A light emitting diode, a light emitting module and a light emitting device

Abstract

This invention discloses a light-emitting diode (LED), a light-emitting module, and a light-emitting device. The LED includes a semiconductor stack comprising a first semiconductor layer, an active layer, and a second semiconductor layer stacked sequentially. The second semiconductor layer has a protrusion forming a first mesa, and a second mesa is formed around the first mesa. The upper surface of the first mesa is higher than the upper surface of the second mesa. In a top-view projection direction, the ratio of the area of ​​the first mesa to the area of ​​the second mesa is between 10% and 35%. Therefore, this invention, by setting the first and second mesa on the second semiconductor layer, restricts current from moving away from the sidewalls, thereby suppressing the edge effect of the LED. Simultaneously, the area ratio of the first and second mesa further improves the brightness and reliability of the device and reduces the forward voltage.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, specifically to a light-emitting diode, a light-emitting module, and a light-emitting device. Background Technology

[0002] Micro-LEDs have become a research hotspot in the field of new displays due to their superior characteristics such as high brightness, low power consumption, long lifespan, and high response speed. For example, in direct-view TV applications, Micro-LEDs with a chip size of less than 50μm are usually used; in wearable devices, the chip size is usually less than 30μm; and in virtual reality (VR) or augmented reality (AR) applications, the chip size needs to be less than 10μm.

[0003] However, as the size of light-emitting diode (LED) chips continues to shrink, edge effects become increasingly pronounced. This is especially true for gallium arsenide (GaAs) micro-LEDs, where edge effects are most severe, leading to a series of problems such as uneven current distribution, uneven light emission, heat accumulation, decreased light extraction efficiency, and increased reliability risks. Therefore, developing effective edge effect suppression techniques has become crucial to overcoming the performance bottlenecks of GaAs micro-LEDs. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a light-emitting diode, a light-emitting module and a light-emitting device, so as to further improve the light extraction efficiency, light emission uniformity and device reliability of the light-emitting diode.

[0005] To achieve the above and other related objectives, the present invention provides a light-emitting diode, comprising:

[0006] A semiconductor stack includes a first semiconductor layer, an active layer, and a second semiconductor layer stacked sequentially.

[0007] The second semiconductor layer has a protrusion forming a first mesa, and a second mesa is formed around the first mesa, with the upper surface of the first mesa being higher than the upper surface of the second mesa.

[0008] In the top-view projection direction, the ratio of the area of ​​the first platform to the area of ​​the second platform is between 10% and 35%.

[0009] According to one aspect of the present invention, a light-emitting module is also provided, the light-emitting module comprising:

[0010] substrate;

[0011] A bonding layer is formed on the substrate;

[0012] A light-emitting diode is disposed on the top of a substrate and connected to the substrate via a bonding layer;

[0013] The light-emitting diode is the aforementioned light-emitting diode.

[0014] According to one aspect of the present invention, a light-emitting device is also provided, the light-emitting device comprising an encapsulation substrate and at least one light-emitting diode disposed on the encapsulation substrate, wherein the light-emitting diode is the light-emitting diode of any one of claims 1 to 17.

[0015] Compared with the prior art, the light-emitting diode, light-emitting module, and light-emitting device described in this invention have at least the following beneficial effects:

[0016] The light-emitting diode (LED) of the present invention includes a semiconductor stack comprising a first semiconductor layer, an active layer, and a second semiconductor layer stacked sequentially. The second semiconductor layer has a protrusion forming a first mesa, and a second mesa is formed around the first mesa. The upper surface of the first mesa is higher than the upper surface of the second mesa. In a top-view projection direction, the ratio of the area of ​​the first mesa to the area of ​​the second mesa is between 10% and 35%. Thus, the present invention, by setting the first and second mesa on the second semiconductor layer, restricts current away from the sidewalls, thereby suppressing the edge effect of the LED. Simultaneously, setting the area ratio of the first and second mesa avoids the problem of insufficient current buffering due to an excessively narrow second mesa or the problem of an excessively large second mesa affecting the overall light output power of the device, or introducing additional non-recombination paths, which is beneficial for high brightness, low forward voltage, and high reliability of the device.

[0017] Furthermore, the present invention also improves the design of the formation position, shape, or contour of the first and second countertops to further avoid edge effects. For example, the first countertop is located at the center of the second countertop, and the outer contour of the first countertop in the top view projection direction is a smooth curve without any concave or convex sharp corners.

