SEMICONDUCTOR LIGHT-EMITTING DEVICE

The present invention relates to a semiconductor light emitting device, and more particularly, to a light emitting device with an increased reliability in light emitting areas in the manufacture of multiple light emitting units that are electrically connected to each other. In the semiconductor light emitting device according to the present invention, at least one of the first upper electrode or the second upper electrode is configured to be electrically connected to the first pad electrode or the second pad electrode, respectively, at least partially on the upper portions of the respective light emitting units that are at least partially covered by the first pad electrode or the second pad electrode.

FIELD

The present disclosure generally relates to a semiconductor light emitting device, and more particularly, to a light emitting device with an increased reliability in light emitting areas in the manufacture of multiple light emitting units that are electrically connected to each other.

BACKGROUND

FIG.1shows an example of a semiconductor light emitting device disclosed in U.S. Pat. No. 7,262,436, wherein the semiconductor light emitting device comprises a substrate100, an n-type semiconductor layer300grown on the substrate100, an active layer400grown on the n-type semiconductor layer300, a p-type semiconductor layer500grown on the active layer400, electrodes901,902,903formed on the p-type semiconductor layer500to serve as reflective films, and an n-side bonding pad800, also serving as an electrode, formed on an etched and exposed portion of the n-type semiconductor layer300.

A chip having this configuration, i.e., with all of the electrodes901,902and903and the electrode800being formed on one side of the substrate100and the electrodes901,902and903functioning as reflective films, is called a flip chip. The electrodes901,902,903are comprised of the electrode901having high reflectivity (e.g., Ag), the electrode903for bonding (e.g., Au) and the electrode902(e.g., Ni) for preventing diffusion between a material of the electrode901and a material of the electrode903. While this metal reflective film structure exhibits a high reflectance and is advantageous for current spreading, light absorption by the metal needs to be overcome.

FIG.2shows an example of a semiconductor light emitting device disclosed in Japanese Patent Application Publication No. 2006-120913, wherein the semiconductor light emitting device comprises a substrate100, a buffer layer200grown on the substrate100, an n-type semiconductor layer300grown on the buffer layer200, an active layer400grown on the n-type semiconductor layer300, a p-type semiconductor layer500grown on the active layer400, a light transmitting conductive film600formed on the p-type semiconductor layer500for current spreading, a p-side bonding pad700formed on the light transmitting conductive film600, and an n-side bonding pad800formed on an etched exposed portion of the n-type semiconductor layer300. Further, a DBR (Distributed Bragg Reflector)900and a metal reflective film904are provided on the light transmitting conductive film600. While this configuration reduces light absorption by the metal reflective film904, current diffusion is relatively poor, compared to using the electrodes901,902,903.

FIG.3shows an example of serially connected LEDs A, B disclosed in U.S. Pat. No. 6,547,249, where a plurality of LEDs is used in series connection due to various advantages. For example, by connecting the LEDs A, B in series, the number of external circuits and wire connections may be reduced, and the light absorption loss due to the wires may be lowered. Moreover, the power supply circuit can be further simplified as the total operating voltage of these serially connected LEDs A, B increases.

To connect these LEDs A, B in series, an interconnector34is usually deposited that connects the p-side electrode32and the n-side electrode32of neighboring LEDs A, B. However, it is not easy to form the interconnector34because, during the isolation process where the plurality of LEDs A, B is electrically insulated and the semiconductor layers are etched to expose a sapphire substrate20, the etch depth is large, taking more time, and the step height is also large. An insulating layer30may be used to for the interconnector34with a gentle slope as illustrated inFIG.3, the LEDs A, B may be spaced farther apart, which can cause problems with integration improvement.

FIG.4shows an example of an LED array disclosure in U.S. Pat. No. 7,417,259, where LEDs are arranged in a two-dimensional pattern on the insulating substrate for high drive voltage and low current operation. The insulating substrate used is a monolithic sapphire substrate, and two LED arrays are connected in inverse parallel on the substrate. Therefore, AC power can be used directly as the driving power.

