Patent Publication Number: US-2012037946-A1

Title: Light emitting devices

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     Some references, which may include patents, patent applications and various publications, are cited and discussed in the description of this invention. The citation and/or discussion of such references is provided merely to clarify the description of the present invention and is not an admission that any such reference is “prior art” to the invention described herein. All references cited and discussed in this specification are incorporated herein by reference in their entireties and to the same extent as if each reference were individually incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates generally to a light emitting device, and more particular to a light emitting device that utilizes an insulator and/or an epitaxial structure formed under the n-electrode to improve the uniformity in the current density of the light emitting device. 
     BACKGROUND OF THE INVENTION 
     Light emitting diodes (LEDs) have been widespread used for lighting with great brightness. Typically, an LED includes a multilayered structure of semiconductors, p- and n-electrodes and their connection pads placed on the surfaces of the multilayered structure. In operation, a current is injected into the LED through external terminals that are connected to the connection pads. The injected current from the p- and n-electrodes spreads into the respective semiconductor layers. Light is generated when the current flows across the p-n junction in the forward direction which causes the recombination of minority carriers at the p-n junction. The intensity of the light emitted by the LED under typical operating conditions is proportional to the current density. For a given current density, the larger the area of the p-n junction is, the greater the intensity generated by the LED. 
     Traditionally, for an LED to output much brighter light, it is implemented by maximizing the light emitting region of the LED so as to promote the flowing direction of the operation current of the LED. For a large scaled LED operated with a large current, if the distribution of the current density in the light emitting region of the LED is non-uniform, it causes the forward voltage and the temperature at interfaces to increase, which leads a reduction in the optical and electrical performance of the LED, particularly for the LED with larger dimensions and operated in conditions of a high current density. In addition, as the irreversible degradation in efficiency of light emission increases with increasing the current density, the non-uniformity in the current density increases the overall rate of degradation, thereby, reducing the lifetime of the LED. 
     U.S. Pat. No. 6,307,218 to Steigerwald et al. discloses an LED design that utilizes paralleled p-electrodes and n-electrodes, as shown in  FIG. 8A , to improve the non-uniformity in the current density of the LED. In Steigerwald et al, the current flowing vertically down to the n-type semiconductor layer from the area of the p-electrode finger  13  distal to the n-connection pad  14   a  has to traverse a current flowing path in the n-type semiconductor layer to reach the n-electrode finger  14  once it has passed vertically through the p-n junction, however, the current flowing path is different from the traverse distance in the n-type semiconductor layer while current flowing vertically down to the n-type semiconductor layer from the area of the p-electrode finger  13  next to the n-connection pad  14   a  to reach the n-electrode  14   a . The differences in the current paths result in uneven distribution of current around the n-connection pad  14   a . Accordingly, the light brightness (intensity) of the LED in an area  15  proximate to an end portion of the n-electrode  14  is uneven than that in the other light emitting area, as shown in  FIG. 8B . The non-uniformity in the light brightness is caused by the non-uniformity in the current density of the LED therein. 
     Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention relates to a light emitting device. In one embodiment, the light emitting device includes a substrate, and a multilayered structure having a first end portion and an opposite, second end portion defining a light emitting region and a non-emission region therebetween, the non-emission region having a first portion located next to the first end portion and a second portion extending from the first portion into the light emitting region. The multilayered structure includes an n-type semiconductor layer formed in the light emitting region and the non-emission region on the substrate, an active layer formed in the light emitting region on the n-type semiconductor layer, and a p-type semiconductor layer formed in the light emitting region on the active layer. 
     The light emitting device also includes a p-electrode formed in the light emitting region and electrically coupled to the p-type semiconductor layer, and an n-electrode formed in the non-emission region and electrically coupled to the n-type semiconductor layer. 
     Further, the light emitting device also includes an insulator formed between the n-electrode and the n-type semiconductor layer in the first portion of the non-emission region to define at least one ohmic contact such that the n-electrode in the first portion of the non-emission region is electrically coupled to the n-type semiconductor layer through the at least one ohmic contact. 
     The light emitting device further has a transparent, conductive layer formed on the p-type semiconductor layer in the light emitting region such that the p-electrode is electrically coupled to the p-type semiconductor layer through the transparent conductive layer. 