[0018] The light-emitting device and light-emitting module of the present invention include the above-mentioned light-emitting diode and similarly possess the above-mentioned technical effects. Attached Figure Description

[0019] Figure 1 This is a top view of the structure of the light-emitting diode in an embodiment of the present invention;

[0020] Figure 2 for Figure 1 Cross-sectional view along the A-A' direction;

[0021] Figure 3 This is a schematic diagram of the structure after forming the semiconductor stack and the second contact electrode in an embodiment of the present invention;

[0022] Figure 4This is a schematic diagram of the structure after the first platform is formed in an embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram of the structure after the second and third platforms are formed in an embodiment of the present invention;

[0024] Figure 6 This is a top view of the light-emitting diode structure in an example of Embodiment 1 of the present invention;

[0025] Figure 7 This is a top view of the light-emitting diode structure in an example of Embodiment 1 of the present invention;

[0026] Figure 8 This is a top view of the light-emitting diode structure in an example of Embodiment 1 of the present invention;

[0027] Figure 9 This is a schematic diagram of the structure of the light-emitting module in an example of Embodiment 1 of the present invention;

[0028] Figure 10 This is a schematic diagram of the structure of the light-emitting module in an example of Embodiment 1 of the present invention;

[0029] Figure 11 This is a graph showing the change in the brightness (LOP) of the light-emitting diode as a function of the injection current (Current: 4μA~10μA) in an embodiment of the present invention.

[0030] Figure 12 This is a graph showing the change of the forward voltage (VF) of the light-emitting diode as a function of the injection current (Current: 2μA~10μA) in an embodiment of the present invention.

[0031] Figure 13 This is a graph showing the change in the brightness (LOP) of the light-emitting diode as a function of the injection current (Current: 0μA~100μA) in an embodiment of the present invention.

[0032] Figure 14 This is a graph showing the change of the forward voltage (VF) of the light-emitting diode with the injection current (Current: 0μA~100μA) in an embodiment of the present invention.

[0033] Illustration of reference numerals in the attached diagram:

[0034] 101, First semiconductor layer; 1011, Roughened structure; 102, Active layer; 103, Second semiconductor layer; 1031, Spacer layer; 1032, Confinement layer; 1033, Window layer; 110, First mesa; 111, First side; 112, Second side; 113, First sidewall; 120, Second mesa; 121, Third side; 122, Fourth side; 123, Second sidewall; 30, Third mesa;

[0035] 201, First contact electrode; 2011, Ohmic contact electrode; 2012, Connecting electrode; 202, Second contact electrode; 203, Support portion; 204, First pad electrode; 205, Second pad electrode;

[0036] 300, Insulating layer; 301, First opening; 302, Second opening;

[0037] 400. Bonding layer; 410. Substrate. Detailed Implementation

[0038] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0039] It should be understood that the illustrations provided in the embodiments of this invention are merely schematic representations of the basic concept of the invention. Although the illustrations only show components relevant to the invention and are not drawn according to the actual number, shape, and size of components in implementation, the shape, quantity, and proportion of each component can be arbitrarily changed in actual implementation, and the component layout may also be more complex. The structures, proportions, sizes, etc., shown in the accompanying drawings are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which this application can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives that the invention can produce, should still fall within the scope of the technical content disclosed in this application.

[0040] To further reduce the edge effect of light-emitting diodes (LEDs) and improve their brightness, this embodiment provides an LED, including:

[0041] A semiconductor stack includes a first semiconductor layer, an active layer, and a second semiconductor layer stacked sequentially.

[0042] The second semiconductor layer has a protrusion forming a first mesa, and a second mesa is formed around the first mesa, with the upper surface of the first mesa being higher than the upper surface of the second mesa.

[0043] In the top-view projection direction, the ratio of the area of ​​the first platform to the area of ​​the second platform is between 10% and 35%. As a result, the second platform can provide sufficient lateral resistance buffering, allowing current to be injected vertically from the first platform, significantly reducing the sidewall composite current, significantly improving the light output power, and reducing the forward voltage.

[0044] Optionally, in the top-view projection direction, the first platform is located at the center of the second platform, which is more conducive to the uniform distribution of the current vertically injected into the first platform and avoids current accumulation.

[0045] Optionally, the outer contour of the first platform in the top-view projection direction is a smooth curve, without any concave or convex sharp corners. Since there are no sharp corners on the first platform, the current density can be evenly distributed along the smooth sidewalls, avoiding current concentration at corners and further avoiding edge effects.

[0046] Optionally, the shape of the first tabletop in the top-view projection direction includes one or more of the following: circle, ellipse, square, regular hexagon, or rectangle, with each corner of the square, regular hexagon, or rectangle set as a rounded chamfer.

[0047] Optionally, in the top-view projection direction, the light-emitting diode has a first direction and a second direction that are perpendicular to each other. The first platform has a first side and a second side arranged adjacent to each other; the second platform has a third side and a fourth side arranged adjacent to each other; wherein the first side and the third side extend along the first direction, and the second side and the fourth side extend along the second direction. The first side is greater than or equal to the second side, and the third side is greater than or equal to the fourth side. Thus, through the shape and layout of the first platform and the second platform, the spacing between the edges of the first platform and the edges of the second platform can be made closer at various positions, avoiding the situation where current is injected along the first platform and current diffusion is faster in a certain direction, leading to current accumulation.

[0048] Optionally, the ratio of the length of the first side to the length of the third side is between 1:2 and 1:5, so as to make the current injection more uniform.