SUMMARY

According to one aspect of the present disclosure, there is provided a semiconductor light emitting device, comprising: a first array of light emitting units1000comprising a first light emitting unit101and a second light emitting unit102spaced apart from each other on a substrate10; a second array of light emitting units2000comprising a third light emitting unit103and a fourth light emitting unit104spaced apart from each other on the substrate10; a first pad electrode70aelectrically connected to the first light emitting unit101; a second pad electrode70belectrically connected to the fourth light emitting unit104; a first upper electrode80aprovided above and electrically connected to the first pad electrode70a; and a second upper electrode80bprovided above and electrically connected to the second pad electrode70b, wherein each of the first to fourth light emitting units101,102,103,104includes a first semiconductor layer30having a first conductivity, a second semiconductor layer50having a second conductivity different from the first conductivity, and an active layer40interposed between the first semiconductor layer30and the second semiconductor layer50for generating light by recombination of electrons and holes, and wherein the first to fourth light emitting units101,102,103,104are electrically connected to one another, and the first pad electrode70ais arranged to cover both the first and second light emitting units101,102.

DETAILED DESCRIPTION

FIG.5shows a three-dimensional schematic view of a semiconductor light emitting device according to one embodiment of the present invention, andFIG.6shows a schematic side view of a semiconductor light emitting device according to one embodiment of the present invention.

Referring toFIGS.5and6, the semiconductor light emitting device may include a first array of light emitting units1000comprising a first light emitting unit101and a second light emitting unit102spaced apart from each other on a substrate10, a second array of light emitting units2000comprising a third light emitting unit103and a fourth light emitting unit104spaced apart from each other on the substrate10, a first pad electrode70aelectrically connected to the first light emitting unit101, a second pad electrode70belectrically connected to the fourth light emitting unit104, a first upper electrode80aprovided above and electrically connected to the first pad electrode70a, and a second upper electrode80bprovided above and electrically connected to the second pad electrode70b. Here, each of the first to fourth light emitting units101,102,103,104includes a first semiconductor layer30having a first conductivity, a second semiconductor layer50having a second conductivity different from the first conductivity, and an active layer40interposed between the first semiconductor layer30and the second semiconductor layer50for generating light by recombination of electrons and holes. The first to fourth light emitting units101,102,103,104are electrically connected to one another, and the first pad electrode70amay be arranged to cover both the first and second light emitting units101,102.

The semiconductor light emitting device according to one embodiment of the present invention may comprise a first array of light emitting units1000including a first light emitting unit101and a second light emitting unit102spaced apart from each other on the substrate; and a second array of light emitting units2000including a third light emitting unit103and a fourth light emitting unit104spaced apart from each other on the substrate.

The first to fourth light emitting units101,102,103,104may be electrically connected to one another.

Each of the first to fourth light emitting units101,102,103,104may have a plurality of semiconductor layers, comprising: a first semiconductor layer30having a first conductivity, a second semiconductor layer50having a second conductivity different from the first conductivity, and an active layer40interposed between the first semiconductor layer30and the second semiconductor layer50for generating light by recombination of electrons and holes.

The substrate10may be made of sapphire, SiC, Si, GaN or the like, which is eventually removed.

The plurality of semiconductor layers may be comprised of a buffer layer (not shown) formed on the substrate10, the first semiconductor layer30having a first conductivity (e.g. a Si-doped GaN layer), the second semiconductor layer50having a second conductivity different from the first conductivity (e.g. a Mg-doped GaN layer), and the active layer40interposed between the first semiconductor layer30and the second semiconductor layer50for generating light by recombination of electrons and holes (e.g. an InGaN/(In)/GaN layer with the multiple quantum well (MQW) structure). Each semiconductor layer may be formed of a multi-layered structure, and the buffer layer may be omitted. The positions of the first and second semiconductor layers30,50can be swapped. Additionally, the first and second semiconductor layers30,50may be made of GaN in the case of Group 3 nitride semiconductor light emitting devices.

The semiconductor light emitting device according to one embodiment of the present invention may comprise the first pad electrode70aelectrically connected to the first light emitting unit101, and the second pad electrode70belectrically connected to the fourth light emitting unit104, as shown inFIGS.5and6.

To elaborate on this by referring back toFIGS.5and6, the first pad electrode70amay be in electrical communication with the first semiconductor layer30of the first light emitting unit101by a first electrical connection71athat passes through the second semiconductor layer50and the active layer40, among the plurality of semiconductor layers. Likewise, the second pad electrode70bmay be in electrical communication with the second semiconductor layer50of the fourth light emitting unit104by a second electrical connection71b.