     In one embodiment, the insulator has at least one layer. The insulator is formed of a single material or a compound of multiple materials. In one embodiment, the insulator is formed of at least one of transparent oxides and nitrides, where the insulator is formed of SiO 2 , SiN, Al 2 O 3 , TiO 2 , or a combination thereof. The insulator may include an epitaxial structure. 
     In one embodiment, the n-electrode has an n-electrode bridge formed on the insulator in the first portion of the non-emission region, and a plurality of n-electrode fingers parallelly formed on the n-type semiconductor layer in the second portion of the non-emission region. Each n-electrode finger has a first end electrically connected to the n-electrode bridge and an opposite, second end extending to the light emitting region of the multilayered structure. The p-electrode has a p-electrode bridge formed proximate to the second end portion of the multilayered structure and a plurality of p-electrode fingers parallelly positioned in the light emitting region. Each p-electrode finger has a first end electrically connected to the p-electrode bridge, and an opposite, second end extending to the first end portion of the multilayered structure and substantially proximate to the n-electrode bridge. The plurality of p-electrode fingers and the plurality of n-electrode fingers are alternately arranged. 
     In one embodiment, the n-electrode bridge includes at least one wire connection pad electrically connected to a corresponding n-electrode finger and positioned over the at least one ohmic contact such that the at least one wire connection pad is electrically connected to the n-type semiconductor layer through at the at least one ohmic contact. As such, in operation, a current flowing path between the corresponding n-electrode finger and one adjacent p-electrode finger is substantially same as that between the at least one ohmic contact under the at least one wire connection pad and the adjacent p-electrode finger. 
     In one embodiment, each of the n-electrode and the p-electrode is formed of a transparent, conductive material. The n-electrode is electrically insulated from the p-electrode, the transparent conductive layer, the p-type semiconductor layer and the active layer. 
     In another aspect, the present invention relates to a method of manufacturing a light emitting device. In one embodiment, the method includes the steps of providing a substrate and forming a multilayered structure on the substrate, where the multilayered structure has an n-type semiconductor layer formed on the substrate, an active layer formed on the n-type semiconductor layer, and a p-type semiconductor layer formed on the active layer. The multilayered structure has a first end portion and an opposite, second end portion defining a light emitting region and a non-emission region therebetween, where the non-emission region has a first portion located next to the first end portion and a second portion extending from the first portion into the light emitting region. 
     The method also includes the steps of etching off the p-type the semiconductor layer and the active layer of the multilayered structure in the non-emission region so as to expose the n-type semiconductor layer therein, and forming an insulator in the first portion of the non-emission region on the exposed n-type semiconductor layer, the insulator defining at least one at least one ohmic contact. 
     Furthermore, the method includes the steps of forming an n-electrode in the non-emission region such that the n-electrode in the first portion of the non-emission region is electrically coupled to the n-type semiconductor layer through the at least one ohmic contact, and the n-electrode in the second portion of the non-emission region is electrically coupled to the n-type semiconductor layer directly, forming a transparent, conductive layer on the p-type semiconductor layer in the light emitting region, and forming a p-electrode on the transparent conductive layer such that the p-electrode is electrically coupled to the p-type semiconductor layer through the transparent conductive layer. 
     In one embodiment, the insulator comprises at least one layer. The insulator is formed of at least one of transparent oxides and nitrides. In one embodiment, the insulator is formed of a single material or a compound of multiple materials. In one embodiment, the insulator has an epitaxial structure. 
     In one embodiment, the n-electrode has an n-electrode bridge formed on the insulator in the first portion of the non-emission region, and a plurality of n-electrode fingers parallelly formed on the n-type semiconductor layer in the second portion of the non-emission region. Each n-electrode finger has a first end electrically connected to the n-electrode bridge and an opposite, second end extending to the light emitting region of the multilayered structure. The p-electrode has a p-electrode bridge formed proximate to the second end portion of the multilayered structure and a plurality of p-electrode fingers parallelly positioned in the light emitting region. Each p-electrode finger has a first end electrically connected to the p-electrode bridge, and an opposite, second end extending to the first end portion of the multilayered structure and substantially proximate to the n-electrode bridge. The plurality of p-electrode fingers and the plurality of n-electrode fingers are alternately arranged. 
     In one embodiment, the n-electrode bridge includes at least one wire connection pad electrically connected to a corresponding n-electrode finger and positioned over the at least one ohmic contact such that the at least one wire connection pad is electrically connected to the n-type semiconductor layer through at the at least one ohmic contact. As such, in operation, a current flowing path between the corresponding n-electrode finger and one adjacent p-electrode finger is substantially same as that between the at least one ohmic contact under the at least one wire connection pad and the adjacent p-electrode finger. 
