Patent Publication Number: US-2022216377-A1

Title: Light Emitting Unit and Display device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation (CA) of U.S. patent application for “bight Emitting Unit and Display device”, U.S. application Ser. No. 17/065,312 filed Oct. 7, 2020, U.S. application Ser. No. 17/065,312 is a continuation of U.S. application Ser. No. 16/385,557 filed Apr. 16, 2019, U.S. application Ser. No. 16/385,557 is a continuation of U.S. application Ser. No. 15/829,395 filed Dec. 1, 2017, and the subject matter of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to a light emitting unit and a display device using the same. 
     2. Description of Related Art 
     With the continuous advancement of technologies related to displays, all the display apparatuses are now developed toward compactness, thinness, and lightness. Applications of thin displays are numerous. Most electronic products for daily use, such as mobile phones, notebook computers, video cameras, still cameras, music displays, mobile navigators, and TV sets, employ such display panels. 
     Herein, one kind of the light source used in the display device can be a light emitting diode. Even though the development of the light emitting diode is getting matured, many manufacturers are desired to provide a light emitting diode with improved chip reliability or enhanced light extraction efficiency. 
     Therefore, it is desirable to provide a light emitting unit and a display device using the same, which has improved chip reliability or enhanced light extraction efficiency. 
     SUMMARY 
     The present disclosure provides an electronic device, comprising: a semiconductor layer; and a protecting layer disposed on the semiconductor layer, wherein the protecting layer has a region in which oxygen atomic percentages decrease toward the semiconductor layer. 
     The present disclosure also provides another electronic device, comprising: a semiconductor layer; and a protecting layer disposed on the semiconductor layer, wherein the protecting layer has a region in which nitrogen atomic percentages increase toward the semiconductor layer. 
     Other novel features of the disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a light emitting unit according to Embodiment 1 of the present disclosure. 
         FIG. 2A  is a diagram showing nitrogen and oxygen atomic percentages in a second semiconductor layer and a first protecting layer of a light emitting unit according to Embodiment 1 of the present disclosure. 
         FIG. 2B  is an enlarged view of a region R 1  indicated in  FIG. 1  according to another embodiment of the present disclosure. 
         FIG. 2C  is an enlarged view of a region R 2  indicated in  FIG. 1  according to another embodiment of the present disclosure. 
         FIG. 3  is a cross-sectional view of a light emitting unit according to Embodiment 2 of the present disclosure. 
         FIG. 4  is a cross-sectional view of a light emitting unit according to Embodiment 3 of the present disclosure. 
         FIG. 5  is a cross-sectional view of a light emitting unit according to Embodiment 4 of the present disclosure. 
         FIG. 6  is a cross-sectional view of a light emitting unit according to Embodiment 5 of the present disclosure. 
         FIG. 7  is a cross-sectional view of a display device according to Embodiment 6 of the present disclosure. 
         FIG. 8  is a cross-sectional view of a display device according to Embodiment 7 of the present disclosure. 
         FIG. 9  is a cross-sectional view of a light emitting unit according to Embodiment 8 of the present disclosure. 
         FIG. 10  is a cross-sectional view of a light emitting unit according to Embodiment 9 of the present disclosure. 
         FIG. 11  is a cross-sectional view of a light emitting unit according to Embodiment 10 of the present disclosure. 
         FIG. 12  is a cross-sectional view of a light emitting unit according to Embodiment 11 of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT 
     The following embodiments when read with the accompanying drawings are made to clearly exhibit the above-mentioned and other technical contents, features and/or effects of the present disclosure. Through the exposition by means of the specific embodiments, people would further understand the technical means and effects the present disclosure adopts to achieve the above-indicated objectives. Moreover, as the contents disclosed herein should be readily understood and can be implemented by a person skilled in the art, all equivalent changes or modifications which do not depart from the concept of the present disclosure should be encompassed by the appended claims. 
     Furthermore, the ordinals recited in the specification and the claims such as “first”, “second” and so on are intended only to describe the elements claimed and imply or represent neither that the claimed elements have any proceeding ordinals, nor that sequence between one claimed element and another claimed element or between steps of a manufacturing method. The use of these ordinals is merely to differentiate one claimed element having a certain designation from another claimed element having the same designation. 