[0049] Optionally, the light-emitting diode further includes a second contact electrode formed on the first mesa and electrically connected to the second semiconductor layer. The second contact electrode of the light-emitting diode extends along the extension direction of the first side of the first mesa.

[0050] Optionally, the light-emitting diode also includes:

[0051] The second contact electrode is formed on the first mesa and is electrically connected to the second semiconductor layer.

[0052] Optionally, the area ratio of the first mesa to the area of ​​the second contact electrode is between 3:1 and 1:1, and the distance between the edge of the second contact electrode and the edge of the first mesa is between 0.5 μm and 3 μm. This avoids the influence of overlay accuracy on the etching of the first mesa, improving product yield.

[0053] Optionally, in the top-view projection direction, the shape of the second contact electrode includes one or more combinations of circles, ellipses, squares, regular hexagons or rectangles, with each corner of the square, regular hexagon or rectangle being rounded.

[0054] Optionally, the second platform has a radial width, which is the distance between the edge of the first platform and the edge of the second platform, and the radial width of the second platform is between 3 μm and 6 μm.

[0055] Optionally, the second semiconductor layer includes a spacer layer, a confinement layer, and a window layer stacked sequentially on the active layer, wherein the spacer layer is covered by the confinement layer, the first mesa is the surface of the window layer, and the second mesa is the surface of the spacer layer not covered by the confinement layer.

[0056] Optionally, the distance from the upper surface of the second mesa to the upper surface of the active layer is less than 0.1 μm, so that the surface of the second mesa can be closer to the quantum well structure in the active layer without causing damage to the active layer, which is more conducive to improving the luminous efficiency of the light-emitting diode.

[0057] Optionally, the first platform has a first sidewall, and the second platform has a second sidewall. The inclination angle of the first sidewall is 50° to 70°, and the inclination angle of the second sidewall is 50° to 70°. The angle settings of the two sidewalls give the sidewalls higher resistance and energy barrier, thus blocking leakage current.

[0058] Optionally, the light-emitting diode also includes:

[0059] The third platform is disposed adjacent to the second platform, and the third platform exposes the first semiconductor layer.

[0060] Optionally, the light-emitting diode also includes:

[0061] The first contact electrode forms an electrical connection with the first semiconductor layer;

[0062] The second contact electrode is formed on the first mesa and is electrically connected to the second semiconductor layer.

[0063] An insulating layer covers the semiconductor stack and the first contact electrode, and a first opening and a second opening are formed on the insulating layer;

[0064] The support portion is formed on the insulating layer;

[0065] The first pad electrode is disposed on the insulating layer and electrically connected to the first contact electrode through the first opening;

[0066] The second pad electrode is disposed on the insulating layer and the support portion, and is electrically connected to the second contact electrode through the second opening.

[0067] This embodiment also provides a light-emitting module, which includes:

[0068] substrate;

[0069] A bonding layer is formed on the substrate;

[0070] A light-emitting diode is disposed on the top of a substrate and connected to the substrate via a bonding layer; the light-emitting diode is the aforementioned light-emitting diode.

[0071] This embodiment also provides a light-emitting device, which includes an encapsulation substrate and at least one light-emitting diode disposed on the encapsulation substrate, wherein the light-emitting diode is the aforementioned light-emitting diode.

[0072] The present invention will now be described in detail with reference to specific embodiments.

[0073] Example 1

[0074] This embodiment provides a light-emitting diode (LED) comprising a semiconductor stack. Optionally, during the fabrication of the LED, a substrate (not shown in the figure) is also formed on the LED. Figure 2 The semiconductor stack includes a first semiconductor layer 101, an active layer 102, and a second semiconductor layer 103 sequentially stacked on a substrate. Optionally, the substrate can be a gallium arsenide substrate. In the final product, the substrate is peeled off from the first semiconductor layer 101 to remove the substrate and expose the first semiconductor layer 101. Optionally, the surface of the exposed first semiconductor layer 101 is further roughened with a roughened structure 1011 to further improve luminous efficiency.

[0075] The first semiconductor layer 101 can be an N-type semiconductor layer, which can provide electrons to the active layer 102 under the action of current. The first semiconductor layer 101 can be an electron-providing material layer by N-type doping. The N-type semiconductor layer can be doped with N-type dopants such as Si, Ge or Sn.

[0076] An active layer 102 is disposed on the first semiconductor layer 101, and the active layer 102 is the region where electron and hole recombination generates light. The active layer 102 can be a quantum well (QW) structure, comprising multiple periodically stacked well layers and barrier layers, such as AlGaN / AlGaN, InAlGaN / InAlGaN, InGaN / AlGaN, AlGaInP / AlGaInP, etc., multi-quantum-well structures. Furthermore, the composition and thickness of the well layers within the active layer 102 determine the wavelength of the light. To improve the luminous efficiency of the active layer 102, the luminous efficiency can be improved by changing the concentration of quantum wells, the number of paired quantum wells and quantum barriers, the thickness, and / or other characteristics within the active layer 102.