     In yet another aspect, the present invention relates to a light emitting device. In one embodiment, the light emitting device includes a substrate, and a multilayered structure having a first end portion and an opposite, second end portion defining a light emitting region and a non-emission region therebetween, the non-emission region having a first portion located next to the first end portion and a second portion extending from the first portion into the light emitting region. The multilayered structure has an n-type semiconductor layer formed on the substrate, an active layer formed on the n-type semiconductor layer; and a p-type semiconductor layer formed on the active layer. 
     The multilayered structure is formed to have an epitaxial structure in the first portion of the non-emission region to define at least one ohmic contact therein. In one embodiment, the epitaxial structure comprises at least one layer. The epitaxial structure comprises a p-layer/active layer/n-layer structure. The epitaxial structure is isolated from the active layer and the p-type semiconductor layer. 
     The light emitting device also includes an n-electrode formed in the non-emission region and electrically coupled to the n-type semiconductor layer, such that the n-electrode in the first portion of the non-emission region is electrically coupled to the n-type semiconductor layer through at the at least one ohmic contact, and a p-electrode formed in the light emitting region and electrically coupled to the p-type semiconductor layer. 
     The light emitting device may also have a transparent, conductive layer formed on the p-type semiconductor layer in the light emitting region such that the p-electrode is electrically coupled to the p-type semiconductor layer through the transparent conductive layer. 
     In one embodiment, the n-electrode has an n-electrode bridge formed on the insulator in the first portion of the non-emission region, and a plurality of n-electrode fingers parallelly formed on the n-type semiconductor layer in the second portion of the non-emission region. Each n-electrode finger has a first end electrically connected to the n-electrode bridge and an opposite, second end extending to the light emitting region of the multilayered structure. The p-electrode has a p-electrode bridge formed proximate to the second end portion of the multilayered structure and a plurality of p-electrode fingers parallelly positioned in the light emitting region. Each p-electrode finger has a first end electrically connected to the p-electrode bridge, and an opposite, second end extending to the first end portion of the multilayered structure and substantially proximate to the n-electrode bridge. The plurality of p-electrode fingers and the plurality of n-electrode fingers are alternately arranged. 
     In one embodiment, the n-electrode bridge includes at least one wire connection pad electrically connected to a corresponding n-electrode finger and positioned over the at least one ohmic contact such that the at least one wire connection pad is electrically connected to the n-type semiconductor layer through at the at least one ohmic contact. As such, in operation, a current flowing path between the corresponding n-electrode finger and one adjacent p-electrode finger is substantially same as that between the at least one ohmic contact under the at least one wire connection pad and the adjacent p-electrode finger. 
     The n-electrode is electrically insulated from the p-electrode, the transparent conductive layer, the p-type semiconductor layer and the active layer. 
     In a further aspect, the present invention relates to a method of manufacturing a light emitting device. In one embodiment, the method includes the steps of providing a substrate, and forming a multilayered structure on the substrate, where the multilayered structure has an n-type semiconductor layer formed on the substrate, an active layer formed on the n-type semiconductor layer, and a p-type semiconductor layer formed on the active layer. The multilayered structure has a first end portion and an opposite, second end portion defining a light emitting region and a non-emission region therebetween. The non-emission region has a first portion located next to the first end portion and a second portion extending from the first portion into the light emitting region. 
     The method also includes the step of etching the multilayered structure in the non-emission region to form an epitaxial structure in the first portion of the non-emission region and expose the n-type semiconductor layer in the second portion of the non-emission region, the epitaxial structure defining at least one ohmic contact therein. 
     In one embodiment, the epitaxial structure comprises at least one layer. The epitaxial structure comprises a p-layer/active layer/n-layer structure. The epitaxial structure is isolated from the active layer and the p-type semiconductor layer. 
     The method further includes the step of forming an n-electrode in the non-emission region such that the n-electrode in the first portion of the non-emission region is electrically coupled to the n-type semiconductor layer through the at least one ohmic contact, and the n-electrode in the second portion of the non-emission region is electrically coupled to the n-type semiconductor layer directly, forming a transparent, conductive layer on the p-type semiconductor layer in the light emitting region, and forming a p-electrode on the transparent conductive layer such that the p-electrode is electrically coupled to the p-type semiconductor layer through the transparent conductive layer. 