     Furthermore, the ordinals recited in the specification and the claims such as “above”, “over”, or “on” are intended not only directly contact with the other element, but also intended indirectly contact with the other element. Similarly, the ordinals recited in the specification and the claims such as “below”, or “under” are intended not only directly contact with the other element but also intended indirectly contact with the other element. 
     In addition, the features in different embodiments of the present disclosure can be mixed to form another embodiment. 
     Embodiment 1 
       FIG. 1  is a cross-sectional view of a light emitting unit of the present embodiment. The light emitting unit of the present embodiment comprises: a first semiconductor layer  11 ; an active layer  12  disposed on the first semiconductor layer  11 ; a second semiconductor layer  13  disposed on the active layer  12 ; and a first protecting layer  14  disposed on the second semiconductor layer  13 , wherein the first protecting layer  14  comprises oxygen, nitrogen, and at least one element selected from the group consisting of Al, Ga, In, and Si. 
     The light emitting unit of the present embodiment may be a light emitting diode. The size of the light emitting unit could be ranged from 0.1 μm to 100 μm, which is called a micro-LED; or ranged from 100 μm to 300 μm, which is called a mini-LED; or above 300 μm, which is called a normal LED. The active layer  12  of the light emitting unit play as a quantum well layer, the material of the active layer  12  could be organic material or inorganic material, and the active layer  12  may have quantum dot material. The material of the first semiconductor layer  11  could be P-type semiconductor or N-type semiconductor, the material of the second semiconductor layer  13  could be N-type semiconductor or P-type semiconductor, and the material of the second semiconductor layer  13  is opposite to the material of the first semiconductor layer  11  (P-N pair). 
     Since the second semiconductor layer  13  may be easily damaged, the first protecting layer  14  is disposed on the second semiconductor layer  13  to prevent the damage of the second semiconductor layer  13 ; thus the reliability of the light emitting unit can further be improved. In addition, the light emitting unit of the present embodiment is a top-emission light emitting unit. While the first protecting layer  14  is disposed between the second semiconductor layer  13  and a layer (not shown in the figure), the refractive index of the first protecting layer  14  is between the refractive index of the second semiconductor layer  13  and the refractive index of the layer to reduce total reflection occurred. 
     Herein, the dominant material of the first semiconductor layer  11 , the active layer  12  and the second semiconductor layer  13  can be GaN or other semiconductor material suitable for a light emitting diode. In consideration of the lattice match between the second semiconductor layer  13  and the first protecting layer  14 , the material for the first protecting layer  14  may comprise oxygen, nitrogen, and at least one element selected from the group consisting of Al, Ga, In, and Si. 
     In one aspect, the material of the second semiconductor layer  13  is GaN, and the material of the first protecting layer  14  is GaO x N y . The refractive index of GaN is 2.5, and the refractive index of GaO x N y  is between 1.8 and 2.5. Hence, the refractive index difference between the second semiconductor layer  13  and the first protecting layer  14  is lowered than the refractive index difference between the second semiconductor layer  13  and the layer (not shown in the figure) above the first protecting layer  14  and the second semiconductor layer  13 , and thus the total reflections can be reduced. 
       FIG. 2A  is a diagram showing nitrogen and oxygen atomic percentages in the second semiconductor layer  13  and the first protecting layer  14  of a light emitting unit. As shown in  FIG. 1  and  FIG. 2A , in the present embodiment, the second semiconductor layer  13  and the first protecting layer  14  can be differentiated via the following measurement procedure. Herein, the atomic percentages in the second semiconductor layer  13  and the first protecting layer  14  can be examined via Energy dispersive spectroscopy (EDX), Secondary-ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS) or other suitable equipment. In the present disclosure, an element content means an atomic percentage (at %) or a ratio of a target element atomic to whole measuring elements&#39; atomics at a measuring region or a measuring point. For example, a nitrogen content or a nitrogen atomic percentage means a percentage or a ratio of nitrogen atomic to whole measuring elements&#39; atomics at a measuring region or a measuring point. 
