Patent Publication Number: US-2023133466-A1

Title: Micro light emitting device and display apparatus including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2021-0145860, filed on Oct. 28, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     The disclosure relates to a micro light emitting device and a display apparatus including the same, and more particularly, to a micro light emitting device having a structure suitable for alignment in a fluidic self assembly method and a display apparatus including the same. 
     2. Description of Related Art 
     Light emitting diodes (LEDs) have increased industrial demand because of their advantages of low power consumption and eco-friendliness, and are used in lighting devices or Liquid Crystal Display (LCD) backlights, and also applied as pixels of display apparatuses. Recently, a micro LED display apparatus using a micro-unit LED chip as a pixel has been developed. In manufacturing a display apparatus using a micro-unit LED chip, a laser lift off or pick and place method is used as a method of transferring the micro LED. However, in this method, as the size of the micro LED decreases and the size of the display apparatus increases, productivity is lowered. 
     SUMMARY 
     A micro light emitting device having a structure suitable for alignment in a fluidic self assembly method is provided. 
     A display apparatus that may be manufactured by a fluidic self-assembly method is provided. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of embodiments of the disclosure. 
     In accordance with an aspect of the disclosure, a micro light emitting device includes a first semiconductor layer doped with a first impurity having a first conductivity; a light emitting layer arranged on an upper surface of the first semiconductor layer; a second semiconductor layer arranged on an upper surface of the light emitting layer, the second semiconductor layer being doped with a second impurity having a second conductivity electrically opposite to the first conductivity; an insulating layer arranged on an upper surface of the second semiconductor layer; a first electrode arranged on an upper surface of the insulating layer and electrically connected to the first semiconductor layer; a second electrode arranged on the upper surface of the insulating layer and electrically connected to the second semiconductor layer; and an aluminum nitride layer arranged on a lower surface of the first semiconductor layer, the aluminum nitride layer comprising a flat surface. 
     A width of the micro light emitting device may be in a range of about 1 μm to about 100 μm. 
     A width of the first semiconductor layer may be greater than a thickness of the micro light emitting device. 
     The thickness of the micro light emitting device may be in a range of about 2 μm to about 10 μm, and the width of the first semiconductor layer may be in a range of about 5 μm to about 50 μm. 
     A width of the second semiconductor layer may be greater than the thickness of the micro light emitting device. 
     A side surface of the micro light emitting device may be inclined such that the width of the first semiconductor layer is greater than the width of the second semiconductor layer. 
     A surface roughness of a surface of the aluminum nitride layer may be about 50 nm or less. 
     The surface roughness of the surface of the aluminum nitride layer may be about 10 nm or less. 
     The micro light emitting device may further include an irregular light scattering structure distributed inside the first semiconductor layer. 
     The aluminum nitride layer may include a plurality of isolated grooves. 
     Each of the plurality of isolated grooves may have a dot shape, and the plurality of isolated grooves may be two-dimensionally arranged in a surface of the aluminum nitride layer. 
     Each the plurality of isolated grooves may have a ring shape, and the plurality of isolated grooves may be arranged concentrically in a surface of the aluminum nitride layer. 
     The second electrode may be arranged at a position corresponding to a center of the second semiconductor layer in a horizontal direction, and the first electrode may be arranged at a position corresponding to an edge of the second semiconductor layer in the horizontal direction. 
     The first electrode may have a symmetrical shape surrounding the second electrode. 
     The micro light emitting device may further include a via hole passing through the second semiconductor layer and the light emitting layer, wherein the insulating layer extends to surround a sidewall of the via hole, and the first electrode is configured to contact the first semiconductor layer through the via hole, and the second electrode may be configured to penetrate the insulating layer and contact the second semiconductor layer. 
     The micro light emitting device may further include a bonding spread prevention wall arranged between the first electrode and the second electrode. 
     The bonding spread prevention wall may have a protruding shape on the upper surface of the insulating layer. 
     The bonding spread prevention wall may have a shape of a groove. 
     The micro light emitting device may have a rectangular cross-section viewed in a vertical direction, and the first electrode may be arranged in two vertex regions facing each other in a diagonal direction. 
     The micro light emitting device may further include a bonding pad arranged in each of two other vertex regions different from the two vertex regions, the two other vertex regions facing each other in another diagonal direction different from the diagonal direction. 
     In accordance with an aspect of the disclosure, a display apparatus includes a display substrate; and a plurality of micro light emitting devices arranged on the display substrate, wherein at least one of the plurality of micro light emitting devices includes a first semiconductor layer doped with a first impurity having a first conductivity; a light emitting layer arranged on an upper surface of the first semiconductor layer; a second semiconductor layer arranged on an upper surface of the light emitting layer, the second semiconductor layer being doped with a second impurity having a second conductivity electrically opposite to the first conductivity; an insulating layer arranged on an upper surface of the second semiconductor layer; a first electrode arranged on an upper surface of the insulating layer and electrically connected to the first semiconductor layer; a second electrode arranged on the upper surface of the insulating layer and electrically connected to the second semiconductor layer; and an aluminum nitride layer arranged on a lower surface of the first semiconductor layer, the aluminum nitride layer comprising a flat surface. 
     The display apparatus may further include a wavelength conversion layer configured to convert a wavelength of light emitted from the plurality of micro light emitting devices. 
     The wavelength conversion layer may include a first wavelength conversion layer configured to convert the light emitted from the plurality of micro light emitting devices into light of a first wavelength band, and a second wavelength conversion layer configured to convert the light emitted from the plurality of micro light emitting devices into light of a second wavelength band different from the first wavelength band. 
     The display apparatus may further include a color filter layer including a first filter arranged to face the first wavelength conversion layer and configured to transmit the light of the first wavelength band; and a second filter arranged to face the second wavelength conversion layer and configured to transmit the light of the second wavelength band. 
     In accordance with an aspect of the disclosure, a micro light emitting device includes a first electrode on a first surface of the micro light emitting device; 
     and an aluminum nitride layer on a second surface of the micro light emitting device opposite to the first surface, wherein a surface roughness of the aluminum nitride layer is 50 nm or less. 
     A first shape of the first electrode may be radially symmetrical with respect to a center of the micro light emitting device. 
     The micro light emitting device may further include a second electrode on the first surface, wherein a second shape of the second electrode is radially symmetrical with respect to the center of the micro light emitting device. 