     In one embodiment, the n-electrode has an n-electrode bridge formed on the insulator in the first portion of the non-emission region, and a plurality of n-electrode fingers parallelly formed on the n-type semiconductor layer in the second portion of the non-emission region. Each n-electrode finger has a first end electrically connected to the n-electrode bridge and an opposite, second end extending to the light emitting region of the multilayered structure. The p-electrode has a p-electrode bridge formed proximate to the second end portion of the multilayered structure and a plurality of p-electrode fingers parallelly positioned in the light emitting region. Each p-electrode finger has a first end electrically connected to the p-electrode bridge, and an opposite, second end extending to the first end portion of the multilayered structure and substantially proximate to the n-electrode bridge. The plurality of p-electrode fingers and the plurality of n-electrode fingers are alternately arranged. 
     In one embodiment, the n-electrode bridge includes at least one wire connection pad electrically connected to a corresponding n-electrode finger and positioned over the at least one ohmic contact such that the at least one wire connection pad is electrically connected to the n-type semiconductor layer through at the at least one ohmic contact. As such, in operation, a current flowing path between the corresponding n-electrode finger and one adjacent p-electrode finger is substantially same as that between the at least one ohmic contact under the at least one wire connection pad and the adjacent p-electrode finger. 
     In yet a further aspect, the present invention relates to a light emitting device. In one embodiment, the light emitting device includes a multilayered structure having a light emitting region and a non-emission region partially extending into the light emitting region, comprising an n-type semiconductor layer, an active layer formed on the n-type semiconductor layer, and a p-type semiconductor layer formed on the active layer, a p-electrode formed in the light emitting region and electrically coupled to the p-type semiconductor layer, and an n-electrode formed in the non-emission region and electrically coupled to the n-type semiconductor layer. 
     The multilayered structure has a first end portion and an opposite, second end portion such that the light emitting region and the non-emission region are defined therebetween, wherein the non-emission region has a first portion located next to the first end portion and a second portion extending from the first portion into the light emitting region. 
     The light emitting device also includes an insulator formed between the n-electrode and the n-type semiconductor layer in the non-emission region defining at least one ohmic contact such that the n-electrode is electrically coupled to the n-type semiconductor layer at least through the at least one ohmic contact. 
     The light emitting device may further comprises a transparent, conductive layer formed on the p-type semiconductor layer in the light emitting region such that the p-electrode is electrically coupled to the p-type semiconductor layer through the transparent conductive layer. 
     In one embodiment, the multilayered structure is formed such that the n-type semiconductor layer is exposed in the non-emission region, wherein the insulator is formed on the n-type semiconductor layer in the first portion of the non-emission region such that the n-electrode in the first portion of the non-emission region is electrically coupled to the n-type semiconductor layer through the at least one ohmic contact, and wherein the n-electrode in the second portion of the non-emission region is electrically coupled to the n-type semiconductor layer directly. 
     In one embodiment, the insulator comprises at least one layer. The insulator is formed of a single material or a compound of multiple materials. In one embodiment, the insulator is formed of at least one of transparent oxides and nitrides. 
     In one embodiment, the insulator includes an epitaxial structure. The epitaxial structure comprises a p-layer/active layer/n-layer structure. The epitaxial structure is isolated from the active layer and the p-type semiconductor layer. 
     In one embodiment, the n-electrode has an n-electrode bridge formed on the insulator in the first portion of the non-emission region, and a plurality of n-electrode fingers parallelly formed on the n-type semiconductor layer in the second portion of the non-emission region. Each n-electrode finger has a first end electrically connected to the n-electrode bridge and an opposite, second end extending to the light emitting region of the multilayered structure. The p-electrode has a p-electrode bridge formed proximate to the second end portion of the multilayered structure and a plurality of p-electrode fingers parallelly positioned in the light emitting region. Each p-electrode finger has a first end electrically connected to the p-electrode bridge, and an opposite, second end extending to the first end portion of the multilayered structure and substantially proximate to the n-electrode bridge. The plurality of p-electrode fingers and the plurality of n-electrode fingers are alternately arranged. 
     In one embodiment, the n-electrode bridge includes at least one wire connection pad electrically connected to a corresponding n-electrode finger and positioned over the at least one ohmic contact such that the at least one wire connection pad is electrically connected to the n-type semiconductor layer through at the at least one ohmic contact. As such, in operation, a current flowing path between the corresponding n-electrode finger and one adjacent p-electrode finger is substantially same as that between the at least one ohmic contact under the at least one wire connection pad and the adjacent p-electrode finger. 