     First, nitrogen content at the center C of the second semiconductor layer  13  is measured, and the obtained nitrogen content at the center C is defined as 100%. Next, a point with a nitrogen content being 90% based on the obtained nitrogen content at the center C is defined. Then, the oxygen content at this point is measured. It can be found that both oxygen and nitrogen are present at this point located in the first protecting layer  14   
     As shown in  FIG. 2A , close to the second semiconductor layer  13 . the first protecting layer  14  has a first oxygen atomic percentage and a first nitrogen atomic percentage, and the first oxygen atomic percentage is less than the first nitrogen atomic percentage. 
     In addition, as shown in  FIG. 1 , the first protecting layer  14  has a first top surface  141 , which is a rough surface. Herein, after forming the first protecting layer  14 , an imprinting process or other patterning process is performed on the first protecting layer  14  to form the rough surface. When the first top surface  141  of the first protecting layer  14  is a rough surface, the light extraction or uniformity of the light emitting unit can further be increased. 
     In addition, the first semiconductor layer  11  has a second top surface  111 . The first top surface  141  has a first roughness, the second top surface  111  has a second roughness, and the first roughness is greater than the second roughness. Herein, the first roughness of the first top surface  141  and the second roughness of the second top surface  111  can be examined. from SEM cross-section image. 
     In the aspect shown in  FIG. 1 , the first top surface  141  is a rough surface with plural uniform arc shapes. However, the present disclosure is not limited thereto. 
     For example,  FIG. 2B  is an enlarged view of a region R 1  indicated in  FIG. 1  according to another embodiment of the present disclosure, in this embodiment, the first top surface  141  is not a uniform rough surface. In addition,  FIG. 2C  is an enlarged view of a region R 2  indicated in  FIG. 1  according to another embodiment of the present disclosure, and the second top surface  111  is also not a uniform rough surface. When the first top surface  141  and the second top surface  111  are not uniform rough surfaces, the first roughness and the second roughness can be defined as follow. First, the region R 1  with a width W 1  ranged from 3 μm to 30 μm and the region R 2  with a width W 2  ranged from 3 μm to 30 μm are examined. Top 5 high peaks and top 5 low peaks can be respectively found in the region R 1  and the region R 2 . The height difference between the third high peak and the third low peak in the region R 1  is defined as the first roughness, and the height difference between the third high peak and the third low peak in the region R 2  is defined as the second roughness. 
     As shown in  FIG. 1 , to form the electrodes of the light emitting unit, a via hole  17  is firstly formed through a lithography process. Next, a passivation layer  18  is formed on the first semiconductor layer  11  and in the via hole  17 . The material for the passivation layer  18  can be, for example, a silicon oxide, a silicon oxynitride, a silicon nitride, aluminum oxide, resin, polymer, photoresist, or a combination thereof, but the present disclosure is not limited thereto. Then, a first contact electrode  151  and a second contact electrode  161  are formed on the same side of the first semiconductor layer  11  and in the via hole  17  by a metalorganic chemical vapor deposition (MOCVD), physical vapor deposition (PVD) process, electroplating process, or other thin film deposition process, but the present disclosure is not limited thereto. Herein, the material for the first contact electrode  151  and the second contact electrode  161  can respectively a reflective electrode material, such as Ag, Al, Ni, Cr, Cu, Au, Pd, Pt, Say, W, Rh, Jr, Ru, Mg, Zn, or an alloy thereof, but the present disclosure is not limited thereto. Finally, a first electrode  15  and a second electrode  16  are formed on the first contact electrode  151  and the second contact electrode  161  by the MOCVD, the PVD, the electro plating process, or other deposition process, but the present disclosure is not limited thereto. Herein, the material for the first electrode  15  and the second electrode  16  can be, for example, Ag, Al Ni, Cr, Cu, Au, Pd, Pt, or an alloy thereof, but the present disclosure is not limited thereto. 