[0077] The second semiconductor layer 103 can be a P-type semiconductor layer, which can provide holes to the active layer 102 under the action of a power source. The second semiconductor layer 103 can be a hole-providing material layer by P-type doping, and the P-type semiconductor layer can be doped with P-type dopants such as Mg, Zn, Ca, Sr or Ba. Optionally, the light-emitting diode is a Micro-LED with a side length dimension of less than 50 μm.

[0078] As chip sizes continue to shrink (e.g., direct-view TVs <50μm, wearable devices <30μm, VR / AR <10μm), edge effects caused by sidewall etching damage become increasingly prominent, especially for GaAs-based Micro-LEDs. This can lead to uneven current distribution, uneven light emission, heat accumulation, decreased light extraction efficiency, and increased reliability risks. To suppress edge effects, the inventors formed two mesas of different heights in the second semiconductor layer 103: a centrally protruding first mesa 110 for direct vertical current injection, and a surrounding second mesa 120 (lower in height, still retaining part of the second semiconductor layer 103) for buffering sidewall recombination current. This structure alleviates current congestion to some extent and improves light emission uniformity.

[0079] However, in actual device fabrication and application, it has been found that such a setup cannot suppress edge effects to the greatest extent. Uneven current distribution, uneven light emission, and heat accumulation still exist. Further improvements are needed to suppress edge effects, improve light emission uniformity, and enhance light extraction efficiency and reliability.

[0080] Based on this, the inventors discovered during the research and development process that the relative size (area ratio) of the first mesa 110 and the second mesa 120 has a decisive influence on the suppression effect of edge effects. If the area of ​​the first mesa 110 is too large and the area of ​​the second mesa 120 is too narrow, the buffering effect is insufficient, and sidewall recombination still dominates, resulting in limited brightness improvement and abnormal forward voltage. Conversely, if the area of ​​the first mesa 110 is too small and the area of ​​the second mesa 120 is too wide, the effective light-emitting area is significantly reduced, the overall light output power of the device decreases, and an excessively large area of ​​the second mesa 120 may introduce additional non-radiative recombination paths, ultimately affecting the high brightness, low forward voltage, and high reliability of the device.

[0081] Therefore, referring to Figure 1 In this embodiment, the area ratio of the first platform 110 and the second platform 120 is designed. In the top projection direction, the ratio of the area of ​​the first platform 110 to the area of ​​the second platform 120 is controlled within the range of 10% to 35%, which can effectively improve the brightness of the light-emitting diode and reduce the forward voltage.

[0082] Specifically, in this embodiment, the second semiconductor layer 103 has a protrusion forming a first mesa 110, and a second mesa 120 is formed around the first mesa 110. The upper surface of the first mesa 110 is higher than the upper surface of the second mesa 120. In a top-view projection direction, the ratio of the area of ​​the first mesa 110 to the area of ​​the second mesa 120 is between 10% and 35%. Optionally, the ratio of the area of ​​the first mesa 110 to the area of ​​the second mesa 120 is between 15% and 20%, for example, 18% or 20%. Thus, the second mesa 120 can provide sufficient lateral resistance buffering, allowing current to be vertically injected from the first mesa 110, significantly reducing sidewall recombination current and significantly improving optical output power.

[0083] Reference Figures 3-5 The first mesa 110 can be formed by etching a portion of the thickness of the second semiconductor layer 103 downwards from its surface. The first mesa 110 is the unetched portion of the second semiconductor layer 103. Optionally, etching continues downwards from the edge of the exposed mesa in the second semiconductor layer 103 until the first semiconductor layer 101 is exposed. The exposed first semiconductor layer 101 forms the third mesa 130. The portion exposed after the first etching but not etched during the second etching process forms the second mesa 120. The third mesa 130 is used to form the first contact electrode 201 electrically connected to the first semiconductor layer 101. At this time, the light-emitting diode is formed as a flip-chip. Of course, when the light-emitting diode is a vertical structure, the mesa exposed after the first etching forms the second mesa 120. This embodiment uses a flip-chip light-emitting diode as an example for explanation. Optionally, in the top-view projection direction, the area of ​​the third mesa 130 is larger than the area of ​​the second mesa 120.

[0084] Optionally, refer to Figure 2 The second semiconductor layer 103 includes a spacer layer 1031, a confinement layer 1032, and a window layer 1033 sequentially stacked on the active layer 102. Specifically, the confinement layer 1032 is located between the spacer layer 1031 and the window layer 1033, and the spacer layer 1031 connects to the active layer 102. The spacer layer 1031 can be made of aluminum indium phosphide (AIP) to prevent dopant atoms from diffusing into the active layer 102 and causing defects. The confinement layer 1032 can be made of AIP to provide holes. The window layer 1033 can be made of gallium phosphide (GaP) and can be used for current spreading, guiding light emission from the active layer 102, and serving as a surface ohmic contact. The confinement layer 1032 covers a portion of the spacer layer 1031. In this embodiment, the first mesa 110 is the surface of the window layer 1033, and the second mesa 120 is the surface of the spacer layer 1031 not covered by the confinement layer 1032. In other words, a portion of the confinement layer 1032 and window layer 1033 of the second semiconductor layer 103 will be removed to expose the spacer layer 1031, thereby forming a first mesa 110 and a second mesa 120. The first mesa 110 is located in the middle region of the second semiconductor layer 103, or in other words, the first mesa 110 is located at the center of the second mesa 120. The surfaces of the window layer 1033 and the spacer layer 1031 not covered by the confinement layer 1032 are both horizontal surfaces.

