Patent Publication Number: US-2021167124-A1

Title: Light emitting element, manufacturing method thereof, and display device including the light emitting element

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a U.S. National Phase Patent Application of Korean International Application No. PCT/KR2019/000537, which claims priority to Korean Patent Application No. 10-2018-0090544 filed on Aug. 3, 2018, the entire content of all of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a light emitting element, a manufacturing method thereof, and a display device including the light emitting element and, in particular, to a light emitting element having an end with a smooth parting surface, a manufacturing method thereof, and a display device including the light emitting element. 
     BACKGROUND ART 
     The importance of display devices has steadily increased with the development of multimedia technology. Accordingly, various types of display devices such as an organic light emitting display (OLED), a liquid crystal display (LCD) and the like have been used. 
     A display device is a device for displaying an image, and includes a display panel, such as an organic light emitting display panel or a liquid crystal display panel. Among them, a light emitting display panel may include a light emitting element. Examples of a light emitting diode (LED) include an organic light emitting diode (OLED) using an organic material as a fluorescent material, and an inorganic light emitting diode using an inorganic material as a fluorescent material. 
     The organic light emitting diode (OLED) using an organic material as a fluorescent material of a light emitting element has advantages in that a manufacturing process is simple and a display device can have flexibility. However, it is known that the organic material is vulnerable to a high-temperature operating environment and the blue light efficiency is relatively low. 
     On the other hand, the inorganic light emitting diode using an inorganic semiconductor as a fluorescent material has advantages in that it has durability even in a high-temperature environment and the blue light efficiency is high compared to the organic light emitting diode. Also, in the manufacturing process, as noted as a drawback of a conventional inorganic light emitting diode, a transfer method using a dielectrophoresis (DEP) method has been developed. Accordingly, continuous studies have been conducted on the inorganic light emitting diode having superior durability and efficiency compared to the organic light emitting diode. 
     DISCLOSURE 
     Technical Problem 
     The inorganic light emitting diode may be manufactured by growing an n-type or p-type doped semiconductor layer and an inorganic fluorescent material layer on a substrate, forming a rod having a specific shape, and separating the rod. In the case of separating a light emitting element using a physical method, however, the lengthwise direction end surface of the light emitting element is likely to be uneven. The uneven, jagged, or rough lengthwise direction end surface of the light emitting element is likely to cause a short circuit problem in the case of contact between the light emitting element and a contact electrode. 
     In view of the above, aspects of the present disclosure provide a light emitting element having an even end surface for contact with a contact electrode and a manufacturing method thereof. 
     Aspects of the present disclosure also provide a display device including a light emitting element that is capable of preventing an open or short circuit problem of an electrode material from occurring in the case of connection with a contact electrode. 
     It should be noted that aspects of the present disclosure are not limited to the above-mentioned aspects, and other unmentioned aspects of the present disclosure will be clearly understood by those skilled in the art from the following descriptions. 
     Technical Solution 
     According to an exemplary embodiment of the present disclosure, a manufacturing method of a light emitting element, comprises preparing a lower substrate including a substrate and a buffer material layer formed on the substrate, forming a separating layer disposed on the lower substrate and including at least one graphene layer, forming an element deposition structure by depositing a first conductivity type semiconductor layer, an active material layer, and a second conductivity type semiconductor layer on the separating layer, forming an element rod by etching the element deposition structure and the separating layer in a vertical direction, and separating the element rod from the lower substrate to form a light emitting element. 
     In the forming of the element rod, the separating layer may be at least partially etched and patterned. 
     An interface attractive force between the separating layer and the lower substrate at a first interface between the separating layer and the lower substrate may be greater than an interface attractive force between the separating layer and the element rod at a second interface between the separating layer and the element rod. 
     In the forming of the light emitting element, the second interface may be peeled off, but the first interface may be not peeled off, and the patterned separating layer may remain on the lower substrate. 
     In the light emitting element, a parting surface, which is a surface where the element rod is peeled off from the second interface, may be substantially flat and parallel to a top surface of the second conductivity type semiconductor layer. 
     In the light emitting element, the parting surface may have a surface roughness in a range of 8 nm Ra to 12 nm Ra. 
     The forming of the element rod may further comprise forming an insulating layer disposed to surround a side surface of the element rod, and the light emitting element may further include the insulating layer disposed to surround side surfaces of the first conductivity type semiconductor layer, the active material layer, and the second conductivity type semiconductor layer. 
     The separating layer may include a first graphene layer and a second graphene layer disposed on the first graphene layer, the first graphene layer may form a third interface with the buffer material layer, the second graphene layer may form a fifth interface with the element rod, and the first graphene layer and the second graphene layer may form a fourth interface. 
     In the forming of the light emitting element, the third interface may be not peeled off, at least a portion of the fourth interface and the fifth interface may be peeled off, the first graphene layer may remain on the lower substrate, and the second graphene layer may be formed on the fourth interface with the first graphene layer or the fifth interface with the element rod. 
     The separating layer may include a first sub-separating layer disposed on the lower substrate and a second sub-separating layer interposed between the substrate and the buffer material layer. 
     The element deposition structure may further include an electrode material layer on the second conductivity type semiconductor layer. 
     The forming of the element rod may comprise forming an etching mask layer on the element deposition structure and an etching pattern layer including one or more nanopatterns separated from each other on the etching mask layer, forming a hole by vertically etching an area formed by the nanopatterns being separated from each other; and removing the etching mask layer and the etching pattern layer. 
     The element deposition structure and the separating layer may include materials different in etch selectivity, and the forming of the hole may comprise vertically etching the element deposition structure to expose at least a portion of an overlapping area between the separating layer and the area formed by the nanopatterns being separated from each other; and etching and patterning the exposed area of the separating layer. 
     In the vertically etching of the element deposition structure, an etchant may include chlorine gas (Cl 2 ) and oxygen gas (O 2 ), and the separating layer and element deposition structure may be etched simultaneously. 
     According to another exemplary of the present disclosure, a light emitting element comprises a first conductivity type semiconductor doped with a first polarity, an active layer disposed on the first conductivity type semiconductor, a second conductivity type semiconductor disposed on the active layer and doped with a second polarity opposite to the first polarity, an electrode material layer disposed on the second conductivity type semiconductor and an insulating material layer disposed to surround side surfaces of the first conductivity type semiconductor, the second conductivity type semiconductor, the active layer, and the electrode material layer, wherein a bottom surface of the first conductivity type semiconductor is substantially flat and parallel to a top surface of the second conductivity type semiconductor. 
     The bottom surface of the first conductivity type semiconductor and the top surface of the second conductivity type semiconductor may have a surface roughness in a range of 8 nm Ra to 12 nm Ra. 
     The light emitting element may have a range of 3.0 μm to 6.0 μm in length measured in a long axis direction, and have a range of 400 nm to 700 nm in length specified in the other direction crossing the long axis direction. 
     According to the other exemplary of the present disclosure, a display device comprises a substrate, at least one first electrode and at least one second electrode extending in a first direction on the substrate and spaced apart from each other in a second direction different from the first direction, at least one light emitting element disposed in a separation space between the first electrode and the second electrode, a first contact electrode partially covering the first electrode and contacting a first end of the light emitting element, and a second contact electrode spaced apart from the first contact electrode and partially covering the second electrode to contact a second end opposite to the first end of the light emitting element, wherein the light emitting element has a flat shape such that each side surface of the first end and the second end is parallel to a plane perpendicular to the substrate. 
     The light emitting element may include a first conductivity type semiconductor, an active layer disposed on the first conductivity type semiconductor, a second conductivity type semiconductor disposed on the active layer and having a polarity opposite to that of the first conductivity type semiconductor, an electrode material layer disposed on the second conductivity type semiconductor layer and an insulating material layer disposed to surround side surfaces of the first conductivity type semiconductor, the active layer, the second conductivity type semiconductor, and the electrode material layer. 
     Each side surface of the first end and the second end of the light emitting element may have a surface roughness in a range of 8 nm Ra to 12 nm Ra. 
     The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings. 
     Advantageous Effects 
     According to an embodiment, the light emitting element manufacturing method is capable of manufacturing the light emitting element to have a flat parting surface by separating an element load grown on a substrate from the substrate through graphene layer peeling. The light emitting element manufacturing method may also be capable of manufacturing a light emitting element in a way of forming an insulating layer on an outer surface of an element rod and separating the element rod from the substrate. Accordingly, the light emitting element manufacturing method is capable of manufacturing a light emitting element, which is flat at both ends thereof, without any additional etching process. 
     The light emitting element being arranged between two electrodes of a display device has two end surfaces that are flat and substantially parallel, and is capable of preventing an open or short circuit problem of a contact electrode material from occurring in the case of connection with a contact electrode. 
     Advantageous effects according to the present disclosure are not limited to those mentioned above, and various other advantageous effects are included herein. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view of a display device according to an embodiment; 
         FIG. 2  is a cross-sectional view taken along lines I-I′, II-II′ and III′-III′ of  FIG. 1 ; 
         FIG. 3A  is a schematic diagram of a light emitting element according to an embodiment; 
         FIG. 3B  is a cross-sectional view taken along line  3   b - 3   b ′ of  FIG. 3A ; 
         FIG. 4  is an enlarged view of part of  FIG. 3A ; 
         FIG. 5  is an enlarged view of part A of  FIG. 2 ; 
         FIGS. 6 to 18  are schematic cross-sectional views schematically showing a method for manufacturing a light emitting element according to an embodiment; and 
         FIGS. 19 to 24  are cross-sectional views schematically illustrating part of a manufacturing method of a light emitting element according to another embodiment. 
     
    
    
     MODES OF THE INVENTION 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will filly convey the scope of the invention to those skilled in the art. 
     It will also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. The same reference numbers indicate the same components throughout the specification. 
     It will be understood that, although the terms “first,” “second,” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For instance, a first element discussed below could be termed a second element without departing from the teachings of the present invention. Similarly, the second element could also be termed the first element. 
     Hereinafter, exemplary embodiments will be described with reference to the accompanying drawings. 
       FIG. 1  is a plan view of a display device according to an embodiment. 
     The display device  10  may include at least one area defined as a pixel PX. The display device  10  may include a display area composed of a plurality of pixels PX, each emitting light in a specific wavelength band to the outside of the display device  10 . Although three pixels PX 1 , PX 2 , and PX 3  are exemplarily illustrated in  FIG. 1 , it is obvious that the display device  10  may include a larger number of pixels. Although it is shown in the drawing that a plurality of pixels PX are arranged in one direction, e.g., first direction D 1 , in cross-sectional view, the plurality of pixels PX may also be arranged in the second direction D 2  crossing the first direction D 1 . Further, each of the pixels PX of  FIG. 1  may be divided into a plurality of portions, and each portion may constitute one pixel PX. The pixels are not necessarily arranged in parallel only in the first direction D 1  as shown in  FIG. 1 , and may have various structures such as being arranged in a vertical direction (or the second direction D 2 ) or in a zigzag manner. 
     Although not shown in the drawing, the display device  10  may include an emission area in which light emitting elements  300  are arranged for emitting certain color lights, and a non-emission area defined as an area remaining after exclusion of the emission area. The non-emission area may be covered by certain members that are not visually perceived from the outside of the display device  10 . Various members for driving the light emitting elements  300  disposed in the emission area may be disposed in the non-emission area. For example, the non-emission area may include a wiring, a circuit unit, and a driving unit for applying an electrical signal to the emission area, but the present disclosure is not limited thereto. 