     In accordance with an aspect of the disclosure, a micro light emitting device includes a first semiconductor layer doped with a first impurity having a first conductivity; a light emitting layer arranged on an upper surface of the first semiconductor layer; a second semiconductor layer arranged on an upper surface of the light emitting layer, the second semiconductor layer being doped with a second impurity having a second conductivity electrically opposite to the first conductivity; an insulating layer arranged on an upper surface of the second semiconductor layer; a first electrode arranged on an upper surface of the insulating layer and electrically connected to the first semiconductor layer; a second electrode arranged on the upper surface of the insulating layer and electrically connected to the second semiconductor layer; a bonding spread prevention wall arranged between the first electrode and the second electrode; a bonding pad arranged on the upper surface of the insulating layer; and an aluminum nitride layer arranged on a lower surface of the first semiconductor layer, the aluminum nitride layer comprising a flat surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a cross-sectional view schematically showing a structure of a micro light emitting device according to an embodiment; 
         FIGS.  2 A to  2 C  are plan views illustrating various electrode structures of a micro light emitting device according to embodiments; 
         FIGS.  3 A to  3 D  are cross-sectional views schematically illustrating a process of manufacturing the micro light emitting device shown in  FIG.  1   ; 
         FIG.  4    is a perspective view showing an example method of aligning a micro light emitting device using a fluidic self assembly method according to an embodiment; 
         FIG.  5    schematically shows a scanning process for aligning a micro light emitting device according to an embodiment; 
         FIG.  6    is a cross-sectional view showing a schematic structure of a transfer substrate according to an embodiment in which micro light emitting devices are arranged; 
         FIG.  7    is a cross-sectional view schematically illustrating a process of transferring a micro light emitting device aligned on a transfer substrate onto a display substrate according to an embodiment; 
         FIG.  8    is a cross-sectional view schematically illustrating a structure of a micro light emitting device according to an embodiment; 
         FIG.  9    is a cross-sectional view schematically illustrating a structure of a micro light emitting device according to an embodiment; 
         FIGS.  10 A and  10 B  are plan views showing examples of a plurality of grooves formed in an aluminum nitride layer of the micro light emitting device shown in  FIG.  9   ; 
         FIG.  11    is a cross-sectional view schematically showing the structure of a micro light emitting device according to an embodiment; 
         FIG.  12    is a cross-sectional view schematically illustrating a structure of a display apparatus according to an embodiment; 
         FIG.  13    is a cross-sectional view schematically illustrating a structure of a display apparatus according to an embodiment; 
         FIG.  14    is a schematic block diagram of an electronic device according to an embodiment; 
         FIG.  15    illustrates an example in which a display apparatus according to embodiments is applied to a mobile device; 
         FIG.  16    illustrates an example in which the display apparatus according to embodiments is applied to a vehicle display apparatus; 
         FIG.  17    illustrates an example in which the display apparatus according to embodiments is applied to augmented reality glasses or virtual reality glasses; 
         FIG.  18    illustrates an example in which the display apparatus according to embodiments is applied to a signage; and 
         FIG.  19    illustrates an example in which the display apparatus according to embodiments is applied to a wearable display. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     Hereinafter, a micro light emitting device and a display apparatus including the same will be described in detail with reference to the accompanying drawings. In the following drawings, the same reference numerals refer to the same components, and the size of each component in the drawings may be exaggerated for clarity and convenience of description. Further, embodiments described below are merely examples, and various modifications are possible from these embodiments. 
     Hereinafter, what is described as “upper part” or “on” may include not only those directly above by contact, but also those above non-contact. The terms of a singular form may include plural forms unless otherwise specified. In addition, when a certain part “includes” a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated. 
     The use of the term “the” and similar designating terms may correspond to both the singular and the plural. If there is no explicit order or contradictory statement about the steps constituting the method, these steps may be performed in an appropriate order, and are not necessarily limited to the order described. 
     In addition, terms such as “unit” and “module” described in the specification mean a unit that processes at least one function or operation, and this may be implemented as hardware or software, or may be implemented as a combination of hardware and software. 
     The connection or connection members of lines between the components shown in the drawings are illustrative of functional connections and/or physical or circuit connections, and may be represented as a variety of functional connections, physical connections, or circuit connections that are replaceable or additional in an actual device. 
     The use of all examples or illustrative terms is merely for describing technical ideas in detail, and the scope is not limited by these examples or illustrative terms unless limited by the claims. 
       FIG.  1    is a cross-sectional view schematically showing the structure of a micro light emitting device according to an embodiment. Referring to  FIG.  1   , a micro light emitting device  100  may include a first semiconductor layer  103 , a light emitting layer  104  arranged on the upper surface of the first semiconductor layer  103 , a second semiconductor layer  105  arranged on the upper surface of the light emitting layer  104 , an insulating layer  106  arranged on the upper surface of the second semiconductor layer  105 , a first electrode  108  arranged on the upper surface of the insulating layer  106  such that the first electrode  108  is electrically connected to the first semiconductor layer  103 , a second electrode  107  arranged on the upper surface of the insulating layer  106  such that the second electrode  107  is electrically connected to the second semiconductor layer  105 , and an aluminum nitride (AlN) layer  102  arranged on the lower surface of the first semiconductor layer  103  and having a flat surface. The first electrode  108  and the second electrode  107  may be arranged on an upper surface (e.g., a first surface) of the micro light emitting device  100 . The AlN layer  102  may be arranged on a lower surface (e.g., a second surface) of the micro light emitting device  100 . 
     The first semiconductor layer  103  and the second semiconductor layer  105  may include, for example, a group III-V or group II-VI compound semiconductor. The first semiconductor layer  103  and the second semiconductor layer  105  may provide electrons and holes to the light emitting layer  104 . For this, the first semiconductor layer  103  and the second semiconductor layer  105  may be electrically doped with opposite types. For example, the first semiconductor layer  103  may be doped with an n-type impurity (e.g., a first impurity having a first conductivity) and the second semiconductor layer  105  may be doped with a p-type impurity (e.g., a second impurity having a second conductivity), or the first semiconductor layer  103  may be doped p-type and the second semiconductor layer  105  may be doped n-type. 
     The light emitting layer  104  has a quantum well structure in which quantum wells are arranged between barriers. Light may be generated as electrons and holes provided from the first and second semiconductor layers  103  and  105  recombine in the quantum well in the light emitting layer  104 . The wavelength of light generated from the light emitting layer  104  may be determined according to the energy band gap of the material forming the quantum well in the light emitting layer  104 . The light emitting layer  104  may have only one quantum well, or may have a multi-quantum well (MQW) structure in which a plurality of quantum wells are alternately arranged with a plurality of barriers. The thickness of the light emitting layer  104  or the number of quantum wells in the light emitting layer  104  may be appropriately selected considering the driving voltage and luminous efficiency of the light emitting device. 