As will be describe later, when an insulating layer35is provided between the plurality of light emitting units, the first electrical connection71aand the second electrical connection71bpass through the insulating layer35to be in electrical communication with the first semiconductor layer30of the first light emitting unit101and the second semiconductor layer50of the fourth light emitting unit104, respectively,

That is, the first pad electrode70aand the second pad electrode70bmay be in electrical communication with the first semiconductor layer30of the first light emitting unit101and the second semiconductor layer50of the fourth light emitting unit104by the first electrical connection71aand the second electrical connection71b, respectively, that pass through the insulating layer35(to be described below).

In another embodiment of the present invention, the first pad electrode70amay be disposed to cover both the first light emitting part101and the second light emitting part102. Similarly, the second pad electrode70bmay be disposed to cover both the third light emitting part103and the fourth light emitting part104.

This configuration of the pad electrode70mitigates impacts or scratches between the chip surface and the multi-layers that can occur during the die bonding process. In this way, potential defects that may occur in the process of manufacturing can be monitored and prevented. Moreover, it is possible to improve the reliability by reducing weak/non-lighting in some of the light emitting areas that are observed in the HV (High-Voltage) chip structure.

As mentioned earlier, the semiconductor light emitting device according to the present invention may include the first upper electrode80aprovided above and electrically connected to the first pad electrode70a, and the second upper electrode80bprovided above and electrically connected to the second pad electrode70b.

To elaborate on this by referring again toFIGS.5and6, the first upper electrode80ais disposed above the first pad electrode70aand electrically connected to the first pad electrode70a. That is, the first upper electrode80acan be arranged such that it can cover the first pad electrode70a. Likewise, the second upper electrode80bis disposed above the second pad electrode70band electrically connected to the second pad electrode70b. That is, the second upper electrode80bcan be arranged such that it can cover the second pad electrode70b.

In another embodiment, the first upper electrode80amay be disposed on the first pad electrode70a, above the first and second light emitting units101,102. Likewise, the second upper electrode80bmay be disposed on the second pad electrode70b, above the third and fourth light emitting units103,104.

In another embodiment, the electrode connection81formed above each of the first and second light emitting units101,102serves to electrically connect the first upper electrode80aand the first pad electrode70a. Likewise, the electrode connection81formed above each of the third and fourth light emitting units103,104serves to electrically connect the second upper electrode80band the second pad electrode70b.

To elaborate on this by referring again toFIGS.5and6, in the upper portions of the respective first and second light emitting units101,102, the first pad electrode70ais arranged to cover both the first light emitting unit101and the second light emitting unit102, and the first upper electrode80adisposed above the first pad electrode70ais configured to be electrically connected to the first pad electrode70a. As illustrated inFIGS.5and6, above each of the first and second light emitting units101,102, the first upper electrode80aand the first pad electrode70aare electrically connected to each other by the first electrode connection81a.

Likewise, in the upper portions of the third and fourth light emitting units103,104, the second pad electrode70bis arranged to cover both the third light emitting unit103and the fourth light emitting unit104, and the second upper electrode80bdisposed above the second pad electrode70bis configured to be electrically connected to the second pad electrode70b. As illustrated inFIGS.5and6, above each of the third and fourth light emitting units103,104, the second upper electrode80band the second pad electrode70bare electrically connected to each other by the second electrode connection81b.

The semiconductor light emitting device of the present invention may further include a first connecting electrode92for electrically connecting the first light emitting unit101and the second light emitting unit102. This first connecting electrode92also electrically connects the third light emitting unit103and the fourth light emitting unit104.

Referring again toFIGS.5and6, the first connecting electrode92includes a first lower connection92a, a first horizontal connection92c, and a second lower connection92b.

The first horizontal connection92cis positioned across the upper portions of the respective first and second light emitting unit101,102. The first lower connection92aelectrically connects one end of the first horizontal connection92cto the second semiconductor layer50of the first light emitting unit101. The second lower connection92belectrically connects the other end of the first horizontal connection92cto the first semiconductor layer30of the second light emitting unit102.

When the insulating layer35is provided between the first light emitting unit101and the second light emitting unit102, the first lower connection92aand the second lower connection92bmay pass through the insulating layer35to be in electrical communication with the second semiconductor layer50of the first light emitting unit101and with the first semiconductor layer30of the second light emitting unit102, respectively.

In another embodiment, the first horizontal connection92ccan be formed on a layer at the same height as the first pad electrode70a.

