Micro light-emitting device

Abstract

An embodiment provides a micro light-emitting device comprising: a semiconductor structure including a first conductive-type semiconductor layer, a second conductive-type semiconductor layer, an active layer disposed between the first conductive-type semiconductor layer and the second conductive-type semiconductor layer, and an optical layer disposed between the second conductive-type semiconductor layer and the active layer; a first electrode electrically connected to the first conductivity-type semiconductor layer; and a second electrode electrically connected to the second conductive-type semiconductor layer, wherein: the optical layer includes a current blocking area formed at the edge thereof and a current path area formed at the center thereof; the first conductive-type semiconductor layer is doped with a first dopant; and the second conductive-type semiconductor layer and the optical layer are doped with a second dopant.

Description

Micro light-emitting devices

[0001] The embodiment relates to a micro light-emitting device.

[0002] Light-emitting diodes (LEDs) are light-emitting devices that emit light when current is applied. Because LEDs can emit high-efficiency light at low voltages, they offer significant energy savings. Recently, the brightness of LEDs has been significantly improved, leading to their widespread use in various devices, including backlight units for liquid crystal displays (LCDs), electronic billboards, indicators, and home appliances.

[0003] Light-emitting devices containing compounds such as AlGaAs, AlGaInP, and AlInGaN have many advantages, such as having a wide and easily tunable band gap energy, and can be used in various ways, such as light-emitting devices, light-receiving devices, and various diodes.

[0004] In particular, light-emitting devices such as light-emitting diodes (LEDs) or laser diodes using semiconductor materials of groups 3-5 or 2-6 can produce various colors such as red, green, blue, and ultraviolet rays through the development of thin film growth technology and device materials, and can also produce efficient white light by using fluorescent materials or combining colors. Compared to existing light sources such as fluorescent lamps and incandescent lamps, they have the advantages of low power consumption, semi-permanent lifespan, fast response speed, safety, and environmental friendliness.

[0005] Recently, research is being conducted on a technology to manufacture light-emitting diodes in micro sizes and use them as pixels in displays.

[0006] The embodiment can provide a micro light-emitting device capable of reducing leakage current.

[0007] The embodiment can provide a micro light-emitting device with improved light-emitting efficiency.

[0008] The embodiment can provide a micro light-emitting device with improved light extraction efficiency.

[0009] The problem to be solved in the embodiment is not limited to this, and it can be said that the purpose or effect that can be understood from the solution or implementation form of the problem described below is also included.

[0010] According to one feature of the present invention, a micro light-emitting device comprises a semiconductor structure including a first conductive semiconductor layer; a second conductive semiconductor layer; an active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer; and an optical layer disposed between the second conductive semiconductor layer and the active layer; a first electrode electrically connected to the first conductive semiconductor layer; and a second electrode electrically connected to the second conductive semiconductor layer, wherein the optical layer includes a current blocking region formed at an edge and a current pass region formed at a center, wherein the first conductive semiconductor layer is doped with a first dopant, and the second conductive semiconductor layer and the optical layer are doped with a second dopant.

[0011] The area of ​​the above current blocking region may be wider than the above current pass region.

[0012] The doping concentration of the optical layer may be higher than the doping concentration of the second conductive semiconductor layer.

[0013] The second dopant doped in the optical layer and the dopant doped in the second conductive semiconductor layer may be of different types.

[0014] The second dopant doped into the optical layer may be carbon, and the dopant doped into the second conductive semiconductor layer may be magnesium or carbon.

[0015] The optical layer may include a first sub-layer, a third sub-layer, and a second sub-layer disposed between the first sub-layer and the third sub-layer.

[0016] The first sub-layer and the third sub-layer may have the same composition, and the second sub-layer may have a different composition from the first sub-layer and the third sub-layer.

[0017] According to an embodiment, the luminescence efficiency can be improved by preventing electrons in the active layer from passing through without participating in luminescence.

[0018] Additionally, the leakage current of the micro light-emitting element can be reduced, thereby improving the light-emitting efficiency.

[0019] Additionally, light extraction efficiency can be improved.

[0020] The various advantageous and beneficial effects of the present invention are not limited to the above-described contents, and will be more easily understood in the course of explaining specific embodiments of the present invention.

[0021] FIG. 1 is a cross-sectional view of a micro light-emitting device according to one embodiment of the present invention.

[0022] FIG. 2 is a drawing showing a state in which a micro light-emitting device according to one embodiment of the present invention is electrically connected to a substrate.

[0023] Figure 3 is a simulation result showing the change in lateral leakage current according to the change in the size of the micro light-emitting element.

[0024] Figure 4 is a simulation result showing the change in effective injection current according to the change in the width of the oxidation region.

[0025] Figure 5 is a diagram showing the energy band gap of a typical micro light-emitting device.

[0026] FIG. 6 is a drawing showing the energy band gap of a micro light-emitting device according to one embodiment of the present invention.

[0027] FIG. 7 is a drawing showing an optical layer of a micro light-emitting device according to another embodiment of the present invention.

[0028] FIG. 8 is a drawing showing an optical layer of a micro light-emitting device according to another embodiment of the present invention.

[0029] FIG. 9 is a drawing showing an optical layer of a micro light-emitting device according to another embodiment of the present invention.

[0030] Figure 10 is a simulation result showing that the energy band gap changes as the doping concentration of the optical layer increases.

[0031] Figure 11 is a simulation result showing that the optical output changes as the doping concentration of the optical layer increases.

[0032] Figure 12 is a simulation result showing that the external quantum efficiency changes as the doping concentration of the optical layer increases.

[0033] Figure 13 is a simulation result showing that the driving voltage changes as the doping concentration of the optical layer increases.

[0034] Figure 14 is a simulation result showing the light output according to the size change of a micro light-emitting device having the same current blocking area.

[0035] Fig. 15 is a first modified example of Fig. 1.

[0036] Fig. 16 is a second modified example of Fig. 1.