     The plurality of pixels PX may display colors by including one or more light emitting elements  300  emitting light of a specific wavelength band. The light emitted from the light emitting element  300  may be projected to the outside through a light emitting member of the display device  10 . In an embodiment, each of the pixels PX presenting different colors may include different light emitting elements  300  emitting different color lights. For example, a first pixel PX 1  presenting a red color may include a light emitting element  300  emitting a red light, a second pixel PX 2  presenting a green color may include a light emitting element  300  emitting a green light, and a third pixel PX 1  presenting a blue color may include a light emitting element  300  emitting a blue light. However, the present disclosure is not limited thereto, and the pixels presenting different colors may, in some cases, include the light emitting elements  300  emitting the same color light (e.g., blue light), or they may each include a wavelength conversion layer or a color filter on a light emission path to produce pixel-specific colors. However, the present disclosure is not limited thereto, and adjacent pixels PX may emit the same color light in some cases. 
     With reference to  FIG. 1 , the display device  10  may include a plurality of electrodes  210  and  220  and a plurality of light emitting elements  300 . At least a portion of each of the electrodes  210  and  220  may be arranged in each pixel PX, and electrically connected to the light emitting elements  300  to apply an electrical signal, in order for the light emitting elements  300  to emit a certain color light. 
     At least a portion of each of the electrodes  210  and  220  may also contribute to producing an electric field in the pixels PX, to align the light emitting elements  300 . In more detail, it is necessary to precisely align the pixel-specific (PX-specific) light emitting elements  300  during the alignment of the light emitting elements  300  emitting different color lights in the plurality of pixels PX. In the case of using an electrophoresis method for aligning the light emitting elements  300 , the light emitting elements  300  may be aligned in a way of depositing a solution including the light emitting elements  300  on the display device  10  and applying alternating power thereto to create a capacitance with an electric field, which produces an electrophoresis force to the light emitting elements  300 . 
     The plurality of electrodes  210  and  220  may include a first electrode  210  and a second electrode  220 . In an exemplary embodiment, the first electrode  210  may be a pixel electrode branched to each pixel PX, and the second electrode  220  may be a common electrode connected in common to the plurality of pixels PX. One of the first and second electrodes  210  and  220  may be an anode electrode of the light emitting element  300 , and the other may be a cathode electrode of the light emitting element  300 . However, the present disclosure is not limited thereto, and the reverse may also be the case. 
     The first and second electrodes  210  and  220  may include respective electrode stems  210 S and  220 S arranged to extend in the first direction D 1 , and at least one respective electrode branches  210 B and  220 B extending, in the second direction D 2  crossing the first direction D 1 , from the respective electrode stems  210 S and  220 S. 
     In detail, the first electrode  210  may include a first electrode stem  210 S, arranged to extend in the first direction D 1 , and at least one first electrode branch  210 B, branched from the first electrode stem  210 S and extending in the second direction D 2 . Although not shown in the drawing, the first electrode stem  210 S may be connected, at one end thereof, to a signal input pad and extend, at the other end thereof, in the first direction D 1 , maintaining electrical disconnection between the pixels PX. The signal input pad may be connected to a power source of the display device  10  or the outside, to apply an electrical signal or, in the case of aligning the light emitting elements  300 , alternating power to the first electrode stem  210 S. 
     The first electrode stem  210 S of one pixel may be arranged substantially on the same line as the first electrode stem  210 S of neighboring pixels belonging to the same row (e.g., adjacent in the first direction D 1 ). That is, the first electrode stem  210 S of one pixel may be arranged such that two ends thereof terminate between corresponding pixels while being spaced apart from each other, and the first electrode stems  210 S of the neighboring pixels may be aligned with an extension line of the first electrode stem  210 S of the one pixel. In this manner, the first electrode stem  210 S may be arranged in a way of being formed as an continuous stem electrode in a manufacturing process, and cut off by a laser or the like to be open, after performing the alignment process of the light emitting elements  300 . Accordingly, the first electrode stems  210 S of the respective pixel PX may apply different electrical signals to the respective first electrode branches  2106 , which may operate independently of each other. 
     The first electrode branch  210 B may be branched from at least part of the first electrode stem  210 S and extend in the second direction D 2 , and may terminate to keep a distance from the second electrode stem  220 S arranged to face the first electrode stem  210 S. That is, the first electrode branch  2106  may be arranged to be connected, at one end thereof, to the first electrode stem  210 S and placed, at the other end thereof, inside the pixel PX keeping a distance from the second electrode stem  220 S. The first electrode branch  210 B may be connected to the first electrode stem  210 S, which is electrically separate per pixel PX, so as to receive a different electrical signal per pixel PX. 
     It may also be possible that one or more first electrode branches  210 B are arranged per pixel PX. Although it is shown in  FIG. 1  that two first electrode branches  210 B are arranged, and the second electrode branch  220 B is arranged therebetween, the present disclosure is not limited thereto, and more first electrode branches  210 B may be arranged. In this case, the first electrode branches  210 B may be arranged alternately to be separated from the plurality of second electrode branches  220 B, such that a plurality light emitting elements  300  are arranged therebetween. In some embodiments, the second electrode branch  220 B may be arranged between the first electrode branches  210 B, such that each pixel PX is symmetrical about the second electrode branch  220 B. However, the present disclosure is not limited thereto. 
     The second electrode  220  may include a second electrode stem  220 S arranged to extend in the first direction D 1  and face the first electrode stem  210 S, keeping a distance from the first electrode stem  210 S, and at least one second electrode branch  220 B branched from the second electrode stem  220 S to extend in the second direction D 2  and face the first electrode branch  210 B, keeping a distance from the first electrode branch  2106 . The second electrode stem  220 S may also be connected to the signal input pad at one end thereof, like the first electrode stem  210 S. However, the second electrode stem  220 S may extend, at the other end thereof, in the first direction D 1  toward the plurality of adjacent pixels PX. That is, the second electrode stem  220 S may be electrically continuous between individual pixels PX. Accordingly, the second electrode stem  220 S of a certain pixel is connected at opposite ends thereof to one of the ends of the second electrode stems  220 S of the neighboring pixels between the pixels PX, to apply the same electrical signal to each pixel PX. 
     The second electrode branch  220 B may be branched from at least part of the second electrode stem  220 S and extend in the second direction D 2 , and may terminate to keep a distance from the first electrode stem  210 S. That is, the second electrode branch  220 B may be arranged to be connected at one end thereof to the second electrode stem  220 S and placed at the other end thereof inside the pixel PX, keeping a distance from the first electrode stem  210 S. The second electrode branch  220 B may be connected to the second electrode stem  220 S, which is electrically continuous in the respective pixels PX, so as to receive the same electrical signal for each pixel PX. 
     The second electrode branch  220 B may be arranged to face the first electrode branch  210 B, keeping a distance from the first electrode branch  210 B. Here, the first and second electrode stems  210 S and  220 S face each other about the center of each pixel PX, keeping a distance, such that the first and second electrode branches  2106  and  220 B extend in the opposite directions. That is, the first electrode branch  210 B may extend to one orientation of the second direction D 2 , and the second electrode branch  220 B may extend to the other orientation of the second direction D 2 , such that one ends of the respective branches are arranged to face opposite orientations about the center of the pixel PX. However, the present disclosure is not limited thereto, and the first and second electrode stems  210 S and  220 S may be arranged to face the same orientation about the center of the pixel PX, keeping a distance from each other. In this case, the first and second electrode branches  2106  and  220 B branched from the respective electrode stems  210 S and  220 S may extend in the same direction. 
     Although it is shown in  FIG. 1  that one second electrode branch  220 B is arranged in each pixel PX, the present disclosure is not limited thereto, and more second electrode branches  220 B may be arranged. 
     The plurality of light emitting elements  300  may be aligned between the first and second electrode branches  210 B and  220 B. In detail, at least part of the plurality of the light emitting elements  300  are each electrically connected at one end thereof to the first electrode branch  2106  and at the other end thereof to the second electrode branch  220 B. 
     The plurality of light emitting elements  300  may be aligned substantially in parallel with one another, keeping a distance in the second direction D 2 . The interval between the light emitting elements  300  is not particularly limited. One plurality of light emitting elements  300  may be adjacently arranged to form a cluster, while another plurality of light emitting elements  300  may be arranged keeping a predetermined distance from one another to form a cluster, and they may also be aligned to face one orientation at a non-uniform density. 
     The first and second electrode branches  210 B and  220 B may have respective contact electrodes  260  arranged thereon. 
     The plurality of contact electrodes  260  may be arranged to extend in the second direction D 2  and spaced apart from one another in the first direction D 1 . The contact electrodes  260  may contact at least one ends of the light emitting elements  300 , and may contact the first and second electrodes  210  and  220  to receive an electrical signal. Accordingly, the contact electrodes  260  may transfer the electrical signal received through the first and second electrodes  220  to the light emitting elements  300 . 
     In detail, the contact electrodes  260  may include a first contact electrode  261  and a second contact electrode  262  arranged on the respective electrode branches  2106  and  220 B to partially cover them and contact one or the other ends of the light emitting elements  300 . 
     The first contact electrode  261  may be arranged on the first electrode branch  210 B to contact one ends of the light emitting elements  300  that are electrically connected to the first electrode  210 . The second contact electrode  262  may be arranged on the second electrode branch  220 B to contact the other ends of the light emitting elements  300  that are electrically connected to the second electrode  220 . 
     In some embodiments, the opposite ends of each of the light emitting elements  300  that are each electrically connected to the first electrode branch  210 B or the second electrode branch  220 B may be an n-type or p-type doped conductive semiconductor layer. In the case where one end of a light emitting element  300  that is electrically connected to the first electrode branch  210 B is a p-type doped conductive semiconductor layer, the other end of the light emitting element  300  that is electrically connected to the second electrode branch  220 B may be an n-type doped conductive semiconductor layer. However, the present disclosure is not limited thereto, and an opposite case may also be possible. 
     The first and second contact electrodes  261  and  262  may be arranged to partially cover the respective first and second electrode branches  210 B and  220 B. As shown in  FIG. 1 , the first and second contact electrodes  261  and  262  may be arranged to extend in the second direction D 2  and face each other keeping a distance. However, the first and second contact electrodes  261  and  262  may terminate at one ends thereof to expose one ends of the respective electrode branches  210 B and  220 B. The first and second contact electrodes  261  and  262  may also terminate at the other ends thereof, so as not to overlap the respective electrode stems  210 S and  220 S and be spaced apart therefrom. However, the present disclosure is not limited thereto, the first and second contact electrodes  261  and  262  may cover the respective electrode branches  210 B and  220 B. 
     Meanwhile, as shown in  FIG. 1 , the first and second electrode stems  210 S and  220 S may be electrically connected to a thin film transistor  120  or a power wiring  161  (to be described later) via respective contact holes, e.g., a first electrode contact hole CNTD and a second electrode contact hole CNTS. Although it is shown in  FIG. 1  that the first and second electrode stems  210 S and  220 S each have a contact hole arranged thereon per pixel PX, the present disclosure is not limited thereto. Because the second electrode stem  220 S may extend to establish an electrical connection with the adjacent pixels PX as described above, the second electrode stem  220 S may, in some embodiments, be electrically connected to the thin film transistor via one contact hole. 
     A description is made hereinafter of the configuration of the plurality of members arranged on the display device  10  in more detail with reference to  FIG. 2 . 
       FIG. 2  is a cross-sectional view taken along lines I-I′, II-II′ and of  FIG. 1 . Although  FIG. 2  shows a single pixel PX, the configuration may be identically applicable to other pixels.  FIG. 2  shows a cross section across one and the other ends of a certain light emitting element  300 . 
     Referring to  FIGS. 1 and 2 , the display device  10  may include a substrate  110 , thin film transistors  120  and  140  disposed on the substrate  110 , and the electrodes  210  and  220  disposed on the thin film transistors  120  and  140 , and the light emitting elements  300 . The thin film transistors may include a first thin film transistor  120  and a second thin film transistor  140 , and they may be a driving transistor and a switching transistor, respectively. Each of the thin film transistors  120  and  140  may include an active layer, a gate electrode, a source electrode, and a drain electrode. The first electrode  210  may be electrically connected to the drain electrode of the first thin film transistor  120 . 
