Patent Publication Number: US-2023143907-A1

Title: Epitaxy structure including a plurality of semiconductor devices

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2021-0154295, filed on Nov. 10, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     Example embodiments of the present disclosure relate to an epitaxy structure including a plurality of semiconductor devices fabricated using remote epitaxy technology. 
     2. Description of Related Art 
     A light emitting diode (LED) with low power consumption and eco-friendliness is known as a next-generation light source having advantages such as long lifespan, low power consumption, fast response speed, and environmental friendliness compared to conventional light sources, and because of these advantages, industrial demand is increasing. LEDs are generally applied and used in various products such as lighting devices and backlights of display devices. 
     Recently, micro-units or nano-units of micro LEDs using group II-VI or group III-V compound semiconductors have been developed. In addition, micro LED displays in which such micro LEDs are directly applied as light emitting elements of display pixels are being developed. However, when the LED is miniaturized in a micro unit or a nano unit as described above, the luminous efficiency of the LED may be lowered. 
     SUMMARY 
     One or more example embodiments provide an epitaxy structure including a plurality of semiconductor devices manufactured using remote epitaxy technology. 
     One or more example embodiments also provide an epitaxy structure including a plurality of nanorod light emitting devices having a high-quality single crystal structure. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of example embodiments of the disclosure. 
     According to an aspect of an example embodiment, there is provided an epitaxy structure including a substrate having an upper surface, the upper surface having a single crystal structure, a two-dimensional material layer disposed on the upper surface of the substrate, and a plurality of nanorod light emitting devices disposed on an upper surface of the two-dimensional material layer, each of the plurality of nanorod light emitting devices having a nanorod shape extending in a vertical direction, wherein each of the plurality of nanorod light emitting devices includes a light emitting nanorod, and a passivation film disposed adjacent to a sidewall of the light emitting nanorod, the passivation film having insulation. 
     The substrate may include a support layer, and a single crystal layer disposed on an upper surface of the support layer. 
     The support layer may include a crystalline material, and the single crystal layer may include a single crystal of a group III-V compound semiconductor having an ionic bond characteristic or an ionic crystal. 
     The support layer may include silicon (Si) or sapphire. 
     The single crystal layer may include at least one single crystal of lithium fluoride (LiF), gallium nitride (GaN), and barium titanate (BaTiO 3 ). 
     The support layer may include an amorphous material. 
     The single crystal layer may include at least one of cerium oxide (CeO 2 ), scandium(III) oxide (Sc 2 O 3 ), magnesium oxide (MgO), barium oxide (BaO), and bromine nitride (BrN) oriented in a (111) direction, a (001) direction, or a (100) direction. 
     The single crystal layer may include at least two sub-layers, each of the at least two sub-layers having a thickness of 0.5 nm to 100 nm. 
     The support layer may include glass or fused silica. 
     The two-dimensional material layer may include a plurality of nanorods respectively extending from a corresponding light emitting nanorod. 
     The single crystal layer may include a plurality of nanorods respectively extending from a corresponding light emitting nanorod. 
     The substrate may include one single layer having a single crystal structure. 
     The substrate may include at least one single crystal from among 4H-SiC, 6H-SiC, and 3C-SiC. 
     The two-dimensional material layer may include a plurality of nanorods respectively extending from a corresponding light emitting nanorod. 
     The two-dimensional material layer may include at least one of graphene, boron nitride, and a transition metal dichalcogenide. 
     The light emitting nanorod may include a first semiconductor layer disposed on an upper surface of the two-dimensional material layer, the first semiconductor layer being doped with a first conductivity type, a light emitting layer disposed on the first semiconductor layer, a second semiconductor layer disposed on the light emitting layer, the second semiconductor layer being doped with a second conductivity type that is electrically opposite to the first conductivity type; and an electrode disposed on the second semiconductor layer. 
     The light emitting nanorod may have a height in a range of 1 μm to 20 μm, and a diameter in a range of 0.05 μm to 1 μm. 
     The passivation film may include an insulating crystalline material having the same crystalline structure as a crystalline structure of the light emitting layer. 
     The passivation film may have a lattice matching epitaxial relationship or a domain matching epitaxial relationship with the light emitting layer. 
     According to another aspect of an example embodiment, there is provided an epitaxy structure including a substrate having an upper surface that has a single crystal structure, an insulating layer disposed on the upper surface of the substrate, a plurality of two-dimensional material layers disposed on the upper surface of the substrate, the plurality of two-dimensional material layers being electrically isolated from each other by the insulating layer, and a plurality of semiconductor devices respectively disposed on the plurality of two-dimensional material layers. 
     The plurality of semiconductor devices may include different semiconductor materials. 
     The plurality of semiconductor devices may include any one of a light source, a photodetector, an optical modulator, and an optical amplifier. 
