This disclosure relates to the technical field of light emitting elements, and more particularly, to a light emitting element and a method of producing the same.
Since the substrate 10 made of sapphire is not electrically conductive, the electrodes must be provided on the top surface of the light emitting diode. That is to say, the positive electrode 81 is formed on the top surface of the p-type GaN layer 40, and the negative electrode 82 is formed on the top surface of the n-type GaN layer 20. In this structure, no matter how the light emitting electrode is placed, the electric current direction thereof is vertical. However, when the negative electrode 82 is being produced, it is necessary to etch the light emitting diode from the surface of the p-type GaN layer 40 to the n-type GaN layer 20, and the etched groove must be wide enough in order to form the negative electrode 82 on the surface of the n-type GaN layer 20 through wire bonding. As a result, a part of the light emitting area originally formed by the area where the light emitting layer 30 is provided is etched, and the light emitting effect may be affected; on the other hand, since the substrate 10 made of sapphire has low thermal conductivity, it may be difficult to timely dissipate the heat generated when the LED emits light, and the performance of the LED may be deteriorated.
The technical problem to be solved by the embodiments includes at least one of the following: how to reduce the light shielding area of the light emitting element, how to improve the electric current distribution efficiency, or how to increase the light emitting area of the light emitting element.
A light emitting element is provided, which comprises: a substrate; a first electrically conductive semiconductor layer located on the substrate; a light emitting layer located on a top surface of the first electrically conductive semiconductor layer; a second electrically conductive semiconductor layer located on a top surface of the light emitting layer; a positive electrode located on a top surface of the second electrically conductive semiconductor layer; and a negative electrode at least partially located on a side surface of the first electrically conductive semiconductor layer.
A method of producing a light emitting element is provided, which comprises the steps of: forming a first electrically conductive semiconductor layer on a substrate; forming a light emitting layer on a top surface of the first electrically conductive semiconductor layer; forming a second electrically conductive semiconductor layer on a top surface of the light emitting layer; forming a first groove extending from the second electrically conductive semiconductor layer to the first electrically conductive semiconductor layer; forming a reflective layer on a top surface of the second electrically conductive semiconductor layer and on a bottom surface and a peripheral surface of the first groove; forming an electrode layer on the reflective layer; and a separation step for removing a part of the reflective layer and a part of the electrode layer so that the electrode layer is separated into a positive electrode located on the top surface of the second electrically conductive semiconductor layer and a negative electrode at least partially located on a side surface of the first electrically conductive semiconductor layer.
In the light emitting diode and the method of producing the same according to the embodiments, by forming the negative electrode on the side surface of the light emitting element, the light shielding area of the conventional light emitting element can be effectively reduced, and/or the electric current distribution efficiency can be improved; moreover, since less part of the light emitting layer needs to be etched to form the negative electrode on the side surface, the light emitting area can be increased, and/or the light emitting quality of the light emitting element can be improved; on the other hand, according to further embodiments, since the light emitting layer which generates heat can be configured closer to the printed circuit board (PCB), the thermal conductivity effect may be improved; further, since the light emitting element produced through the method provided by the embodiments can be bonded or soldered to the PCB by adopting the flip-chip technique, the wire connection cost may be reduced.
a)-3(d) illustrate cross sectional views in respective steps of the method of producing a light emitting element according to one embodiment;
e) illustrates a perspective view corresponding to
a)-6(e) illustrate cross sectional views in respective steps of a method of producing a light emitting element according to a further embodiment;
a)-7(b) are respectively an illustrative structural diagram of a PCB to be coupled to the light emitting element shown in
a)-10(b) illustrate respectively a perspective view and a cross sectional view of a light emitting element having a negative electrode on three surfaces according to one embodiment;
a)-14(c) illustrate respectively a perspective view, a cross sectional view and a top view of a light emitting element having several positive electrodes according to one embodiment;
a)-17(b) illustrate respectively a cross sectional view and a top view of a high-voltage LED according to one embodiment.
10: substrate; 20: n-type GaN layer; 30: light emitting layer; 40: p-type GaN layer; 50: first groove; 60: second groove; 61: protective layer; 70: reflective layer; 80: electrode layer; 81: positive electrode; 82: negative electrode; 90: ITO layer; 91: PCB; 92: thermally conductive insulation layer; 93: slot.
d) is a structural diagram of a light emitting element according to one embodiment, the light emitting element comprising: a substrate 10; a first electrically conductive semiconductor layer 20, a light emitting layer 30 and a second electrically conductive semiconductor layer 40 formed in this order on the substrate 10; a positive electrode 81; and a negative electrode 82, where the positive electrode 81 is formed on a top surface of the second electrically conductive semiconductor layer 40, and the negative electrode 82 is at least partially formed on a side surface of the first electrically conductive semiconductor layer 20.