     To easily align the micro light emitting device  100  in a fluidic self assembly method to be described below, both the first electrode  108  and the second electrode  107  may be arranged on one surface of the micro light emitting device  100 . For example, with reference to  FIG.  1   , the insulating layer  106  may be formed on the upper surface of the second semiconductor layer  105 , and both of the first electrode  108  and the second electrode  107  may be arranged on the upper surface of the insulating layer  106 . To electrically connect the first electrode  108  to the first semiconductor layer  103 , the micro light emitting device  100  may further include a via hole V passing through the second semiconductor layer  105  and the light emitting layer  104 . The insulating layer  106  may extend to surround the sidewall of the via hole V. In other words, a portion of the second semiconductor layer  105  exposed by the via hole V and a portion of the light emitting layer  104  exposed by the via hole V may be covered by the insulating layer  106 . The first electrode  108  extends from the upper surface of the insulating layer  106  to the upper surface of the first semiconductor layer  103  exposed through the via hole V to contact the first semiconductor layer  103  through the via hole V. The second electrode  107  may be configured to penetrate the insulating layer  106  and contact the second semiconductor layer  105 . Also, a portion of the second electrode  107  may further extend laterally from the upper surface of the insulating layer  106 . 
     The AlN layer  102  may provide a flat lower surface to easily align the micro light emitting device  100  in a fluidic self assembly method. For this, the AlN layer  102  may have a very smooth and flat lower surface. For example, the root mean square (RMS) of the surface roughness of the lower surface of the AlN layer  102  may be about 50 nm or less, or about 10 nm or less. 
     In addition, to easily align the micro light emitting device  100  in a fluidic self assembly method, the micro light emitting device  100  may have a shape in which the diameter or width of the micro light emitting device  100  is greater than the thickness of the micro light emitting device  100 . In particular, the diameter or width W 1  of the first semiconductor layer  103  may be greater than the thickness T of the micro light emitting device  100 . For example, the thickness T of the micro light emitting device  100  may be less than about 20 μm, for example, in the range of about 1 μm to about 20 μm, or in the range of about 2 μm to about 10 μm and, the diameter or width W 1  of the first semiconductor layer  103  may be less than about 100 μm, for example, in the range of about 1 μm to about 100 μm, or in the range of about 5 μm to about 50 μm. For example, the diameter or width W 1  of the first semiconductor layer  103  may be greater than the thickness T, or greater than two times, or five times the thickness T of the micro light emitting device  100 . Here, the size, that is, the diameter or width of the micro light emitting device  100 , may be defined as the diameter or width W 1  of the widest portion of the first semiconductor layer  103 . Accordingly, the size, that is, the diameter or width of the micro light emitting device  100 , may be, for example, in the range of about 1 μm to about 100 μm, or in the range of about 5 μm to about 50 μm. 
     According to an embodiment, the micro light emitting device  100  may have an inclined side surface such that the diameter or width W 1  of both of the AlN layer  102  and the first semiconductor layer  103  is greater than the diameter or width W 2  of the second semiconductor layer  105  and the insulating layer  106 . For example, the diameter or width W 2  of the second semiconductor layer  105  may be 0.7 times or more of the diameter or width W 1  and less than the diameter or width W 1 , or 0.8 times or more of the diameter or width W 1  and 0.95 times or less of the diameter or width W 1  of the first semiconductor layer  103 . Accordingly, the areas of both of the AlN layer  102  and the first semiconductor layer  103  may be larger than those of the second semiconductor layer  105  and the insulating layer  106 . In addition, the diameter or width W 2  of the second semiconductor layer  105  of the micro light emitting device  100  may also be greater than the thickness T of the micro light emitting device  100 . 
     In addition, the micro light emitting device  100  may further include a bonding spread prevention wall  109  arranged between the first electrode  108  and the second electrode  107  on the upper surface of the insulating layer  106 . When bonding the first electrode  108  and the second electrode  107  of the micro light emitting device  100  to the corresponding electrode pads on the display substrate of the display apparatus in the process of manufacturing the display apparatus, for example, the bonding spread prevention wall  109  prevents a bonding material such as a solder bump from spreading between the first electrode  108  and the second electrode  107  to prevent a short circuit. The bonding spread prevention wall  109  may have a shape protruding above the upper surface of the insulating layer  106 . The thickness of the bonding spread prevention wall  109  may be less than or equal to the thickness of the first and second electrodes  108  and  107 . In addition, the bonding spread prevention wall  109  may be made of an electrically insulating material. 
     To easily bond the first electrode  108  and the second electrode  107  of the micro light emitting device  100  to the corresponding electrode pads on the display substrate in the process of manufacturing the display apparatus, the first electrode  108  and the second electrode  107  may have a symmetrical shape. In other words, for example, the first electrode  108  and the second electrode  107  may have a first shape and a second shape, respectively, that each have radial symmetry with respect to a center of the micro light emitting device  100 .  FIGS.  2 A to  2 C  are plan views illustrating various electrode structures of the micro light emitting device  100 . 
     Referring to  FIG.  2 A , a horizontal cross-section of the micro light emitting device  100  (e.g., a cross-section when viewed in a vertical direction) may have a circular shape. The second electrode  107  may be arranged at the center of the second semiconductor layer  105 , that is, a position corresponding to the center of the micro light emitting device  100  in the horizontal direction (e.g., the width direction). The second electrode  107  may have a circular shape. However, the disclosure is not necessarily limited thereto, and the second electrode  107  may have a quadrangle or another polygonal shape. The first electrode  108  may be arranged at an edge of the micro light emitting device  100 , that is, a position corresponding to the edge of the second semiconductor layer  105  in the horizontal direction. The first electrode  108  may have a symmetrical shape surrounding the second electrode  107 . For example, the first electrode  108  may have the form of two separated semicircular rings surrounding the second electrode  107 . In  FIG.  2 A , the first electrode  108  is illustrated as having the shape of two separated rings as an example, but the disclosure is not limited thereto. The first electrode  108  may have, for example, the shape of three or more separated rings. Even if the first electrodes  108  have separated portions, they may be electrically connected to each other when they are bonded to the electrode pads on the display substrate. 