     According to another aspect of an example embodiment, there is provided a monolithic optical integrated circuit including an epitaxy structure including a substrate having an upper surface that has a single crystal structure, an insulating layer disposed on the upper surface of the substrate, a plurality of two-dimensional material layers disposed on the upper surface of the substrate, the plurality of two-dimensional material layers being electrically isolated from each other by the insulating layer, and a plurality of semiconductor devices respectively disposed on the plurality of two-dimensional material layers, wherein the plurality of semiconductor devices include one of a light source, a photodetector, an optical modulator, and an optical amplifier. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects, features, and advantages of example embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIGS.  1 A,  1 B,  10 ,  1 D,  1 E, and  1 F  are example cross-sectional views illustrating a method of manufacturing an epitaxy structure including a plurality of nanorod light emitting devices according to an example embodiment; 
         FIG.  2    is a cross-sectional view showing a schematic configuration of a nanorod light emitting device according to an example embodiment; 
         FIG.  3    is a plan view of the nanorod light emitting device shown in  FIG.  2   ; 
         FIGS.  4  and  5    are cross-sectional views exemplarily showing a method of manufacturing an epitaxy structure including a plurality of nanorod light emitting devices according to another example embodiment; 
         FIGS.  6  and  7    are example cross-sectional views illustrating a method of manufacturing an epitaxy structure including a plurality of nanorod light emitting devices according to another example embodiment; 
         FIG.  8    is a cross-sectional view schematically illustrating a structure of a substrate according to another example embodiment; 
         FIG.  9    is a cross-sectional view illustrating an epitaxy structure including a plurality of semiconductor devices according to another example embodiment; 
         FIG.  10    is a conceptual diagram schematically showing the configuration of a display device according to an example embodiment using a nanorod light emitting device; 
         FIG.  11    is a schematic block diagram of an electronic device according to an example embodiment; 
         FIG.  12    illustrates an example in which a display device according to example embodiments is applied to a mobile device; 
         FIG.  13    illustrates an example in which a display device according to example embodiments is applied to a vehicle display device; 
         FIG.  14    illustrates an example in which a display device according to example embodiments is applied to augmented reality glasses or virtual reality glasses; 
         FIG.  15    shows an example in which the display device according to the example embodiments is applied to a signage; and 
         FIG.  16    illustrates an example in which a display device according to example embodiments is applied to a wearable display. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the example embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the example embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, the expression, “at least one of a, b, and c,” should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c. 
     Hereinafter, a nanorod light emitting device, an epitaxy structure including a plurality of nanorod light emitting devices, and a method of manufacturing the epitaxy structure will be described in detail with reference to the accompanying drawings. In the following drawings, the same reference numerals refer to the same components, and the size of each component in the drawings may be exaggerated for clarity and convenience of description. Further, the embodiments described below are merely exemplary, and various modifications are possible from these example embodiments. 
     Hereinafter, what is described as “upper part” or “on” may include not only those directly above by contact, but also those above non-contact. The terms of a singular form may include plural forms unless otherwise specified. In addition, when a certain part “includes” a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated. 
     The use of the term “the” and similar designating terms may correspond to both the singular and the plural. If there is no explicit order or contradictory statement about the steps constituting the method, these steps may be performed in an appropriate order, and are not necessarily limited to the order described. 
     In addition, terms such as “unit” and “module” described in the specification mean a unit that processes at least one function or operation, and this may be implemented as hardware or software, or may be implemented as a combination of hardware and software. 
     The connection or connection members of lines between the components shown in the drawings are illustrative of functional connections and/or physical or circuit connections, and may be represented as a variety of functional connections, physical connections, or circuit connections that are replaceable or additional in an actual device. 
     The use of all examples or illustrative terms is merely for describing technical ideas in detail, and the scope is not limited by these examples or illustrative terms unless limited by the claims. 
       FIGS.  1 A to  1 F  are example cross-sectional views illustrating a method of manufacturing an epitaxy structure including a plurality of nanorod light emitting devices according to an example embodiment. 
     First, referring to  FIG.  1 A , a substrate  101  having an upper surface having a single crystal structure is prepared. In addition, a two-dimensional material layer  103  may be formed on the upper surface of the substrate  101 . The substrate  101  may include, for example, a support layer  101   a  including a crystalline material and a single crystal layer  101   b  disposed on an upper surface of the support layer  101   a  and having a single crystal material. The single crystal layer  101   b  may be epitaxially grown directly on the upper surface of the support layer  101   a . The two-dimensional material layer  103  may be disposed on an upper surface of the single crystal layer  101   b . The support layer  101   a  may include, for example, silicon (Si) or sapphire. The single crystal layer  101   b  may include a single crystal of a group III-V compound semiconductor having an ionic bond characteristic or an ionic crystal. Also, the single crystal layer  101   b  may have the same crystal structure as semiconductor crystals to be described later formed on the two-dimensional material layer  103 . For example, the single crystal layer  101   b  may include a single crystal of lithium fluoride (LiF), gallium nitride (GaN), or barium titanate (BaTiO 3 ). 
     The two-dimensional material layer  103  may include a two-dimensional crystal having a hexagonal structure. For example, the two-dimensional material layer  103  may include graphene, boron nitride (BN), or transition metal dichalcogenide, which is a compound of a transition metal and a chalcogen element. For example, the transition metal dichalcogenide may include molybdenum disulfide (MoS 2 ), tungsten disulfide (WS 2 ), tantalum sulfide (TaS 2 ), hafnium sulfide (HfS 2 ), rhenium sulfide (ReS 2 ), titanium sulfide (TiS 2 ), niobium sulfide (NbS 2 ), tin sulfide (SnS 2 ), molybdenum diselenide (MoSe 2 ), tungsten diselenide (WSe 2 ), tantalum diselenide (TaSe 2 ), hafnium diselenide (HfSe 2 ), rhenium diselenide (ReSe 2 ), titanium diselenide (TiSe 2 ), niobium diselenide (NbSe 2 ), tin diselenide (SnSe 2 ), molybdenum telluride (MoTe 2 ), tungsten telluride (WTe 2 ), tantalum telluride (TaTe 2 ), hafnium telluride (HfTe 2 ), rhenium telluride (ReTe 2 ), titanium telluride (TiTe 2 ), niobium telluride (NbTe 2 ), tin telluride (SnTe 2 ), and the like. The two-dimensional material layer  103  may be transferred as a monolayer or a bilayer on the upper surface of the single crystal layer  101   b.    