[0085] Optionally, to further reduce the edge effect, refer to Figure 1 The first platform 110 has a smooth, curved outer contour in its top-view projection direction, without any concave or convex sharp corners. Therefore, since the first platform 110 has no sharp corners, the current density can be evenly distributed along the smooth sidewalls, avoiding current concentration at corners and further preventing edge effects. Optionally, the shape of the first platform 110 in its top-view projection direction includes one or more combinations of a circle, ellipse, square, regular hexagon, or rectangle, with each corner of the square, regular hexagon, or rectangle being rounded. In one example, refer to... Figure 1 and 7 The first platform 110 is rectangular in shape. In one example, refer to... Figure 6 The first platform is square in shape. In one example, refer to... Figure 8 The first tabletop is circular in shape.

[0086] Optionally, refer to Figure 1 , Figure 6 or Figure 7In a top-view projection direction, the light-emitting diodes have a first direction and a second direction that are perpendicular to each other. The first mesa 110 has adjacent first sides 111 and 112, and the second mesa 120 has adjacent third sides 121 and 122. The first side 111 and the third side 121 extend along the first direction, and the second side 112 and the fourth side 122 extend along the second direction. The first side 111 is greater than or equal to the second side 112, and the third side 121 is greater than or equal to the fourth side 122. Optionally, the ratio of the length of the first side to the length of the third side is between 1:2 and 1:5. Therefore, through the shape arrangement of the first mesa 110 and the second mesa 120, the distance between the edge of the first mesa 110 and the edge of the second mesa 120 can be made closer at various locations, avoiding current injection along the first mesa 110 and the situation where current diffusion is faster in a certain direction, leading to current accumulation. In one example, refer to... Figure 1 The first side of the first platform 110 is larger than the second side 112, and the third side 121 of the second platform 120 is larger than the second side 122. Thus, the long side of the first platform 110 corresponds to the long side of the second platform 120, and the distance from the edge of the second platform 120 to the edge of the first platform 110 tends to be consistent at various locations, which is beneficial for uniform current distribution. In one example, refer to... Figure 6 In this design, the first side of the first platform 110 is equal to the second side 112, and the third side 121 of the second platform 120 is equal to the second side 122. This design is also more conducive to the uniform distribution of current. In one example, refer to... Figure 7 The first platform 110 is rectangular, and the second platform 120 is square. The area ratio of the two platforms is greater than 20%, which also contributes to improving the brightness of the LED. In one example, refer to... Figure 8 The first mesa 110 is circular, and the second mesa 120 is square. As a result, the current density is uniformly distributed along the circumference, and the sidewall area of ​​the first mesa 110 formed by this shape is the smallest, resulting in the lowest surface recombination loss.

[0087] Optionally, refer to Figure 1 or Figure 2 The second platform 120 has a radial width D1, which is the distance between the edge of the first platform 110 and the edge of the second platform 120. Optionally, the radial width D1 of the second platform 120 is between 3 μm and 6 μm.

[0088] Optionally, refer to Figure 2 The distance H1 between the upper surface of the first platform 110 and the upper surface of the second platform 120 is between 0.5 μm and 0.8 μm. For example, 0.5 μm, 0.6 μm, 0.7 μm, and 0.8 μm.

[0089] Optionally, refer to Figure 2The distance H1 between the upper surface of the first mesa 110 and the upper surface of the second mesa 120 is less than the thickness of the second semiconductor layer 103, and the distance H2 between the upper surface of the second mesa 120 and the upper surface of the active layer 102 is less than 0.1 μm, so that the surface of the second mesa 120 can be closer to the quantum well structure in the active layer 102 without causing damage to the active layer 102, which is more conducive to improving the luminous efficiency of the light-emitting diode.

[0090] Optionally, refer to Figure 2 The first platform 110 has a first sidewall 113, and the second platform 120 has a second sidewall 123. The tilt angle α1 of the first sidewall 113 is 50°~70°, and the tilt angle α2 of the second sidewall 123 is 50°~70°. For example, both tilt angles α1 and α2 are 60°. The angle settings of the two sidewalls give the sidewalls higher resistance and energy barrier, blocking sidewall leakage current.