[0037] FIG. 17a and FIG. 17b are drawings showing a method for manufacturing a micro light-emitting device according to one embodiment of the present invention.

[0038] FIGS. 18a to 18d are drawings showing a method for manufacturing a micro light-emitting device according to another embodiment of the present invention.

[0039] Figure 19 is a drawing showing the light extraction efficiency of a typical micro light-emitting device.

[0040] FIG. 20 is a drawing showing the light extraction efficiency of a micro light-emitting device according to one embodiment of the present invention.

[0041] FIG. 21 is a drawing of a display device according to one embodiment of the present invention.

[0042] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated and described in the drawings. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0043] Terms including ordinal numbers, such as "second," "first," etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, a second component may be referred to as a "first component," and similarly, a first component may also be referred to as a "second component." The term "and / or" includes a combination of multiple related items described herein or any of multiple related items described herein.

[0044] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0045] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0046] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0047] Hereinafter, embodiments will be described in detail with reference to the attached drawings. Regardless of the drawing numbers, identical or corresponding components are given the same reference numbers, and redundant descriptions thereof will be omitted.

[0048] In addition, the micro light-emitting device according to the present embodiment may be a light-emitting device having a micro size or a nano size. The micro light-emitting device may have a size of 1 μm to 100 μm, but is not necessarily limited thereto.

[0049] Fig. 1 is a cross-sectional view of a micro light-emitting device according to one embodiment of the present invention. Fig. 2 is a drawing showing a state in which a micro light-emitting device according to one embodiment of the present invention is electrically connected to a substrate.

[0050] Referring to FIGS. 1 and 2, a micro light-emitting device according to an embodiment may include a light-emitting structure (CS1) and electrodes (91, 92). The light-emitting structure (CS1) may include a first conductive semiconductor layer (30), an active layer (40), an optical layer (60), and a second conductive semiconductor layer (70).

[0051] The light-emitting structure (CS1) may have a structure in which a first conductive semiconductor layer (30), an active layer (40), an optical layer (60), and a second conductive semiconductor layer (70) are sequentially laminated. A substrate (10) and a buffer layer (20) may be formed at the bottom of the light-emitting structure (CS1). The substrate (10) and the buffer layer (20) may be removed during the process of transferring the micro light-emitting element to the panel. However, the present invention is not limited thereto, and the substrate (10) and the buffer layer (20) may be transferred to the panel without being removed.

[0052] The substrate (10) may be formed of a material or carrier wafer suitable for semiconductor material growth, may be formed of a material with excellent thermal conductivity, and may include a conductive material or an insulating material. For example, at least one of sapphire (Al2O3), SiO2, SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge, and Ga2O3 may be used.

[0053] The buffer layer (20) may be disposed between the substrate (10) and the light-emitting structure (CS1). When the light-emitting structure (CS1) is disposed on the substrate (10), dislocations, melt-back, cracks, pits, and surface morphology defects that deteriorate crystallinity can be prevented. The buffer layer (20) may be at least one of InP, GaAs, GaN, AlGaN, and AlN, but is not necessarily limited thereto.

[0054] The light-emitting structure (CS1) can be formed using a method such as Metal Organic Chemical Vapor Deposition (MOCVD), Chemical Vapor Deposition (CVD), Plasma-Enhanced Chemical Vapor Deposition (PECVD), Molecular Beam Epitaxy (MBE), Hydride Vapor Phase Epitaxy (HVPE), or Sputtering.

[0055] The first conductive semiconductor layer (30) can be implemented as a compound semiconductor of group III-V, group II-VI, etc., and a first dopant can be doped into the first conductive semiconductor layer (30). The first conductive semiconductor layer (30) is A x B y C (1-x-y) D z E (1-z) It may be a semiconductor material having a composition formula of (0≤x≤1, 0≤y≤1, 0≤x+y≤1, 0≤z≤1). Here, A, B, C may be one of Al, Ga, and In, and D, E may be one of As, P, N, and Sb.

[0056] For example, the first conductive semiconductor layer (30) may be formed of one or more of GaN, InGaN, InAlGaN, AlGaAs, GaP, GaAs, GaAsP, AlGaInP, InGaAsP, InAlGaAs, InAlGaAsP, and InGaAsSb, but is not limited thereto. When the first dopant is an n-type dopant such as Si, Ge, Sn, Se, or Te, the first conductive semiconductor layer (30) may be an n-type semiconductor layer.

[0057] The first conductive semiconductor layer (30) may be formed by stacking a plurality of layers. For example, the first conductive semiconductor layer (30) may include a first contact layer (31) disposed on a substrate (10) and composed of n-GaAs, a first sub-semiconductor layer (33) composed of n-AlInP, and a second sub-semiconductor layer (32) disposed between the first contact layer (31) and the first sub-semiconductor layer (33) and composed of n-AlGaInP. The second sub-semiconductor layer (32) may reduce a voltage drop due to an energy potential difference between the first contact layer (31) and the first sub-semiconductor layer (33), and may reduce resistance compared to using only the AlInP layer.

[0058] The active layer (40) is a layer where electrons (or holes) injected through the first conductive semiconductor layer (30) and holes (or electrons) injected through the second conductive semiconductor layer (70) meet. The active layer (40) transitions to a lower energy level as electrons and holes recombine, and can generate light having a corresponding wavelength.

[0059] The active layer (40) may have any one of a single well structure, a multi-well structure, a single quantum well structure, a multi-quantum well (MQW) structure, a quantum dot structure, or a quantum wire structure, and the structure of the active layer (40) is not limited thereto. For example, the active layer (40) may have a structure in which a well layer (41) and a barrier layer (42) are alternately arranged.

[0060] The active layer (40) can generate light in the visible wavelength range. The active layer (40) can output light in any one of blue, green, and red wavelengths. For example, the active layer (40) can be a red micro light-emitting element that outputs light in the red wavelength range. However, it is not necessarily limited thereto, and the active layer (40) can also generate light in the ultraviolet wavelength range or light in the infrared wavelength range. When the active layer is composed of AlGaInP, it can output red light in the wavelength range of 600 nm to 690 nm.