     When the single crystal layer  101   b  having a polarity by an ion bond exists under the two-dimensional material layer  103 , it is possible to directly epitaxially grow a semiconductor crystal on the two-dimensional material layer  103 . As the polarity of the single crystal layer  101   b  is stronger, a force that induces the growth of semiconductor crystals on the two-dimensional material layer  103  may be increased. Accordingly, a semiconductor crystal having a predetermined crystal structure according to the crystal direction of the single crystal layer  101   b  may be grown on the two-dimensional material layer  103  without direct chemical bonding with the single crystal layer  101   b  below. In this case, because the stress may be relieved by the two-dimensional material layer  103  as well as not chemically bonded to the single crystal layer  101   b  below, the semiconductor crystal grown on the two-dimensional material layer  103  may be a high-quality single crystal having a relatively low dislocation density. Accordingly, by using the two-dimensional material layer  103 , a semiconductor single crystal having a relatively large difference in lattice constant from the substrate  101  may be grown with high quality. 
     For example, referring to  FIG.  1 B , a first semiconductor layer  104 , a light emitting layer  105 , a second semiconductor layer  106 , and an electrode  107  may be sequentially grown on the upper surface of the two-dimensional material layer  103 . The first semiconductor layer  104  may include a single crystal semiconductor material doped with a first conductivity type, such as an n-type, and the second semiconductor layer  106  may include a single crystal semiconductor material doped with a second conductivity type that is electrically opposite to the first conductivity type, such as a p-type. For example, the first semiconductor layer  104  may be doped with silicon (Si) and the second semiconductor layer  106  may be doped with zinc (Zn). 
     The light emitting layer  105  has a quantum well structure in which quantum wells are disposed between barriers. Light may be generated as electrons and holes provided from the first and second semiconductor layers  104  and  106  are recombined in the quantum well in the light emitting layer  105 . The wavelength of light generated from the light emitting layer  105  may be determined according to the energy band gap of the material forming the quantum well in the light emitting layer  105 . The light emitting layer  105  may have one quantum well, but embodiments are not limited thereto, and the light emitting layer  105  may have a multi-quantum well (MQW) in which a plurality of quantum wells and a plurality of barriers are alternately arranged. The thickness of the light emitting layer  105  or the number of quantum wells in the light emitting layer  105  may be appropriately selected in consideration of the driving voltage and luminous efficiency of the light emitting device. For example, the thickness of the light emitting layer  105  may be selected to be equal to or less than twice the diameter of the light emitting layer  105 . 
     The first semiconductor layer  104  disposed between the light emitting layer  105  and the single crystal layer  101   b  may be selected such that the lattice constant difference between the first semiconductor layer  104  and the single crystal layer  101   b  is less than the lattice constant difference between the quantum well of the light emitting layer  105  and the single crystal layer  101   b . For example, the first semiconductor layer  104  may have a lattice constant between the lattice constant of the single crystal layer  101   b  and the lattice constant of the quantum well of the light emitting layer  105 . For example, the first semiconductor layer  104  may include n-In x Ga 1-x N (0&lt;x&lt;0.2), and the quantum well of the light emitting layer  105  may include In y Ga 1-y N (0.25&lt;=y&lt;1). For example, the first semiconductor layer  104  may include, for example, n-In 0.2 Ga 0.8 N, and the quantum well of the light emitting layer  105  may include, for example, In 0.35 Ga 0.65 N. Then, the lattice mismatch is alleviated, so that the crystal quality of the light emitting layer  105  may be further improved. 
     The first and second semiconductor layers  104  and  106  and the light emitting layer  105  may include various other III-V compound semiconductor materials in addition to indium gallium nitride (InGaN). For example, the first and second semiconductor layers  104 ,  106  and the light emitting layer  105  may include materials such as aluminum gallium nitride (AlGaN), aluminum indium gallium nitride (AlInGaN), gallium arsenide (GaAs), GaN, indium phosphide (InP), and the like, and the emission wavelength and/or lattice constant of the first and second semiconductor layers  104 ,  106  and the light emitting layer  105  may be adjusted according to the composition ratio of the materials. 
     After forming the electrode  107 , as shown in  FIG.  10   , a hard mask  120  having a plurality of openings arranged at regular intervals on the electrode  107  is formed. For example, after the material of the hard mask  120  is entirely formed on an upper surface of the electrode  107 , the hard mask  120  having a plurality of openings arranged at regular intervals may be formed by patterning the material of the hard mask  120  in a lithographic method. The hard mask  120  may be formed of, for example, a single layer of silicon oxide (SiO 2 ) or a double layer of SiO 2 /Al. The hard mask  120  may have a plurality of two-dimensionally arranged openings when viewed from the top. 
     Thereafter, referring to  FIG.  1 D , areas not covered with the hard mask  120  may be removed by etching using a dry etching method. For example, the electrode  107 , the second semiconductor layer  106 , the light emitting layer  105 , the first semiconductor layer  104 , the two-dimensional material layer  103 , and the single crystal layer  101   b  under the opening of the hard mask  120  may be sequentially dry-etched and removed.  FIG.  1 D  illustrates that etching is performed up to the single crystal layer  101   b  and the etching is stopped at the support layer  101   a , however, embodiments are not limited thereto. For example, etching may be performed up to the first semiconductor layer  104  and etching is stopped in the two-dimensional material layer  103 , or etching may be performed up to the two-dimensional material layer  103  and the etching may be stopped in the single crystal layer  101   b . Then, the electrode  107 , the second semiconductor layer  106 , the light emitting layer  105 , and the first semiconductor layer  104  may be patterned in the form of a plurality of nanorods. Accordingly, a plurality of light emitting nanorods  110  each including the first semiconductor layer  104 , the light emitting layer  105 , the second semiconductor layer  106 , and the electrode  107  may be formed at once. 
     Then, for example, through a wet treatment with a potassium hydroxide (KOH) solution or a tetramethyl ammonium hydrooxide (TMAH) solution, it is possible to make the diameters of the plurality of light emitting nanorods  110  uniform along the height direction. In this process, the hard mask  120  may also be removed. 