     Specifically, the substrate  110  may be an insulating substrate. The substrate  110  may be made of an insulating material such as glass, quartz, or polymer resin. Examples of the polymer material may include polyethersulphone (PES), polyacrylate (PA), polyarylate (PAR), polyetherimide (PEI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyallylate, polyimide (PI), polycarbonate (PC), cellulose triacetate (CAT), cellulose acetate propionate (CAP), or a combination thereof. Further, the substrate  110  may be a rigid substrate, but may also be a flexible substrate which can be bent, folded or rolled. 
     A buffer layer  115  may be disposed on the substrate  110 . The buffer layer  115  can prevent diffusion of impurity ions, prevent penetration of moisture or external air, and perform a surface planarization function. The buffer layer  115  may include silicon nitride, silicon oxide, silicon oxynitride, or the like. 
     A semiconductor layer is disposed on the buffer layer  115 . The semiconductor layer may include a first active layer  126  of the first thin film transistor  120 , a second active layer  146  of the second thin film transistor  140 , and an auxiliary layer  163 . The semiconductor layer may include polycrystalline silicon, monocrystalline silicon, oxide semiconductor, and the like. 
     A first gate insulating layer  170  is disposed on the semiconductor layer. The first gate insulating layer  170  covers the semiconductor layer. The first gate insulating layer  170  may function as a gate insulating film of the thin film transistor. The first gate insulating layer  170  may include silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, tantalum oxide, hafnium oxide, zirconium oxide, titanium oxide, or the like. These may be used alone or in combination with each other. 
     A first conductive layer is disposed on the first gate insulating layer  170 . The first conductive layer may include a first gate electrode  121  disposed on the first active layer  126  of the first thin film transistor  120 , a second gate electrode  141  disposed on the second active layer  146  of the second thin film transistor  140 , and a power wiring  161  disposed on the auxiliary layer  163 , with the first gate insulating layer  170  interposed therebetween, respectively. The first conductive layer may include at least one metal selected from the group consisting of molybdenum (Mo), aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), calcium (Ca), titanium (Ti), tantalum (Ta), tungsten (W) and copper (Cu). The first conductive layer may be a single layer or a multilayer. 
     A second gate insulating layer  180  is disposed on the first conductive layer. The second gate insulating layer  180  may be an interlayer insulating layer. The second gate insulating layer  180  may be formed of an inorganic insulating material such as silicon oxide, silicon nitride, silicon oxynitride, hafnium oxide, aluminum oxide, titanium oxide, tantalum oxide, zinc oxide, and the like. 
     A second conductive layer is disposed on the second gate insulating layer  180 . The second conductive layer includes a capacitor electrode  128  disposed on the first gate electrode  121 , with the second gate insulating layer  180  interposed therebetween. The capacitor electrode  128  may form a storage capacitor in cooperation with the first gate electrode  121 . 
     In the same way as the first conductive layer described above, the second conductive layer may include at least one metal selected from the group consisting of molybdenum (Mo), aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), calcium (Ca), titanium (Ti), tantalum (Ta), tungsten (W) and copper (Cu). 
     An interlayer insulating layer  190  is disposed on the second conductive layer. The interlayer insulating layer  190  may be an interlayer insulating film. Further, the interlayer insulating layer  190  may perform a surface planarization function. The interlayer insulating layer  190  may include an organic insulating material selected from the group consisting of acrylic resin, epoxy resin, phenolic resin, polyamide resin, polyimide resin, unsaturated polyester resin, polyphenylene resin, polyphenylenesulfide resin and benzocyclobutene (BCB). 
     A third conductive layer is disposed on the interlayer insulating layer  190 . The third conductive layer includes a first drain electrode  123  and a first source electrode  124  of the first thin film transistor  120 , a second drain electrode  143  and a second source electrode  144  of the second thin film transistor  140 , and a power electrode  162  disposed on the power wiring  161 . 
     The first source electrode  124  and the first drain electrode  123  may be electrically connected to the first active layer  126  through a first contact hole  129  passing through the interlayer insulating layer  190  and the second gate insulating layer  180 . The second source electrode  144  and the second drain electrode  143  may be electrically connected to the second active layer  146  through a second contact hole  149  passing through the interlayer insulating layer  190  and the second gate insulating layer  180 . The power electrode  162  may be electrically connected to the power wiring  161  through a third contact hole  169  passing through the interlayer insulating layer  190  and the second gate insulating layer  180 . 
     The third conductive layer may include at least one metal selected from the group consisting of aluminum (Al), molybdenum (Mo), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), calcium (Ca), titanium (Ti), tantalum (Ta), tungsten (W) and copper (Cu). The third conductive layer may be a single layer or a multilayer. For example, the third conductive layer may have a stacked structure of Ti/Al/Ti, Mo/Al/Mo, Mo/AlGe/Mo, or Ti/Cu. 
     An insulating substrate layer  200  is disposed on the third conductive layer. The insulating substrate layer  200  may be formed of an organic insulating material selected from the group consisting of acrylic resin, epoxy resin, phenolic resin, polyamide resin, polyimide resin, unsaturated polyester resin, polyphenylene resin, polyphenylenesulfide resin and benzocyclobutene (BCB). The surface of the insulating substrate layer  200  may be flat. 
     The insulating substrate layer  200  may include a plurality of banks  410  and  420 . The plurality of banks  410  and  420  may be arranged to face each other, keeping a distance therebetween, inside each pixel PX, and the distanced banks  410  and  420 , e.g., a first bank  410  and a second bank  420 , may have the first electrode  210  and the second electrode  220  arranged respectively thereon. As shown in  FIG. 1 , three banks  410  and  420 , i.e., two first banks  410  and one second bank  420 , are arranged to be covered by the respective first and second electrodes  210  and  220  within one pixel PX. Although  FIG. 2  shows only a cross section of one first bank  410  and one second bank  420  among them, the arrangement configuration thereof may be identically applicable to the other first bank  410  not shown in  FIG. 2 . 
     However, the present disclosure is not limited thereto, and more banks  410  and  420  may be arranged within one pixel PX. For example, it may be possible that more banks  410  and  420  are arranged along with more first and second electrodes  210  and  220 . The banks  410  and  420  may include at least one first bank  410  on which the first electrode  210  is arranged, and at least one second bank  420  on which the second electrode  220  is arranged. In this case, the first and second banks  410  and  420  may be arranged to face each other keeping a distance therebetween, such that the plurality of banks are alternately arranged in one direction. In some embodiments, it may be possible that two first banks  410  are arranged, keeping a distance therebetween, and one second bank  420  is arranged between the distanced first banks  410 . 
     Furthermore, although not shown in  FIG. 2 , the first and second electrodes  210  and  220  may include the respective electrode stems  210 S and  220 S and the respective electrode branches  210 B and  220 B as described above. It may be understood in  FIG. 2  that the first and second electrode branches  2106  and  220 B are respectively arranged on the first and second banks  410  and  420 . 
     The plurality of banks  410  and  420  may be formed with the substantially same material in a single process. In this case, the banks  410  and  420  may form a grid pattern. The banks  410  and  420  may include polyimide. 
     Meanwhile, although not shown in the drawing, at least part of the plurality of banks  410  and  420  may be arranged on a boundary of the pixels PX to make them distinct. Such banks may be arranged in a substantially grid pattern along with the aforementioned first and second banks  410  and  420 . At least part of the banks  410  and  420  arranged on the boundary of the pixels PX may be formed to cover electrode lines of the display device  10 . 
     The plurality of banks  410  and  420  may each have a structure protruding at least partially from the insulating substrate layer  200 . The banks  410  and  420  may protrude upward from a flat plane on which the light emitting elements  300  are arranged, such that a protruding part may at least partially have slopes. The banks  410  and  420  having a protruded structure with slopes may have reflection layers  211  and  221  (to be described later) arranged thereon to reflect incident light. The light directed from the light emitting element  300  to the reflection layers  211  and  221  may be reflected to the outside of the display device  10 , i.e., upward from the banks  410  and  420 . The banks  410  and  420  with the protruded structure may not be limited in shape. Although it is shown in  FIG. 2  that the banks have a shape with a flat top surface and angular corners, the present disclosure is not limited thereto, and the banks may be protruded to have round corners. 
     The plurality of banks  410  and  420  may have reflection layers  211  and  221  arranged thereon. 
     The first reflection layer  211  covers the first bank  410  and is partially electrically connected to the first drain electrode  123  of the first thin film transistor  120  via a fourth contact hole  319 _ 1  penetrating the insulating substrate layer  200 . The second reflection layer  221  covers the second bank  420  and is partially electrically connected to the power electrode  162  via a fifth contact hole  319 _ 2  penetrating the insulating substrate layer  200 . 
     The first reflection layer  211  may be electrically connected to the first drain electrode  123  of the first thin film transistor  120  via the fourth contact hole  319 _ 1  within the pixel PX. Accordingly, the first thin film transistor  120  may be arranged in an area overlapping the pixel PX.  FIG. 1  shows electrical connection to the first thin film transistor  120  via the first electrode contact hole CNTD arranged on the first electrode stem  210 S. That is, the first electrode contact hole CNTD may be the fourth contact hole  319 _ 1 . 
     The second reflection layer  221  may also be electrically connected to the power electrode  162  via the fifth contact hole  319 _ 2  within the pixel PX.  FIG. 2  shows that the second reflection layer  221  is connected through the fifth contact hole  319 _ 2  within one pixel PX.  FIG. 1  shows that the second electrode  220  of each pixel PX is electrically connected to the power wiring  161  via the plurality of second electrode contact holes CNTS on the second electrode stem  220 S. That is, the second contact holes CNTS may be the fifth contact hole  319 _ 2 . 
     As described with reference to  FIG. 1 , the first and second contact holes CNTD and CNTS may be respectively arranged on the first and second electrode stems  210 S and  220 S. In this respect,  FIG. 2  shows that, in the cross-sectional view of the display device  10 , the first and second electrodes  210  and  220  are electrically connected to the first thin film transistor  120 , or the power wiring  161 , via the respective fourth and fifth contact holes  319 _ 1  and  319 _ 2 , in an area separated from the banks  410  and  420  on which the first and second electrode branches  210 B and  220 B are arranged. 
     However, the present disclosure is not limited thereto. For example, in  FIG. 1 , the second electrode contact holes CNTS may be arranged at various positions on the second electrode stem  220 S and, in some cases, on the second electrode branch  220 B. In some embodiments, the second reflection layer  221  may also be connected to one second electrode contact hole CNTS, or the fifth contact hole  319 _ 2 , in an area out of one pixel PX. 
     In an area outside the emission area in which the pixels PX of the display device  100  are arranged, e.g., an outside area of the emission area, there may be a non-emission area in which no light emitting elements  300  are arranged. As described above, the second electrodes  220  of each pixel PX may be electrically connected via the second electrode stem  220 S, so as to receive the same electrical signal. 
     In some embodiments, in the case of the second electrode  220 , the second electrode stem  220 S may be electrically connected to the power electrode  162  via one second electrode contact hole CNTS in the non-emission area as the outside area of the display device  10 . Unlike the display device  10  of  FIG. 1 , because the second electrode stem  220 S is arranged to extend to adjacent pixels and be electrically connected to each other, even though the second electrode stem  220 S is connected to the power electrode  162  via one contact hole, it may be possible to apply the same electrical signal to the second electrode branches  220 B of the respective pixels PX. In the case of the second electrode  220  of the display device  10 , the position of the contact hole for receiving an electrical signal from the power electrode  162  may vary according to the structure of the display device  10 . However, the present disclosure is not limited thereto. 
     Meanwhile, with reference back to  FIGS. 1 and 2 , the reflection layers  211  and  221  may include a material having high reflectivity for reflecting the light emitted from the light emitting elements  300 . For example, the reflection layers  211  and  221  may include, but are not limited to, a material such as silver (Ag) and copper (Cu). 