[0061] The second conductive semiconductor layer (70) may be disposed on the active layer (40). The second conductive semiconductor layer (70) may be implemented with a compound semiconductor of group III-V, group II-VI, etc., and a second dopant may be doped into the second conductive semiconductor layer (70). The second conductive semiconductor layer (70) may be A x B y C (1-x-y) D z E (1-z) It can be formed of a semiconductor material having a composition formula of (0≤x≤1, 0≤y≤1, 0≤x+y≤1, 0≤z≤1). Here, A, B, and C can be one of Al, Ga, and In, and D and E can be one of As, P, N, and Sb.

[0062] For example, the second conductive semiconductor layer (70) may be formed of one or more of GaN, InGaN, InAlGaN, AlGaAs, GaP, GaAs, GaAsP, AlGaInP, InGaAsP, InAlGaAs, InAlGaAsP, and InGaAsSb. When the second dopant is a p-type dopant such as Mg, Zn, Ca, Sr, Ba, etc., the second conductive semiconductor layer (70) doped with the second dopant may be a p-type semiconductor layer.

[0063] The optical layer (60) can be placed between the second conductive semiconductor layer (70) and the active layer (40). The optical layer (60) has a relatively high Al composition ratio and A x B y C(1-x-y) D z E (1-z) It may be a semiconductor material having a composition formula of (0≤x≤1, 0≤y≤1, 0≤x+y≤1, 0≤z≤1) (wherein A, B, and C are one of Al, Ga, and In, and D and E are one of As, P, N, and Sb). The optical layer (60) may be formed of one or more of AlGaN, InAlGaN, AlGaAs, AlAsP, AlGaP, AlGaAsP, AlGaInP, InAlGaAs, InAlGaAsP, and AlInGaAsSb.

[0064] According to an embodiment, the side surface of the optical layer (60) can be exposed to water vapor to form an unoxidized central region (61) and an oxidized edge region (62). The edge region (62) may have higher resistance and lower refractive index than the central region (61) due to oxidation. Accordingly, the edge region (62) can function as a current blocking region, and the central region (61) can function as a current passing region.

[0065] Referring to FIG. 2, a micro light-emitting element may have a first electrode (91) electrically connected to a first conductive semiconductor layer (30) disposed at the bottom, and a second electrode (92, 93) electrically connected to a second conductive semiconductor layer (70) disposed at the top. The second electrodes (92, 93) may be composed of a plurality of layers. The substrate (10) and the buffer layer (20) were removed during the process of transferring the micro light-emitting element to the panel substrate (101).

[0066] In Fig. 2, the micro light-emitting element is shown to be mounted upside down during the transfer process, but this is not necessarily limited to the first conductive semiconductor layer (30) may be placed on the panel.

[0067] The first electrode (91) and the second electrode (92, 93) may be formed by including at least one of ITO (indium tin oxide), IZO (indium zinc oxide), IZTO (indium zinc tin oxide), IAZO (indium aluminum zinc oxide), IGZO (indium gallium zinc oxide), IGTO (indium gallium tin oxide), AZO (aluminum zinc oxide), ATO (antimony tin oxide), GZO (gallium zinc oxide), IZON (IZO Nitride), AGZO (Al-Ga ZnO), IGZO (In-Ga ZnO), ZnO, IrOx, RuOx, NiO, RuOx / ITO, Ni / IrOx / Au, Ni / AuGe / Au, and Ti / Pt / Au, but are not limited to these materials.

[0068] For example, the first electrode (91) may be composed of Ni / AuGe / Au. The second electrode (92, 93) may include a first layer (92) composed of ITO and a second layer (93) composed of Ti / Pt / Au and connected to the panel substrate (101). However, the composition of each electrode is not necessarily limited thereto and may be modified in various ways.

[0069] Figure 3 is a simulation result showing the change in lateral leakage current according to the change in the size of the micro light-emitting element.

[0070] When a current is injected into a micro light-emitting device with a side length of 30 μm, it can be seen that there is a current that leaks out to the side of the micro light-emitting device (hereinafter referred to as the side leakage current) and a current that is injected into the interior of the micro light-emitting device and participates in light emission (hereinafter referred to as the effective injection current). The sum of the side leakage current and the effective injection current may be the total amount of current applied to the micro light-emitting device.

[0071] Lateral leakage current refers to current that does not flow into the interior of the micro light-emitting device but instead flows along the side of the micro light-emitting device, thus not participating in light emission. Therefore, since a significant portion of the applied current leaks out, the smaller the size of the micro light-emitting device, the lower its light-emitting efficiency.

[0072] Referring to Fig. 3, it can be seen that as the size of the micro light-emitting device decreases, the ratio of the lateral leakage current among the applied current increases. When the size of the micro light-emitting device is 200㎛, the ratio of the lateral leakage current is only about 10%, but when the size of the micro light-emitting device is 100㎛, the ratio of the lateral leakage current increases by nearly two times to about 20%.

[0073] When the size of the micro light-emitting device is 50㎛, the ratio of the lateral leakage current increases to approximately 35%, and when the size of the micro light-emitting device is 20㎛, the ratio of the lateral leakage current increases rapidly to approximately 85%.

[0074] To increase display resolution, the size of micro-LEDs needs to decrease. For use as pixel light sources in high-resolution displays, it may be advantageous to manufacture micro-LEDs with a size of 50㎛ or less. Therefore, it is crucial to prevent the reduction in luminous efficiency that occurs with decreasing micro-LED size.

[0075] In an embodiment, the light emitting efficiency of a micro light emitting device can be effectively improved by forming an optical layer (60) inside the micro light emitting device to reduce lateral leakage current.

[0076] Referring to FIGS. 1 and 2, the optical layer (60) may have a higher composition of aluminum compared to the active layer (40) and the second conductive semiconductor layer (70). For example, the optical layer (60) may be composed of one or more of AlGaN, InAlGaN, AlGaAs, AlGaP, AlAsP, AlGaAsP, AlGaInP, InAlGaAs, InAlGaAsP, or AlInGaAsSb having a high Al composition ratio.