     Referring to  FIG.  1 E , a passivation film  108  having a uniform thickness may be formed on the surface of the light emitting nanorod  110 . The passivation film  108  may serve to protect the light emitting nanorod  110  from external physical and chemical impact and also to insulate the light emitting nanorod  110  to prevent leakage of current. For example, the passivation film  108  may simply be made of an insulator material. 
     According to another example embodiment, the passivation film  108  may include an insulating crystalline material having the same crystal structure as that of the light emitting layer  105 . In particular, the passivation film  108  may have a lattice matching epitaxy relationship or a domain matching epitaxy relationship with the light emitting layer  105 . The lattice matching epitaxial relationship means a relationship in which the lattice constant of the passivation film  108  is substantially equal to the lattice constant of the light emitting layer  105 . In addition, the domain matching epitaxy relationship means a relationship in which the lattice constant of the passivation film  108  is approximately equal to an integer multiple of the lattice constant of the light emitting layer  105 , or the lattice constant of the light emitting layer  105  is almost equal to an integer multiple of the lattice constant of the passivation film  108 . In this case, because atoms located on the outer surface of the light emitting layer  105  may mostly combine with the atoms of the passivation film  108 , dangling bonds on the outer surface of the light emitting layer  105  are reduced, and thus surface defects are also reduced. Accordingly, a current may flow relatively uniformly in the entire area of the light emitting layer  105  and light emission may occur relatively uniformly in the entire area of the light emitting layer  105 . Accordingly, the luminous efficiency of the light emitting layer  105  may be increased. As such, the passivation film  108  having an epitaxial relationship with the light emitting layer  105  may include at least one material of zirconium oxide (ZrO), strontium oxide (SrO), magnesium oxide (MgO), barium oxide (BaO), cerium oxide (CeO 2 ), gandolinium oxide (Gd 2 O 3 ), oxycalcium (CaO), hafnium oxide (HfO 2 ), titanium oxide (TiO 2 ), aluminum oxide (AlO x ), barium nitride (BaN), silicon nitride (SiN), titanium nitride (TiN), cerium nitride (CeN), aluminum nitride (AlN), zinc selenide (ZnSe), zinc sulfide (ZnS), aluminum gallium nitride (AlGaN), and Al x Ga 1-x As (x≥0.9), for example. 
     Finally, referring to  FIG.  1 F , the passivation film  108  present on the upper surface of the light emitting nanorod  110  may be removed. The remaining passivation film  108  is provided adjacent to and surrounds the sidewall of the light emitting nanorod  110 . The passivation film  108  may surround the entire sidewall of the electrode  107  or may surround a part of the sidewall of the electrode  107 . In addition, when etching is performed up to the two-dimensional material layer  103 , the passivation film  108  may extend to the sidewall of the patterned two-dimensional material layer  103 , and when etching is performed up to the single crystal layer  101   b , the passivation film  108  may extend to the sidewall of the patterned single crystal layer  101   b.    
     In the above-described manner, a plurality of nanorod light emitting devices  100  having a nanorod shape and an epitaxy structure  1000  including a plurality of nanorod light emitting devices  100  may be formed. The epitaxy structure  1000  may include a substrate  101  having an upper surface having a single crystal structure, a two-dimensional material layer  103  disposed on the upper surface of the substrate  101 , and a plurality of nanorod light emitting devices  100  disposed on the upper surface of the two-dimensional material layer  103 . The plurality of nanorod light emitting devices  100  may be arranged to extend in a direction perpendicular to the upper surface of the substrate  101 . In addition, each nanorod light emitting device  100  may include a light emitting nanorod  110  and a passivation film  108  surrounding a sidewall of the light emitting nanorod  110 . A plurality of nanorod light emitting devices  100  may be two-dimensionally arranged on the substrate  101 . 
     In addition, the single crystal layer  101   b  and the two-dimensional material layer  103  of the substrate  101  may be patterned to have the same cross-sectional shape as the plurality of light emitting nanorods  110 . Accordingly, the single crystal layer  101   b  of the substrate  101  and the two-dimensional material layer  103  may have the form of a plurality of nanorods respectively extending from the plurality of corresponding light emitting nanorods  110 . 
     The plurality of nanorod light emitting devices  100  may be more easily separated from the two-dimensional material layer  103 . Accordingly, a chemical process for separating the plurality of nanorod light emitting devices  100  from the epitaxy structure  1000  is not required. In addition, the cut surface of the separated portion of the nanorod light emitting device  100  may have a relatively smooth surface. Although the nanorod light emitting device  100  individually separated from the epitaxy structure  1000  may be distributed/traded, the epitaxy structure  1000  itself may be distributed/traded. For example, a manufacturer of a display device may purchase the epitaxy structure  1000  on which a plurality of nanorod light emitting devices  100  are formed, and may manufacture a display device by separating the nanorod light emitting devices  100  from the epitaxy structure  1000 . 
       FIG.  2    is a cross-sectional view showing a schematic configuration of a nanorod light emitting device according to an example embodiment. In particular,  FIG.  2    exemplarily shows the configuration of the nanorod light emitting device  100  separated from the epitaxy structure  1000  shown in  FIG.  1 F . Referring to  FIG.  2   , the nanorod light emitting device  100  may include a light emitting nanorod  110  and a passivation film  108  provided adjacent to and surrounding sidewalls of the light emitting nanorod  110 . The light emitting nanorod  110  may include a first semiconductor layer  104 , a light emitting layer  105  disposed on the first semiconductor layer  104 , and a second semiconductor layer  106  disposed on the light emitting layer  105 . In addition, the light emitting nanorod  110  may further include an electrode  107  disposed on the second semiconductor layer  106 . The light emitting nanorod  110  may further include a contact layer disposed between the second semiconductor layer  106  and the electrode  107 . 