     Hence, the light emitting unit of the present embodiment further comprises a first electrode  15  and a second electrode  16  disposed at the same side of the light emitting unit, the first electrode  15  electrically connects to the second semiconductor layer  13 , and the second electrode  16  electrically connects to the first semiconductor layer  11 . In addition, the second electrode  16  is disposed below the first semiconductor layer  11 , the first electrode  15  is disposed below the first semiconductor layer  11 , and a via hole  17  penetrates through the first semiconductor layer  11  and the active layer  12 , and at least a part of the first electrode disposed in the via hole  17 . A part of the via hole  17  is further extended into the second semiconductor  13 , and a part of the first electrode  15  is further embedded into the second semiconductor layer  13 . 
     In the present embodiment, the via hole  17  is firstly formed through a lithography process, which required high accuracy. However, when the first electrode  15  is formed in the via hole  17  to electrically connect to the second semiconductor layer  13 , the area for forming the first electrode  15  can be reduced, all the area except the region with the via hole  17  can emit light, and therefore the area capable of emitting light can be increased. 
     Furthermore, the light emitting unit further comprises a passivation layer  18 , the passivation layer  18  is disposed between the first electrode  15  in the via hole  17  and the first semiconductor layer  11 , and the passivation layer  18  could be also disposed on a side wall  171  of the via hole  17 . 
     In the present embodiment, the light emitting unit further comprises a first contact electrode  151  and a second contact electrode  161 , which can facilitate the formation of the first electrode  15  and the second electrode  16 . However, in another embodiment of the present disclosure, the light emitting unit does not comprise the aforesaid first contact electrode  151  and the second contact electrode  161 . 
     In addition, the light emitting unit further comprises a first encapsulating layer  19 , the first encapsulating layer  19  is around a part of the first electrode  15  and a part of the second electrode  16  and is disposed on a side wall  112  of the first semiconductor layer  11 , a side wall  121  of the active layer  12  and a side wall  131  of the second semiconductor layer  13 . Herein, the material for the first encapsulating layer  19  can be silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, resin, polymer, photoresist, other non-sulfur inorganic or organic encapsulating material, or a combination thereof. 
     Embodiment 2 
       FIG. 3  is a cross-sectional view of a light emitting unit of the present embodiment. The light emitting unit of the present embodiment is similar to that shown in Embodiment 1, except that the first electrode  15  is not erg Bedded into the second semiconductor layer  13 . More specifically, the first electrode  15  contacts a bottom surface  132  of the second semiconductor layer  13 . 
     Embodiment 3 
       FIG. 4  is a cross-sectional view of a light emitting unit of the present embodiment. The light emitting unit of the present embodiment is similar to that shown in Embodiment 1, except the following differences. 
     In the present embodiment, a mesa process is performed to form a cavity  133  near to the first semiconductor layer  11  and the active layer  12 . Next, a first electrode  15  is formed in the cavity  133  and a second electrode  16  is formed on the first semiconductor layer  11 . Then, a first encapsulating layer  19  is formed, wherein the first encapsulating layer  19  is around a part of the first electrode  15  and a part of the second electrode  16  and is disposed on a side wall  112  of the first semiconductor layer  11 , a side wall  121  of the active layer  12  and a side wall  131  of the second semiconductor layer  13 . The first encapsulating layer  19  may be disposed in a part of the cavity  133 . 
     The process for forming the light emitting unit of Embodiment 1 is more complex than the process of the present embodiment. However, since the area of first semiconductor layer  11  and the active layer  12  on the second semiconductor layer  13  is decreased in the present embodiment, the area capable of emitting light in the light emitting unit of the present embodiment is less than the area capable of emitting light in Embodiment 1. 
     Embodiment 4 
       FIG. 5  is a cross-sectional view of a light emitting unit of the present embodiment. The light emitting unit of the present embodiment is similar to that shown in Embodiment 1, except the following difference. 
     In the present embodiment, the light emitting unit further comprises a second protecting layer  21  disposed on the first protecting layer  14 , wherein the first protecting layer  14  has a first top surface  141 , the second protecting layer  21  has a third top surface  211 , the first top surface  141  has a first roughness, the third top surface  211  has a third roughness, and the first roughness is greater than the third roughness. In another embodiment of the present disclosure, the third top surface  211  is not a uniform rough surface; in this case, the third roughness can be defined by the same method. shown in  FIG. 2B  and  FIG. 2C . 