     In addition, the bonding spread prevention wall  109  may be arranged in the form of a ring between the first electrode  108  and the second electrode  107 . The bonding spread prevention wall  109  may have the shape of two or more separated rings like the first electrode  108 , and may be arranged to completely block a path between the first electrode  108  and the second electrode  107 . 
     Referring to  FIG.  2 B , each of the first electrode  108  and the bonding spread prevention wall  109  may have the form of one complete ring. 
     Referring to  FIG.  2 C , a cross-section of the micro light emitting device  100  may have a rectangular shape. The second electrode  107  is arranged at the center of the micro light emitting device  100  and may have a circular or polygonal shape. The first electrode  108  may be respectively arranged in two vertex regions of the rectangular shape facing each other in a diagonal direction. In addition, the micro light emitting device  100  may further include bonding pads  110  respectively arranged at two different vertex regions facing each other in different diagonal directions. In other words, the bonding pads  110  may be arranged at the two other vertex regions of the rectangular shape that face each other in another diagonal direction of the rectangular shape. When the first electrode  108  and the second electrode  107  of the micro light emitting device  100  are bonded to the electrode pad on the display substrate, the bonding pad  110  is bonded to the display substrate so that the micro light emitting device  100  may be stably mounted on the display substrate. Alternatively, the first electrode  108  may be arranged in all four vertex regions without the bonding pad  110 . 
       FIGS.  3 A to  3 D  are cross-sectional views schematically illustrating a process of manufacturing the micro light emitting device  100  shown in  FIG.  1   . 
     Referring to  FIG.  3 A , the AlN layer  102 , the first semiconductor layer  103 , the light emitting layer  104 , and the second semiconductor layer  105  may be sequentially grown on a growth substrate  101 . The growth substrate  101  may be, for example, a silicon substrate. The AlN layer  102  may serve as a buffer layer used to grow a compound semiconductor on a silicon substrate. 
     Referring to  FIG.  3 B , the first semiconductor layer  103  may be exposed by partially etching the second semiconductor layer  105  and the light emitting layer  104  to form a via hole V. 
     Referring to  FIG.  3 C , an insulating layer  106  may be formed on the second semiconductor layer  105 . The insulating layer  106  extends to the inner sidewall of the via hole V so that a portion of the second semiconductor layer  105  exposed by the via hole V and a portion of the light emitting layer  104  exposed by the via hole V may be covered by the insulating layer  106 . Then, the first electrode  108  and the second electrode  107  may be formed to be in contact with the first semiconductor layer  103  and the second semiconductor layer  105 , respectively, and a bonding spread prevention wall  109  may be formed between the first electrode  108  and the second electrode  107 . 
     Referring to  FIG.  3 D , the insulating layer  106 , the second semiconductor layer  105 , the light emitting layer  104 , the first semiconductor layer  103 , and the AlN layer  102  are partially etched to form a plurality of micro light emitting devices  100 . Although one micro light emitting device  100  is illustrated in  FIG.  3 D  for convenience, a large number of micro light emitting devices  100  may be formed on one growth substrate  101 . 
     Thereafter, the micro light emitting device  100  may be separated from the growth substrate  101  through a chemical lift off method. When the micro light emitting device  100  is separated through chemical lift off, the lower surface of the micro light emitting device  100 , that is, the lower surface of the AlN layer  102 , may be very smooth. 
     Before being mounted on the display substrate of the display apparatus, the micro light emitting device  100  formed in such a way may first be aligned on a separate transfer substrate using a fluidic self assembly method.  FIG.  4    is a perspective view showing an example method of aligning the micro light emitting device  100  using a fluidic self assembly method. 
     Referring to  FIG.  4   , a plurality of micro light emitting devices  100  may be supplied on the upper surface of a transfer substrate  130  having grooves  135  that are two dimensionally arranged. The plurality of micro light emitting devices  100  may be directly sprayed on the transfer substrate  130  after supplying the liquid to the grooves  135  of the transfer substrate  130  or supplied on the transfer substrate  130  in a state included in a suspension. 
     The liquid supplied to the grooves  135  may be any kind of liquid as long as the liquid does not corrode or damage the micro light emitting device  100 , and may be supplied to the grooves  135  by various methods, such as a spray method, a dispensing method, an inkjet dot method, a method for flowing a liquid to the transfer substrate  130 , and the like. The liquid may include, for example, any one or more from among water, ethanol, alcohol, polyol, ketone, halocarbon, acetone, flux, and organic solvent. The organic solvent may include, for example, isopropyl alcohol (IPA). The amount of liquid supplied may be varied to fit or overflow from the grooves  135 . 
     The plurality of micro light emitting devices  100  may be directly sprayed on the transfer substrate  130  without another liquid, or may be supplied on the transfer substrate  130  in a state included in a suspension. As a supply method of the micro light emitting device  100  included in the suspension, a spray method, a dispensing method for dropping a liquid, an inkjet dot method for discharging a liquid like a printing method, a method for flowing a suspension to the transfer substrate  130 , and the like may be used in various ways. 
       FIG.  5    schematically shows a scanning process for aligning the micro light emitting device  100 . Referring to  FIG.  5   , an absorber  10  may scan the transfer substrate  130 . While passing through the plurality of grooves  135  and while in contact with the transfer substrate  130  according to the scanning, the absorber  10  may move the micro light emitting devices  100  into the grooves  135 , and may also absorb the liquid L in the grooves  135 . The absorber  10  is sufficient as long as the absorber  10  is a material that may absorb the liquid L, and its shape or structure is not limited. The absorber  10  may include, for example, fabric, tissue, polyester fiber, paper, or a wiper. 
     The absorber  10  may be used alone without other auxiliary devices, but is not limited thereto, and may be coupled to a support  20  for convenient scanning of the transfer substrate  130 . The support  20  may have various shapes and structures suitable for scanning the transfer substrate  130 . For example, the support  20  may have the form of a rod, a blade, a plate, a wiper, or the like. The absorber  10  may be provided on either side of the support  20  or wrap around the support  20 . The shape of the support  20  and the absorber  10  is not limited to the illustrated rectangular cross-sectional shape, and may have a circular or other cross-sectional shape. 