     The light emitting nanorod  110  may have a very small size of a nano-scale or a micro-scale. For example, the light emitting nanorod  110  may have a diameter D in the range of about 0.05 μm to about 1 μm. The light emitting nanorod  110  may have a substantially uniform diameter along the height direction. For example, diameters of the first semiconductor layer  104 , the light emitting layer  105 , the second semiconductor layer  106 , and the electrode  107  may be substantially the same. When the length between the lower surface of the first semiconductor layer  104  and the upper surface of the electrode  107  is the height H of the light emitting nanorod  110 , the height H of the light emitting nanorod  110  may be approximately in the range of about 1 μm to about 20 μm. In addition, the light emitting nanorod  110  may have a relatively large aspect ratio of, for example, 5 or more. For example, the light emitting nanorod  110  may have a diameter D of about 500 nm to about 600 nm and a height H of about 4 μm to about 5 μm. 
     Because the size of the nanorod light emitting device  100  is very small, deformation due to stress may have a significant effect on the performance of the nanorod light emitting device  100 . According to an example embodiment, the nanorod light emitting device  100  having a high-quality single crystal structure may be formed by using the remote epitaxy technique using the two-dimensional material layer  103 . Accordingly, because the nanorod light emitting device  100  has a high-quality single crystal structure, there are relatively few defects, so that the luminous efficiency of the nanorod light emitting device  100  may be improved. In addition, by using a relatively inexpensive substrate material such as silicon, the epitaxy structure  1000  including a plurality of nanorod light emitting devices  100  having a high-quality single crystal structure may be manufactured at a relatively low cost. 
       FIG.  3    is a plan view of the nanorod light emitting device  100  shown in  FIG.  2   . Referring to  FIG.  3   , the passivation film  108  may be placed to completely surround the sidewall of the light emitting nanorod  110 . Therefore, the passivation film  108  may have a ring shape in a plan view, and may have a cylindrical shape as a whole. Although the light emitting nanorod  110  is illustratively shown as having a circular shape in  FIG.  3   , embodiments are not limited thereto. The thickness t of the passivation film  108  according to the diameter direction of the nanorod light emitting device  100 , that is, the distance between the inner sidewall and the outer sidewall of the passivation film  108 , may be in the range of about 5 nm to about 70 nm. 
       FIGS.  4  and  5    are cross-sectional views exemplarily illustrating a method of manufacturing an epitaxy structure including a plurality of nanorod light emitting devices according to an example embodiment. 
     Referring to  FIG.  4   , the substrate  201  may include one single layer having an upper surface having a single crystal structure. For example, the substrate  201  may include a single crystal of silicon carbide (SiC). In particular, the substrate  201  may include a single crystal of 4H-SiC, 6H-SiC, or 3C-SiC. In this case, the substrate  201  may be a single crystal having a polarity or an ionic bond characteristic. 
     In the example embodiment shown in  FIG.  1 A , it has been described that the two-dimensional material layer  103  is transferred onto the single crystal layer  101   b , but the two-dimensional material layer  103  may be directly grown on the upper surface of the substrate  201  including silicon carbide without transfer. After growing the two-dimensional material layer  103  on the substrate  201 , a first semiconductor layer  104 , a light emitting layer  105 , a second semiconductor layer  106 , and an electrode  107  may be sequentially grown on the upper surface of the two-dimensional material layer  103 . 
     Thereafter, an epitaxy structure including a plurality of nanorod light emitting devices  100  may be formed by performing the processes described with reference to  FIGS.  10  to  1 F . Referring to  FIG.  5   , the epitaxy structure  1100  may include a substrate  201  and a plurality of nanorod light emitting devices  100  disposed on the upper surface of the substrate  201 . The two-dimensional material layer  103  is disposed between the upper surface of the substrate  201  and each nanorod light emitting device  100 . The two-dimensional material layer  103  is illustrated in  FIG.  5    as being patterned to have the same cross-sectional shape as the plurality of light emitting nanorods  110 , but only the first semiconductor layer  104  may be patterned and the two-dimensional material layer  103  may not be patterned. 
     According to another example embodiment, it is also possible to form the nanorod light emitting device  100  including a single crystal material on an amorphous material such as glass.  FIGS.  6  and  7    are example cross-sectional views illustrating a method of manufacturing an epitaxy structure including a plurality of nanorod light emitting devices according to another example embodiment. 
     Referring to  FIG.  6   , the substrate  301  may include a support layer  301   a  including an amorphous material such as glass or fused silica, and a single crystal layer  301   b  disposed on an upper surface of the support layer  301   a . On the support layer  301   a  including the amorphous material, the single crystal layer  301   b  may be grown using, for example, an ion beam assisted deposition (IBAD) method. For example, the single crystal layer  301   b  may include CeO 2 , scandium(III) oxide (Sc 2 O 3 ), MgO, BaO, bromine nitride (BrN), and the like oriented in a (111) direction, a (001) direction, or a (100) direction. The two-dimensional material layer  103  may be transferred or directly grown on an upper surface of the single crystal layer  301   b . In addition, the first semiconductor layer  104 , the light emitting layer  105 , the second semiconductor layer  106 , and the electrode  107  may be sequentially grown on the upper surface of the two-dimensional material layer  103 . The first semiconductor layer  104 , the light emitting layer  105 , and the second semiconductor layer  106  may include various III-V compound semiconductor materials in addition to InGaN, for example, AlGaN, AlInGaN, GaAs, GaN, InP, and the like depending on the material and orientation of the single crystal layer  301   b.    