     The first and second reflection layers  211  and  221  may include first and second electrode layers  212  and  222  arranged respectively thereon. 
     The first electrode layer  212  may be arranged directly on the first reflection layer  211 . The first electrode layer  212  may have a pattern substantially identical with that of the first reflection layer  211 . The second electrode layer  222  may be arranged directly on the second reflection layer  221  to be spaced apart from the first electrode layer  212 . The second electrode layer  222  may have a pattern that is substantially identical with that of the second reflection layer  221 . 
     In an embodiment, the electrode layers  212  and  222  may cover the reflection layers  211  and  221  respectively therebeneath. That is, the electrode layers  212  and  222  may be formed to be larger in size than the reflection layers  211  and  221 , to cover the side end surfaces of the reflection layers  211  and  221 . However, the present disclosure is not limited thereto. 
     The first and second electrode layers  212  and  222  may transfer, to contact electrodes  261  and  262  (to be described later), an electrical signal directed to the first and second reflection layers  211  and  221  connected to the first thin film transistor  120  or the power electrode  162 . The electrode layers  212  and  222  may include a transparent conductive material. For example, the electrode layers  212  and  222  may include a material such as indium tin oxide (ITO), indium zinc oxide (IZO), and indium tin zinc oxide (ITZO), but are not limited thereto. In some embodiments, the reflective layers  211  and  221  and the electrode layers  212  and  222  may have a structure in which at least one transparent conductive layer such as ITO, IZO, or ITZO and at least one metal layer such as silver (Ag) or copper (Cu) are stacked. For example, the reflective layers  211  and  221  and the electrode layers  212  and  222  may have a stacked structure of ITO/Ag/ITO. 
     The first reflective layer  211  and the first electrode layer  212  disposed on the first bank  410  form the first electrode  210 . The first electrode  210  may protrude to regions extending from both ends of the first bank  410 , and accordingly, the first electrode  210  may contact the insulating substrate layer  200  in the protruding region. The second reflective layer  221  and the second electrode layer  222  disposed on the second bank  420  form the second electrode  220 . The second electrode  220  may protrude to regions extending from both ends of the second bank  420 , and accordingly, the second electrode  220  may contact the insulating substrate layer  200  in the protruding region. 
     The first and second electrodes  210  and  220  may be respectively arranged to cover the entire areas of the first and second banks  410  and  420 . However, as described above, the first and second electrodes  210  and  220  are arranged to face each other keeping a distance therebetween. Between the electrodes, a first insulating layer  510 , which is to be described later, may be arranged, and the light emitting elements  300  may be arranged thereon. 
     In addition, the first reflective layer  211  may receive a driving voltage from the first thin film transistor  120 , and the second reflective layer  221  may receive a source voltage from the power wiring  161 . Thus, the first electrode  210  and the second electrode  220  receive the driving voltage and the source voltage, respectively. The first electrode  210  may be electrically connected to the first thin film transistor  120 , and the second electrode  220  may be electrically connected to the power wiring  161 . Accordingly, the first and second contact electrodes  261  and  262  arranged respectively on the first and second electrodes  210  and  220  may receive the driving voltage and the source voltage. The driving voltage and the source voltage may be transferred to the light emitting elements  300 , such that the light emitting elements  300  emit light with a predetermined electric current flowing therethrough. 
     The first insulating layer  510  is arranged to partially cover the first and second electrodes  210  and  220 . The first insulating layer  510  may be arranged to mostly cover the top surfaces of the first and second electrodes  210  and  220  and partially expose the first and second electrodes  210  and  220 . The first insulating layer  510  may also be arranged in the space between the first and second electrodes  210  and  220 . The first insulating layer  510  may have an islet or line shape formed along the space between the first and second electrode branches  2106  and  220 B in plan view. 
       FIG. 2  shows that the first insulating layer  510  is arranged in the space between one first electrode  210  (e.g., first electrode branch  210 B) and one second electrode  220  (e.g., second electrode branch  220 B). However, as described above, there may be a plurality of the first and second electrodes  210  and  220 , such that the first insulating layer  510  may be also arranged between one first electrode  210  and another second electrode  220 , or between one second electrode  220  and another first electrode  210 . The first insulating layer  510  may be arranged to partially cover the side surfaces of the first and second electrodes  210  and  220  that are opposite to the side surfaces facing each other. That is, the first insulating layer  510  may be arranged to expose center parts of the first and second electrodes  210  and  220 . 
     On the first insulating layer  510 , the light emitting element  300  is arranged. The first insulating layer  510  may be arranged between the light emitting element  300  and the insulating substrate layer  200 . The first insulating layer  510  may have a bottom surface contacting the insulating substrate layer  200 , and the light emitting element  300  may be arranged on the top surface of the first insulating layer  510 . The first insulating layer  510  may contact the electrodes  210  and  220  at both side surfaces thereof to electrically insulate the first and second electrodes  210  and  220  from each other. 
     The first insulating layer  510  may overlap a partial area on the electrodes  210  and  220 , e.g., part of the area protruding in a direction in which the first and second electrodes  210  and  220  face each other. The first insulating layer  510  may also be arranged on the areas where the sloping surfaces and flat top surfaces of the banks  410  and  420  overlap the electrodes  210  and  220 . 
     For example, the first insulating layer  510  may cover the end parts protruding in the direction in which the first and second electrodes  210  and  220  face each other. The first insulating layer  510  may contact the insulating substrate layer  200  partially on the bottom surface of the first insulating layer  510 , and may contact the electrodes  210  and  220  partially on the bottom surface thereof and on the side surfaces thereof. Accordingly, the first insulating layer  510  may protect regions overlapping the respective electrodes  210  and  220  and electrically insulate them. Further, the first insulating layer  510  may prevent a first conductivity type semiconductor  310  and a second conductivity type semiconductor  320  of the light emitting element  300  from directly contacting other members, thereby preventing damage to the light emitting element  300 . 
     However, the present disclosure is not limited thereto, and the first insulating layer  510  may be arranged only on the areas overlapping the sloping side surfaces of the banks  410  and  420  in the areas on the first and second electrodes  210  and  220  in some embodiments. In this case, the bottom surface of the first insulating layer  510  may terminate on the sloping side surfaces of the banks  410  and  420 , and the electrodes  210  and  220  arranged on part of the sloping side surfaces of the banks  410  and  420  may be exposed to contact the contact electrodes  260 . 
     The first insulating layer  510  may also be arranged to expose both ends of the light emitting element  300 . Accordingly, the contact electrodes  260  may contact the exposed top surfaces of the electrodes  210  and  220  and both ends of the light emitting element  300 , and the contact electrode  260  may transfer the electrical signal applied to the first and second electrodes  210  and  220  to the light emitting element  300 . 
     At least one light emitting element  300  may be disposed between the first electrode  210  and the second electrode  220 . Although it is shown in  FIG. 2  that one light emitting element  300  is arranged between the first and second electrodes  210  and  220 , it is apparent that a plurality light emitting elements  300  may be arranged in a different direction (e.g., second direction D 2 ) in plan view as shown in  FIG. 1 . 
     In detail, the light emitting element  300  may be electrically connected to the first electrode  210  at one end thereof and the second electrode  220  at the other end thereof. The both ends of the light emitting elements  300  may respectively contact the first and second contact electrodes  261  and  262 . 
     Meanwhile,  FIG. 1  exemplifies the case where only the light emitting elements  300  emitting the same color light are arranged in each pixel PX. However, the present disclosure is not limited thereto, and as described above, the light emitting elements  300  emitting light of different colors may be disposed together in one pixel PX. 
     The light emitting element  300  may be a light emitting diode. The light emitting element  300  may be a nanostructure mostly having a nano-size. The light emitting element  300  may be an inorganic light emitting diode made of an inorganic material. When the light emitting element  300  is an inorganic light emitting diode, a light emitting material having an inorganic crystal structure is disposed between two electrodes facing each other, and an electric field is formed in a specific direction in the light emitting material. Then, the inorganic light emitting diode may be aligned between the two electrodes having a specific polarity. 
     In some embodiments, the light emitting element  300  may have a stacked structure including a first conductivity type semiconductor  310 , an element active layer  330 , a second conductivity type semiconductor  320 , and an electrode material layer  370 . The light emitting element  300  may be manufactured by depositing, horizontally, the first conductivity type semiconductor  310 , the element active layer  330 , and the second conductivity type semiconductor  320 , and the electrode material layer  370  in order on the insulating substrate layer  200 . That is, the light emitting elements  300  formed by depositing the plurality of layers may be arranged in the widthwise direction parallel with the insulating substrate layer  200 . However, the present disclosure is not limited thereto, and the light emitting elements  300  may be manufactured such that the layers are deposited in the reverse order between the first and second electrodes  210  and  220 . 
     The second insulating layer  520  may be arranged to overlap at least part of the light emitting element  300 . The second insulating layer  520  may protect the light emitting element  300 , and simultaneously fix the light emitting element  300  between the first and second electrodes  210  and  220 . 
     Although it is shown in  FIG. 2  that the second insulating layer  520  is arranged only on the top surface of the light emitting element  300  in cross-sectional view, the second insulating layer  520  may be arranged to surround the outer surface of the light emitting element  300 . That is, like the first insulating layer  510 , the second insulating layer  520  may be arranged to have an islet or line shape extending in the second direction D 2  along the space between the first and second electrode branches  210 B and  220 B in plan view. 
     Part of the material of the second insulating layer  520  may also be arranged at the area where the bottom surface of the light emitting element  300  and the first insulating layer  510  overlap each other. That part may be formed when the light emitting element  300  is aligned on the first insulating layer  510 , and then the second insulating layer  520  is disposed thereon during the manufacture of the display device  10 . That part may also be formed by the second insulating layer  520  partially permeating, during the formation of the second insulating layer  520 , into pores formed in a section of the first insulating layer  510  contacting the bottom surface of the light emitting element  300 . 
     The second insulating layer  520  may be arranged to expose both end surfaces of the light emitting element  300 . That is, in cross-sectional view, the second insulating layer  520  arranged on the top surface of the light emitting element  300  is shorter in length, measured in an axis direction, than the light emitting element  300 , such that the second insulating layer  520  may be contracted inward in comparison with the both ends of the light emitting element  300 . Accordingly, the first insulating layer  510 , the light emitting element  300 , and the second insulating layer  520  may be deposited such that the side surfaces thereof are aligned in a stepwise manner. This may facilitate contact between the contact electrodes  261  and  262  and both end surfaces of the light emitting element  300 . However, the present disclosure is not limited thereto. The second insulating layer  520  and the light emitting element  300  may have the same length, and both sides thereof may be aligned. 
     Meanwhile, the second insulating layer  520  may be formed in a way of depositing the corresponding material on the first insulating layer  510 , and patterning the corresponding material in an area, e.g., area exposed for contact of the light emitting element  300  to the contact electrode  260 . Patterning the second insulating layer  520  may be performed with a conventional dry etching or wet etching process. Here, the first and second insulating layers  510  and  520  may include materials different in etch selectivity, to prevent the first insulating layer  510  from being patterned. That is, the first insulating layer  510  may serve as an etching stopper in patterning the second insulating layer  520 . 
     Accordingly, the first insulating layer  510  may not undergo material damage even when the second insulating layer  520  covering the outer surface of the light emitting element  300  is patterned to expose the both ends of the light emitting element  300 . In particular, the first insulating layer  510  and the light emitting element  300  may have smooth contact surfaces at the both ends of the light emitting element  300  where the light emitting element  300  and the contact electrode  260  contact each other. 
     On the second insulating layer  520 , the first contact electrode  261  disposed on the first electrode  210  and overlapping at least part of the second insulating layer  520 , and the second contact electrode  262  disposed on the second electrode  220  and overlapping at least part of the second insulating layer  520 , may be arranged. 
