polarity of the upper electrode layer 150 is determined by the second-type semiconductor layer 143. The electrode polarity of the conductive layer 130 is opposite to the electrode polarity of the upper electrode layer 150. The conductive layer 130 can be, for example, a P electrode or an anode electrode, and the upper electrode layer 150 is an electrode with a polarity opposite to that of the conductive layer 130, such as an N electrode or a cathode electrode, and vice versa.

[0124] In some embodiments, the passivation layer 160 coats the side surfaces of the lower electrode layer 120, the conductive layer 130, and the light-emitting mesa 140. In some embodiments, the passivation layer 160 may also cover a part of the side surface of the upper electrode layer 150, and a part of the top surface of the upper electrode layer 150 is exposed to form an electrical connection with the top electrode. In other embodiments of the present invention, the passivation layer 160 does not cover the top surface and the side surface of the upper electrode layer 150, so that the upper electrode layers 150 of adjacent LED structures can be connected to each other as a whole to form a common cathode or anode. In some embodiments, the passivation layer 160 coats the side surfaces of the lower electrode layer 120, the conductive layer 130, the first-type semiconductor layer 141, the light-emitting layer 142, and a part of the side surface of the second-type semiconductor layer 143.

[0125] In some embodiments, the electrode 180 is disposed on the surface of the upper electrode layer 150 and is located between two light-emitting mesas. In some embodiments, the electrode 180 is an annular reflective electrode, which is formed by magnetron sputtering or evaporation, and its material can be, for example, Al or an Al alloy metal as the sidewall reflective mirror surface, and the electrode stack metal can be metal materials such as Ni, Al, Ti, Ni, Pt, Au, etc. In some embodiments, the electrodes are connected to each other.

[0126] In some embodiments, the material of the passivation layer is a transparent insulating material, for example, one or more of silicon oxide, silicon oxynitride, aluminum oxide, and silicon nitride.

[0127] The optical element as described above, and the light-emitting device using the optical element can be applied to a display panel, a display system, and a near-eye display device. The display panel includes, for example, a light-emitting diode display panel, a micro light-emitting diode display panel, etc., and the display system includes, for example, a light-emitting diode display system, a micro light-emitting diode display system, etc. By providing the stacked lens structure, the light condensing effect of these display devices and display systems can be improved.

[0128] Although the embodiments of the present invention have been described above, it should be understood that they are presented only as examples and not as limitations. It is obvious to those skilled in the relevant art that various combinations, deformations, and changes can be made thereto without departing from the spirit and scope of the present invention. Therefore, the width and scope of the present invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should be defined only by the appended claims and their equivalents.

Claims

1. An optical element, characterized in that: include: A first light transmission layer, a light emitting module is disposed on one side of the first light transmission layer; as well as A second light transmission layer, wherein the second light transmission layer is arranged on a side of the first light transmission layer away from the light emitting module, and a refractive index of the first light transmission layer is smaller than a refractive index of the second light transmission layer.

2. The optical element according to claim 1, characterized in that The material of the first light transmission layer is one or more of SiO2, Al2O3 or BN.

3. The optical element according to claim 1, characterized in that The material of the second light transmission layer is one or more of Si3N4, ZrO2, TiO2, TiO or HfO2.

4. The optical element according to claim 1, characterized in that The second light transmissive layer includes an upper curvature.

5. The optical element according to claim 4, characterized in that The curvature radius at each point of the upper curvature portion is the same or different.

6. The optical element according to claim 5, characterized in that The radius of curvature at each point of the upper curvature portion is 1.7 to 2.1 micrometers.

7. The optical element according to claim 4, characterized in that The width of the upper curvature portion is greater than the width of the light emitting module.

8. The optical element according to claim 4, characterized in that The height of the upper curvature portion is 0.5 to 1.5 microns.

9. The optical element according to claim 4, characterized in that The curvature radius at each point of the upper curvature portion gradually decreases from bottom to top.

10. The optical element according to claim 4, characterized in that The thickness of the first light transmission layer satisfies that: the focus of the upper curvature portion is located in the light emitting module.