In a further embodiment of the semiconductor light emitting device, the first pad electrode70ais positioned across a central region in the upper portions of the respective first and second light emitting units101,102to cover both the first light emitting unit101and the second light emitting unit102, and the first horizontal connection92cmay be positioned at a distance from the first pad electrode70a, along the left and/or right edges in the upper portions of the respective first and second light emitting units101,102.

To elaborate on this by referring back toFIGS.5and6, the first pad electrode is positioned across a central region in the upper portions of the respective first and second light emitting units101,102, such that it may cover both the first light emitting unit101and the second light emitting unit102. In this case, the first horizontal connection92cis spaced from the first pad electrode70aby a certain distance, along the left and/or right edges in the upper portions of the respective first and second light emitting units101,102(i.e., along the shorter sides), and electrically connects the first light emitting unit101and the second light emitting unit102.

Likewise, the second pad electrode70bis positioned across a central region in the upper portions of the third and fourth light emitting units103,104, such that it may cover both the third light emitting unit103and the fourth light emitting unit104. In this case, the first horizontal connection92cis spaced from the second pad electrode70bby a certain distance, along the left and/or right edges in the upper portions of the third light emitting unit103and the fourth light emitting unit104(i.e., along the shorter sides), and electrically connects the third light emitting unit103and the fourth light emitting unit104.

Additionally, the first horizontal connection92cof the first connecting electrode92may be formed on a layer at the same height as the pad electrode70. Thus, when the pad electrode70is disposed to cover both the first light emitting unit101and the second light emitting unit102, the first horizontal connection92cof the first connecting electrode92may be formed on a layer at the same height as the pad electrode70to electrically connect the first light emitting unit101and the second light emitting unit102. While the first horizontal connection92cof the first connecting electrode92is formed on a layer at the same height as the pad electrode70, they are both electrically insulated from each other, i.e., they are arranged not to be overlapped with each other.

In another embodiment of the semiconductor light emitting device, a first branched finger electrode75amay be formed on the second semiconductor layer50of the first light emitting unit101, in the horizontal direction relative to the second semiconductor layer50. Likewise, a second branched finger electrode75bmay be formed on the first semiconductor layer30of the second light emitting unit102, in the horizontal direction relative to the first semiconductor layer30.

In a preferred embodiment, the first branched finger electrode75aand/or the second branched finger electrode75bmay be arranged such that they are covered by the first pad electrode70aand the first upper electrode80a.

As illustrated inFIGS.5and6, the first branched finger electrode75amay be formed on the second semiconductor layer50, extending outwards from the bottom of the first lower connection92a, and the second branched finger electrode75bmay be formed on the first semiconductor layer30, extending outwards from the bottom of the second lower connection92b.

In a preferred embodiment, when the first horizontal connection92cof the first connecting electrode92is formed along the left and/or right edges of the respective light emitting units (i.e., along the shorter sides), the second branched finger electrode75bmay be formed such that it interconnects between the second lower connections92bof the first connecting electrodes92formed along the left and/or right edges of the respective light emitting units.

Another embodiment of the semiconductor light emitting device may further include a second connecting electrode92′ for connecting the second light emitting unit102and the third light emitting unit103. This second connecting electrode92′ may include a first-a lower connection92a′, a second horizontal connection92c′ and a second-a lower connection92b′.

The second horizontal connection92c′ is positioned across the upper portions of the second light emitting unit102and the third light emitting unit103. The first-a lower connection92a′ electrically connects one end of the second horizontal connection92c′ to the second semiconductor layer50of the second light emitting unit102. The second-a lower connection92b′ electrically connects the other end of the second horizontal connection92c′ to the first semiconductor layer30of the third light emitting unit103.

The second horizontal connection92c′ may be formed on a layer at the same height as the first pad electrode70a, on an upper portion of the second light emitting unit102that is not covered by the first pad electrode70a.

Further, the second horizontal connection92c′ may be formed on a layer at the same height as the second pad electrode70b, on an upper portion of the third light emitting unit103that is not covered by the second pad electrode70b.

FIG.7shows a schematic top view of a semiconductor light emitting device according to one embodiment of the present invention.