In a possible implementation, the first electrically conductive semiconductor layer 20 in this embodiment is made of a n-type GaN layer, and the second electrically conductive semiconductor layer 40 is made of a p-type GaN layer.
In this embodiment, the surface of the p-type GaN layer 40 that is away from the light emitting layer 30 is called a top surface, and the surface of the p-type GaN layer 40 that comes into contact with the light emitting layer 30 is called a back surface, and the remaining four surfaces of the p-type GaN layer 40 are called side surfaces. The surface of the n-type GaN layer 20 that comes into contact with the light emitting layer 30 is called a top surface, and the surface of the n-type GaN layer 20 that comes into contact with the substrate 10 is called a back surface. The surface of the light emitting layer 30 that comes into contact with the p-type GaN layer 40 is called a top surface, and the surface of the light emitting layer 30 that comes into contact with the n-type GaN layer 20 is called a back surface, and the four surfaces of the light emitting layer 30 that do not come into contact with the n-type GaN layer 20 and the p-type GaN layer 40 are called side surfaces.
In a possible implementation of this embodiment, the negative electrode 82 is only formed on the side surface of the n-type GaN layer 20 in a direction perpendicular to the horizontal plane where the n-type GaN layer 20 is provided. In other embodiments, the negative electrode 82 may also be formed on the side surface and the surface substantially parallel to the top surface of the n-type GaN layer 20 based on actual demands (the structure is shown in
Moreover, the negative electrode 82 in this embodiment may be formed on four side surfaces of the n-type GaN layer 20 (the structure is shown in
Further, the light emitting element according to this embodiment may also comprise a protective layer 61 formed between the positive electrode 81 and the negative electrode 82 and extending from the p-type GaN layer 40 to the n-type GaN layer 20 (the structure is shown in
In addition, in order to improve the electric current distribution efficiency, and considering that the electric conduction only by means of the negative electrode 82 on the side surface when the light emitting element is too large might make less electric current flowing to the middle portion of the light emitting element which may reduce the light emitting efficiency of the middle portion, the protective layer 61 may be designed in a grid shape (e.g. “” shape) or to have several stripes so as to divide the positive electrode 81 into several rectangles (the structure is shown in
Step S 10: Forming the first electrically conductive semiconductor layer 20, the light emitting layer 30 and the second electrically conductive semiconductor layer 40 in this order on the substrate 10.
In this embodiment, the substrate 10 is a sapphire substrate. The material of the first electrically conductive semiconductor layer 20 may be n-type GaN or n-type AlGaInP. The material of the second electrically conductive semiconductor layer 40 may be p-type GaN or p-type AlGaInR In a possible implementation, the first electrically conductive semiconductor layer 20 and the second electrically conductive semiconductor layer 40 are made of n-type GaN and p-type GaN respectively.
Step S20: Forming at least one first groove 50 on the structure obtained from step S10 and shown in
In this step, the number, width and shape of the first groove 50 are not specifically defined. The first groove 50 may be formed on four side surfaces and have a loop shape. The first groove 50 may also be formed on one, two or three side surface(s).
Step S30: Forming the reflective layer 70 and the electrode layer 80 in this order on the structure obtained from step S20 and shown in
Specifically, the reflective layer 70 may be formed on the top surface of the p-type GaN layer 40, and on the bottom surface and the peripheral surface of the first groove 50. The material of the reflective layer 70 may be metal or semiconductor having good electric conductivity. When the reflective layer 70 is being formed, in order to increase the contact area with the surface, the step coverage process in the prior art may be adopted. The material of the electrode layer 80 is gold or any other kind of electrically conductive metal, and the electrode layer 80 may completely cover the reflective layer 70, as shown in
Step S40: Removing part of the reflective layer 70 and part of the electrode layer 80 so that the electrode layer 80 is separated into the positive electrode 81 located on the top surface of the p-type GaN layer 40 and the negative electrode 82 located on the side surface of the n-type GaN layer 20.
This step can be realized through the etching or peeling process. The size of the positive electrode 81 differs as the packaging method differs. If the flip-flop technique is adopted to perform the packaging, the larger is the area of the positive electrode 81, the better (as shown in
Further, in order to protect the light emitting layer exposed due to the etching of the groove, before the step S20 or after the step S40, the method may further comprises the following step:
Step S20′: Forming at least one second groove 60 on the structure obtained from the previous step, the second groove 60 extending from the p-type GaN layer 40 to the n-type GaN layer 20, and a protective layer 61 being formed in the second groove 60.