     These and other aspects of the present invention will become apparent from the following description of the preferred embodiment taken in conjunction with the following drawings, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate one or more embodiments of the invention and together with the written description, serve to explain the principles of the invention. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment, and wherein: 
         FIG. 1  shows schematically a top view of a light emitting region and a non-emission region of a light emitting device according to one embodiment of the present invention; 
         FIG. 2  shows schematically another top view of the light emitting region and the non-emission region of the light emitting device as shown in  FIG. 1 ; 
         FIG. 3  shows schematically a top view of the light emitting device as shown in  FIG. 1 ; 
         FIG. 4  shows schematically cross sectional views of the light emitting device as shown in  FIG. 3 , (a) along with the A-A′ line and (b) along with the B-B′ line; 
         FIG. 5  shows schematically a fabricating process (a)-(c) of the light emitting device as shown in  FIG. 3 ; 
         FIG. 6  shows schematically a fabricating process (a) and (b) of a light emitting device according to another embodiment of the present invention; 
         FIG. 7  shows schematically a light emitting device in operation according to one embodiment of the present invention; and 
         FIG. 8  shows schematically (a) a top view of a conventional light emitting device and (b) the conventional light emitting device in operation. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. 
     It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” or “has” and/or “having” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 
     Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element&#39;s relationship to another element as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. The exemplary term “lower”, can therefore, encompasses both an orientation of “lower” and “upper,” depending of the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     The term “layer”, as used herein, refers to a thin sheet or thin film. 
     The term “electrode”, as used herein, is an electrically conductive layer or film formed of one or more electrically conductive materials. 
     As used herein, the term “ohmic contact” refers to a region on a semiconductor device that has been prepared so that the current-voltage curve of the device is linear and symmetric. 
     The description will be made as to the embodiments of the present invention in conjunction with the accompanying drawings of  FIGS. 1-7 . In accordance with the purposes of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to a light emitting device. 
     Referring to  FIGS. 1-5 , and particularly to  FIGS. 3 and 4 , a light emitting device  100  is shown according to one embodiment of the present invention. In the exemplary embodiment, the light emitting device  100  includes a multilayered structure  120  formed on a substrate  110 , a p-electrode  130  and an n-electrode  140  electrically coupled to the multilayered structure  120  for injecting an operative current thereto. The n-electrode  140  and the p-electrode  130  are formed of a conductive material, or different conductive materials. 
     The multilayered structure  120  has a first end portion  121   a  and an opposite, second end portion  121   b  defining a light emitting region  123  and a non-emission region  125  of the light emitting device  100  therebetween. As shown in  FIG. 4 , the multilayered structure  120  includes an n-type semiconductor layer  122  formed in the light emitting region  123  and the non-emission region  125  on the substrate  110 , an active layer  124  formed in the light emitting region  123  on the n-type semiconductor layer  122 , and a p-type semiconductor layer  126  formed in the light emitting region  123  on the active layer  124 . In one example, the active layer  124  can be an MQW (Multiple Quantum Well) layer. The p-electrode  130  is formed in the light emitting region  123  and electrically coupled to the p-type semiconductor layer  126  through a transparent, conductive layer  128  formed on the p-type semiconductor layer  126 . The n-electrode  140  is formed in the non-emission region  125  and electrically coupled to the n-type semiconductor layer  122 . 
     As shown in  FIG. 1 , the non-emission region  125  is defined in the form of a recess in the multilayered structure  120 , such that the n-type semiconductor layer  122  is exposed therein. The non-emission region  125  has a first portion  125   a  located next to the first end portion  121   a  of the multilayered structure  120  and a second portion  125   b  extending from the first portion  125   a  into the light emitting region  123 . In this embodiment, the first portion  125   a  includes two half-obround shaped recesses  125   c , and the second portion  125   b  includes a plurality of grooves/slots  125   b  parallelly and spatially formed in the light emitting region  123 . Each half-obround shaped recess  125   c  has a width, D 1 . Each groove  125   b  has a width, D 2 , which is less than D 1 . 