[0077] The optical layer (60) may have the largest energy band gap within the light-emitting structure (CS1) due to its high aluminum composition. Accordingly, the flow of electrons supplied from the first conductive semiconductor layer (30) to the second conductive semiconductor layer (70) may be blocked, thereby increasing the probability of electrons and holes recombining within the active layer (40). In other words, the optical layer (60) may function as an electron blocking layer.

[0078] The optical layer (60) may include a second dopant that is the same as or different from the second conductive semiconductor layer (70). For example, the second conductive semiconductor layer (70) may be doped with magnesium (Mg) as the second dopant, while the optical layer (60) may be doped with magnesium (Mg) or carbon (C). Hereinafter, it will be described that the optical layer (60) is doped with carbon.

[0079] As the doping amount of carbon increases, the hole concentration of the optical layer (60) increases. Generally, carbon does not function as a p-type dopant because it is a group 14 element, the same as silicon. However, when the optical layer is AlGaAs, carbon can function as a p-type dopant.

[0080] When carbon is doped into AlGaAs, carbon, which has four electrons in its outer shell, can substitute for As, which has five electrons in its outer shell, and thus bond. Therefore, it can become a p-type semiconductor, which conducts with one electron missing and frees up holes.

[0081] Because the activation energy of carbon acceptor in AlGaAs thin films is low, carbon is used as 5E18 (5×10 18 / cm) can be doped.

[0082] As the hole concentration increases, the Fermi level moves down toward the valence band (VB), and since the Fermi level of the optical layer must match the surrounding Fermi levels, the conduction band (CB) of the optical layer moves up toward high energy. According to this configuration, the energy band gap of the optical layer (60) can be moved upward toward the conduction band, thereby improving its function as an electron blocking layer. Therefore, even if the aluminum concentration of the optical layer (60) is low, it can sufficiently function as an electron blocking layer.

[0083] Magnesium (Mg) may be doped into the optical layer (60), but since magnesium easily diffuses, magnesium may diffuse into the active layer (40) adjacent to the optical layer (60). Therefore, it may be difficult to sufficiently shift the energy band gap because it is difficult to increase the amount of magnesium doping.

[0084] According to an embodiment, the optical layer (60) may be co-doped with carbon and magnesium. In this case, magnesium may be doped less than carbon to minimize diffusion. For example, when carbon and magnesium are co-doped, the carbon doping amount may be at least twice that of magnesium. Therefore, the doping of magnesium is minimized, thereby minimizing magnesium diffusion into adjacent semiconductor layers.

[0085] The optical layer (60) may have a higher aluminum composition than the first conductive semiconductor layer (30), the active layer (40), and the second conductive semiconductor layer (70). The aluminum composition may be 70% to 100%. Therefore, upon contact with water vapor, oxidation may occur from the side of the optical layer (60).

[0086] The optical layer (60) may include an unoxidized central region (61) and an oxidized edge region (62). The edge region (62) may have higher resistance and lower refractive index than the central region (61) due to oxidation. Therefore, injected carriers may be blocked by the high-resistance edge region (62) and may not move along the side of the light-emitting element, but may be bent toward the low-resistance central region (61). Therefore, according to an embodiment, current leaking to the side can be reduced.

[0087] The thickness of the oxidized edge region (62) may be 1 µm to 10 µm. If the thickness of the edge region (62) is less than 1 µm, the thickness is too thin, so carriers may pass through the edge region (62) and move along the side of the light-emitting element. If the thickness of the edge region (62) is greater than 10 µm, the oxidation time increases, and there is a risk that other semiconductor layers may also be oxidized.

[0088] A first intermediate layer (50) may be placed between the optical layer (60) and the active layer (40). The first intermediate layer (50) may play a role in helping to form a high-quality interface between the optical layer (60) and the active layer (40) when the optical layer (60) is epitaxially grown on the active layer (40). That is, the film quality of the optical layer (60) and the active layer (40) may be improved by the first intermediate layer (50).

[0089] The first intermediate layer (50) may have the same composition as the second conductive semiconductor layer (70). For example, the first intermediate layer (50) may be undoped i-AlGaInP. However, this is not necessarily limited to the first intermediate layer (50), and the first intermediate layer (50) may also be doped with a p-type dopant.

[0090] Referring to Fig. 4, it can be seen that as the width (W1) of the oxidized edge region (62) increases, the density of the effective injection current increases. When the width of the oxidized edge region (62) is 1 μm, the injected current density is approximately 1 A / cm. 2On the other hand, when the width of the oxidized edge region (62) is 5 μm, the current density is about 1.25 A / cm 2 increased. When the width of the oxidized edge region (62) is 10㎛, the current density is approximately 1.8A / cm 2 , and when the width of the oxidized edge region (62) is 12 μm, the current density is about 2.4 A / cm 2 It can be seen that it has increased.

[0091] However, when the width of the oxidized edge region (62) is 12 μm, a problem may arise in which the current is concentrated in the central region (61) of the optical layer (60), thereby increasing the driving voltage. Therefore, when the width of the oxidized edge region (62) is controlled to 5 μm to 11 μm, the current density can be increased without excessively increasing the driving voltage in the central region (61) of the optical layer (60), thereby improving the luminous efficiency.

[0092] According to an embodiment, the area of ​​the edge region (62) of the optical layer (60) may be wider than the area of ​​the central region (61). For example, in a square-shaped optical layer (60) having a width of 30 μm, if the width (W1) of the edge region (62) is 5 μm, the width (W2) of the central region (61) may be 20 μm. Accordingly, the total area of ​​the optical layer (60) may be 900 μm. 2 And the area of ​​the central region (61) is 400㎛ 2 Therefore, the area of ​​the edge region (62) is 500㎛ 2 That is, in order to block the side leakage current, the area of ​​the edge region (62) may be wider than the area of ​​the center region (61).