     The absorber  10  may be scanned while pressing the transfer substrate  130  with an appropriate pressure. Because a partition wall  131  of the transfer substrate  130  includes a flexible polymer material, even if pressure is applied to the transfer substrate  130 , the original thickness of the partition wall  131  may be restored after scanning. Scanning may be performed in various methods, for example, a sliding method, a rotating method, a translating motion method, a reciprocating motion method, a rolling method, a spinning method, and/or a rubbing method of the absorber  10 , and may include both a regular manner and an irregular manner. Scanning may be performed by moving the transfer substrate  130  instead of moving the absorber  10 , and scanning of the transfer substrate  130  may also be performed in a manner such as a sliding, rotating, translational reciprocating, rolling, spinning, and/or rubbing method. In addition, scanning may be performed by the cooperation of the absorber  10  and the transfer substrate  130 . 
     The operation of supplying the liquid L to the grooves  135  of the transfer substrate  130  and the operation of supplying the micro light emitting devices  100  to the transfer substrate  130  may be performed in the reverse order to the order described above. In addition, the operation of supplying the liquid L to the grooves  135  of the transfer substrate  130  and the operation of supplying the micro light emitting devices  100  to the transfer substrate  130  may be simultaneously performed in one operation. For example, by supplying a suspension including the micro light emitting devices  100  to the transfer substrate  130 , the liquid L and the micro light emitting devices  100  may be simultaneously supplied to the transfer substrate  130 . After the absorber  10  scans the transfer substrate  130 , the micro light emitting devices  100  remaining in the transfer substrate  130  without entering the grooves  135  may be removed. The processes described above may be repeated until the micro light emitting devices  100  are seated in all the grooves  135 . As described above, a large number of micro light emitting devices  100  may be aligned on a large-area transfer substrate  130  using a fluidic self assembly method. 
       FIG.  6    is a cross-sectional view showing a schematic structure of a transfer substrate  130  according to an embodiment in which the micro light emitting devices  100  are arranged. Referring to  FIG.  6   , the transfer substrate  130  may include the partition wall  131  arranged on the upper surface of the transfer substrate  130  and having a plurality of grooves  135 . The partition wall  131  may be made of a flexible polymer material. For example, the partition wall  131  may include at least one of an acrylic polymer, a silicone-based polymer, and an epoxy-based polymer. In addition, the partition wall  131  may further include a photosensitive material. When the partition wall  131  includes a photosensitive material, a plurality of grooves  135  may be formed by a photolithography method. When the partition wall  131  does not include a photosensitive material, the plurality of grooves  135  may be formed by etching and molding. The thickness (e.g., the height) of the partition wall  131  may be slightly greater than or slightly less than the thickness of the micro light emitting device  100 . For example, the thickness of the partition wall  131  may be 0.8 to 1.2 times the thickness of the micro light emitting device  100 . 
     Using the fluidic self assembly method described above, one micro light emitting device  100  may be arranged in each groove  135 . In this case, the partition wall  131  may surround the micro light emitting device  100 . The micro light emitting device  100  may be disposed such that the first and second electrodes  108  and  107  face up, that is, out of the groove  135 , and the AlN layer  102  contacts the bottom surface  132  of the groove  135 . For this, the bottom surface  132  of the groove  135  that comes into contact with the lower surface of the micro light emitting device  100  may be made of a dielectric material having high hydrophilicity and a very smooth surface. For example, the RMS surface roughness of the bottom surface  132  of the groove  135  may be about 50 nm or less, or about 10 nm or less. In addition, the AlN layer  102  in contact with the bottom surface  132  of the groove  135  may also have hydrophilicity and an RMS surface roughness of about 50 nm or less, or about 10 nm or less. 
     Therefore, when the AlN layer  102  comes into contact with the bottom surface  132  of the groove  135  during the fluidic self assembly process, due to the high surface energy, the micro light emitting device  100  settles in the groove  135  without exiting the groove  135 . In addition, due to the structure of the micro light emitting device  100  having a larger diameter or width than the thickness, when the AlN layer  102  comes into contact with the bottom surface  132  of the groove  135 , the contact area is relatively large, so that surface energy may be further increased. In addition, in the structure of the micro light emitting device  100  having an inclined side surface, because the area of the AlN layer  102  is larger than the area of the insulating layer  106 , when the AlN layer  102  contacts the bottom surface  132  of the groove  135 , the surface energy may further increase. 
     On the other hand, when the first and second electrodes  107  and  108  contact the bottom surface  132  of the groove  135  within the groove  135 , because the surface energy is low, the micro light emitting device  100  may easily come out of the groove  135  even with a weak force. Therefore, when aligning the micro light emitting device  100  using the fluidic self assembly method, the first and second electrodes  107  and  108  may face the outside of the groove  135  when the micro light emitting device  100  is fixed in the groove  135 . In addition, the first and second electrodes  107  and  108  may allow the micro light emitting device  100  that is not fixed in the groove  135  and remains on the partition wall  131  to be easily separated from the transfer substrate  130  in the cleaning operation. In this regard, the disclosed micro light emitting device  100  may have a structure suitable for alignment in a fluidic self assembly method. Although not shown in the drawing, a concave-convex pattern may be further formed on the upper surface of the partition wall  131  so that the micro light emitting device  100  may be more easily separated from the partition wall  131 . 
     A plurality of micro light emitting devices  100  aligned on the transfer substrate  130  may be transferred onto a display substrate of the display apparatus for manufacturing the display apparatus.  FIG.  7    is a cross-sectional view schematically showing a process of transferring the micro light emitting device  100  aligned on the transfer substrate  130  onto the display substrate. 
     Referring to  FIG.  7   , a display substrate  210  may include a plurality of first electrode pads  211  and a plurality of second electrode pads  212 . The display substrate  210  may further include a driving circuit including a plurality of thin film transistors for independently controlling the plurality of micro light emitting devices  100 . For example, a plurality of thin film transistors are arranged under the first electrode pad  211  and the second electrode pad  212  in the display substrate  210 , and the plurality of thin film transistors may be electrically connected to the first and second electrode pads  211  and  212  through wiring. 
     The transfer substrate  130  may be arranged such that the first and second electrodes  108  and  107  of the micro light emitting device  100  face the display substrate  210 . Then, the transfer substrate  130  may be pressed onto the display substrate  210  such that the first electrode  108  of the micro light emitting device  100  is in contact with the first electrode pad  211  of the display substrate  210 , and the second electrode  107  is in contact with the second electrode pad  212  of the display substrate  210 . Then, the first electrode  108  may be bonded to the first electrode pad  211  and the second electrode  107  may be bonded to the second electrode pad  212  through a bonding material such as solder bumps. In this way, when the micro light emitting device  100  is completely fixed to the display substrate  210 , the transfer substrate  130  may be detached from the micro light emitting device  100 . As described above, by using the micro light emitting device  100  having a structure suitable for alignment in the fluidic self-assembly method, a large-area display apparatus may be relatively easily manufactured by the fluidic self-assembly method. 