     As shown in  FIG. 2 , an insulator  150  is deposited in the first portion  125   a  of the non-emission region  125  on the n-type semiconductor layer  122 , so as to cover the n-type semiconductor layer  122  in the first portion  125   a  of the non-emission region  125 , except that, over each half-obround shaped recess  125   c , the insulator  150  is deposited into two portions  151   a  and  151   b  separated by a gap  152   a  having a width, d, where the n-type semiconductor layer  122  is exposed. The width d of the gap  152   a  is substantially same as the width D 2  of each groove  125   b . It is the gap  152   a  that defines an ohmic contact through which the n-electrode  140  in the first portion of the non-emission region  125  is electrically coupled to the n-type semiconductor layer  122 . The insulator  150  includes one or more layers, and is formed of a single material or a compound of multiple materials. In one embodiment, the insulator  150  is formed of at least one of transparent oxides and nitrides. Specifically, the insulator is formed of SiO 2 , SiN, Al 2 O 3 , TiO 2 , or the like. The insulator  150  may include an epitaxial structure. 
     In this embodiment shown in  FIGS. 1-5 , and particularly in  FIG. 3 , the n-electrode  140  has an n-electrode bridge  141  formed on the insulator  150  in the first portion  125   a  of the non-emission region  125 , and a plurality of n-electrode fingers  142  parallelly formed on the n-type semiconductor layer  140  in the second portion  125   b  of the non-emission region  125 . Each n-electrode finger  142  has a first end  142   a  electrically connected to the n-electrode bridge  141  and an opposite, second end  142   b  extending to the light emitting region  123  of the multilayered structure  120 . The n-electrode bridge  141  includes one or more wire connection pads  143  formed on the insulator  150  over the corresponding half-obround shaped recess  125   c  of the first portion  125   a  of the non-emission region  125 . The wire connection pads  143  are adapted for providing the electrical connection of extra-terminals to the n-electrode  140 . Each connection pad  143  is electrically connected to a corresponding n-electrode finger  142  and positioned over the corresponding ohmic contact  152 . Accordingly, the wire connection pad  143  is electrically connected to the n-type semiconductor layer  122  through the ohmic contact  152 . In addition, the n-electrode  140  in the second portion  125   b  of the non-emission region  125  is electrically connected to the n-type semiconductor layer  122  directly, since the plurality of n-electrode fingers  142  is parallelly formed on the n-type semiconductor layer  140  in the second portion  125   b  of the non-emission region  125 . 
     The p-electrode  130  has a p-electrode bridge  131  formed proximate to the second end portion  121   b  of the multilayered structure  120  and a plurality of p-electrode fingers  132  parallelly positioned in the light emitting region  123 . Each p-electrode finger  132  has a first end  132   a  electrically connected to the p-electrode bridge  131 , and an opposite, second end  132   b  extending to the first end portion  121   a  of the multilayered structure  120 . According to the invention, the second end  132   b  of each p-electrode finger  132  is substantially proximate to the n-electrode bridge  141 . Further, the p-electrode bridge  131  may have one or more wire connection pads  133  for providing the electrical connection of extra-terminals to the p-electrode  130 . 
     Additionally, the plurality of p-electrode fingers  132  and the plurality of n-electrode fingers  142  are alternately arranged, as shown in  FIGS. 3 and 4 , such that the injected current is uniformly distributed through out the light emitting device  100 . 
     For such a light emitting device  100 , when a current is injected at the p-electrode  130 , the current flows from the p-electrode fingers  132  along the shortest path (i.e., usually vertically) across the p-n junction to the n-type semiconductor layer  122 . The current then spreads laterally within the n-type semiconductor layer  122  to reach the n-electrode  140 . Because of the ohmic contact  152  defined on the wire connection pad  143 , the current reaching the n-electrode  140  at the area of the wire connection pad  143  is through the ohmic contact  152 , which makes the current flowing path  161   b  ( 162   b ) from a p-electrode finger  132  to a corresponding n-electrode finger  142  at the area distal to the wire connection pad  143  substantially same as that  161   a  ( 162   a ) from the p-electrode finger  132  to the corresponding n-electrode  140  at the area of the wire connection pad  143 . This results in the uniformity in the current density of the light emitting device  100 . Additionally, according to the invention, the ends  132   b  of the p-electrode fingers  132  of the p-electrode  130  extends into the first end portion  121   a  of the multilayered structure  120  and substantially close to the n-electrode bridge  141  and the wire connection pad  143  of the n-electrode  140 , as shown in  FIG. 3 , which further improves the uniformity in the current density at least in the peripheral portion of the light emitting device  100 . Accordingly, the brightness (intensity) of light emitted from the light emitting device is uniform over the light emitting region of the light emitting device  100 , as shown in  FIG. 7 . 