[0093] For example, the area of ​​the central region (61) may be 9% to 45% of the total area of ​​the optical layer (60), and the area of ​​the edge region (62) may be 55% to 91% of the total area of ​​the optical layer (60). However, this is not necessarily limited to this, and the area of ​​the edge region (62) may be adjusted to be the same as the area of ​​the central region (61).

[0094] Fig. 5 is a diagram showing the energy band gap of a typical micro light-emitting device. Fig. 6 is a diagram showing the energy band gap of a micro light-emitting device according to one embodiment of the present invention.

[0095] Referring to Fig. 5, in the case of a typical micro light-emitting device, there is a problem in that the band gap gradually rises in the region between the active layer (40) and the second conductive semiconductor layer (70), so that electrons injected from the first conductive semiconductor layer (30) do not participate in light emission in the active layer (40) and easily move to the second conductive semiconductor layer (70). Therefore, there is a problem in that the light emission efficiency is reduced.

[0096] Referring to FIG. 6, in the case of the micro light-emitting device according to the embodiment, since carbon is doped into the optical layer (60), the bandgap discontinuity in the conduction band (CB) increases. Accordingly, electrons passing through the active layer (40) are blocked from moving to the second conductive semiconductor layer (70), thereby increasing the probability of participating in light emission in the active layer (40). Accordingly, the luminous efficiency at room temperature can be improved, and the decrease in luminous efficiency at high temperatures can be improved.

[0097] In addition, in the case of the micro light emitting device according to the embodiment, since the optical layer (60) is composed of AlGaAs, the doping amount may be higher than that of the second conductive semiconductor layer (70) composed of AlGaInP. For example, in the case of AlGaInP, the amount that can be doped may be smaller than that of AlGaAs due to the material properties. Therefore, the doping amount of carbon doped into the optical layer (60) may be higher than the doping amount of magnesium doped into the second conductive semiconductor layer (70). For example, the doping amount of carbon doped into the optical layer (60) is 5E18 (5×10 18 / cm), whereas the doping amount of magnesium doped into the second conductive semiconductor layer (70) is 5E17 (5×10 17 / cm) may be.

[0098] As described above, when the hole concentration of the optical layer increases due to high carbon doping, the Fermi level gradually moves down toward the valence band (VB), and since the Fermi level of the optical layer must match the surrounding Fermi levels, the conduction band (CB) and valence band (VB) of the optical layer rise toward high energy. Accordingly, the potential difference based on the bandgap discontinuity in the valence band (VB) becomes smaller, so that holes generated in the second conductive semiconductor layer (70) can move to the active layer (40) relatively easily.

[0099] That is, due to carbon doping, the potential difference between the conduction band (CB) of the optical layer (60) and the surroundings increases, thereby suppressing electron movement, while in the valence band (VB), the potential difference between the surroundings and the surroundings decreases, thereby improving hole movement.

[0100] Carbon doped in the optical layer (60) does not diffuse well even if the doping amount is high. Therefore, the thickness of the diffusion barrier layer (not shown) formed to prevent the diffusion of magnesium can be minimized to improve resistance and current injection efficiency. The diffusion barrier layer is made of i-Al. 0.5 In 0.5It is desirable to minimize the thickness as it may be P and may have relatively high resistance. However, magnesium may diffuse into the diffusion barrier layer.

[0101] Fig. 7 is a drawing showing an optical layer of a micro light-emitting device according to another embodiment of the present invention. Fig. 8 is a modified example of Fig. 7. Fig. 9 is a drawing showing an optical layer of a micro light-emitting device according to another embodiment of the present invention.

[0102] Referring to FIG. 7, the optical layer (60) of the micro light-emitting device may include a plurality of sub-layers. For example, the optical layer (60) may include a first sub-layer (LS1), a third sub-layer (LS3), and a second sub-layer (LS2) disposed between the first sub-layer (LS1) and the third sub-layer (LS3). The central region (61) and the edge region (62) may both be composed of the first to third sub-layers (LS1, LS2, LS3).

[0103] The first sub-layer (LS1) and the third sub-layer (LS3) may have the same composition. The second sub-layer (LS2) may have a different composition from the first sub-layer (LS1) and the third sub-layer (LS3). The first sub-layer (LS1) and the third sub-layer (LS3) may have a composition similar to the second conductive semiconductor layer (70). For example, the first sub-layer (LS1) and the third sub-layer (LS3) may be AlAsP, and the second sub-layer (LS2) may be AlGaAs, but the present invention is not limited thereto.

[0104] In addition, the first sublayer (LS1) and the third sublayer (LS3) can be made of a material that follows the composition formula of AxByC(1-xy)DzE(1-z) (0≤x≤1, 0≤y≤1, 0≤x+y≤1, 0≤z≤1) (wherein A, B, C are one of Al, Ga, and In, and D, E are one of As, P, N, and Sb), and x, y, and z can be configured to be graded within the layer.

[0105] The first sublayer (LS1) and the third sublayer (LS3) may have different compositions. For example, one of the first sublayer (LS1) and the third sublayer (LS3) may be AlAsInP, and the other may be AlAsP. Additionally, the second sublayer may be AlGaAsP. In this case, the P content may be adjusted to 5% or less to facilitate oxidation.

[0106] The second sub-layer (LS2) may be thicker than the first sub-layer (LS1) and the third sub-layer (LS3). The second sub-layer (LS2) may be 10 nm to 200 nm, and the first sub-layer (LS1) and the third sub-layer (LS3) may be 0.1 nm to 100 nm. However, this is not necessarily limited thereto, and the thicknesses of the first to third sub-layers (LS1, LS2, LS3) may be the same.