       FIG.  8    is a cross-sectional view schematically illustrating a structure of a micro light emitting device according to an embodiment. In  FIG.  1   , the bonding spread prevention wall  109  has been described as having an embossed structure protruding above the insulating layer  106 , but the disclosure is not limited thereto. Referring to  FIG.  8   , a micro light emitting device  100   a  may include a bonding spread prevention wall  109   a  having an engraved structure, for example, a concave groove. For example, a trench may be formed by etching a portion of the second semiconductor layer  105  and a portion of the light emitting layer  104  at the position of the bonding spread prevention wall  109   a  when forming the via hole V. Thereafter, the insulating layer  106  may be formed to cover the sidewalls and the bottom surface of the trench with a preset thickness. Then, because the bonding material flows along the engraved groove of the bonding spread prevention wall  109   a,  the bonding material may be prevented from spreading widely between the first electrode  108  and the second electrode  107 . Other structures of the micro light emitting device  100   a  not described with reference to  FIG.  8    may be the same as those of the micro light emitting device  100  shown in  FIG.  1   . 
       FIG.  9    is a cross-sectional view schematically illustrating a structure of a micro light emitting device according to an embodiment. Referring to  FIG.  9   , a micro light emitting device  100   b  may further include a plurality of grooves  111  formed in the lower surface of the AlN layer  102 . The plurality of grooves  111  may be formed by etching the AlN layer  102 . The plurality of grooves  111  may be formed by etching up to a portion of the first semiconductor layer  103 . The plurality of grooves  111  may have a closed structure isolated from each other. 
       FIGS.  10 A and  10 B  are plan views showing examples of a plurality of grooves  111  formed in the AlN layer  102  of the micro light emitting device  100   b  shown in  FIG.  9   . Referring to  FIG.  10 A , the plurality of grooves  111  may have a dot shape and may be two-dimensionally arranged in the lower surface of the AlN layer  102 . In addition, referring to  FIG.  10 B , the plurality of grooves  111  may have a ring shape and may be arranged in a concentric circle shape in the lower surface of the AlN layer  102 . 
     When aligning the micro light emitting device  100   b  on the transfer substrate  130  through the fluidic self assembly method described with reference to  FIGS.  4  and  5   , the plurality of grooves  111  may be filled with a liquid used for fluidic self assembly. The liquid filled in the plurality of grooves  111  may further increase the surface energy when the AlN layer  102  contacts the bottom surface  132  of the groove  135  of the transfer substrate  130 . Accordingly, the micro light emitting device  100   b  may be more stably settled in the groove  135  of the transfer substrate  130 . For this, the plurality of grooves  111  may have an isolated closed structure so that the liquid filled in the plurality of grooves  111  does not leak. For example, the plurality of grooves  111  may be arranged in the lower surface of the AlN layer  102  so that the liquid does not leak over the edge of the lower surface of the AlN layer  102 . 
     In addition, the plurality of grooves  111  may serve as a light scattering structure that helps light generated from the light emitting layer  104  of the micro light emitting device  100   b  to pass through the AlN layer  102  to be emitted to the outside. Light generated from the light emitting layer  104  may be relatively uniformly emitted outside the AlN layer  102  while being refracted in the plurality of grooves  111 . For this, the plurality of grooves  111  may be irregularly arranged. 
       FIG.  11    is a cross-sectional view schematically illustrating a structure of a micro light emitting device according to an embodiment. Referring to  FIG.  11   , a micro light emitting device  100   c  may further include a light scattering structure  112  distributed in the first semiconductor layer  103 . The light scattering structure  112  may be made of air, a void, a transparent dielectric material, or a semiconductor material different from that of the first semiconductor layer  103 . The width, thickness, shape of the light scattering structure  112  or the distance between the light scattering structures  112  may be irregularly distributed. Accordingly, light generated from the light emitting layer  104  may be relatively uniformly emitted to the outside by the irregular light scattering structure  112  in the first semiconductor layer  103 . 
       FIG.  12    is a cross-sectional view schematically illustrating a structure of a display apparatus according to an example embodiment. Referring to  FIG.  12   , a display apparatus  200  may include a display substrate  210 , a plurality of micro light emitting devices  100  mounted on the display substrate  210 , and a wavelength conversion layer  220  arranged on the plurality of micro light emitting devices  100 . In addition, the display apparatus  200  may further include an upper substrate  230  arranged on the wavelength conversion layer  220 .  FIG.  12    shows that the micro light emitting device  100  shown in  FIG.  1    is used, but micro light emitting devices  100   a,    100   b,  and  100   c  according to other embodiments may also be used. 
     The wavelength conversion layer  220  may include a first wavelength conversion layer  220 R for converting light emitted from the micro light emitting device  100  into light of a first wavelength band, a second wavelength conversion layer  220 G for converting the light emitted from the micro light emitting device  100  into light of a second wavelength band different from the first wavelength band, and a third wavelength conversion layer  220 B for converting the light emitted from the micro light emitting device  100  into light of a third wavelength band different from the first and second wavelength bands. For example, the light of the first wavelength band may be red light, the light of the second wavelength band may be green light, and the light of the third wavelength band may be blue light. The first wavelength conversion layer  220 R, the second wavelength conversion layer  220 G, and the third wavelength conversion layer  220 B are arranged spaced apart with a diaphragm  221  arranged therebetween, and may be arranged to face the corresponding micro light emitting devices  100 , respectively. 
     When the micro light emitting device  100  emits blue light, the third wavelength conversion layer  220 B may include a resin that transmits blue light. The second wavelength conversion layer  220 G may convert blue light emitted from the micro light emitting device  100  to emit green light. The second wavelength conversion layer  220 G may include quantum dots or phosphors that are excited by blue light to emit green light. The first wavelength conversion layer  220 R may change blue light emitted from the micro light emitting device  100  into red light to be emitted. The first wavelength conversion layer  220 R may include quantum dots or phosphors that are excited by blue light to emit red light. 
     The quantum dots included in the first wavelength conversion layer  220 R or the second wavelength conversion layer  220 G may have a core-shell structure having a core portion and a shell portion, or may have a particle structure without a shell. The core-shell structure may be a single-shell or multi-shell structure, such as a double-shell structure. The quantum dots may include a group II-VI series semiconductor, a group III-V series semiconductor, a group IV-VI series semiconductor, a group IV series semiconductor, and/or graphene quantum dots. The quantum dots may include, for example, Cd, Se, Zn, S and/or InP, and each quantum dot may have a diameter of several tens of nm or less, for example, a diameter of about 10 nm or less. The quantum dots included in the first wavelength conversion layer  220 R and the second wavelength conversion layer  220 G may have different sizes. 