The material of the protective layer 61 must be insulative, have low electric conductivity and a stable structure, and cannot easily have chemical reactions with other materials. In a possible implementation, the material of the protective layer 61 is silica (SiO2).
In a possible implementation, in order to save costs, several light emitting elements can be packaged on one PCB 91 based on actual demands (the structure is shown in
Further, several light emitting elements can be connected in series to produce a high-voltage LED (HVLED). Under such a circumstance, the first groove 50 may be etched to the substrate 10, and the negative electrodes 82 are separated from each other by the substrate 10 which is not electrically conductive. However, the electrode layer 80 is still plated on the n-type GaN layer 20. That is to say, the negative electrodes 82 are still formed on the side surfaces of the n-type GaN layer 20. The protective layer 61 is plated in the portion of the first groove 50 other than the electrode layer 80, and then the positive electrodes 81 and the negative electrodes 82 are respectively connected in series (the structure is shown in
In addition, fluorescent powder may be covered on the light emitting element in this embodiment to produce a white light LED.
Hereinafter the method of producing a light emitting element is explained in detail by the embodiments.
a)-3(d) are cross sectional views in respective steps of the method of producing a light emitting element according to the embodiment. In the light emitting element produced by this method, the positive electrode 81 is located on the top surface of the p-type GaN layer 40, and the negative electrode 82 is located on the side surface of the n-type GaN layer 20. This method comprises:
Step S101: Forming the n-type GaN layer 20, the light emitting layer 30 and the p-type GaN layer 40 in this order on the substrate 10.
In this step, the substrate 10 can be a sapphire substrate, and the structure obtained from this step is shown in
Step S102: Forming the first groove 50 on the structure obtained from step S101.
As shown in
Step S103: Forming the reflective layer 70 and the electrode layer 80 in this order on the structure obtained from step S102.
As shown in
Step S104: Removing a part of the reflective layer 70 and a part of the electrode 80 to separate the electrode layer 80 into the positive electrode 81 and the negative electrode 82.
As shown in
Steps S201-S203: The same as steps S101-S103 (see
Step S204: Removing a part of the reflective layer 70 and a part of the electrode layer 80 to separate the electrode layer 80 into the positive electrode 81 and the negative electrode 82.
As shown in
In the subsequent packaging process that adopts the flip-flop technique, as shown in
a)-(e) are cross sectional views in respective steps of a method of producing a light emitting element according to a further embodiment. In the light emitting element produced by this method, the negative electrode 82 may be formed on the top surface and the side surface of the p-type GaN layer 40, the side surface of the light emitting layer 30, and the side surface of the n-type GaN layer 20. This method comprises:
Step S301: The same as step 5101 (see
Step S302: Forming the second groove 60 on the structure obtained from the previous step, and forming the protective layer 61 in the second groove 60.
As shown in
Step S303: Forming the first groove 50 on the structure obtained from step S202.
As shown in
Step S304: Forming the reflective layer 70 and the electrode layer 80 in this order on the structure obtained from the previous step.
Specifically, as shown in
Step S305: Removing a part of the reflective layer 70 and a part of the electrode layer 80 to separate the electrode layer 80 into the positive electrode 81 and the negative electrode 82.
Specifically, as shown in
Step S306: Cutting the light emitting element obtained from the previous step along the loop where the first groove 50 is provided, so as to form the positive electrode 81 located on the top surface of the p-type GaN layer 40 and the negative electrode 82 located on the top surface and the side surface of the p-type GaN layer 40, on the side surface of the light emitting layer 30, and on the side surface of the n-type GaN layer 20 (the structure is shown in
a) is a structural diagram of another PCB 91.
In the light emitting diode and the method of producing the same according to the embodiments, by forming the negative electrode on the side surface of the light emitting element, the light shielding area of the conventional light emitting element can be effectively reduced, and/or the electric current distribution efficiency can be improved; moreover, since less part of the light emitting layer needs to be etched in order to form the negative electrode on the side surface, the light emitting area can be increased, and/or the light emitting quality of the light emitting element can be improved; on the other hand, according to further embodiments, since the heat generated by the light emitting layer can be configured closer to the PCB, the thermal conductivity effect may be improved; further, since the light emitting element produced through the method provided by the embodiments can be bonded or soldered to the PCB by adopting the flip-chip technique, the wire connection cost may be reduced.
The above are merely embodiments of the present invention, and the protection scope of the present invention is not limited to these embodiments. Any modifications or equivalent structures and functions that can be easily thought out by a person skilled in the art within the range of the technology disclosed by the present invention should fall within the protection scope of the present invention. Thus, the protection scope of the present invention should be determined based on the protection scope of the claims.
Number | Date | Country | Kind |
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201210227813.5 | Jul 2012 | CN | national |