[0107] Referring to FIG. 8, the second sub-layer (LS2) can be oxidized faster than the first sub-layer (LS1) and the third sub-layer (LS3) under the same conditions. The boundary between the central region (61) and the edge region (62) can be formed to be inclined. That is, the central region (61) can be formed to have the narrowest width (d1) in the second sub-layer (LS2), and can be formed to have a relatively wide width (d2) in the first sub-layer (LS1) and the third sub-layer (LS3). According to this configuration, current concentration toward the center can be facilitated, and the oxidized first sub-layer (LS1) and the third sub-layer (LS3) layers can play a role in alleviating the stress between the oxidized second sub-layer (LS2) and the active layer.

[0108] Referring to Fig. 9, the optical layer (60) may be manufactured with different materials in the central region (61) and the edge region (62). For example, the central region (61) may be composed of one or more of AlGaN, InAlGaN, AlGaAs, AlGaP, AlAsP, AlGaAsP, AlGaInP, InAlGaAs, InAlGaAsP, or AlInGaAsSb. For example, the optical layer may be AlGaAs or AlGaAsP. At this time, the content of P may be adjusted to 5% or less to facilitate oxidation.

[0109] The edge region (62) may be composed of an insulating material such as SiO2 or SiN. In addition, various materials used as insulating layers in the semiconductor technology field may be applied without limitation. Alternatively, the edge region (62) may be an air gap.

[0110] The central region (61) may include a plurality of sub-layers. For example, the central region (61) of the optical layer (60) may include a first sub-layer (LS1), a third sub-layer (LS3), and a second sub-layer (LS2) disposed between the first sub-layer (LS1) and the third sub-layer (LS3).

[0111] The first sub-layer (LS1) and the third sub-layer (LS3) may have the same composition. In addition, the second sub-layer (LS2) may have a different composition from the first sub-layer (LS1) and the third sub-layer (LS3). The first sub-layer (LS1) and the third sub-layer (LS3) may have a composition similar to the second conductive semiconductor layer (70). For example, the first sub-layer (LS1) and the third sub-layer (LS3) may be AlAsP, and the second sub-layer (LS2) may be AlGaAs, but the present invention is not limited thereto. In contrast, the edge region (62) may be formed of a single layer of an insulating material such as SiO2 or SiN.

[0112] Fig. 10 is a simulation result showing that the energy band gap changes as the doping concentration of the optical layer increases. Fig. 11 is a simulation result showing that the light output changes as the doping concentration of the optical layer increases. Fig. 12 is a simulation result showing that the external quantum efficiency changes as the doping concentration of the optical layer increases. Fig. 13 is a simulation result showing that the driving voltage changes as the doping concentration of the optical layer increases. Fig. 14 is a simulation result showing the light output according to the change in the size of a micro light-emitting device having a current blocking region.

[0113] Referring to Fig. 10, it can be seen that the energy level changes depending on the concentration of carbon doped into the optical layer (60). When carbon is doped at 1E17, the energy level rises relatively gradually, making it difficult to effectively block electron movement. In addition, there is a problem that the barrier width (W11) in the valence band is wide at approximately 60 nm, which increases resistance.

[0114] When the doping concentration of the optical layer (60) is 1E18, the height difference with the surrounding area is 0.52 eV, and a step difference is generated, which can effectively block electron movement. In addition, the width of the barrier in the valence band is reduced to approximately 26 nm, which can reduce resistance.

[0115] When the doping concentration of the optical layer (60) is 5E18, the height difference from the surrounding area is 0.56 eV, and a sharp step difference occurs, which can more effectively block electron movement. In addition, the width of the barrier in the valence band is reduced to approximately 10 nm, which can reduce resistance.

[0116] Referring to FIG. 11, it can be seen that when the doping concentration of the optical layer (60) is 5E18, the light output increases by 64% compared to when the doping concentration is 1E18, and referring to FIGS. 12 and 13, it can be seen that when the doping concentration of the optical layer (60) is , the decrease in external light extraction efficiency is improved and the driving voltage is improved at high current compared to when the doping concentration is 1E18.

[0117] Referring to Fig. 14, it can be confirmed that in the case of a device having a 2.5 ㎛ wide AlOx border by oxidizing the edge region of the optical layer, the light output is improved compared to the case where the edge region of the optical layer is not oxidized at all driving current densities.

[0118] For example, it can be confirmed that the light output of a 30㎛ micro light-emitting device (30_oxide) having a 2.5㎛ wide AlOx formed thereon is improved compared to a 30㎛ micro light-emitting device (30_W_O_OX) having a 2.5㎛ wide AlOx not formed thereon. In the case of micro light-emitting devices (60_oxide, 80_oxide, 120_oxide) having a size of 60㎛, 80㎛, and 120㎛, it can be confirmed that the light output is improved compared to a light-emitting device that is not oxidized when the edge region is oxidized. It can be confirmed that as the size of the micro light-emitting device decreases, the light output increases compared to a case where the edge region is not oxidized.

[0119] According to an embodiment, the edge region (62) of the optical layer (60) forms a current blocking region, thereby reducing current leakage to the side of the micro light-emitting element. In addition, the optical layer (60) may be doped with carbon and may serve to block the flow of electrons attempting to move from the active layer (40) to the second conductive semiconductor layer (70).

[0120] Fig. 15 is a first modified example of Fig. 1. Fig. 16 is a second modified example of Fig. 1.

[0121] Referring to FIG. 15, a micro light-emitting device according to an embodiment may include a first optical layer (60A) disposed between an active layer (40) and a second conductive semiconductor layer (70), and a second optical layer (60B) disposed between the active layer (40) and the first conductive semiconductor layer (30).

[0122] A first intermediate layer (50) may be arranged between the first optical layer (60A) and the active layer (40). In addition, a second intermediate layer (34) may be arranged between the second optical layer (60B) and the active layer (40).

[0123] The first intermediate layer (50) and the second intermediate layer (34) may be undoped i-AlGaInP. However, this is not necessarily limited to the first intermediate layer (50) and the second intermediate layer (34) may be doped with a p-type dopant and the second intermediate layer (34) may be doped with an n-type dopant.

[0124] Referring to FIG. 16, the micro light-emitting element may be arranged with only the second optical layer (60B).