Referring toFIG.7, the semiconductor light emitting device may include a first array of light emitting units comprising a first light emitting unit101, a second light emitting unit102and a third light emitting unit103that are spaced apart from one another on the substrate, a second array of light emitting units comprising a fourth light emitting unit104, a fifth light emitting unit105and a sixth light emitting unit106that are spaced apart from each other on the substrate, a first pad electrode70aelectrically connected to the first light emitting unit101, a second pad electrode70belectrically connected to the sixth light emitting unit106, a first upper electrode80aprovided above and electrically connected to the first pad electrode70a, and a second upper electrode80bprovided above and electrically connected to the second pad electrode70b.

Other components of the semiconductor light emitting device inFIG.7have similar functions and features as described above with reference toFIGS.5and6, except that a second connecting electrode92′ for connecting the third light emitting unit103and the fourth light emitting unit104is additionally included. The second connecting electrode92′ may include a first-a lower connection92a′, a second horizontal connection92c′, and a second-a lower connection92b′. The lower connections are not shown inFIG.7.

The second horizontal connection92c′ is positioned across the upper portions of the third and fourth light emitting units103,104. The first-a lower connection92a′ electrically connects one end of the second horizontal connection92c′ to the second semiconductor layer50of the third light emitting unit103. The second-a lower connection92b′ electrically connects the other end of the second horizontal connection92c′ to the first semiconductor layer30of the fourth light emitting unit104.

The second horizontal connection92c′ may be formed on a layer at the same height as the first pad electrode70a, on an upper portion of the third light emitting unit103that is not covered by the first pad electrode70a.

Further, the second horizontal connection92c′ may be formed on a layer at the same height as the second pad electrode70b, on an upper portion of the fourth light emitting unit104that is not covered by the second pad electrode70b.

The following will now describe a method for manufacturing a semiconductor light emitting device (for example, a Group III nitride semiconductor light emitting device) according to one embodiment of the present invention.

First, a plurality of semiconductor layers30,40,50is formed on a substrate10, and individual light emitting units are isolated by mesa etching, for example. In this embodiment, the semiconductor light emitting device comprises a first to a fourth light emitting unit101,102,103,104. Additionally, or alternatively, the number of light emitting units can vary. For example, three or at least five light emitting units can be provided.

In each light emitting unit, a trench is formed by removing the surrounding area of the plurality of semiconductor layers30,40,50. Thus, each light emitting unit itself is electrically isolated or insulated from each other. In this embodiment, each light emitting unit may have a substantially rectangular shape when viewed from above, so that one side (which is often referred to as the length) faces its opposite side. One pair of opposite sides are longer (i.e., longer sides) than the other pair (i.e., shorter sides).

Next, an insulating layer35is formed between the plurality of light emitting units. The insulating layer35in this embodiment may be formed under the first horizontal connection92cof the first connecting electrode92. The insulating layer35is a passivation layer having light-transmitting properties that is made of a material such as SiO2, TiO2, Al2O3or the like, preferably in-between the entire light emitting units facing each other. In the case of a semiconductor light emitting device operating at a high voltage, if the space between the neighboring light emitting units is narrow, it is advantageous to form the insulating layer35for electrical insulation as in this embodiment, by connecting the plurality of light emitting devices in series. Additionally, as the insulating layer35extends to an exposed portion of the substrate10at the edges of the light emitting units, it may further enhance the reliability of electrical insulation and may help to alleviate or even out any unevenness (e.g. step) or height differences when forming the insulating reflective layer R (to be described later).

A branched finger electrode75and an ohmic electrode72, which will be described later, may be formed over the second semiconductor layer50. Also, it is desirable to have a light absorption barrier under the electrodes to reflect light or to prevent the current from flowing directly below the electrodes. In this embodiment, the insulating layer35can also serve as a light absorption barrier as it is extended.

Once the insulating layer35is formed, a current spreading conductive layer can be formed on top of the second semiconductor layer50. When this p-type second semiconductor layer50is made of GaN, the current spreading conductive layer can be very helpful as P-type GaN is known to have a poor current spreading ability. Exemplary materials for the current spreading conductive layer include ITO, Ni/Au or the like.

To continue, the first connecting electrode92, the branched finger electrode75and the ohmic electrode72are formed.

The first connecting electrode92in each of the light emitting units is formed using the same process. The first connecting electrode92for connecting the first light emitting unit101and the second light emitting unit102includes, for example, a first lower connection92a, a first horizontal connection92c, and a second lower connection92b.