     Thereafter, an epitaxy structure including a plurality of nanorod light emitting devices  100  may be formed by performing the processes described with reference to  FIGS.  10  to  1 F . Referring to  FIG.  7   , the epitaxy structure  1200  may include a substrate  301  and a plurality of nanorod light emitting devices  100  disposed on the upper surface of the substrate  301 . The two-dimensional material layer  103  is disposed between the upper surface of the substrate  301 , that is, the upper surface of the single crystal layer  301   b , and each nanorod light emitting device  100 .  FIG.  7    shows that only the two-dimensional material layer  103  is patterned to have the same cross-sectional shape as the plurality of light emitting nanorods  110 , but the single crystal layer  301   b  may also be patterned to have the same cross-sectional shape as the plurality of light emitting nanorods  110 . 
     Although the single crystal layer  301   b  is illustrated as including only one single layer in  FIG.  6   , the single crystal layer  301   b  may have a multilayer structure having two or more sub-layers as needed.  FIG.  8    is a cross-sectional view schematically illustrating a structure of a substrate according to another example embodiment. Referring to  FIG.  8   , the single crystal layer  301   b  may include, for example, a plurality of sub-layers  301 - 1   b ,  301 - 2   b , and  301 - 3   b  each having a thin thickness of about 0.5 nm to about 100 nm. Each of the plurality of sub-layers  301 - 1   b ,  301 - 2   b , and  301 - 3   b  may include CeO 2 , Sc 2 O 3 , MgO, BaO, or BrN oriented in a (111) direction, a (001) direction, or a (100) direction. Although the single crystal layer  301   b  is illustrated as including three sub-layers in  FIG.  8   , the example embodiment is not limited thereto. The single crystal layer  301   b  may include two sub-layers or four or more sub-layers. 
     An example of forming the nanorod light emitting device  100  on a substrate using remote epitaxy technology has been described, but in addition to the nanorod light emitting device  100 , various other semiconductor devices may be formed.  FIG.  9    is a cross-sectional view illustrating an epitaxy structure including a plurality of semiconductor devices according to another embodiment. 
     Referring to  FIG.  9   , the epitaxy structure  1300  may include a substrate  101 , an insulating layer  1301  disposed on an upper surface of the substrate  101 , a plurality of two-dimensional material layers  103  disposed on the upper surface of the substrate  101  and electrically isolated from each other by an insulating layer  1301 , and a plurality of semiconductor devices  1310 ,  1320 , and  1330  respectively disposed on the plurality of two-dimensional material layers  103 . The plurality of semiconductor devices  1310 ,  1320 , and  1330  may include different semiconductor materials and may be configured to perform different functions. For example, the plurality of semiconductor devices  1310 ,  1320 , and  1330  may include at least one semiconductor material selected from among InGaN, AlGaN, AlInGaN, GaAs, GaN, InP, Si, and Ge. In addition, the plurality of semiconductor devices  1310 ,  1320 , and  1330  may include any one of a light source, a photodetector, an optical modulator, and an optical amplifier. 
     The epitaxy structure  1300  may further include various optical elements disposed on the upper surface of the substrate  101  in addition to the plurality of semiconductor devices  1310 ,  1320 , and  1330 . For example, the optical element may include an optical waveguide, an optical coupler, a beam splitter, and the like. Such an epitaxy structure  1300  may be used to implement, for example, a monolithic photonic integrated circuit, and may be applied to a laser imaging detection and ranging (LiDAR) sensor for autonomous driving, an optical connection device for a data center, and the like. In addition, although the epitaxy structure  1300  is illustrated in  FIG.  9    as including the substrate  101  shown in  FIG.  1   , the epitaxy structure  1300  may include the substrate  201  illustrated in  FIG.  4    or the substrate  301  illustrated in  FIG.  6   . 
     The nanorod light emitting device  100  described above according to an example embodiment is capable of various applications. In particular, the nanorod light emitting device  100  may be used as a light emitting element of pixels of a next-generation display device. For example,  FIG.  10    is a conceptual diagram schematically showing a configuration of a display device according to an embodiment using a nanorod light emitting device. 
     Referring to  FIG.  10   , the display apparatus  2000  may include a plurality of first pixel electrodes  2002 B, a first common electrode  2003 B corresponding to the plurality of first pixel electrodes  2002 B, a plurality of second pixel electrodes  2002 G, a second common electrode  2003 G corresponding to the plurality of second pixel electrodes  2002 G, a plurality of third pixel electrodes  2002 R, a third common electrode  2003 R corresponding to the plurality of third pixel electrodes  2002 R, a plurality of first nanorod light emitting devices  100 B connected between each of the first pixel electrodes  2002 B and the first common electrode  2003 B, a plurality of second nanorod light emitting devices  100 G connected between each second pixel electrode  2002 G and a second common electrode  2003 G, and a plurality of third nanorod light emitting devices  100 R connected between each third pixel electrode  2002 R and the third common electrode  2003 R. 
     For example, the first nanorod light emitting device  100 B may be configured to emit blue light, the second nanorod light emitting device  100 G may be configured to emit green light, and the third nanorod light emitting device  100 R may be configured to emit red light. In addition, one first pixel electrode  2002 B may form one blue sub-pixel together with the first common electrode  2003 B, one second pixel electrode  2002 G may form one green sub-pixel together with the second common electrode  2003 G, and one third pixel electrode  2002 R may form one red sub-pixel together with the third common electrode  2003 R. 
     In addition, the above-described nanorod light emitting device  100  may be applied without limitation to display devices of various sizes and various uses. For example,  FIGS.  11  to  16    exemplarily show various devices including a display device to which nanorod light emitting devices  100  according to an embodiment are applied. 