[0091] Optionally, refer to Figure 2 The light-emitting diode also includes a first contact electrode 201 and a second contact electrode 202. The first contact electrode 201 is formed on a third mesa 130 and forms an electrical connection with the first semiconductor layer 101 exposed on the third mesa 130. Optionally, the first contact electrode 201 can be a single-layer, double-layer, or multi-layer structure. For example, it can be a stacked structure such as Ti / Al, Ti / Al / Ti / Au, Ti / Al / Ni / Au, V / Al / Pt / Au, AuGe, AuGeNi, etc. Optionally, the first contact electrode 201 includes an ohmic contact electrode 2011 and a connecting electrode 2012, wherein the ohmic contact electrode 2011 is used to form an ohmic contact with the first semiconductor layer 101, and the connecting electrode 2012 is used to connect the ohmic contact electrode 2011 and the subsequently formed pad electrode, and serves to elevate the first pad electrode 204 to a position equal to the height of the other pad electrode to facilitate the transfer or die bonding of the light-emitting diode. Optionally, the difference between the vertical distance H3 between the first mesa 110 and the third mesa 130 and the height of the first contact electrode 201 is less than 0.3 μm, which is beneficial to the subsequent Micro-LED mass transfer process.

[0092] Reference Figure 2The second contact electrode 202 is formed on the first mesa 110 and is electrically connected to the second semiconductor layer 103. The second contact electrode 202 can be made of a transparent conductive material or a metallic material. Optionally, the second contact electrode 202 is made of a transparent conductive material, such as indium tin oxide, zinc indium oxide, indium oxide, tin oxide, cadmium tin oxide, tin antimony oxide, etc. Optionally, the area of ​​the second contact electrode 202 is less than or equal to the area of ​​the first mesa 110. Due to process overlay precision issues, the area of ​​the first mesa 110 is larger than the area of ​​the second contact electrode 202. In this embodiment, the step of forming the first mesa 110 includes: firstly, referring to... Figure 3 A first semiconductor layer 101, an active layer 102, and a second semiconductor layer 103 are sequentially formed above the substrate 100. A second contact electrode 202 is formed on the second semiconductor layer 103. (Refer to...) Figure 4 The second semiconductor layer 103 is etched to a certain depth based on the second contact electrode 202 to form a first mesa 110. Subsequent etching of the etched mesa exposes portions of the first semiconductor layer 101, forming a second mesa 120 and a third mesa 130. In this embodiment, the area ratio of the first mesa 110 to the area of ​​the second contact electrode 202 is between 3:1 and 1:1, which avoids the influence of overlay accuracy on the etching of the first mesa 110 and improves product yield. Optionally, the distance D2 between the edge of the second contact electrode 202 and the edge of the first mesa 110 is between 0.5 μm and 3 μm. Optionally, the second contact electrode 202 extends along the extension direction of the first side 111 of the first mesa 110 to improve the uniformity of the current distribution injected into the first mesa 110. Optionally, in the first direction (parallel to the extension direction of the first side 111), the distance D2 between the edge of the second contact electrode 202 and the edge of the first platform is between 1.5 μm and 3.0 μm, and in the second direction perpendicular to the first direction, D2 is between 0.5 μm and 1.0 μm.

[0093] Optionally, in the top-view projection direction, the shape of the second contact electrode 202 includes one or more combinations of a circle, ellipse, square, regular hexagon, or rectangle, with each corner of the square, regular hexagon, or rectangle being rounded. For example... Figure 8 As shown, the shape of the second contact electrode 202 can be the same as or different from the shape of the first mesa 110, such as... Figure 7 As shown. This embodiment does not impose any limitations on this.

[0094] Reference Figure 2An insulating layer 300 covers the semiconductor stack and the first contact electrode 201, and the insulating layer 300 has a first opening 301 and a second opening 302. The material of the insulating layer 300 can be one or more of silicon dioxide, silicon nitride, silicon oxynitride, titanium oxide, aluminum oxide, tantalum oxide, or niobium oxide. Alternatively, the insulating layer 300 can also be a Bragg reflector (DBR) formed by repeatedly stacking two materials with different refractive indices. The insulating layer 300 completely covers the second mesa 120 and the sidewall region of the second mesa 120 to protect the edges of the light-emitting diode and reduce nonradiative recombination caused by surface defects.

[0095] Optionally, refer to Figure 2 The light-emitting diode also includes a support portion 203. The support portion 203 is disposed on the insulating layer 300 and is used to support the second pad electrode 205 subsequently formed above the insulating layer 300. Optionally, the support portion 203 can be an insulating material or a metallic material, as long as it fulfills its supporting function. Further, to further improve light extraction efficiency, the support portion 203 can have mirror properties to reflect light incident on the pad electrode, preventing light absorption by the pad electrode. For example, the material of the support portion 203 includes gold, silver, or aluminum. Optionally, the material of the support portion 203 is a stack of metallic materials such as Cr, Ti, Ni, Pt, and Au. Optionally, the difference between the height of the support portion 203 and the vertical distance H1 from the upper surface of the first mesa 110 to the upper surface of the second mesa 120 is less than 0.3 μm, effectively improving the flatness above the second mesa 120, which will benefit subsequent Micro-LED mass transfer processes.