The insulating layer35has an opening in which the first lower connection92ais formed. The second lower connection92bis formed in another opening present in the insulating layer35, the second semiconductor layer50and the active layer40. The first horizontal connection92cis formed on the insulating layer35such that it covers the upper portions of the respective first and second light emitting units101,102. As such, the first lower connection92ais configured to pass through the insulating layer35to electrically connect the first horizontal connection92cto the first semiconductor layer30of the first light emitting unit101, while the second lower connection92bis configured to pass through the insulating layer35, the second semiconductor layer50and the active layer to electrically connect the first horizontal connection92cto the second semiconductor layer50of the second light emitting unit102. Moreover, the first horizontal connection92cof the first connecting electrode92may be formed on a layer at the same height as a layer on which the pad electrode70is formed (to be described later).

In particular, the first horizontal connection92cof the first connecting electrode92may be formed on a layer at the same height as the first pad electrode70a(to be described later), along the left and/or right edges (i.e., along the shorter sides) of each of the first and second light emitting units101,102in the longitudinal direction where the first light emitting unit101and the second light emitting unit102are connected, thereby electrically connecting the first light emitting unit101and the second light emitting unit102.

Referring back toFIG.5, the second light emitting unit102and the third light emitting unit103may be electrically connected by a second connecting electrode92′. The second horizontal connection92c′ of the second connecting electrode92′ that electrically connects the second light emitting unit102and the third light emitting unit103may be formed on a layer at the same height as the first pad electrode70aand the second pad electrode70b, along the longer sides of each of the second and third light emitting units102,103that are not covered by the first and second pad electrodes70a,70b.

Additionally, the branched finger electrode75is formed at the bottom of each of the first and second lower connections92a,92bof the first connecting electrode92. In particular, in the case of the first light emitting unit101and the second light emitting unit102, for example, a first branched finger electrode72ais formed at the bottom of the first lower connection92aand over the second semiconductor layer50. Likewise, a second branched finger electrode75bis formed at the bottom of the second lower connection92band over the first semiconductor layer30.

In another embodiment, the first horizontal connection92cof the first connecting electrode92is formed along the left and/or right edges (i.e., along the shorter sides) of each of the light emitting units, and in this case the second branched finger electrode75bis formed such that it interconnects between the second lower connections92bof the first connecting electrodes92formed along the left and/or right edges of the respective light emitting units.

In another embodiment, the first and second branched finger electrodes75a, are formed such that they are partly covered by a pad electrode70and an upper electrode (to be described later). In a preferred embodiment, the first and second branched finger electrodes75a,75bmay be arranged vertically below the pad electrode and the upper electrode80.

The pad electrode70is formed on a layer at the same height as the first horizontal connection92cof the first connecting electrode92. A first electrical connection71ais provided into an opening that is formed in the insulating layer35, second semiconductor layer50and active layer40of the first light emitting unit101. A second electrical connection71bis provided into an opening that is formed in the insulating layer of the fourth light emitting unit104. As such, the first pad electrode70acan be in electrical communication with the first semiconductor layer30of the first light emitting unit101, by the first electrical connection71athat passes through the insulating layer35, second semiconductor layer50and active layer40of the first light emitting unit101. Likewise, the second pad electrode70bcan be in electrical communication with the second semiconductor layer50of the fourth light emitting unit104, by the second electrical connection71bthat passes through the insulating layer35of the second pad electrode70b.

The ohmic electrode72is formed on the upper portions of the respective first and second semiconductor layers30,50, and the first electrical connection71aand the second electrical connection71bare each connected to this ohmic electrode72. Optionally, the ohmic electrode72may be omitted but is preferably provided to reduce contact resistance and to ensure the stability of electrical connection.

The first pad electrode70ais arranged to cover both the first light emitting unit101and the second light emitting unit102that are electrically connected to each other. The second pad electrode70bis arranged to cover both the third light emitting unit103and the fourth light emitting unit104that are electrically connected to each other.

The first horizontal connection92cof the first connecting electrode92and the pad electrode70are electrically insulated from each other on the layers of the same height, and they are arranged not to overlap each other.