[0125] FIG. 17a and FIG. 17b are drawings showing a method for manufacturing a micro light-emitting device according to one embodiment of the present invention.

[0126] Referring to FIGS. 17a and 17b, after forming a micro light-emitting element, oxidation may occur from the side of the optical layer (60) when the side is exposed to water vapor. Thereafter, oxidation may be performed to an appropriate depth to adjust the diameter of the central region (current pass region, 61).

[0127] The optical layer (60) may be formed as a single layer (e.g., AlGaAs, AlGaAsP), or may be formed by stacking first to third sub-layers (LS1, LS2, LS3). When formed as the first to third sub-layers (LS1, LS2, LS3), the width of the central region (61) of the optical layer (60) may be formed to be inclined in the thickness direction.

[0128] FIGS. 18a to 18d are drawings showing a method for manufacturing a micro light-emitting device according to another embodiment of the present invention.

[0129] Referring to FIGS. 18a and 18b, after forming a micro light-emitting element, the edge of the optical layer (60) can be removed by etching from the side. The etching method is not particularly limited. For example, the remaining area except for the portion corresponding to the optical layer (60) among the side surfaces of the light-emitting element can be masked, and then the edge of the optical layer (60) can be etched (ET).

[0130] For example, after forming a micro light-emitting device, if it is additionally exposed to an HF series etching solution, only the AlGaAs layer can be selectively etched.

[0131] If the optical layer (60) is configured as a three-layer structure such as AlAsP / AlGaAs / AlAsP, the AlAsP layers of the optical layer (60) are relatively less easily etched by the etching solution, so that the active layer or the second conductive semiconductor layer can be prevented from coming into contact with the etching solution. However, this is not necessarily limited to this, and various semiconductor etching methods can be applied without limitation.

[0132] Referring to Fig. 18c, the edge region (62) of the optical layer (60) can be formed by filling an insulating layer. At this time, the insulating layer (64) can be formed entirely up to the side and upper surface of the light-emitting structure (CS1). That is, the edge region (62) of the optical layer (60) can be formed integrally with the insulating layer (64) formed on the side and upper surface of the light-emitting element and can be composed of the same material.

[0133] Referring to Fig. 18d, after forming an opening (64a) in the insulating layer (64) formed on the upper surface, a second electrode can be formed on the exposed second contact layer (80). Thereafter, after removing the substrate (10) and the buffer layer (20), a first electrode can be formed on the first conductive semiconductor layer (30).

[0134] Fig. 19 is a drawing showing the light extraction efficiency of a general micro light-emitting device, and Fig. 20 is a drawing showing the light extraction efficiency of a micro light-emitting device according to an embodiment of the present invention.

[0135] Referring to Fig. 19, in the case of a conventional micro light-emitting device, each semiconductor layer is composed of AlGaAs, and the refractive index is approximately 3.3, which is the refractive index of air 1, so the critical angle is approximately 17.6 degrees according to Snell's law. Therefore, since most of the light is larger than the critical angle, it is totally reflected, resulting in a very low light extraction efficiency.

[0136] However, according to the embodiment as shown in Fig. 20, since the oxidized edge region (62) has a composition of AlOx, the refractive index decreases to 1.55, and thus the critical angle with air increases to 40.2 degrees. Accordingly, a portion (L2) of the light emitted from the active layer (40) can be emitted to the outside through the edge region (62). Therefore, according to the embodiment, the leakage current can be reduced by the edge region (62) while the light extraction efficiency can be improved.

[0137] According to an embodiment, a rough surface may be formed on the side surface of the light-emitting element. The rough surface may be fabricated using a semiconductor mask process. Accordingly, the roughness of the outer surface of the optical layer may be increased, thereby improving light extraction efficiency.

[0138] FIG. 21 is a drawing of a display device according to one embodiment of the present invention.

[0139] Referring to FIG. 21, a display device including a light-emitting element as an embodiment may include a panel substrate (410), a driving thin film transistor (T2), a planarization layer (430), a common electrode (CE), a pixel electrode (AE), and a micro light-emitting element (10).

[0140] The driving thin film transistor (T2) may include a gate electrode (GE), a semiconductor layer (SCL), an ohmic contact layer (OCL), a source electrode (SE), and a drain electrode (DE).

[0141] The driving thin film transistor (T2) is a driving element that is electrically connected to the light-emitting element and can drive the light-emitting element.

[0142] A gate electrode (GE) may be formed together with a gate line. Such a gate electrode (GE) may be covered with a gate insulating layer (440).

[0143] The gate insulating layer (440) may be composed of a single layer or multiple layers made of an inorganic material, and may be made of silicon oxide (SiOx), silicon nitride (SiNx), or the like.

[0144] The semiconductor layer (SCL) may be arranged in a preset pattern (or island) shape on the gate insulating layer (440) so as to overlap with the gate electrode (GE). The semiconductor layer (SCL) may be composed of a semiconductor material made of any one of amorphous silicon, polycrystalline silicon, oxide, and organic material, but is not limited thereto.

[0145] The ohmic contact layer (OCL) may be arranged in a preset pattern (or island) shape on the semiconductor layer (SCL). The ohmic contact layer (PCL) may be for ohmic contact between the semiconductor layer (SCL) and the source / drain electrodes (SE, DE).

[0146] The source electrode (SE) is formed on the other side of the ohmic contact layer (OCL) so as to overlap with one side of the semiconductor layer (SCL).

[0147] The drain electrode (DE) may be formed on the other side of the ohmic contact layer (OCL) so as to overlap with the other side of the semiconductor layer (SCL) and be spaced apart from the source electrode (SE). The drain electrode (DE) may be formed together with the source electrode (SE).

[0148] The planarization layer (430) may be disposed on the second panel substrate (410). A driving thin film transistor (T2) may be disposed inside the planarization layer (430). According to an example, the planarization layer (430) may include an organic material such as benzocyclobutene or photo acryl, but is not limited thereto.