     The first and second contact electrodes  261  and  262  may be respectively arranged on the top surfaces of the first and second electrodes  210  and  220 . In detail, the first and second contact electrodes  261  and  262  may respectively contact the first and second electrode layers  212  and  222  in the area where the first insulating layer  510  is patterned to expose parts of the first and second electrodes  210  and  220 . The first and second contact electrodes  261  and  262  may contact one end side of the light emitting element  300 , e.g., the first conductivity type semiconductor  310 , the second conductivity type semiconductor  320 , or the electrode material layer  370 . Accordingly, the first and second contact electrodes  261  and  262  may transfer the electrical signal applied to the first and second electrode layers  212  and  222  to the light emitting element  300 . 
     The first contact electrode  261  may be arranged on the first electrode  210  to cover the first electrode  210  in part, and contact the light emitting element  300  and the first and second insulating layers  510  and  520  in part on the bottom surface of the first contact electrode  261 . One end of the first contact electrode  261  that is oriented toward the second contact electrode  262  is arranged on the second insulating layer  520 . The second contact electrode  262  may be arranged on the second electrode  220  to cover the second electrode  220  in part, and contact the light emitting element  300  and the first and third insulating layers  510  and  530  in part on the bottom surface of the second contact electrode  262 . One end of the second contact electrode  262  that is oriented toward the first contact electrode  261  is arranged on the third insulating layer  530 . 
     The first and second insulating layers  510  and  520  may be patterned into an area to cover the first and second electrodes  210  and  220  on the top surface of the first and second banks  410  and  420 . Accordingly, the first and second electrode layers  212  and  222  of the respective first and second electrodes  210  and  220  may be exposed to be electrically connected to the respective contact electrodes  261  and  262 . 
     The first contact electrode  261  and the second contact electrode  262  may be spaced apart from each other on the second insulating layer  520  or the third insulating layer  530 . That is, the first and second contact electrode  261  and  262  may be arranged to contact the light emitting element  300  and the second insulating layer  520  or the third insulating layers  530  together and, on the second insulating layer  520 , to be spaced apart in the deposition direction for electrical insulation. Accordingly, the first and second contact electrodes  261  and  262  may respectively receive different powers from the first thin film transistor  120  and the power wiring  161 . For example, the first contact electrode  261  may receive a driving voltage applied from the first thin film transistor  120  to the first electrode  210 , and the second contact electrode  262  may receive a common source voltage applied from the power wiring  161  to the second electrode  220 . However, the present disclosure is not limited thereto. 
     Meanwhile, as shown in  FIG. 1 , neither the first contact electrode  261  nor the second contact electrode  262  is arranged on the first and second contact holes CNTD and CNTS formed on the first and second electrode stems  210 S and  220 S. That is, even in  FIG. 5 , the first and second contact electrodes  261  and  262  may not respectively overlap the areas where the first and second electrode contact holes CNTD and CNTS are arranged. However, the present disclosure is not limited thereto, and the first and second contact electrode  261  and  262 , in some cases, may partially overlap the area where the first electrode contact hole CNTD or the second electrode contact hole CNTD is arranged on the respective first and second electrodes  210  and  220 . 
     The contact electrodes  261  and  262  may include a conductive material. For example, they may include ITO, IZO, ITZO, aluminum (Al), or the like. However, the present disclosure is not limited thereto. 
     Further, the contact electrodes  261  and  262  may include the same material as the electrode layers  212  and  222 . The contact electrodes  261  and  262  may be arranged to have substantially the same pattern on the electrode layers  212  and  222  to contact the electrode layers  212  and  222 . For example, the first and second contact electrodes  261  and  262  contacting the first and second electrode layers  212  and  222  may transfer the electrical signals applied to the first and second electrode layers  212  and  222  to the light emitting element  300 . 
     The third insulating layer  530  may be arranged on the first contact electrode  261  to electrically insulate the first and second contact electrodes  261  and  262  from each other. The third insulating layer  530  may be arranged to cover the first contact electrode  261  and not to overlap an area of the light emitting element  300 , such that the light emitting element  300  contacts the second contact electrode  262 . The third insulating layer  530  may partially contact the first contact electrode  261 , the second contact electrode  262 , and the second insulating layer  520  on the top surface of the second insulating layer  520 . The third insulating layer  530  may be disposed to cover one end of the first contact electrode  261  on the top surface of the second insulating layer  520 . Accordingly, the third insulating layer  530  may protect the first contact electrode  261  and electrically insulate the first contact electrode  261  from the second contact electrode  262 . 
     One end of the third insulating layer  530  that is oriented to the second electrode  220  may be aligned with one side surface of the second insulating layer  520 . 
     Meanwhile, in some embodiments, the third insulating layer  530  may be omitted in the display device  10 . Accordingly, the first contact electrode  261  and the second contact electrode  262  may be disposed on substantially the same plane, and may be electrically insulated from each other by a passivation layer  550  to be described later. 
     The passivation layer  550  may be formed on the third insulating layer  530  and the second contact electrode  262  to protect members disposed on the insulating substrate layer  200  against the external environment. When the first contact electrode  261  and the second contact electrode  262  are exposed, a problem of disconnection of the contact electrode material may occur due to electrode damage, so it is required to cover them with the passivation layer  550 . That is, the passivation layer  550  may be disposed to cover the first electrode  210 , the second electrode  220 , the light emitting element  300 , and the like. In addition, as described above, when the third insulating layer  530  is omitted, the passivation layer  550  may be formed on the first contact electrode  261  and the second contact electrode  262 . In this case, the passivation layer  550  may electrically insulate the first contact electrode  261  and the second contact electrode  262  from each other. 
     Each of the above-described first insulating layer  510 , second insulating layer  520 , third insulating layer  530 , and passivation layer  550  may include an inorganic insulating material. For example, the first insulating layer  510 , the second insulating layer  520 , the third insulating layer  530 , and the passivation layer  550  may include a material such as silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy), aluminum oxide (Al 2 O 3 ), aluminum nitride (AlN), and the like. The first insulating layer  510 , the second insulating layer  520 , the third insulating layer  530 , and the passivation layer  550  may be made of the same material, but may also be made of different materials. In addition, various materials that impart insulating properties to the first insulating layer  510 , the second insulating layer  520 , the third insulating layer  530 , and the passivation layer  550  are applicable. 
     Meanwhile, the first and second insulating layers  510  and  520  may differ in etch selectivity as described above. As one example, when the first insulating layer  510  includes silicon oxide (SiOx), the second insulating layer  520  may include silicon nitride (SiNx). As another example, when the first insulating layer  510  includes silicon nitride (SiNx), the second insulating layer  520  may include silicon oxide (SiOx). However, the present disclosure is not limited thereto. 
     Meanwhile, the light emitting element  300  may be manufactured on a substrate by epitaxial growth. A seed crystal layer for forming a semiconductor layer may be formed on the substrate, and a desired semiconductor material may be deposited to grow. Hereinafter, the structure of the light emitting element  300  according to various embodiments will be described in detail with reference to  FIG. 3 . 
       FIG. 3A  is a schematic diagram of a light emitting element according to an embodiment.  FIG. 3B  is a cross-sectional view taken along line  3   b - 3   b ′ of  FIG. 3A . 
     With reference to  FIG. 3 , the light emitting element  300  may include a plurality of conductivity type semiconductors  310  and  320 , an element active layer  330  arranged between the plurality of conductivity type semiconductors  310  and  320 , an electrode material layer  370 , and an insulating material layer  380 . The electrical signal received through the first and second electrodes  210  and  220  may be transferred to the element active layer  330  via the plurality of conductivity type semiconductors  310  and  320  to emit light. 
     In detail, the light emitting element  300  may include the first conductivity type semiconductor  310 , the second conductivity type semiconductor  320 , the element active layer  330  arranged between the first and second conductivity type semiconductors  310  and  320 , the electrode material layer  370  arranged on the second conductivity type semiconductor  320 , and the insulating material layer  380 . Although it is shown in  FIG. 3A  that the light emitting element  300  has a layered structure in which the first conductivity type semiconductor  310 , the element active layer  330 , the second conductivity type semiconductor  320 , and the electrode material layer  370  are deposited in order in the lengthwise direction thereof, the present disclosure is not limited thereto. The electrode material layer  370  may be omitted and, in some embodiments, it may be arranged on at least one of both side surfaces of each of the first and second conductivity type semiconductor  310  and  320 . Hereinafter, a description is made of the exemplary light emitting element  300  of  FIG. 3A , and it is obvious that the following description of the light emitting element  300  is identically applicable to light emitting elements  300  including different structures. 
     The first conductivity type semiconductor  310  may be an n-type semiconductor layer. As one example, when the light emitting element  300  emits light of a blue wavelength band, the first conductivity type semiconductor  310  may include a semiconductor material having a chemical formula of In x Al y Ga 1-x-y N (0≤x≤1, 0≤y≤1, 0≤x+y≤1). For example, it may be any one or more of n-type doped InAlGaN, GaN, AlGaN, InGaN, AlN and InN. The first conductivity type semiconductor  310  may be doped with a first conductive dopant. For example, the first conductive dopant may be Si, Ge, Sn, or the like. The length of the first conductivity type semiconductor  310  may have a range of 1.5 μm to 5 μm, but is not limited thereto. 
     The second conductivity type semiconductor  320  may be a p-type semiconductor layer. As one example, when the light emitting element  300  emits light of a blue wavelength band, the second conductivity type semiconductor  320  may include a semiconductor material having a chemical formula of In x Al y Ga 1-x-y N (0≤x≤1, 0≤y≤1, 0≤x+y≤1). For example, it may be any one or more of p-type doped InAlGaN, GaN, AlGaN, InGaN, AlN and InN. The second conductivity type semiconductor  320  may be doped with a second conductive dopant. For example, the second conductive dopant may be Mg, Zn, Ca, Se, Ba, or the like. The length of the second conductivity type semiconductor  320  may have a range of 0.08 μm to 0.25 μm, but is not limited thereto. 
     The element active layer  330  is disposed between the first conductivity type semiconductor  310  and the second conductivity type semiconductor  320 , and may include a material having a single or multiple quantum well structure. When the element active layer  330  includes a material having a multiple quantum well structure, a plurality of quantum layers and well layers may be stacked alternately. The element active layer  330  may emit light by coupling of electron-hole pairs according to an electric signal applied through the first conductivity type semiconductor  310  and the second conductivity type semiconductor  320 . For example, when the element active layer  330  emits light of a blue wavelength band, it may include a material such as AlGaN or AlInGaN. In particular, when the element active layer  330  has a multiple quantum well structure in which quantum layers and well layers may be stacked alternately, the quantum layer may include a material such as AlGaN or AlInGaN, and the well layer may include a material such as GaN or AlGaN. However, the present disclosure is not limited thereto, and the element active layer  330  may have a structure in which semiconductor materials having large band gap energy and semiconductor materials having small band gap energy are alternately stacked, and may include other Group III to V semiconductor materials according to the wavelength band of the emitted light. The light emitted by the element active layer  330  is not limited to light of a blue wavelength band, but may also emit light of a red or green wavelength band in some cases. The length of the element active layer  330  may have a range of 0.05 μm to 0.25 μm, but is not limited thereto. 
     The light emitted from the element active layer  330  may be projected through both side surfaces, as well as the outer surface of the light emitting element  300 , in a longitudinal direction. The directionality of light emitted from the element active layer  330  is not limited to one direction. 
     The electrode material layer  370  may be an ohmic contact electrode. However, the present disclosure is not limited thereto, and the electrode material layer  370  may be a Schottky contact electrode. The electrode material layer  370  may include conductive metal. For example, the electrode material layer  370  may include at least one of aluminum (Al), titanium (Ti), indium (In), gold (Au), or silver (Ag). The electrode material layer  370  may include the same material or different materials. However, the present disclosure is not limited thereto. 