       FIG.  13    is a cross-sectional view schematically illustrating a structure of a display apparatus according to an embodiment. Referring to  FIG.  13   , a display apparatus  300  may further include a capping layer  250  arranged on the wavelength conversion layer  220  and a color filter layer  240  arranged on the capping layer  250 . The capping layer  250  and the color filter layer  240  may be arranged between the wavelength conversion layer  220  of the display apparatus  200  shown in  FIG.  12    and the upper substrate  230 . The color filter layer  240  includes a first filter  240 R, a second filter  240 G, and a third filter  240 B spaced apart with a black matrix  241  therebetween. The first filter  240 R, the second filter  240 G, and the third filter  240 B are arranged facing the first wavelength conversion layer  220 R, the second wavelength conversion layer  220 G, and the third wavelength conversion layer  220 B, respectively. The first filter  240 R, the second filter  240 G, and the third filter  240 B transmit red light, green light, and blue light, respectively, and absorb light of different colors. When the color filter layer  240  is provided, light other than red light emitted without wavelength conversion in the first wavelength conversion layer  220 R, or light other than the green light emitted without wavelength conversion in the second wavelength conversion layer  220 G may be removed by the first filter  240 R and the second filter  240 G, respectively, so that the color purity of the display apparatus  300  may be increased. 
     The display apparatuses described above may be applied to various electronic devices having a screen display function.  FIG.  14    is a schematic block diagram of an electronic device according to an example embodiment. Referring to  FIG.  14   , an electronic device  8201  may be provided in a network environment  8200 . In the network environment  8200 , the electronic device  8201  may communicate with another electronic device  8202  through a first network  8298  (such as a short-range wireless communication network and the like), or communicate with another electronic device  8204  and/or a server  8208  through a second network  8299  (such as a remote wireless communication network). The electronic device  8201  may communicate with the other electronic device  8204  through the server  8208 . The electronic device  8201  may include a processor  8220 , a memory  8230 , an input device  8250 , an audio output device  8255 , a display apparatus  8260 , an audio module  8270 , a sensor module  8276 , and an interface  8277 , a haptic module  8279 , a camera module  8280 , a power management module  8288 , a battery  8289 , a communication module  8290 , a subscriber identification module  8296 , and/or an antenna module  8297 . In the electronic device  8201 , some of these components may be omitted or other components may be added. Some of these components may be implemented as one integrated circuit. For example, the sensor module  8276  (a fingerprint sensor, an iris sensor, an illuminance sensor, etc.) may be implemented by being embedded in the display apparatus  8260  (a display, etc.). 
     The processor  8220  may execute software (a program  8240 , etc.) to control one or a plurality of other components (such as hardware, software components, etc.) of the electronic device  8201  connected to the processor  8220 , and perform various data processing or operations. As part of data processing or operation, the processor  8220  may load commands and/or data received from other components (the sensor module  8276 , the communication module  8290 , etc.) into a volatile memory  8232 , process commands and/or data stored in the volatile memory  8232 , and store result data in a nonvolatile memory  8234 . The nonvolatile memory  8234  may include an internal memory  8236  mounted in the electronic device  8201  and a removable external memory  8238 . The processor  8220  may include a main processor  8221  (such as a central processing unit, an application processor, etc.) and a secondary processor  8223  (such as a graphics processing unit, an image signal processor, a sensor hub processor, a communication processor, etc.) that may be operated independently or together. The secondary processor  8223  may use less power than the main processor  8221  and may perform specialized functions. 
     The secondary processor  8223  may control functions and/or states related to some of the components of the other electronic device  8202  (such as the display apparatus  8260 , the sensor module  8276 , the communication module  8290 , etc.) instead of the main processor  8221  while the main processor  8221  is in an inactive state (sleep state), or with the main processor  8221  while the main processor  8221  is in an active state (an application execution state). The secondary processor  8223  (such as an image signal processor, a communication processor, etc.) may be implemented as part of other functionally related components (such as the camera module  8280 , the communication module  8290 , etc.). 
     The memory  8230  may store various data required by components of the electronic device  8201  (such as the processor  8220 , the sensor module  8276 , etc.). The data may include, for example, software (such as the program  8240 , etc.) and input data and/or output data for commands related thereto. The memory  8230  may include the volatile memory  8232  and/or the nonvolatile memory  8234 . 
     The program  8240  may be stored as software in the memory  8230  and may include an operating system  8242 , middleware  8244 , and/or an application  8246 . 
     The input device  8250  may receive commands and/or data to be used for components (such as the processor  8220 , etc.) of the electronic device  8201  from outside (a user) of the electronic device  8201 . The input device  8250  may include a remote controller, a microphone, a mouse, a keyboard, and/or a digital pen (such as a stylus pen). 
     The audio output device  8255  may output an audio signal to the outside of the electronic device  8201 . The audio output device  8255  may include a speaker and/or a receiver. The speaker may be used for general purposes such as multimedia playback or recording playback, and the receiver may be used to receive incoming calls. The receiver may be combined as a part of the speaker or may be implemented as an independent separate device. 
     The display apparatus  8260  may visually provide information to the outside of the electronic device  8201 . The display apparatus  8260  may include a display, a hologram device, or a projector and a control circuit for controlling the device. The display apparatus  8260  may include the above-described driving circuit, micro light emitting device, side reflection structure, bottom reflection structure, and the like. The display apparatus  8260  may include a touch circuit set to sense a touch, and/or a sensor circuit (such as a pressure sensor) set to measure the strength of a force generated by the touch. 
     The audio module  8270  may convert sound into an electrical signal, or conversely, may convert an electrical signal into sound. The audio module  8270  may acquire sound through the input device  8250  or output sound through speakers and/or headphones of the audio output device  8255 , and/or other electronic devices (such as the other electronic device  8202 ) directly or wirelessly connected to the electronic device  8201 . 
     The sensor module  8276  may detect an operating state (such as power, temperature, and the like) of the electronic device  8201  or an external environmental state (such as a user state and the like), and generate an electrical signal and/or data value corresponding to the detected state. The sensor module  8276  may include a gesture sensor, a gyro sensor, a barometric pressure sensor, a magnetic sensor, an acceleration sensor, a grip sensor, a proximity sensor, a color sensor, an infrared (IR) sensor, a biometric sensor, a temperature sensor, a humidity sensor, and/or an illuminance sensor. 