In addition, the first pad electrode70ais positioned across a central region of the upper portions of the respective first and second light emitting units101,102, such that it may cover both the first light emitting unit101and the second light emitting unit102. Here, the first horizontal connection92cof the first connecting electrode92is formed along the left and/or right edges (i.e., along the shorter sides) of each of the first light emitting unit101and the second light emitting unit102, in the longitudinal direction where the first light emitting unit101and the second light emitting unit102are electrically connected. Also, the first horizontal connection92cof the first connecting electrode92is formed on a layer at the same height as the first pad electrode70a, thereby electrically connecting the first light emitting unit101and the second light emitting unit102. Likewise, the second pad electrode70bis positioned across a central region of the upper portions of the third and fourth light emitting units103,104, along the left and/or right edges (i.e., along the shorter sides) of each of the third light emitting unit103and the fourth light emitting unit104, in the longitudinal direction where the third light emitting unit103and the fourth light emitting unit104are electrically connected. Also, the second pad electrode is formed on a layer at the same height as the second pad electrode70b, thereby electrically connecting the third light emitting unit103and the fourth light emitting unit104.

An insulating reflective layer R is then formed to cover the plurality of semiconductor light emitting units, the insulating layer35, the first horizontal connection92cof the first connecting electrode92, and the pad electrode70.

The insulating reflective layer R reflects light from the active layer40towards the substrate10. In this embodiment, the insulating reflective layer R is made of an insulating material to reduce light absorption by the metal reflective film. Additionally, or optionally, the insulating reflective layer R may be a single layer, but it preferably has a structure of multilayers sequentially stacked, including a DBR (Distributed Bragg Reflector) or ODR (Omni-Directional Reflector). For example, the insulating reflective layer R may include a dielectric layer, a DBR layer, and a clad layer,

It should be more cautious when forming the insulating reflective layer R due to possible structural features such as height differences present in the structures below the insulating reflective layer R, for example, height differences between the plurality of light emitting units and its surrounding area, or uneven structures due to the first connecting electrode92, the branched finger electrode75and the ohmic electrode72. For example, when the insulating reflective layer R is a multi-layered structure including the DBR, each material layer should have a specially designed thickness for the insulating reflective layer R to function well. In one example, the DBR may be composed of repeatedly stacked layers of SiO2/TiO2, SiO2/Ta2O2, or SiO2/HfO. The SiO2/TiO2layers provide good reflection efficiency for blue light, while the SiO2/Ta2O2or SiO2/HfO layers provide good reflection efficiency for UV light. The DBR is preferably obtained by PVD (Physical Vapor Deposition), in particular, E-Beam Evaporation, sputtering, or thermal evaporation. Before depositing the DBR, which requires high precision, forming a dielectric layer of a certain thickness can help stabilize the manufacturing process of the DBR and improve light reflection. A suitable material for the dielectric layer may be SiO2, with a thickness ranging from 0.2 μm to 1.0 μm. The clad layer may be made of Al2O3, SiO2, SiON, MgF, CaF, or the like. For example, the total thickness of the insulating reflective layer R may range from 1 μm to 8 μm, for example.

Subsequently, an opening is formed in the insulating reflective layer R, an electrode connection is formed in the opening, and a first upper electrode80aand a second upper electrode80bare formed on the insulating reflective layer R.

The first upper electrode80aand the second upper electrode80bare arranged to cover the first pad electrode70aand the second pad electrode70b, respectively. Also, the first upper electrode80aand the second upper electrode80bare connected to the first pad electrode70aand the second pad electrode70bby a first electrode connection81aand a second electrode connection81b, respectively. The first upper electrode80aand the second upper electrode80bare positioned only on top of the first pad electrode70aand the second pad electrode70b, respectively.

Furthermore, the first pad electrode70ais arranged to cover both the first light emitting unit101and the second light emitting unit102. In this case, the first upper electrode80ais formed to be electrically connected to the first pad electrode70aby the first electrode connection81a, in the upper portions of the respective first and second light emitting units101,102, respectively. In other words, a plurality of openings is formed in the insulating reflective layer R present in the upper portions of the respective first and second light emitting units101,102, the first electrode connection81ais formed in each opening, and the first upper electrode80ais formed on the insulating reflective layer R.

Likewise, the second pad electrode70bis arranged to cover both the third light emitting unit103and the fourth light emitting unit104. In this case, the second upper electrode80bis formed to be electrically connected to the second pad electrode70bby the second electrode connection81b, in the upper portions of the third and fourth light emitting units103,104, respectively. In other words, a plurality of openings is formed in the insulating reflective layer R present in the upper portions of the respective third and fourth light emitting units103,104, the second electrode connection81bis formed in each opening, and the second upper electrode80bis formed on the insulating reflective layer R.