     The insulating material layer  380  may be formed outside the light emitting element  300  to protect the light emitting element  300 . For example, the insulating material layer  380  may be formed to surround the side surface of the light emitting element  300 , and may not be formed at both ends of the light emitting element  300  in the longitudinal direction, e.g., at both ends where the first conductivity type semiconductor  310  and the second conductivity type semiconductor  320  are disposed. However, the present disclosure is not limited thereto. The insulating material layer  380  may include materials having insulating properties, for example, silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy), aluminum nitride (AlN), aluminum oxide (A 2 O 3 ), and the like. Accordingly, an electrical short circuit that may occur when the element active layer  330  directly contacts the first electrode  210  or the second electrode  220  can be prevented. Furthermore, the insulating material layer  380  includes the element active layer  330  to protect the outer surface of the light emitting element  300 , which may prevent degradation in light emission efficiency. 
     The insulating material layer  380  may be formed to extend in the lengthwise direction to cover the first conductivity type semiconductor  310  to the electrode material layer  370 . However, the present disclosure is not limited thereto, and the insulating material layer  380  may cover only the first conductivity type semiconductor  310 , the element active layer  330 , and the second conductivity type semiconductor  320 , or only part of the outer surface of the electrode material layer  370  and expose part of the outer surface of the electrode material layer  370 . 
     In some embodiments, the insulating material layer  380  may be surface-processed so as to disperse rather than to cohere with other insulating material layers  380  in a solution. In this case, the light emitting element  300  may remain in a dispersed state in the solution to be aligned independently between the first and second electrodes  210  and  220  during the alignment of the light emitting element  300  as to be described later. For example, the insulating material layer  380  may be surface-processed in a hydrophobic or hydrophilic manner, such that the light emitting elements  300  remain in a mutually dispersed state in the solution. 
     The thickness of the insulating material layer  380  may have a range of 0.5 μm to 1.5 μm, but is not limited thereto. 
     The light emitting element  300  may have a cylindrical shape. As shown in  FIG. 3B , the cross section taken by halving the light emitting element  300  in the lengthwise direction crossing the two ends of the light emitting element  300  may have a rectangular shape. However, the shape of the light emitting element  300  is not limited thereto, and may have various shapes such as a regular cube, a rectangular parallelepiped and a hexagonal prism. The light emitting element  300  may have a length I of 1 μm to 10 μm or 2 μm to 5 μm, and preferably about 4 μm. In addition, the diameter of the light emitting element  300  may have a range of 400 nm to 700 nm, and preferably may be about 500 nm. 
     Although the following description is made of the exemplary light emitting element  300  shown in  FIG. 3A  for convenience of explanation, the present disclosure may be identically applicable to the light emitting elements including more electrode material layers  370  or other structures. 
     Meanwhile,  FIG. 4  is an enlarged view of part of  FIG. 3A , and  FIG. 5  is an enlarged view of part A of  FIG. 2 . 
     With reference to  FIG. 4 , the light emitting element  300  according to an embodiment may have a parting surface  390  that is flat and relatively less rough. The light emitting element  300  may include the first conductivity type semiconductor  310  of which the end surface becomes the parting surface  390  in the manufacture of the light emitting element  300  as to be described later. The first conductivity type semiconductor  310  of the light emitting element  300  may be formed to have an even surface, which prevents an open circuit problem from occurring when contacting the first contact electrode  261 . 
     With reference to  FIG. 5 , the shape of the parting surface  390  of the end of the light emitting element  300  may determine the contact quality on the plane (line  5   a - 5   a ′ in  FIG. 5 ) where the parting surface  390  of one end of the light emitting element  300  and a surface of the first contact electrode  261  contact each other. For example, if the parting surface  390  of the light emitting element  300  is rough or protruded, or recessed to form a slope, this may degrade the thin film step coverage of the contact electrode material when contacting the first contact electrode  261 , which leads to a partial cutoff of the electrode material. That is, the faulty contact between the light emitting element  300  and the first contact electrode  261  at the contact area ( 5   a - 5   a ′ of  FIG. 5 ) may block an electrical signal from reaching the light emitting element  300 , leading to a light emission error. 
     Meanwhile, if the parting surface  390  of the light emitting element  300  is even as shown in  FIG. 5 , this makes it possible to prevent a short circuit problem of the contact electrode material from occurring at the area ( 5   a - 5   a ′ of  FIG. 5 ) where the light emitting element  300  and the contact electrode  260  contact each other. This may be able to improve reliability of the light emitting element  300  of the display device  10 . According to an embodiment, the parting surface  390  of the light emitting element  300  may have a roughness value of 8 nm Ra to 12 nm Ra. However, the present disclosure is not limited thereto. Meanwhile, although not shown in the drawing, the above-described approach may be identically applicable to the second conductivity semiconductor  320  contacting the second contact electrode  262 , or the side surface formed by the electrode material layer  370 . 
     The evenness of the parting surface  390  of the light emitting element  300  may be accomplished by separating the light emitting element  300  from a lower substrate layer on which the light emitting element  300  was grown in the process of manufacturing the light emitting element  300 , in a way of peeling a separating layer  1300  (shown in  FIG. 7 ) on which the light emitting element  300  was formed. That is, the light emitting element  300  may be separated from the lower substrate layer without any external physical force, by letting the material grown on the parting surface  390  of one end of the light emitting element  300  be cut off by peeling the separating layer  1300  on which the light emitting element  300  was grown. 
     In this manner, the light emitting element  300  according to an embodiment may be manufactured to have the both ends with the flat even parting surface  390  contacting the first and second contact electrodes  261  and  262 , which makes it possible to prevent a short circuit problem from occurring with the material of the contact electrodes  261  and  262 . A description is made hereinafter of the method for manufacturing the light emitting element  300  in detail with reference to  FIGS. 6 to 18 . 
       FIGS. 6 to 18  are schematic cross-sectional views schematically showing a method for manufacturing a light emitting element according to an embodiment. 
     First, with reference to  FIG. 6 , a lower substrate layer  1000  including a base substrate  1100  and a buffer material layer  1200  formed on the base substrate  1100  is prepared. As shown in  FIG. 6 , the lower substrate layer  1000  may have a layered structure formed by depositing the base substrate  1100  and the buffer material layer  1200  in order. 
     The base substrate  1100  may include a transparent substrate such as a sapphire (Al 2 O 3 ) substrate and a glass substrate. However, the present disclosure is not limited thereto, and it may be formed of a conductive substrate material such as GaN, SiC, ZnO, Si, GaP and GaAs. The following description is directed to an exemplary case where the base substrate  1100  is a sapphire (Al 2 O 3 ) substrate. Although not limited, the base substrate  1100  may have, for example, a thickness in the range of 400 μm to 1500 μm. 
     On the base substrate  1100 , a plurality of conductivity type semiconductor layers are formed. The plurality of conductivity type semiconductor layers grown by an epitaxial growth method may be grown by forming a seed crystal and depositing a crystal material thereon. Here, the conductivity type semiconductor layer may be formed using one of electron beam deposition, physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma laser deposition (PLD), dual-type thermal evaporation, sputtering, and metal organic chemical vapor deposition (MOCVD), preferably, using the metal organic chemical vapor deposition (MOCVD). However, the present disclosure is not limited thereto. 
     Typically, a precursor material for forming the plurality of conductivity type semiconductor layers may be selected to form a target material in a typically selectable range without any limitation. For example, the precursor material may be a metal precursor including an alkyl group such as a methyl group or an ethyl group. Examples of the precursor material may include, but are not limited to, trimethylgallium Ga(CH 3 ) 3 , trimethylaluminum Al(CH 3 ) 3 , and triethyl phosphate (C 2 H 5 ) 3 PO 4 . Hereinafter, with the omission of the description of the method and processing conditions for forming the plurality of conductivity type semiconductor layers, a description is made of the processing order of the method for manufacturing the light emitting element  300  and the layered structure of the light emitting element  300  in detail. 
     A buffer material layer  1200  is formed on the base substrate  1100 . Although it is shown in the drawing that one buffer material layer  1200  is deposited, the present disclosure is not limited thereto, and a plurality of layers may be formed. 
     At a step to be described later, a separating layer  1300  may be disposed on the buffer material layer  1200  and then a crystal for the first conductivity type semiconductor layer  3100  may grow on the separating layer  1300 . The buffer material layer  1200  may be interposed between the base substrate  1100  and the separating layer  1300  to reduce a grid constant difference of the first conductivity type semiconductor layer  3100 . Although the first conductivity type semiconductor layer  3100  may be directly formed on the separating layer  1300  disposed on the base substrate  1100 , the buffer material layer  1200  may provide the seed crystal to facilitate crystal growth to the first conductivity type semiconductor layer  3100 . 
     For example, the buffer material layer  1200  may include an undoped semiconductor, and may be a material including substantially the same material as the first conductivity type semiconductor layer  3100  that is neither n-type doped nor p-type doped. In an exemplary embodiment, the buffer material layer  1200  may be, but is not limited to, at least one of undoped InAlGaN, GaN, AlGaN, InGaN, AlN, or InN. 
     Meanwhile, in some embodiments, a plurality of layers may be formed on the buffer material layer  1200 , and the separating layer  1300  may be deposed thereon. The buffer material layer  1200  may also be omitted, depending on the base substrate  1100 . A detailed description thereof will be given with reference to other embodiments. Hereinafter, a description is made of the exemplary case where the buffer material layer  1200  including an undoped semiconductor material is formed on the base substrate  1100 . 
     Next, with reference to  FIG. 7 , the separating layer  1300  is formed on the lower substrate layer  1000 . 
     The separating layer  1300  may have the first conductivity type semiconductor layer  3100  formed thereon. That is, the separating layer  1300  may be interposed between the first conductivity type semiconductor layer  3100  and the buffer material layer  1200 , and the separating layer  1300  may include a material facilitating growth of the crystal of the first conductivity type semiconductor layer  3100 . The separating layer  1300  may be peeled off from the lower substrate layer  1000  to separate the light emitting element  300  manufactured thereon at a step to be described later. 
     In an exemplary embodiment, the separating layer  1300  may include a graphene layer. The graphene may facilitate crystal growth of the conductivity type semiconductor layer due to the nature of surface characteristics thereof. Particularly in the case of pure graphene that barely includes graphene oxide (GO) as an impurity, conductivity type semiconductors may grow in the epitaxial process for manufacturing the light emitting element  300 . 
     The graphene layer may have a two-dimensional plane single layer structure of carbon atoms, which forms a relatively weak mutual attraction between layers. That is, the graphene layer may be disposed on an interface between two different material layers to facilitate peeling one material layer off from the other material layer. That is, the separating layer  1300  including the graphene layer may be disposed on the interface between the buffer material layer  1200  and the first conductivity type semiconductor layer  3100  to facilitate separating the manufactured light emitting element  300 . 
     For example, the separating layer  1300  may have a structure formed with a single pure graphene layer or two laminated graphene layers. Although it is shown in  FIG. 7  that the separating layer  1300  includes a single graphene layer, the separating layer  1300  may have a structure of two laminated graphene layers in some cases. As a consequence, in the separation process of the light emitting element  300  to be described later, the separating layer  1300  and the first conductivity type semiconductor layer  3100  may be separated on the interface therebetween, or between the plurality of graphene layers constituting the separating layer  1300 . In an exemplary embodiment, the separating layer  1300  may have a thickness in a range from 0.3 nm to 1.0 nm. The single graphene layer may have a thickness of about 0.35 nm. Accordingly, the separating layer  1300  composed of one or two graphene layers may have a thickness in the aforementioned range. A more detailed description thereof is made later, and a description is made hereinafter of the exemplary case where the separating layer  1300  includes a single graphene layer. 