[0096] Reference Figure 2A first pad electrode 204 is disposed on the insulating layer 300 and electrically connected to the first contact electrode 201 through a first opening 301. A second pad electrode 205 is disposed on the insulating layer 300 and the support portion 203 and electrically connected to the second contact electrode 202 through a second opening 302. The first pad electrode 204 and the second pad electrode 205 can be metal pads and can be formed together in the same process using the same material, thus having the same layer structure. The first pad electrode 204 and the second pad electrode 205 can be composed of stacked metal materials such as vapor-deposited Cr, Ti, Ni, Pt, Au, etc., and can also have metal mirror characteristics. Optionally, the height difference between the upper surface of the first pad electrode 204 and the upper surface of the second pad electrode 205 on the same horizontal plane parallel to the substrate 100 is less than 0.3 μm (in the figure, the upper surfaces of the first pad electrode 204 and the second pad electrode 205 are flush, and the height difference is 0). Optionally, the distance D3 between the first pad electrode 204 and the second pad electrode 205 along the direction parallel to the substrate 100 is less than 20 μm to improve surface flatness and enhance the performance of the light-emitting diode. Optionally, in the top-view projection direction, the area of ​​the second pad electrode 205 is smaller than the sum of the areas of the first mesa 110 and the support portion 203, so that the second pad electrode 205 formed above the first mesa 110 and the support portion 203 is better supported, avoiding flatness problems during fabrication that could lead to abnormal skew during subsequent mass transfer and result in yield loss.

[0097] The performance of the three LED products in this embodiment is tested below. In the first sample, the size of the first mesa 110 is 5.5 × 3.5 μm (the area of ​​the first mesa 110 / second mesa 120 is approximately 11%). In the second sample, the size of the first mesa 110 is 5.5 × 5.5 μm (the area of ​​the first mesa 110 / second mesa 120 is approximately 18.1%). In the third sample, the size of the first mesa 110 is 5.5 × 9.5 μm (the area of ​​the first mesa 110 / second mesa 120 is approximately 29%). The distance from the upper surface of the first mesa 110 to the upper surface of the second mesa 120 is 6300 Å in all samples, and other structures and parameters are also the same. The test results are referenced... Figures 11-14 Analysis of the test results shows that the brightness of the three samples was improved to varying degrees. The second sample showed the greatest brightness improvement under both high and low current conditions, exhibiting the best light enhancement effect. At 10uA, it can improve luminous efficiency by more than 30%, and the higher the operating current, the greater the improvement in luminous efficiency. This not only solves the efficiency improvement problem in low-current-density operation of small-sized wearable applications such as watches, but also contributes significantly to luminous efficiency improvement in high-current-density applications such as TVs or AR / VR.

[0098] Example 2

[0099] This embodiment provides a light-emitting module, which includes a substrate 410, a bonding layer 400, and light-emitting diodes (LEDs). The bonding layer 400 is formed on the substrate 410, and the LEDs are bonded to the substrate through the bonding layer 400. The LEDs are the LEDs in Embodiment 1, and the number of LEDs can be one or more. When the number of LEDs is multiple, the multiple LEDs are spaced apart on the top of the substrate.

[0100] Specifically, refer to Figure 9 The bonding layer 400 covers the insulating layer 300, the first pad electrode 204, and the second pad electrode 205 of the light-emitting diode. The substrate 410 is disposed on the side of the bonding layer 400 away from the semiconductor stack of the light-emitting diode. Optionally, the surface of the first semiconductor layer 101 of the semiconductor stack is provided with a roughened structure 1011 to further improve the light extraction efficiency of the light-emitting diode. Optionally, the substrate 410 is a sapphire substrate 410, and optionally, the material of the bonding layer 400 can be BCB material or PI material.

[0101] In this embodiment, the light-emitting diode can be replaced with a substrate 410 by wafer bonding combined with laser lift-off (LLO) process, and the first semiconductor layer 101 can be roughened to further improve the light extraction efficiency of the light-emitting diode.

[0102] Example 3

[0103] This embodiment provides a light-emitting module, which includes a substrate 410, a bonding layer 400, and light-emitting diodes (LEDs). The bonding layer 400 is formed on the substrate 410, and the LEDs are bonded to the substrate through the bonding layer 400. The LEDs are the LEDs described in Embodiment 1, and the number of LEDs can be one or more. When there are multiple LEDs, they are spaced apart on the top of the substrate.

[0104] Specifically, refer to Figure 10 The bonding layer 400 covers the surface of the first semiconductor layer 101 of the semiconductor stack, and the substrate 410 is disposed on the side of the bonding layer 400 away from the light-emitting diode semiconductor stack. Optionally, the surface of the first semiconductor layer 101 of the semiconductor stack is provided with a roughened structure 1011 to further improve the light extraction efficiency of the light-emitting diode. Optionally, the substrate 410 is a sapphire substrate 410, and optionally, the material of the bonding layer 400 can be BCB material or PI material.