[0149] The micro light-emitting element (10) may be placed on a planarization layer (430). The first electrode and the second electrode of the micro light-emitting element (10) may be connected to a circuit (not shown) of the display device.

[0150] The second electrode of the micro light-emitting element (10) can be electrically connected to the source electrode (SE) of the driving thin film transistor (T2) via the pixel electrode (AE). And the first electrode of the light-emitting element can be connected to a common power line (CL) via the common electrode (CE).

[0151] The pixel electrode (AE) can electrically connect the source electrode (SE) of the driving thin film transistor (T2) and the second electrode of the light-emitting element.

[0152] A common electrode (CE) can electrically connect a common power line (CL) and the first electrode of the light-emitting element.

[0153] The pixel electrode (AE) and the common electrode (CE) may each include a transparent conductive material. The transparent conductive material may include, but is not limited to, a material such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide).

[0154] The display device according to an embodiment of the present invention may be implemented with a resolution of SD (Standard Definition) level (760×480), HD (High definition) level (1180×720), FHD (Full HD) level (1920×1080), UH (Ultra HD) level (3480×2160), or a resolution higher than UHD level (e.g., 4K (K=1000), 8K, etc.). In this case, the light-emitting elements according to the embodiment may be arranged and connected in multiple numbers according to the resolution.

[0155] Additionally, the display device can be a billboard or TV with a diagonal size of 100 inches or more, and the pixels can be implemented using light-emitting diodes (LEDs). Consequently, power consumption can be reduced, maintenance costs can be reduced, and a long lifespan can be achieved, providing a high-brightness, self-illuminating display.

[0156] The light-emitting element according to the embodiment may further include optical members such as a light guide plate, a prism sheet, and a diffusion sheet, and may function as a backlight unit. In addition, the light-emitting element according to the embodiment may further be applied to a display device, a lighting device, and an indicator device.

[0157] At this time, the display device may include a bottom cover, a reflector, a light-emitting module, a light guide plate, an optical sheet, a display panel, an image signal output circuit, and a color filter. The bottom cover, the reflector, the light-emitting module, the light guide plate, and the optical sheet may form a backlight unit.

[0158] A reflector is placed on the bottom cover, and a light-emitting module emits light. A light guide plate is placed in front of the reflector to guide light emitted from the light-emitting module forward, and an optical sheet, including a prism sheet or the like, is placed in front of the light guide plate. A display panel is placed in front of the optical sheet, an image signal output circuit supplies an image signal to the display panel, and a color filter is placed in front of the display panel.

[0159] In addition, the lighting device may include a light source module including a substrate and a light-emitting element of the embodiment, a heat dissipation unit that dissipates heat from the light source module, and a power supply unit that processes or converts an electrical signal provided from the outside and provides the signal to the light source module. Furthermore, the lighting device may include a lamp, a head lamp, or a street lamp.

[0160] Additionally, the camera flash of the mobile terminal may include a light source module including the light-emitting element of the embodiment.

[0161] Although the above description focuses on examples, these are merely examples and do not limit the present invention. Those skilled in the art will appreciate that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the present invention. For example, each component specifically shown in the examples can be modified and implemented. In addition, differences related to such modifications and applications should be construed as being included within the scope of the present invention defined in the appended claims.

Claims

1. A semiconductor structure including a first conductive semiconductor layer; a second conductive semiconductor layer; an active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer; and an optical layer disposed between the second conductive semiconductor layer and the active layer. A first electrode electrically connected to the first challenge type semiconductor layer; and A second electrode electrically connected to the second challenge type semiconductor layer is included, The optical layer includes a current blocking region formed at the edge and a current passing region formed at the center, The above first challenge type semiconductor layer is doped with a first dopant, A micro light-emitting device, wherein the second challenge type semiconductor layer and the optical layer are doped with a second dopant.

2. In paragraph 1, A micro light-emitting element wherein the area of ​​the current blocking region is equal to or larger than the area of ​​the current pass region.

3. In paragraph 1, A micro light-emitting device, wherein the doping concentration of the optical layer is higher than the doping concentration of the second conductive semiconductor layer.

4. In paragraph 1, A micro light-emitting device, wherein the second dopant doped in the optical layer and the dopant doped in the second conductive semiconductor layer are of different types.

5. In paragraph 4, A micro light-emitting device, wherein the second dopant doped in the optical layer is carbon, and the dopant doped in the second conductive semiconductor layer is magnesium.

6. In paragraph 4, A micro light-emitting device, wherein the second dopant doped into the optical layer includes carbon and magnesium, and the concentration of carbon doped into the optical layer is higher than the concentration of magnesium.

7. In paragraph 1, The above optical layer is, A micro light-emitting device comprising a first sub-layer, a third sub-layer, and a second sub-layer disposed between the first sub-layer and the third sub-layer.

8. In paragraph 7, The first sub-layer and the third sub-layer have the same composition, A micro light-emitting device, wherein the second sub-layer has a different composition from the first sub-layer and the third sub-layer.

9. In paragraph 7, The first sub-layer and the third sub-layer have different compositions, A micro light-emitting device, wherein the second sub-layer has a different composition from the first sub-layer and the third sub-layer.

10. In paragraph 7, A micro light-emitting device, wherein the thickness of the first sub-layer and the third sub-layer is thinner than the thickness of the second sub-layer.

11. In paragraph 8, A micro light-emitting device, wherein the width of the current pass region of the second sub-layer is narrower than the width of the current pass region of the first sub-layer.

12. In paragraph 1, A micro light-emitting device, wherein the current blocking region and the current pass region have different compositions.

13. In paragraph 12, A micro light-emitting device, wherein the current blocking region includes AlGaAs and the current pass region includes an insulating layer.

14. In paragraph 12, A micro light-emitting device, wherein the current blocking region includes AlGaAsP having a P composition ratio of 1% or less, and the current pass region includes an insulating layer.

15. In paragraph 1, Including an insulating layer arranged on a side of the semiconductor structure, A micro light-emitting element, wherein the insulating layer is made of the same material as the edge region of the optical layer.

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