11. The optical element according to claim 4, characterized in that The thickness of the first light transmission layer is 1.1 to 1.7 microns.

12. The optical element according to claim 4, characterized in that The second light transmission layer further includes a lower spacer, and the lower spacer is disposed on a surface of the first light transmission layer.

13. The optical element according to claim 12, characterized in that The sum of the thickness of the lower spacing portion and the thickness of the first light transmission layer satisfies that: the focus of the upper curvature portion is located in the light emitting module.

14. The optical element according to claim 12, characterized in that The thickness of the lower spacer is not greater than 1.4 micrometers, and the thickness of the first light transmission layer is 0.3 to 1.7 micrometers, and the sum of the thicknesses of the lower spacer and the first light transmission layer is 1.1 to 1.7 micrometers.

15. The optical element according to claim 1, characterized in that The refractive index of the light emitting module is greater than the refractive index of the first light transmission layer.

16. A light emitting device, characterized in that: The optical element comprises a plurality of optical elements as claimed in any one of claims 1 to 15 arranged in an array.

17. The light emitting device according to claim 16, characterized in that: The optical element is arranged on the light emitting module, and the light emitting module is arranged on a driving backplane.

18. The light emitting device according to claim 17, characterized in that: The light emitting module comprises: a first type semiconductor layer; a light emitting layer; and A second type semiconductor layer, wherein the first type semiconductor layer and the second type semiconductor layer are different.

19. The light emitting device according to claim 18, characterized in that: The light emitting layer includes a quantum well layer.

20. The light emitting device according to claim 18, characterized in that The area of ​​the first type semiconductor layer is smaller than the area of ​​the second type semiconductor layer, wherein: The second type semiconductor layer comprises: a stepped portion electrically connected to the light emitting layer; and The base portion extends from the step portion to both sides of the light-emitting table.

21. The light emitting device according to claim 18, characterized in that Also includes: a passivation layer, comprising a side portion and an extension portion, wherein the side portion surrounds a side surface of the light emitting module, or also covers at least a portion of a bottom surface of the light emitting module, and the extension portion extends from the side surface of the light emitting module to both sides of the light emitting module; A reflective layer, which is disposed on the surface of the passivation layer and is electrically connected to the driving backplane through a conductive column; an electrode, which is disposed on the top surface of the base portion of the second type semiconductor layer and is located between two adjacent light emitting modules; a conductive layer disposed on a bottom surface of the first type semiconductor layer; a dielectric layer covering the exposed bottom surface of the passivation layer and the outer surface of the reflective layer; A first current spreading layer is disposed on the top surface of the base portion of the second type semiconductor layer, and the electrode is disposed on the first current spreading layer and / or a surface of the base portion of the second type semiconductor layer not covered by the electrode; as well as The second current spreading layer at least covers the top surface of the electrode, or also covers the side surface of the electrode and the top surface of the base portion of the second type semiconductor layer, or also covers the side surface of the electrode and the surface of the first current spreading layer not covered by the electrode.

22. The light emitting device according to claim 17, characterized in that: An area of ​​the first type semiconductor layer of the light emitting module of the optical element is greater than an area of ​​the second type semiconductor layer.

23. The light emitting device according to claim 22, characterized in that: Also includes: a passivation layer covering the side surface of the light emitting module, or also covering at least a portion of the top surface of the light emitting module; An electrode, which is arranged between two adjacent light-emitting modules; as well as The top conductive layer is disposed on the surface of the passivation layer and contacts and covers the top surface of each of the light emitting modules.

24. A display panel, characterized in that: Comprising the optical element according to any one of claims 1 to 15.

25. The display panel according to claim 24, wherein: The display panel includes a micro light emitting diode display panel.

26. A display system, characterized in that: The optical element comprises the optical element as claimed in any one of claims 1 to 15.

27. The display system according to claim 26, characterized in that: The display system includes a micro light emitting diode display system.

28. A near-eye display device, characterized in that: The optical element comprises the optical element as claimed in any one of claims 1 to 15.

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