     Herein, the material for the second protecting layer  21  can be, for example, silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, resin, polymer, photoresist, or a combination thereof, but the present disclosure is not limited thereto. 
     In one aspect of the present disclosure, when the second protecting layer  21  is an oxide film, the second protecting layer  21  has a second oxygen atomic percentage, and the first oxygen atomic percentage of the first protecting layer  14  is less than the second oxygen atomic percentage of the second protecting layer  21 . 
     In another aspect of the present disclosure, when the second protecting layer  21  is a nitride film, the second protecting layer  21  has a second nitrogen atomic percentage, and the first nitrogen atomic percentage of the first protecting layer  14  is less than the second nitrogen atomic percentage of the second protecting layer  21 . 
     Embodiment 5 
       FIG. 6  is a cross-sectional view of a light emitting unit of the present embodiment. The light emitting unit of the present embodiment is similar to that shown in Embodiment 4, except the following difference. 
     In the present embodiment, the light emitting unit further comprises a reflecting layer  22 , the first semiconductor layer  11  has a bottom surface  113 , the second electrode  16  is disposed on the bottom surface  113 , and the reflecting layer  22  is disposed on the bottom surface  113  without the second electrode  161  formed thereon. 
     In addition, the reflecting layer  22  is further disposed on a side wall  112  of the first semiconductor layer  11 , a side wall  121  of the active layer  12  and a side wall  131  of the second semiconductor layer  13 . 
     Furthermore, the reflecting layer  22  can be served as a distributed Bragg reflector (DBR), which can increase the light reflection. The reflecting layer  22  has a multilayer structure, and therefore a total reflection can be occurred at the reflecting layer  22 . Herein, each layer of the multilayer structure can be an insulating layer, such as an oxide film, a nitride film, or an oxynitride film. For example, the material for each layer of the multilayer structure can be SiO 2 , SiN x , SiO x N y , TiO 2 , Al 2 O 3 , ZrO 2 , TiN, AlN, TiAlN, TiSiN, or a combination thereof However, the present disclosure is not limited thereto. 
     The light emitting units disclosed in the aforesaid Embodiments 1 to  5  can be applied to a display device. Hereinafter, several examples of the display devices of the present disclosure are illustrated. 
     Embodiment 6 
       FIG. 7  is a cross-sectional view of a display device of the present embodiment. In the present embodiment, the structure shown in  FIG. 5  is used, so only the structure differences are illustrated below. 
     In the present embodiment, the light emitting unit further comprises a light converting layer  23  disposed on the first protecting layer  14 . Herein, the light converting layer  23  is also disposed on the second protecting layer  21 . The light converting layer  23  comprises an encapsulating layer  231  (for example, a surfer-based encapsulating layer) and quantum dots  232  dispersed in the encapsulating layer  231 . The quantum dots play as light color converting elements. 
     In addition, in the present embodiment, the display device further comprises a base  3 , wherein a first pad  31  and a second pad  32  are disposed on the base  3 . Herein, the material for the first pad  31  and the second pad  32  can be, for example, Ag, Al, Ni, Cr, Cu, Au Pd, Pt or an alloy thereof, but the present disclosure is not limited thereto. 
     In the present embodiment, the light emitting unit is disposed on the base  3 , the first electrode  15  electrically connects to the first pad  31 , the second electrode  16  electrically connects to the second pad  32 , and a second encapsulating layer  4  is around a part of the first electrode  15 , a part of the second electrode  16 , the first pad  31  and the second pad  32 . Herein, the second encapsulating layer  4  can be silicon-based encapsulating layer. The material for the silicon-based encapsulating layer can be, for example, silicon oxide, silicon nitride, silicon oxynitride or a combination thereof, but the present disclosure is not limited thereto. 
     The encapsulating material for encapsulating the quantum dots  232  is a surfer-based material, which may cause the sulfidation of the first electrode  15 , the second electrode  16 , the first pad  31  and the second pad  32 . Hence, in the present embodiment, when the second encapsulating layer  4  is disposed to be around the first electrode  15 , the second electrode  16 , the first pad  31  and the second pad  32 , the sulfidation of the first electrode  15 , the second electrode  16 , the first pad  31  and the second pad.  32  can be prevented. 