     As shown in  FIG. 5 , the light emitting device  100  can be fabricated according to the following processes. 
     At first, the multilayered structure  120  is formed on the substrate  110 . The multilayered structure  120  includes the n-type semiconductor layer  122  formed on the substrate  110 , the active layer  124  formed on the n-type semiconductor layer  122 , and the p-type semiconductor layer  126  formed on the active layer  124 . 
     Then, the p-type the semiconductor layer  126  and the active layer  124  of the multilayered structure  120  are etched off at pre-selected locations to expose the n-type semiconductor layer  122  so as to define the non-emission region  125  therein, as shown in  FIG. 5   a . The remaining area of the multilayered structure  120  is corresponding to the light emitting region  123 . The non-emission region  125  is defined to have a first portion  125   a  located next to the first end portion  121   a  of the multilayered structure  120  and a second portion  125   b  extending from the first portion  125   a  into the light emitting region  123 . The first portion  125   a  of the non-emission region  125  includes one or more half-obround shaped recesses  125   c , and the second portion  125   b  includes a plurality of grooves/slots  125   b  parallelly and spatially formed in the light emitting region  123 . Each half-obround shaped recess  125   c  has a width, D 1 . Each groove  125   b  has a width, D 2 , which is less than D 1 . 
     The next process is to deposit an insulating material on the exposed n-type semiconductor layer  122  in the first portion  125   a  of the non-emission region  125  to form the insulator  150 , as shown in  FIG. 5   b . Over each half-obround shaped recess  125   c , the insulator  150  is deposited into two portions  151   a  and  151   b  separated by a gap  152   a  having a width, d, where the n-type semiconductor layer  122  is exposed. The width d of the gap  152   a  is substantially same as the width D 2  of each groove  125   b.    
     The transparent, conductive layer  128  is optionally formed on the p-type semiconductor layer  126  in the light emitting region  123 . The n-electrode  140  is then formed in the non-emission region  125  such that the n-electrode  140  in the first portion  125   a  of the non-emission region  125  is electrically coupled to the n-type semiconductor layer  122  through the ohmic contact  152  defined in the a gap  152   a , as shown in  FIG. 5   c , while the n-electrode  140  in the second portion  125   b  of the non-emission region  125  is electrically coupled to the n-type semiconductor layer  122  directly. It is the gap  152   a  that defines an ohmic contact  152  through which the n-electrode  140  in the first portion of the non-emission region  125  is electrically coupled to the n-type semiconductor layer  122 . 
     Finally, the p-electrode  130  is formed on the transparent conductive layer  128  such that the p-electrode  130  is electrically coupled to the p-type semiconductor layer  126  through the transparent conductive layer  128 . However, the p-electrode  130  can also be formed together with the n-electrode  140  using the same process steps. 
     Referring to  FIG. 6 , a light emitting device  600  is shown according to another embodiment of the present invention. The light emitting device  600  is similar to the light emitting device  100  as shown in  FIGS. 1-5 . The light emitting device  600  includes a multilayered structure  120  having an n-type semiconductor layer  622  formed on a substrate  610 , an active layer  624  formed on the n-type semiconductor layer  622  and a p-type semiconductor layer  626  formed on the active layer  624 . In one example, the active layer  624  can be an MQW (Multiple Quantum Well) layer. The light emitting device  600  also includes a transparent conductive layer  628  formed on the p-type semiconductor layer  626 . The multilayered structure  120  has a first end portion and an opposite, second end portion defining a light emitting region  623  and a non-emission region  625  therebetween. The non-emission region  625  has a first portion  625   a  located next to the first end portion and a second portion extending from the first portion into the light emitting region  623 . 
     Instead of an insulator  150  formed in the first portion  125   a  of the non-emission region  125  of the light emitting device  100 , the multilayered structure  620  defines an epitaxial structure  650  in the first portion  625   a  of the non-emission region  625  of the light emitting device  600 . According to the present invention, the epitaxial structure  650  includes at least one layer. As shown in  FIG. 6 , the epitaxial structure  650  has a p-layer/active layer/n-layer structure, and is isolated from the active layer  624  and the p-type semiconductor layer  626  of the multilayered structure  620 . Specifically, the epitaxial structure  650  is spatially isolated from the active layer  624  and the p-type semiconductor layer  626  of the multilayered structure  620  by a gap  651  with a width, g. Further, the epitaxial structure  650  defines one or more grooves  652   a  to expose the n-type semiconductor layer  622  for providing ohmic contacts. 