     The separating layer  1300  may also serve as an etching stopper between an element deposition structure  3000  and the buffer material layer  1200  during the process of etching the element deposition structure  3000 . That is, when the element deposition structure  3000  is etched, the separating layer  1300  may be patterned simultaneously in one process or patterned separately in a different process. There is no limitation on the method of manufacturing the light emitting element  300 . 
     However, the present disclosure is not limited thereto, and more separating layers  1300  may be arranged in the element deposition structure  3000  or the lower substrate layer  1000 , and regions such as on the interface between the buffer material layer  1200  and the first conductivity type semiconductor layer  1300 . A detailed description thereof will be given with reference to other embodiments. 
     Next, with reference to  FIG. 8 , the element deposition structure  3000  is formed by depositing a first conductivity type semiconductor layer  3100 , an active material layer  3300 , a second conductivity type semiconductor layer  3200 , and a conductive electrode material layer  3700  in order on the separating layer  1300 . 
     The element deposition structure  3000  may be partially etched to form the light emitting element  300  in a step to be described later. The plurality of material layers included in the element deposition structure  3000  may be formed through a conventional process as described above. On the separating layer  1300 , the first conductivity type semiconductor layer  3100 , the active material layer  3300 , the second conductivity type semiconductor layer  3200 , and the conductive electrode material layer  3700  may be deposited in order, and they may respectively include the same materials as those of the first conductivity type semiconductor  310 , the element active layer  330 , the second conductivity type semiconductor  320 , and the electrode material layer  370  of the light emitting element  300 . 
     Meanwhile, the light emitting element  300  may be manufactured with the omission of the electrode material layer  370 , or with the further inclusion of a different electrode material layer  370  formed on the bottom surface of the first conductivity type semiconductor  310 . That is, the conductive electrode material layer  3700  formed on the second conductivity type semiconductor layer  3200  may be omitted as shown in  FIG. 11 . The following description is made of the exemplary case where the element deposition structure  3000  includes the conductive electrode material layer  3700 . 
     Next, with reference to  FIGS. 9 to 12 , the light emitting element  300  may be manufactured in a way of etching the element deposition structure  3000  in the vertical direction to form an element rod ROD and then forming an insulating layer  3800  partially covering the outer surface of the element rod ROD. 
     First, with reference to  FIGS. 9 and 10 , forming the element rod ROD by vertically etching the element deposition structure  3000  may include a patterning process that may be conventionally carried out. For example, forming the element rod ROD by etching the element deposition structure  300  may include forming an etching mask layer  1600  and an etching pattern layer  1700  on the element deposition structure  3000 , and etching the element deposition structure  3000  according to a pattern of the etching pattern layer  1700 , and removing the etching mask layer  1600  and the etching pattern layer  1700 . 
     The etching mask layer  1600  may serve as a mask for consecutively etching the first conductivity type semiconductor layer  3100 , the active material layer  3300 , the second conductivity type semiconductor layer  3200 , and the conductive electrode material layer  3700  of the element deposition structure  3000 . The etching mask layer  1600  may include a first etching mask layer  1610  including an insulating material, and a second etching mask layer  1620  including metal. 
     The insulating material included in the first etching mask layer  1610  of the etching mask layer  1600  may be an oxide or a nitride. Examples of the insulating material may include silicon oxide (SiOx), silicon nitride (SiNx), and silicon oxynitride (SiOxNy). The first etching mask layer  1610  may have a thickness in the range of 0.5 μm to 1.5 μm without being limited thereto. 
     The second etching mask layer  1620  may not be limited in material as long as it can serve as a mask for consecutively etching the element deposition structure  3000 . For example, the second etching mask layer  1620  may include chrome (Cr). 
     The second etching mask  1620  may have a thickness in the range from 30 nm to 150 nm without being limited thereto. 
     The etching pattern layer  1700  formed on the etching mask layer  1600  may include at least one nanopattern separated from each other thereon. The etching pattern layer  1700  may serve as a mask for consecutively etching the element deposition structure  3000 . There is no limitation on the etching method as long as it can form a pattern including a polymer, a polyethylene sphere, or a silica sphere on the etching pattern layer  1700 . 
     For example, in the case where the etching pattern layer  1700  includes a polymer, it may be possible to employ a conventional method for forming a pattern with the polymer. For example, it may be possible to use a method such as photolithography, e-beam lithography, nanoimprint lithography to form the etching pattern layer  1700  including the polymer. 
     Particularly, the structure, shape, and separation interval of the etching pattern layer  1700  may be associated with the shape of the finally manufactured light emitting element  300 . However, because the light emitting element  300  may have a different shape as described above, the etching pattern layer  1700  is not particularly limited in structure. For example, if the etching pattern layer  1700  has a pattern of circles separated from each other, the element deposition structure  300  may be vertically etched to manufacture the light emitting element  300  having a cylinder shape. However, the present disclosure is not limited thereto. 
     Next, the element deposition structure  3000  may be etched according to the pattern of the etching pattern layer  17000  to form the element rod ROD. The spaces between the plurality of nanopatterns in the etching pattern layer  1700  may be vertically etched to form a hole, which is selectively formed to have a depth from the etching mask layer  1600  to the separating layer  1300 . 
     The hole may be formed using a conventional method. For example, the etching process may be performed with dry etching, wet etching, reactive ion etching (RIE), inductively coupled plasma reactive ion etching (ICP-RIE), or the like. The dry etching is capable of anisotropic etching, which may be appropriate for forming a hole through vertical etching. In the case of using the aforementioned etching technique, it may be possible to use Cl 2  or O 2  as etchant. However, the present disclosure is not limited thereto. 
     In some embodiments, etching the element deposition structure  3000  may be carried out with a combination of the dry etching and the wet etching. For example, it may be possible to perform etching in a depth direction with the dry etching, and then anisotropic etching with the wet etching, such that the etched sidewalls are placed on the plane perpendicular to the surface. 
     Meanwhile, forming the element rod ROD by etching the element deposition structure  3000  may include patterning the separating layer  1300  together during one etching process, or patterning part of the separating layer  1300  after the element rod ROD is formed through another etching process. 
     That is, the separating layer  1300  may be patterned together in the etching process of forming the hole by etching the element deposition structure  3000 , or patterned in a separate process after acting as an etching stopper in the process of etching the element deposition structure  3000 . 
     For example, in the case where the etchant for use in patterning the element deposition structure  3000  includes substance for removing the separating layer  1300 , the element deposition structure  3000  and the separating layer  1300  may be simultaneously patterned in one process. On the other hand, with reference to  FIG. 11 , if the etchant is prepared for etching only the element deposition structure  3000 , the separating layer  1300  may serve as an etching stopper such that the etchant etches only the element deposition structure and does etch the separating layer  1300 . Accordingly, the element rod ROD may be formed in the state where the separating layer  1300  is not etched, and the separating layer  1300  may be patterned through a different etching process. 
     In some embodiments, if the separating layer  1300  includes a graphene layer and the etchant includes oxygen gas (O 2 ), it may be possible to simultaneously pattern the element deposition structure  3000  and the separating layer  1300 . In another embodiment, if the etchant does not include oxygen gas (O 2 ), the element rod ROD may be formed by patterning the element deposition structure  3000 , and the separating layer  1300  may be selectively etched in another etching process. 
     As described with reference to  FIG. 12 , the mask layer  1600  and the etching pattern layer  1700  remaining on the vertically etched element deposition structure  3000  may be removed by a conventional method, e.g., dry etching and wet etching, to form the element rod ROD. 
     Next, with reference to  FIGS. 13 and 14 , the insulating layer  3800  may be formed to partially cover the outer surface of the element rod ROD to manufacture the light emitting element  300 . 
     The insulating layer  3800  is an insulating material formed on the outer surface of the element rod ROD and may be formed by depositing the insulating material on the outer surface of the vertically etched element rod ROD or dipping the element rod ROD in the insulating material without being limited thereto. For example, the insulating layer  3800  may be formed using atomic layer deposition (ALD). The insulating layer  3800  may form an insulating material layer  380  of the light emitting element  300 . As described above, the insulating layer  3800  may include a material such as silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy), aluminum oxide (Al 2 O 3 ), and aluminum nitride (AlN). 
     With reference to  FIG. 13 , the insulating layer  3800  may be formed on the side and top surfaces of the element rod ROD, and between the buffer material layer  1200  and the separating layer  1300  exposed to the outside in the course of etching to form the elements rods ROD separately. In order to expose both end side surfaces of the element rod ROD, the insulating layer  3800  formed on the top surface of the element rod ROD may be removed. Accordingly, it may be necessary to partially remove the insulating layer  3800  formed in a direction perpendicular to the lengthwise direction of the element rod ROD, i.e., the direction parallel with the base substrate  1100 . That is, as shown in  FIG. 14 , the top surface of the element rod ROD may be exposed by removing the insulating layer  3800  at least on the top surface of the element rod ROD, and between the buffer material layer  1200  and the separating layer  1300 . In order to accomplish this, a process such as dry etching as anisotropic etching, or etch-back, may be performed. Through the above-described process, it may be possible to manufacture the light emitting element  300  including the insulating layer  3800  covering the outer surface of the element rod ROD. 
     Finally, as shown in  FIG. 15 , the light emitting element  300  may be separated from the separating layer  1300  formed on the lower substrate layer  1000 . 
     As described above, the separating layer  1300  including the graphene layer may form a relatively weak attractive force on the interface between different material layers. However, the separating layer  1300  may form a relatively strong attractive force with one of the different material layers and a relatively weak attractive force with another material layer. In this case, in the case where the separating layer  1300  is peeled off such that the two material layers are separated, the separating layer  1300  may remain on one of the two material layers. 
     In a method for manufacturing the light emitting element  300  according to an embodiment, the separating layer  1300  may have an interface attractive force with the buffer material layer  1200  that is greater than another interface attractive force with the first conductivity type semiconductor layer  3100 . That is, when the manufactured light emitting element  300  is separated, the separating layer  1300  may remain on the buffer material layer  1200  with the relatively storing attractive force, and the first conductivity type semiconductor layer  3100  may be peeled off such that the light emitting element  300  is separated. Here, when the first conductivity type semiconductor layer  3100  is peeled off from the separating layer  1300 , because the inter-crystal attractive force of the first conductivity type semiconductor layer  3100  is stronger than the interface attractive force associated with the separating layer  1300 , the first conductivity type semiconductor layer  3100  may be separated from the lower substrate layer  1000  without any damage. 
     In this respect, the separating layer  1300  is peeled off on the parting surface  390  of the manufactured light emitting element  300 , which makes it possible for the parting surface  390  to remain even, and simultaneously to secure uniformity of the parting surfaces  390  of the plurality of light emitting elements  300 . 
     Meanwhile, there is no limitation on the method for separating the light emitting element  300  by peeling off the separating layer  1300 . In some embodiments, the light emitting element  300  may be separated from the lower substrate layer  1000  through physical separation (Mechanically Lift Off) or chemical separation (Chemically Lift Off). 
       FIGS. 16 to 18  are schematic views showing a method for separating the light emitting element  300  according to an embodiment. 
     First, with reference to  FIGS. 16 and 17 , an adhesive layer LOA is formed on the top surfaces of the light emitting elements  300  manufactured on the lower substrate layer  1000 . The adhesive layer LOA may be a material layer having adhesive components, and is not limited as long as it incurs no damage to the material of the light emitting element  300 . Examples of the adhesive layer LOA may include, but are not limited to, polymethylmethacrylate (PMMA), polydimethylsiloxane (PMDS), viscosity variation film, and thermal release tape (TRT). 
     The plurality of light emitting elements  300  manufactured on the lower substrate layer  1000  may be simultaneously adhered, on the top surfaces thereof, to the adhesive layer LOA and physically lifted, as shown in  FIG. 17 , in order for the separating layer  1300  to be peeled off from the lower substrate layer  1000 . Although not shown in the drawing, the adhesive layer LOA may be removed by a conventional method. 