     First,  FIG.  11    is a schematic block diagram of an electronic device according to an example embodiment. Referring to  FIG.  11   , an electronic device  8200  may be provided in a network environment  8201 . In the network environment  8200 , the electronic device  8201  may communicate with another electronic device  8202  through a first network  8298  (such as a short-range wireless communication network, and the like), or communicate with another electronic device  8204  and/or a server  8208  through a second network  8299  (such as a remote wireless communication network). The electronic device  8201  may communicate with the electronic device  8204  through the server  8208 . The electronic device  8201  may include a processor  8220 , a memory  8230 , an input device  8250 , an audio output device  8255 , a display device  8260 , an audio module  8270 , a sensor module  8276 , and an interface  8277 , a haptic module  8279 , a camera module  8280 , a power management module  8288 , a battery  8289 , a communication module  8290 , a subscriber identification module  8296 , and/or an antenna module  8297 . In the electronic device  8201 , some of these components may be omitted or other components may be added. Some of these components may be implemented as one integrated circuit. For example, the sensor module  8276  (fingerprint sensor, iris sensor, illuminance sensor, etc.) may be implemented by being embedded in the display device  8260  (display, etc.). 
     The processor  8220  may execute software (the program  8240 , etc.) to control one or a plurality of other components (such as hardware, software components, etc.) of the electronic device  8201  connected to the processor  8220 , and perform various data processing or operations. As part of data processing or operation, the processor  8220  may load commands and/or data received from other components (the sensor module  8276 , the communication module  8290 , etc.) into the volatile memory  8232 , process commands and/or data stored in the volatile memory  8232 , and store result data in the nonvolatile memory  8234 . The nonvolatile memory  8234  may include an internal memory  8236  mounted in the electronic device  8201  and a removable external memory  8238 . The processor  8220  may include a main processor  8221  (such as a central processing unit, an application processor, etc.) and a secondary processor  8223  (such as a graphics processing unit, an image signal processor, a sensor hub processor, a communication processor, etc.) that may be operated independently or together. The secondary processor  8223  may use less power than the main processor  8221  and may perform specialized functions. 
     The secondary processor  8223  may control functions and/or states related to some of the components of the electronic device  8202  (such as the display device  8260 , the sensor module  8276 , the communication module  8290 , etc.) instead of the main processor  8221  while the main processor  8221  is in an inactive state (sleep state), or with the main processor  8221  while the main processor  8221  is in an active state (application execution state). The secondary processor  8223  (such as an image signal processor, a communication processor, etc.) may be implemented as part of other functionally related components (such as the camera module  8280 , the communication module  8290 , etc.). 
     The memory  8230  may store various data required by components of the electronic device  8201  (such as the processor  8220 , the sensor module  8276 , etc.). The data may include, for example, software (such as the program  8240 , etc.) and input data and/or output data for commands related thereto. The memory  8230  may include a volatile memory  8232  and/or a nonvolatile memory  8234 . 
     The program  8240  may be stored as software in the memory  8230  and may include an operating system  8242 , a middleware  8244 , and/or an application  8246 . 
     The input device  8250  may receive commands and/or data to be used for components (such as the processor  8220 , etc.) of the electronic device  8201  from outside (a user) of the electronic device  8201 . The input device  8250  may include a remote controller, a microphone, a mouse, a keyboard, and/or a digital pen (such as a stylus pen). 
     The audio output device  8255  may output an audio signal to the outside of the electronic device  8201 . The audio output device  8255  may include a speaker and/or a receiver. The speaker may be used for general purposes such as multimedia playback or recording playback, and the receiver may be used to receive incoming calls. The receiver may be combined as a part of the speaker or may be implemented as an independent separate device. 
     The display device  8260  may visually provide information to the outside of the electronic device  8201 . The display device  8260  may include a display, a hologram device, or a projector and a control circuit for controlling the device. The display device  8260  may include the above-described driving circuit, micro semiconductor light emitting device, side reflection structure, bottom reflection structure, and the like. The display device  8260  may include a touch circuit set to sense a touch, and/or a sensor circuit (such as a pressure sensor) set to measure the strength of a force generated by the touch. 
     The audio module  8270  may convert sound into an electrical signal, or conversely, may convert an electrical signal into sound. The audio module  8270  may acquire sound through the input device  8250  or output sound through speakers and/or headphones of the audio output device  8255 , and/or other electronic devices (such as the electronic device  8202 ) directly or wirelessly connected to the electronic device  8201 . 
     The sensor module  8276  may detect an operating state (such as power, temperature, and the like) of the electronic device  8201  or an external environmental state (such as a user state, and the like), and generate an electrical signal and/or data value corresponding to the detected state. The sensor module  8276  may include a gesture sensor, a gyro sensor, a barometric pressure sensor, a magnetic sensor, an acceleration sensor, a grip sensor, a proximity sensor, a color sensor, an infrared (IR) sensor, a biometric sensor, a temperature sensor, a humidity sensor, and/or an illuminance sensor. 
     The interface  8277  may support one or more specified protocols that may be used for the electronic device  8201  to connect directly or wirelessly with another electronic device (such as the electronic device  8102 ). The interface  8277  may include a High Definition Multimedia Interface (HDMI), a Universal Serial Bus (USB) interface, an SD card interface, and/or an audio interface. 
     The connection terminal  8278  may include a connector through which the electronic device  8201  may be physically connected to another electronic device (such as the electronic device  8202 ). The connection terminal  8278  may include an HDMI connector, a USB connector, an SD card connector, and/or an audio connector (such as a headphone connector). 
     The haptic module  8279  may convert an electrical signal into a mechanical stimulus (such as vibration, movement, etc.) or an electrical stimulus that a user may perceive through a tactile or motor sense. The haptic module  8279  may include a motor, a piezoelectric element, and/or an electrical stimulation device. 