The electrode connection and the upper electrode can be formed together in the same process.

In this embodiment, the semiconductor light emitting device is a flip chip, in which the upper electrode is provided on the opposite side of the plurality of serially semiconductor layers30,40,50with respect to the insulating reflective layer R, and a plurality of light emitting units is serially connected.

Throughout the description and claims, the terms “comprise”, “including”, “having”, and “contain” and their variations should be understood as meaning “including but not limited to” and are not intended to exclude other components unless specifically so stated.

It will be appreciated that variations to the embodiments of the invention can be made while still falling within the scope of the invention. Alternative features serving the same, equivalent or similar purpose can replace features disclosed in the specification, unless stated otherwise. Thus, unless stated otherwise, each feature disclosed represents one example of a generic series of equivalent or similar features.

Set out below are clauses that describe diverse features of further aspects of the present disclosure.(1) A semiconductor light emitting device, comprising: a first array of light emitting units comprising a first light emitting unit and a second light emitting unit spaced apart from each other on a substrate; a second array of light emitting units comprising a third light emitting unit and a fourth light emitting unit spaced apart from each other on the substrate; a first pad electrode electrically connected to the first light emitting unit; a second pad electrode electrically connected to the fourth light emitting unit; a first upper electrode provided above and electrically connected to the first pad electrode; and a second upper electrode provided above and electrically connected to the second pad electrode, wherein, each of the first to fourth light emitting units includes a first semiconductor layer having a first conductivity, a second semiconductor layer having a second conductivity different from the first conductivity, and an active layer interposed between the first semiconductor layer and the second semiconductor layer for generating light by recombination of electrons and holes, the first to fourth light emitting units are electrically connected to one another, and the first pad electrode is arranged to cover both the first and second light emitting units.(2) There is also provided, the semiconductor light emitting device of clause (1), wherein the first upper electrode is disposed above the first pad electrode in the upper portions of the respective first and second light emitting units.(3) There is also provided, the semiconductor light emitting device of clause (2), wherein the first upper electrode and the first pad electrode are electrically connected by an electrode connection formed in the upper portion of each of the first and second light emitting units.(4) There is also provided, the semiconductor light emitting device of clause (1) or clause (2), further comprising: a first connecting electrode for electrically connecting the first light emitting unit and the second light emitting unit, wherein the first connecting electrode includes a first lower connection, a first horizontal connection, and a second lower connection, the first horizontal connection is positioned across the upper portions of the respective first and second light emitting units, the first lower connection electrically connects one end of the first horizontal connection to the second semiconductor layer of the first light emitting unit, and the second lower connection electrically connects the other end of the first horizontal connection to the first semiconductor layer of the second light emitting unit.(5) There is also provided, the semiconductor light emitting device of clause 4, wherein the first horizontal connection and the first pad electrode are formed on layers having the same height.(6) There is also provided, the semiconductor light emitting device of clause (4), wherein the first pad electrode is positioned across a central region in the upper portions of the respective first and second light emitting units to cover both the first light emitting unit and the second light emitting unit, and the first horizontal connection is positioned at a distance from the first pad electrode, along the left and/or right edges in the upper portions of the respective first and second light emitting units.(7) There is also provided, the semiconductor light emitting device of clause (4), further comprising: a first branched finger electrode formed in the horizontal direction on the second semiconductor layer of the first light emitting unit, and/or a second branched finger electrode formed in the horizontal direction on the first semiconductor layer of the second light emitting unit, wherein the first branched finger electrode and/or the second branched finger electrode is arranged to be covered by the first pad electrode and the first upper electrode.(8) There is also provided, the semiconductor light emitting device of clause (4), further comprising: a second connecting electrode for connecting the second light emitting unit and the third light emitting unit, wherein the second connecting electrode includes a first-a lower connection, a second horizontal connection, and a second-a lower connection, the second horizontal connection is positioned across the upper portions of the respective second and third light emitting units, the first-a lower connection electrically connects one end of the second horizontal connection to the second semiconductor layer of the second light emitting unit, the second-a lower connection electrically connects the other end of the second horizontal connection to the first semiconductor layer of the third light emitting unit, and the second horizontal connection is formed on a layer at the same height as the first pad electrode, in an upper portion of the second light emitting unit that is not covered by the first pad electrode.