     However, in other embodiment of the present disclosure, if the light converting layer  23  does not comprise quantum dots but comprises phosphors or other light color converting materials, the material for encapsulating the phosphors may be or not be the surfer-based encapsulating. 
     Embodiment 7 
       FIG. 8  is a cross-sectional view of a display device of the present embodiment. The display device of the present embodiment is similar to that shown in Embodiment 6, except that the light emitting unit further comprises a third protecting layer  24  disposed on the light converting layer  23 . The disposition of the third protecting layer  24  can prevent the deterioration of the quantum dots  232 . The material for the third protecting layer  24  can be, for example, silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, resin, polymer, photoresist, or a combination thereof, but the present disclosure is not limited thereto. 
     Embodiment 8 
       FIG. 9  is a cross-sectional view of a light emitting unit of the present embodiment. In the present embodiment, the structure shown in  FIG. 6  is used, so only the structure differences are illustrated below. 
     In the present embodiment, the light emitting unit further comprises a light converting layer  23  disposed on the first protecting layer  14 . Herein, the light converting layer  23  is also disposed on the second protecting layer  21 . The light converting layer  23  comprises an encapsulating layer  231  (for example, a surfer-based encapsulating layer) and quantum dots  232  dispersed in the encapsulating layer  231 . 
     In addition, the light emitting unit further comprises a third protecting layer  24 , and the third protecting layer  24  is disposed on the light converting layer  23  and a side wall  191  of the first encapsulating layer  19 . 
     Embodiment 9 
       FIG. 10  is a cross-sectional view of a light emitting unit of the present embodiment. The display device of the present embodiment is similar to that shown in Embodiment 8, except that the light converting layer  23  is further disposed between the third protecting layer  24  and the side wall  191  of the first encapsulating layer  19 . 
     Embodiment 10 
       FIG. 11  is a cross-sectional view of a light emitting unit of the present embodiment. The light emitting unit of the present embodiment comprises: a first semiconductor layer  11 ; an active layer  12  disposed on the first semiconductor layer  11 ; a second semiconductor layer  13  disposed on the active layer  12 ; and a first protecting layer  14  disposed on the second semiconductor layer  13 . Herein, the first protecting layer  14  is further disposed on a side wall  131  of the second semiconductor layer  13 , a side wall  121  of the active layer  12 , and a side wall  112  of the first semiconductor layer  11 . 
     In addition, the light emitting unit further comprises: a first electrode  15  and a second electrode  16 , the first electrode  15  electrically connects to the second semiconductor layer  13 , and the second electrode  16  electrically connects to the first semiconductor layer  11 . Herein, the first electrode  15  is disposed on the second semiconductor layer  13 , and the second electrode  16  is disposed under the first semiconductor layer  11 . The first protecting layer  14  is disposed on a region of the second semiconductor layer  13  without the first electrode  15  formed thereon. 
     Other features of the light emitting unit of the present embodiment are similar to those illustrated in the aforementioned embodiments, and not repeated again. 
     Embodiment 11 
       FIG. 12  is a cross-sectional view of a light emitting unit of the present embodiment. The light emitting unit of the present embodiment is similar to that shown in Embodiment 10, except that the light emitting unit of the present embodiment further comprises: a second protecting layer  21  disposed on the first protecting layer  14 . More specifically, all the surfaces of the first protecting layer  14  are covered by the second protecting layer  21 . 
     Other features of the light emitting unit of the present embodiment are similar to those illustrated in the aforementioned embodiments, and not repeated again. 
     The light emitting unit made as described in any of the embodiments of the present disclosure as described previously can be applied to various fields, such as lamps, display devices, or other light source contained in an electronic device. 
     In addition, the display device made as described in any of the embodiments of the present disclosure as described previously can be co-used with a touch panel to form a touch display device. Meanwhile, a display device or touch display device may be applied to any electronic devices known in the art that need a display screen, such as displays, mobile phones, laptops, video cameras, still cameras, music players, mobile navigators, TV sets, and other electronic devices that display images. 
     Although the present disclosure has been explained in relation to its embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the disclosure as hereinafter claimed.