     The camera module  8280  may capture a still image and a video. The camera module  8280  may include a lens assembly including one or more lenses, image sensors, image signal processors, and/or flashes. The lens assembly included in the camera module  8280  may collect light emitted from a subject that is a target of image capturing. 
     The power management module  8288  may manage power supplied to the electronic device  8201 . The power management module  8288  may be implemented as a part of a Power Management Integrated Circuit (PMIC). 
     The battery  8289  may supply power to components of the electronic device  8201 . The battery  8289  may include a non-rechargeable primary cell, a rechargeable secondary cell, and/or a fuel cell. 
     The communication module  8290  may support establishing a direct (wired) communication channel and/or a wireless communication channel, and performing communication through the established communication channel between the electronic device  8201  and other electronic devices (such as the electronic device  8202 , the electronic device  8204 , the server  8208 , and the like). The communication module  8290  may include one or more communication processors that operate independently of the processor  8220  (such as an application processor) and support direct communication and/or wireless communication. The communication module  8290  may include a wireless communication module  8292  (such as a cellular communication module, a short-range wireless communication module, a Global Navigation Satellite System (GNSS) communication module, and the like) and/or a wired communication module  8294  (such as a local area network (LAN) communication module, a power line communication module, and the like). Among these communication modules, a corresponding communication module may communicate with other electronic devices through a first network  8298  (a short-range communication network such as Bluetooth, WiFi Direct, or Infrared Data Association (IrDA)) or a second network  8299  (a cellular network, the Internet, or a telecommunication network such as a computer network (such as LAN, WAN, and the like)). These various types of communication modules may be integrated into one component (such as a single chip, and the like), or may be implemented as a plurality of separate components (a plurality of chips). The wireless communication module  8292  may check and authenticate the electronic device  8201  in a communication network such as the first network  8298  and/or the second network  8299  using the subscriber information (such as international mobile subscriber identifier (IMSI), etc.) stored in the subscriber identification module  8296 . 
     The antenna module  8297  may transmit signals and/or power to the outside (such as other electronic devices) or receive signals and/or power from the outside. The antenna may include a radiator made of a conductive pattern formed on a substrate (such as PCB, etc.). The antenna module  8297  may include one or a plurality of antennas. If multiple antennas are included, an antenna suitable for a communication method used in a communication network such as the first network  8298  and/or the second network  8299  may be selected from the plurality of antennas by the communication module  8290 . Signals and/or power may be transmitted or received between the communication module  8290  and another electronic device through the selected antenna. In addition to the antenna, other components (such as RFIC) may be included as part of the antenna module  8297 . 
     Some of the components are connected to each other and may exchange signals (such as commands, data, and the like) through communication method between peripheral devices (such as bus, General Purpose Input and Output (GPIO), Serial Peripheral Interface (SPI), Mobile Industry Processor Interface (MIPI), and the like). 
     The command or data may be transmitted or received between the electronic device  8201  and the external electronic device  8204  through the server  8208  connected to the second network  8299 . The other electronic devices  8202  and  8204  may be the same or different types of devices as or from the electronic device  8201 . All or some of the operations executed by the electronic device  8201  may be executed by one or more of the other electronic devices  8202 ,  8204 , and  8208 . For example, when the electronic device  8201  needs to perform a certain function or service, instead of executing the function or service itself, the electronic device  8201  may request one or more other electronic devices to perform the function or part or all of the service. One or more other electronic devices that receive the request may execute an additional function or service related to the request, and transmit a result of the execution to the electronic device  8201 . For this, cloud computing, distributed computing, and/or client-server computing technology may be used. 
       FIG.  12    illustrates an example in which a display device according to example embodiments is applied to a mobile device. The mobile device  9100  may include a display device  9110 , and the display device  9110  may include the above-described driving circuit, micro semiconductor light emitting device, side reflection structure, bottom reflection structure, and the like. The display device  9110  may have a foldable structure, for example, a multi-foldable structure. 
       FIG.  13    illustrates an example in which the display device according to the example embodiments is applied to a vehicle display device. The display device may be a vehicle head-up display device  9200 , and may include a display  9210  provided in an area of the vehicle, and a light path changing member  9220  that converts an optical path so that the driver may see the image generated on the display  9210 . 
       FIG.  14    illustrates an example in which a display device according to example embodiments is applied to augmented reality glasses or virtual reality glasses. The augmented reality glasses  9300  may include a projection system  9310  that forms an image, and an element  9320  that guides the image from the projection system  9310  into the user&#39;s eye. The projection system  9310  may include the above-described driving circuit, micro semiconductor light emitting device, side reflection structure, bottom reflection structure, and the like. 
       FIG.  15    illustrates an example in which a display device according to example embodiments is applied to a signage. A signage  9400  may be used for outdoor advertisement using a digital information display, and may control advertisement contents and the like through a communication network. The signage  9400  may be implemented, for example, through the electronic device described with reference to  FIG.  11   . 
       FIG.  16    illustrates an example in which a display device according to example embodiments is applied to a wearable display. The wearable display  9500  may include the above-described driving circuit, micro semiconductor light emitting device, side reflection structure, bottom reflection structure, and the like, and may be implemented through the electronic device described with reference to  FIG.  11   . 
     The display device according to the example embodiment may also be applied to various products such as a rollable TV and a stretchable display. 
     The above-described nano-rod light-emitting device, the epitaxial structure including a plurality of nano-rod light-emitting devices, and the method of manufacturing the epitaxial structure have been described with reference to the example embodiments shown in the drawings, but this is only exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible therefrom. Therefore, the disclosed example embodiments are to be considered in an illustrative rather than a restrictive sense. The scope of rights is indicated in the claims rather than the above description, and all differences within the scope of equivalents should be construed as being included in the scope of rights. 
     It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each example embodiment should typically be considered as available for other similar features or aspects in other embodiments. While example embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims and their equivalents.