[0105] Example 4

[0106] This embodiment provides a light-emitting device, which includes a packaging substrate and a light-emitting diode disposed on the packaging substrate. The light-emitting diode is the light-emitting diode in Embodiment 1.

[0107] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A light-emitting diode, characterized in that, include: A semiconductor stack includes a first semiconductor layer, an active layer, and a second semiconductor layer stacked sequentially. The second semiconductor layer has a protrusion that forms a first mesa, and a second mesa is formed around the first mesa, with the upper surface of the first mesa being higher than the upper surface of the second mesa. In the top-view projection direction, the ratio of the area of ​​the first platform to the area of ​​the second platform is between 10% and 35%.

2. The light-emitting diode according to claim 1, characterized in that, In a top-down projection direction, the first platform is located at the center of the second platform.

3. The light-emitting diode according to claim 1, characterized in that, The outer contour of the first platform in the top-view projection direction is a smooth curve, without any concave or convex sharp corners.

4. The light-emitting diode according to claim 1, characterized in that, The shape of the first platform in the top-view projection direction includes one or a combination of one or more of the following: circle, ellipse, square, regular hexagon, or rectangle, and each corner of the square, the regular hexagon, or the rectangle is set as a rounded chamfer.

5. The light-emitting diode according to claim 1, characterized in that, In the top-view projection direction, the light-emitting diode has a first direction and a second direction that are perpendicular to each other. The first platform has a first side and a second side that are adjacent to each other. The second platform has a third side and a fourth side that are adjacent to each other. The first side and the third side extend along the first direction, and the second side and the fourth side extend along the second direction. The first side is greater than or equal to the second side, and the third side is greater than or equal to the fourth side.

6. The light-emitting diode according to claim 5, characterized in that, The ratio of the length of the first side to the length of the third side is between 1:2 and 1:

5.

7. The light-emitting diode according to claim 5, characterized in that, The light-emitting diode further includes a second contact electrode, which is formed on the first mesa and electrically connected to the second semiconductor layer. The second contact electrode of the light-emitting diode extends along the extension direction of the first side of the first mesa.

8. The light-emitting diode according to claim 1, characterized in that, The light-emitting diode also includes: The second contact electrode is formed on the first mesa and is electrically connected to the second semiconductor layer.

9. The light-emitting diode according to claim 8, characterized in that, The ratio of the area of ​​the first platform to the area of ​​the second contact electrode is between 3:1 and 1:1, and the distance between the edge of the second contact electrode and the edge of the first platform is between 0.5 μm and 3 μm.

10. The light-emitting diode according to claim 8, characterized in that, In the top-view projection direction, the shape of the second contact electrode includes one or a combination of one or more of the following: circle, ellipse, square, regular hexagon, or rectangle, wherein each corner of the square, the regular hexagon, or the rectangle is set as a rounded chamfer.

11. The light-emitting diode according to claim 1, characterized in that, The second platform has a radial width, which is the distance between the edge of the first platform and the edge of the second platform, and the radial width of the second platform is between 3 μm and 6 μm.

12. The light-emitting diode according to claim 1, characterized in that, The second semiconductor layer includes a spacer layer, a confinement layer, and a window layer stacked sequentially on the active layer. The confinement layer covers a portion of the spacer layer. The first mesa is the surface of the window layer, and the second mesa is the surface of the spacer layer not covered by the confinement layer.

13. The light-emitting diode according to claim 1, characterized in that, The distance from the upper surface of the second platform to the upper surface of the active layer is less than 0.1 μm.

14. The light-emitting diode according to claim 1, characterized in that, The first tabletop has a first sidewall, and the second tabletop has a second sidewall. The inclination angle of the first sidewall is 50° to 70°, and the inclination angle of the second sidewall is 50° to 70°.

15. The light-emitting diode according to claim 1, characterized in that, The light-emitting diode also includes: A third platform is disposed adjacent to the second platform, and the third platform exposes the first semiconductor layer.

16. The light-emitting diode according to claim 1, characterized in that, The light-emitting diode also includes: The first contact electrode forms an electrical connection with the first semiconductor layer; The second contact electrode is formed on the first mesa and is electrically connected to the second semiconductor layer. An insulating layer covers the semiconductor stack and the first contact electrode, and a first opening and a second opening are formed on the insulating layer; The support portion is formed on the insulating layer; The first pad electrode is disposed on the insulating layer and electrically connected to the first contact electrode through the first opening; The second pad electrode is disposed on the insulating layer and the support portion, and is electrically connected to the second contact electrode through the second opening.

17. A light-emitting module, characterized in that, The light-emitting module includes: substrate; A bonding layer is formed on the substrate; A light-emitting diode is disposed above the substrate and connected to the substrate through the bonding layer; The light-emitting diode is any one of claims 1 to 16.

18. A light-emitting device, characterized in that, The light-emitting device includes a packaging substrate and at least one light-emitting diode disposed on the packaging substrate, wherein the light-emitting diode is any one of claims 1 to 16.

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