     Additionally, the p-electrode  630  is formed on the transparent conductive layer  628  in the light emitting region  623  and electrically coupled to the p-type semiconductor layer  626  through the transparent conductive layer  628 . The n-electrode  640  is formed in the non-emission region  625  and electrically coupled to the n-type semiconductor layer  622 . Similarly, the n-electrode  640  has an n-electrode bridge  641  formed on the epitaxial structure  650  in the first portion  625   a  of the non-emission region  625 , and a plurality of n-electrode fingers parallelly formed on the n-type semiconductor layer  640  in the second portion of the non-emission region  625 . The n-electrode bridge  641  includes one or more wire connection pads  643  formed on the epitaxial structure  650 . Each connection pad  643  is electrically connected to a corresponding n-electrode finger and positioned over the corresponding one ohmic contact  652 . Accordingly, the wire connection pad  645  is electrically connected to the n-type semiconductor layer  622  through the ohmic contact  652 . The p-electrode  630  has a p-electrode bridge formed proximate to the second end portion of the multilayered structure  620  and a plurality of p-electrode fingers  632  parallelly positioned in the light emitting region  623 . The plurality of p-electrode fingers  632  and the plurality of n-electrode fingers are alternately arranged. 
     For such a light emitting device  600 , the epitaxial structure  650  is effectively of the insulator  150  of the light emitting device  100  shown in  FIGS. 1-5  and functions like a diode. When a current is injected at the p-electrode  630 , the current flows from the p-electrode finger  632  along the shortest path (i.e., usually vertically) across the p-n junction to the n-type semiconductor layer  622 . The current then spreads laterally within the n-type semiconductor layer  622  to reach the n-electrode  640 . Because of the ohmic contact  652  defined on the wire connection pad  643 , the current reaching the n-electrode  640  at the area of the wire connection pad  643  is through the ohmic contact  652 , which makes the current flowing path from the p-electrode finger  632  to a corresponding n-electrode finger at the area distal to the wire connection pad  643  substantially same as that from the p-electrode finger  632  to the corresponding n-electrode finger at the area of the wire connection pad  643 . This results in the uniformity in the current density of the light emitting device  600 . Accordingly, the brightness (intensity) of light emitted from the light emitting device is uniform over the light emitting region of the light emitting device  600 , as shown in  FIG. 7 . 
     As shown in  FIGS. 6   a  and  6   b , in one aspect of the present invention, the method of manufacturing the light emitting device  600  includes forming the multilayered structure  620  on the substrate  610 , and etching the multilayered structure  620  in the non-emission region  625  to form an epitaxial structure  650  in the first portion  625   a  of the non-emission region  625  and expose the n-type semiconductor layer  622  in the second portion of the non-emission region  625 . The epitaxial structure  650  defines one or more grooves  652   a  to expose the n-type semiconductor layer  622  for providing ohmic contacts. 
     The method may include forming the transparent conductive layer  628  on the p-type semiconductor layer  626  in the light emitting region  623 . The method further includes forming the n-electrode  640  in the non-emission region  625  such that the n-electrode  640  in the first portion  625   a  of the non-emission region  625  is electrically coupled to the n-type semiconductor layer  622  through the ohmic contact  652 , while the n-electrode  640  in the second portion of the non-emission region  625  is electrically coupled to the n-type semiconductor layer  622  directly. Together with or after the n-electrode  640  is formed, forming a p-electrode  630  on the transparent conductive layer  628  such that the p-electrode  630  is electrically coupled to the p-type semiconductor layer  626  through the transparent conductive layer  628 . 
     In sum, the present invention, among other things, recites a light emitting device having an insulator and/or an epitaxial structure formed under an n-electrode such that a current flowing path between an n-electrode finger and one adjacent p-electrode finger is substantially same as that between the ohmic contact under the wire connection pad and the adjacent p-electrode finger, which results in the uniformity in the current density of the light emitting device. Accordingly, the brightness (intensity) of light emitted from the light emitting device is uniform over the light emitting region of the light emitting device. 
     The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching. 
     The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to activate others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.