     In another embodiment, the light emitting elements  300  may be separated from the lower substrate layer  1000  by a vibration in a solution. With reference to  FIG. 18 , the light emitting elements  300  manufactured on the separating layer  1300  may be separated in a way of applying a vibration in the state of being immerged in a separation solution S together with the lower substrate layer  1000 . As described above, because the interface attractive force of the separating layer  1300  including the graphene layer is relatively weak, the separating layer  1300  may be peeled off by a relatively weak vibration. Accordingly, the light emitting elements  300  may be separated from the lower substrate layer  1000  by immerging them in the separation solution S and applying a vibration thereto. The separation solution S is not limited in kind as long as it incurs no damage to the light emitting element  300 . Examples of the separation solution S may include an organic solvent. The method for separating the light emitting elements  300  is not limited by any of the steps described with reference to  FIGS. 16 to 18 . Although not shown in the drawings, the light emitting elements  300  may also be manufactured by chemically dissolving the separating layer  1300 . 
     The method for manufacturing the light emitting elements  300  according to an embodiment may include forming the separating layer  1300  on the lower substrate layer  1000 , and separating the light emitting elements  300  grown on the separating layer  1300  from the lower substrate layer  1000 . The separating layer  1300  may include at least one graphene layer, which may facilitate separating the light emitting elements  300  manufactured thereon from the separating layer  1300  with a relatively weak interface attractive force. Because the attractive force between the separating layer  1300  and the first conductivity type semiconductor layer  3100  of the light emitting element  300  is weaker than the inter-crystal attractive force of the first conductivity type semiconductor layer  3100 , the light emitting elements  300  may be separated with no damage on the parting surface  390  thereof, while the parting surface  390  remains even. This makes it possible to prevent an open circuit of the contact electrode material from occurring at the interface (e.g., parting surface  390 ) at which the light emitting element  300  and the contact electrode  260  contact each other, which leads to improvement of light emission reliability of the display device  10 . 
     Meanwhile, the arrangement of the separating layer  1300  is not limited to the arrangement shown in  FIG. 7 . As described above, in the process of manufacturing the light emitting elements  300 , one or more separating layers  1300  may be arranged on the element deposition structure  3000  or the lower substrate layer  1000 , or one separating layer  1300  may include a plurality of sub-separating layers. A description is made hereinafter of the separating layer  1300  arranged on the lower substrate layer  1000  or the element deposition structure  3000  according to another embodiment. 
       FIG. 19  is a cross-sectional view schematically illustrating a structure of a separating layer according to another embodiment.  FIG. 20  is a schematic view illustrating a process for separating light emitting elements by the separating layer of  FIG. 19 . 
     With reference to  FIG. 19 , a separating layer  1300 _ 1  may include a plurality of graphene layers GL. The plurality of graphene layers GL may include a first graphene layer GL 1  formed on and contacting a buffer material layer  1200 _ 1  and a second graphene layer GL 2  arranged on the first graphene layer GL 1  and contacting the parting surface  390  of the light emitting elements  300 . The method for manufacturing the light emitting elements is identical with that described with reference to  FIGS. 6 to 18 , with the exception that the separating layer  1300 _ 1  includes a plurality of graphene layers GL. Hereinafter, a description is made of the method for separating the separating layer  1300 _ 1  and the light emitting elements  300  from each other in detail. 
     With reference to  FIG. 20 , when the light emitting elements  300  grown on the separating layer  1300 _ 1  are separated, the separation may respectively occur on a first interface INF 1  between a buffer material layer  1200 _ 1  and the first graphene layer GL 1 , a second interface INF 2  between the first graphene layer GL 1  and the second graphene layer GL 2 , and a third interface INF 3  between the second graphene layer GL 2  and the parting surface  390  of the light emitting elements  300 . 
     By adjusting the interface attractive force on the first interface INF 1  between the buffer material layer  1200 _ 1  and the first graphene layer GL 1  as described above, the first graphene layer GL 1  may remain on the buffer material layer  1200 _ 1  after the light emitting elements  300  are separated. That is, the light emitting elements  300  may be separated from the lower substrate layer  1000 _ 1  by a split at the second interface INF 2  or the third interface INF 3 , where the attractive force is weak. 
     Here, in the case where the attractive force at the second interface INF 2  is greater than the attractive force at the third interface INF 3 , the separated light emitting elements  300  may expose the first conductivity type semiconductor  310 , i.e., the parting surface  390 , as shown in  FIG. 20 . In contrast, if the attractive force at the third interface INF 3  is greater than the attractive force at the second interface INF 2 , the separated light emitting elements  300  may not expose the first conductivity type semiconductor  310  because the second graphene layer GL 2  partially remains on the parting surface  390 . In this case, the second graphene layer GL 2  including graphene having conductivity may form the electrode material layer  370  at one end of the light emitting element  300 . 
     Meanwhile, in some embodiments, it may also be included to remove impurities from the parting surface  390  of the separated light emitting elements  300 . As described above, in the case where the separating layer  1300 _ 1  includes the plurality of graphene layers GL, the layered structure on the parting surface  390  of the light emitting elements  300  may vary according to the attractive forces at the plurality of interfaces INF. However, in the case where the attractive forces of the interfaces INF are not accurately controlled, the uniformity of the parting surface  390  of the light emitting elements  300  may decrease and, in order to overcome this, a post-processing process may be performed on the separated light emitting element  300 . 
     As shown in  FIG. 20 , in order to remove the separating layer  1300 _ 1 , e.g., the second graphene layer GL 2 , remaining on the parting surface  390  of the separated light emitting element  300 , the above-described separation process may be repetitively performed. Because the attractive force at the interface between second graphene layer GL 2  of the separating layer  1300 _ 1  and the parting surface  390  of the light emitting element  300  is relatively weak, the second graphene layer GL 2  may be removed by repeating the process described with reference to  FIGS. 18 to 20 . 
       FIGS. 21 to 24  are cross-sectional views schematically illustrating arrangement of a separating layer in an element deposition structure according to still another embodiment. 
     The separating layer  1300  may be arranged in the first conductivity type semiconductor layer  3100  of the element deposition structure  3000  and, in some cases, directly on the base substrate  1100  with the omission of the buffer material layer  1200 . 
     With reference to  FIG. 21 , the separating layer  1300 _ 2  may be arranged on a first sub-conductivity type semiconductor layer  3100 ′_ 2  deposited on a buffer material layer  1200 _ 2 , and a first conductivity type semiconductor layer  3100 _ 2  may be deposited on the separating layer  1300 _ 2 . The first sub-conductivity type semiconductor layer  3100 ′_ 2  may include a material substantially identical with that of the first conductivity type semiconductor layer  3100 _ 2 . That is, the separating layer  1300 _ 2  may be arranged in the first conductivity type semiconductor layer  3100 _ 2 . 
     As described above, the buffer material layer  1200  may provide a seed crystal of the first conductivity type semiconductor layer  3100  growing on the separating layer  1300 , and may reduce the grid constant of the interfaces. The element deposition structure of  FIG. 21  may facilitate crystal growth of the first conductivity type semiconductor layer  3100 _ 2  by substantially including the separating layer  1300 _ 2  in the first conductivity type semiconductor layer  3100 _ 2 . 
     With reference to  FIG. 22 , in the case where the base substrate  1100 _ 3  includes a material substantially identical with that of the first conductivity type semiconductor layer  3100 _ 3 , the buffer material layer  1200  may be omitted, and the separating layer  1300 _ 3  may be directly arranged on the base substrate  1100 _ 3 . 
     For example, in the case where the first conductivity type semiconductor layer  3100 _ 3  includes n-type doped gallium nitride (GaN), and the base substrate  1100 _ 3  is a GaN substrate, the grid constant difference between the base substrate  1100 _ 3  and the first conductivity type semiconductor layer  3100 _ 3  may be small. In this case, even though the buffer material layer  1200  is omitted, the grid constant difference between the base substrate  1100 _ 3  and the first conductivity type semiconductor layer  3100 _ 3  may be small, and the GaN substrate may provide the seed crystal. According to an embodiment, in the process of manufacturing the light emitting elements  300 , the separating layer  1300 _ 3  may be directly arranged on the base substrate  1100 _ 3 , and the first conductivity type semiconductor layer  3100 _ 3  may grow on the separating layer  1300 _ 3 . 
     Meanwhile, it may be possible to include one or more separating layers that are arranged on different layers in the element deposition structure  3000  and the lower substrate layer  1000 . 
     With reference to  FIG. 23 , the separating layer may include a first sub-separating layer  1310 _ 4  arranged between the buffer material layer  1200 _ 4  and the first sub-conductivity type semiconductor layer  3100 ′_ 4 , and a second sub-separating layer  1320 _ 4  arranged between the first sub-conductivity type semiconductor layer  3100 ′_ 4  and the first conductivity type semiconductor layer  3100 _ 4 . That is, in  FIG. 23 , it may be the case that the second sub-separating layer  1320 _ 4  is further arranged in the first conductivity type semiconductor layer  3100 _ 4  in comparison with the element deposition structure  3000  of  FIG. 7 . 
     In this case, if the manufactured light emitting elements  300  are separated, the second sub-separating layer  1320 _ 4  remains on the first sub-conductivity type semiconductor layer  3100 ′_ 4 . The element deposition structure may be manufactured by removing the second sub-separating layer  1320 _ 4  remaining on the first sub-conductivity type semiconductor layer  3100 ′_ 4  and then forming the second sub-separating layer  1320 _ 4  again. That is, it may be possible to use the first sub-conductivity type semiconductor layer  3100 ′_ 4  providing the seed crystal of the first conductivity type semiconductor layer  3100 _ 4  repetitively several times. 
     Furthermore, with reference to  FIG. 24 , the first sub-separating layer  1310 _ 5  may be arranged between the buffer material layer  1200 _ 5  and the first conductivity type semiconductor layer  3100 _ 5 , and the second sub-separating layer  1320 _ 5  may be arranged between the base substrate  1100 _ 5  and the buffer material layer  1200 _ 5 . That is, in  FIG. 24 , it may be the case that the second sub-separating layer  1320 _ 5  is further arranged between the base substrate  1100 _ 5  and the buffer material layer  1200 _ 5  in comparison with the lower substrate layer  1000  of  FIG. 7 . 
     As described above, the separating layer including graphene has a weak interface attractive force with a certain surface, which facilitates separation or peeling off. In  FIG. 24 , the first sub-separating layer  1310 _ 5  may serve to separate the light emitting elements  300  from the lower substrate layer  1000 _ 5 , and the second sub-separating layer  1320 _ 5  may serve to separate the base substrate  1100 _ 5  and the buffer material layer  1200 _ 5  from each other. In the case where the interface attractive force between the second sub-separating layer  1320 _ 5  and the base substrate  1100 _ 5  is stronger than the interface attractive force between the second sub-separating layer  1320 _ 5  and the buffer material layer  1200 _ 5 , the base substrate  1100 _ 5  and the buffer material layer  1200 _ 5  may be easily separated from each other. In this case, after the light emitting elements  300  are manufactured, the base substrate  1100 _ 5  of the lower substrate layer  1000 _ 5  may be reused by separating the buffer material layer  1200 _ 5  therefrom. For example, if the base substrate  1100 _ 5  is a high-priced substrate such as SiC substrate, reusing the base substrate  1100 _ 5  may make it possible to reduce the manufacturing costs of the light emitting elements  300 . 
     In concluding the detailed description, those skilled in the art will appreciate that many variations and modifications can be made to the preferred embodiments without substantially departing from the principles of the present invention. Therefore, the disclosed preferred embodiments of the invention are used in a generic and descriptive sense only and not for purposes of limitation.