     The interface  8277  may support one or more specified protocols that may be used for the electronic device  8201  to connect directly or wirelessly with another electronic device (such as the other electronic device  8202 ). The interface  8277  may include a High Definition Multimedia Interface (HDMI), a Universal Serial Bus (USB) interface, an SD card interface, and/or an audio interface. 
     A connection terminal  8278  may include a connector through which the electronic device  8201  may be physically connected to another electronic device (such as the other electronic device  8202 ). The connection terminal  8278  may include an HDMI connector, a USB connector, an SD card connector, and/or an audio connector (such as a headphone connector). 
     The haptic module  8279  may convert an electrical signal into a mechanical stimulus (such as vibration, movement, etc.) or an electrical stimulus that a user may perceive through a tactile or motor sense. The haptic module  8279  may include a motor, a piezoelectric element, and/or an electrical stimulation device. 
     The camera module  8280  may capture a still image and a video. The camera module  8280  may include a lens assembly including one or more lenses, image sensors, image signal processors, and/or flashes. The lens assembly included in the camera module  8280  may collect light emitted from a subject that is a target of image capturing. 
     The power management module  8288  may manage power supplied to the electronic device  8201 . The power management module  8288 may be implemented as a part of a Power Management Integrated Circuit (PMIC). 
     The battery  8289  may supply power to components of the electronic device  8201 . The battery  8289  may include a non-rechargeable primary cell, a rechargeable secondary cell, and/or a fuel cell. 
     The communication module  8290  may support establishing a direct (wired) communication channel and/or a wireless communication channel, and performing communication through the established communication channel between the electronic device  8201  and other electronic devices (such as the other electronic device  8202 , the other electronic device  8204 , the server  8208 , and the like). The communication module  8290  may include one or more communication processors that operate independently of the processor  8220  (such as an application processor) and support direct communication and/or wireless communication. The communication module  8290  may include a wireless communication module  8292  (such as a cellular communication module, a short-range wireless communication module, a Global Navigation Satellite System (GNSS) communication module, and the like) and/or a wired communication module  8294  (such as a local area network (LAN) communication module, a power line communication module, and the like). Among these communication modules, a corresponding communication module may communicate with other electronic devices through the first network  8298  (a short-range communication network such as Bluetooth, WiFi Direct, or Infrared Data Association (IrDA)) or the second network  8299  (a cellular network, the Internet, or a telecommunication network such as a computer network (such as LAN, WAN, and the like)). These various types of communication modules may be integrated into one component (such as a single chip and the like), or may be implemented as a plurality of separate components (a plurality of chips). The wireless communication module  8292  may check and authenticate the electronic device  8201  in a communication network such as the first network  8298  and/or the second network  8299  using subscriber information (such as an international mobile subscriber identifier (IMSI), etc.) stored in the subscriber identification module  8296 . 
     The antenna module  8297  may transmit signals and/or power to the outside (such as other electronic devices) or receive signals and/or power from the outside. The antenna may include a radiator made of a conductive pattern formed on a substrate (such as a printed circuit board (PCB), etc.). The antenna module  8297  may include one or a plurality of antennas. If antennas are included, an antenna suitable for a communication method used in a communication network such as the first network  8298  and/or the second network  8299  may be selected from the plurality of antennas by the communication module  8290 . Signals and/or power may be transmitted or received between the communication module  8290  and another electronic device through the selected antenna. In addition to the antenna, other components (such as a radio-frequency integrated circuit (RFIC) may be included as part of the antenna module  8297 . 
     Some of the components are connected to each other and may exchange signals (such as commands, data, and the like) through a communication method between peripheral devices (such as a bus, a General Purpose Input and Output (GPIO), a Serial Peripheral Interface (SPI), a Mobile Industry Processor Interface (MIPI), and the like). 
     The command or data may be transmitted or received between the electronic device  8201  and the other electronic device  8204  through the server  8208  connected to the second network  8299 . The other electronic devices  8202  and  8204  may be the same or different types of devices as or from the electronic device  8201 . All or some of the operations executed by the electronic device  8201  may be executed by one or more of the other electronic devices, that is, the other electronic devices  8202  and  8204  and the server  8208 . For example, when the electronic device  8201  needs to perform a certain function or service, instead of executing the function or service itself, the electronic device  8201  may request one or more other electronic devices to perform the function or part or all of the service. One or more other electronic devices that receive the request may execute an additional function or service related to the request, and transmit a result of the execution to the electronic device  8201 . For this, cloud computing, distributed computing, and/or client-server computing technology may be used. 
       FIG.  15    illustrates an example in which a display apparatus according to embodiments is applied to a mobile device. A mobile device  9100  may include a display apparatus  9110 , and the display apparatus  9110  may include the above-described driving circuit, micro light emitting device, side reflection structure, bottom reflection structure, and the like. The display apparatus  9110  may have a foldable structure, for example, a multi-foldable structure. 
       FIG.  16    illustrates an example in which the display apparatus according to the embodiments is applied to a vehicle display apparatus. The display apparatus may be a vehicle head-up display apparatus  9200 , and may include a display  9210  provided in an area of the vehicle, and a light path changing member  9220  that converts an optical path so that the driver may see the image generated on the display  9210 . 
       FIG.  17    illustrates an example in which a display apparatus according to embodiments is applied to augmented reality glasses or virtual reality glasses. Augmented reality glasses  9300  may include a projection system  9310  that forms an image, and an element  9320  that guides the image from the projection system  9310  into the user&#39;s eye. The projection system  9310  may include the above-described driving circuit, micro light emitting device, side reflection structure, bottom reflection structure, and the like. 
       FIG.  18    illustrates an example in which a display apparatus according to embodiments is applied to a signage. A signage  9400  may be used for outdoor advertisement using a digital information display, and may control advertisement content and the like through a communication network. The signage  9400  may be implemented, for example, through the electronic device described with reference to  FIG.  14   . 
       FIG.  19    illustrates an example in which a display apparatus according to embodiments is applied to a wearable display. A wearable display  9500  may include the above-described driving circuit, micro light emitting device, side reflection structure, bottom reflection structure, and the like, and may be implemented through the electronic device described with reference to  FIG.  14   . 
     The display apparatus according to example embodiments may also be applied to various products such as a rollable TV and a stretchable display. 
     It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.