This application claims the priority benefit of Taiwan application serial no. 100117781, filed on May 20, 2011. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
1. Field of the Invention
The invention generally relates to a light-emitting structure, and more particularly, to a semiconductor light-emitting structure.
2. Description of Related Art
Along with the progress of photoelectric technology, the fabrication and the application of a light-emitting diode (LED) has gradually reached their ripe stage. Since
LEDs have advantages of low pollution, low power consumption, short response time and long lifetime, so that LEDs have been gradually applied in various fields of light source or illumination to substitute traditional light-emitting components such as fluorescent lamp, incandescent bulb or halogen bulb. Around the world, environmental awareness is growing and growing and thus it can be expected the LEDs would become the major illumination light source in the future to substitute the current position of the fluorescent lamp.
In general speaking, the LED's electrode disposing way can be categorized into horizontal disposing way and vertical disposing way, in which the horizontal disposing way means the two positive and negative electrodes are disposed at a same side of an LED epitaxy structure, while the vertical disposing way means the two positive and negative electrodes are respectively disposed at two opposite sides of an LED epitaxy structure. In more details, in an LED structure with the horizontal disposing way of its electrodes, the positive electrode is disposed on a p-type semiconductor layer, while the negative electrode is disposed on an n-type semiconductor layer, and the two electrodes are not overlapped with each other on a direction perpendicularly to the light-emitting layer thereof. Usually, the two electrodes are made of non-transparent metal. When the distribution area of the two electrodes is small, the situation that the light emitted from the light-emitting layer is blocked by the two electrodes can be reduced and the light extraction rate can be accordingly not decreased, however, the current flowing from the p-type semiconductor layer to the n-type semiconductor layer would be excessively concentrated in a small area between the two electrodes. As a result of excessively concentrated current distribution, it leads to non-uniformity of the emitted light and to heat-dissipation difficulty and easier damage of the LED due to the excessively concentrated heat produced during the current passing, and the LED's light-emitting efficiency is reduced. On the other hand, when the distribution range between the two electrodes is increased by design, the excessively concentrated current distribution problem can be lightened, but the electrodes would block too much light, which leads to largely reducing the light extraction rate.
Accordingly, the invention is directed to a semiconductor light-emitting structure capable of effectively advancing the uniformity of the exiting light.
An embodiment of the invention provides a semiconductor light-emitting structure, which includes a substrate, a first doped type semiconductor layer, a light-emitting layer, a second doped type semiconductor layer, a first electrical transmission layer and at least one first conductor. The first doped type semiconductor layer is disposed over the substrate. The light-emitting layer is disposed over the first doped type semiconductor layer and the second doped type semiconductor layer is disposed over the light-emitting layer. The first electrical transmission layer is disposed on the first doped type semiconductor layer, in which a first interface is formed between the first electrical transmission layer and the first doped type semiconductor layer. The first conductor is disposed on the first doped type semiconductor layer. A second interface is formed between the first conductor and the first doped type semiconductor layer, and the resistance of the second interface is less than the resistance of the first interface.
Another embodiment of the invention also provides a semiconductor light-emitting structure, which includes a substrate, an n-type semiconductor layer, a light-emitting layer, a p-type semiconductor layer, a first electrical transmission layer and at least one first conductor. The n-type semiconductor layer is disposed over the substrate. The light-emitting layer is disposed over the n-type semiconductor layer and the p-type semiconductor layer is disposed over the light-emitting layer. The first electrical transmission layer is disposed on the n-type semiconductor layer. The first conductor is disposed on the n-type semiconductor layer and passes through the first electrical transmission layer to connect the n-type semiconductor layer.
In the semiconductor light-emitting structure of the embodiments of the invention, the first electrical transmission layer connected to the first conductors serves as an extension of the first conductors, so that the semiconductor light-emitting structure of the embodiments of the invention can make the current more dispersed. In this way, the semiconductor light-emitting structure of the embodiments of the invention can effectively resolve the problem of non-uniform current distribution and thereby advance the light exiting efficiency.
Other objectives, features and advantages of the present invention will be further understood from the further technological features disclosed by the embodiments of the present invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
In the embodiment, the first electrical transmission layer 160 is disposed on the first doped type semiconductor layer 130, and the first conductors 170 are disposed on the first doped type semiconductor layer 130 and pass through the first electrical transmission layer 160 to connect the first doped type semiconductor layer 130. In the embodiment, the first conductors 170 are separately disposed on the first doped type semiconductor layer 130 and the first electrical transmission layer 160 connects the first conductors 170. In addition, in the embodiment, a first interface J1 is formed between the first electrical transmission layer 160 and the first doped type semiconductor layer 130, a second interface J2 is formed between each of the first conductors 170 and the first doped type semiconductor layer 130, and the resistance of the second interface J2 is less than the resistance of the first interface J1.
In the embodiment, each of the first conductors 170 passes through the first electrical transmission layer 160 and has a first end E1 and a second end E2 opposite to the first end E1. The first end E1 contacts the first doped type semiconductor layer 130 to form the second interface J2, while the second end E2 is exposed outside the first electrical transmission layer 160. In the embodiment, the first conductors 170 are, for example, respectively a metallic conductor. Taking an example, the metallic conductor is, for example, clad metal layers, which are, for example, chrome layer and gold layer sequentially-stacked from the position close to an end of the second interface J2 (the first end E1) to the position far away from another end of the second interface J2 (the second end E2), or, for example, chrome layer, platinum layer and gold layer sequentially-stacked from the position close to an end of the second interface J2 (the first end E1) to the position far away from another end of the second interface J2 (the second end E2), which the invention is not limited to. Moreover in the embodiment, the second interface J2 is, for example, an ohmic contact surface and the first interface J1 is, for example, a Schottky contact surface, which the invention is not limited to.
One of the first conductors 170 (for example, first conductor 172) in the embodiment is an electrode connecting external power serving for connecting an external conductive path, in which the volume of the electrode connecting external power is greater than the volume of each of the other first conductors 170. For example, the electrode connecting external power (the first conductor 172) can be electrically connected to an external power through a bonding wire 52; in other embodiments, the electrode connecting external power (the first conductor 172) can be electrically connected to an external power through a conductive bump or other conductive structures. In the embodiment, the disposing pattern of the first conductors 170 includes spot-shaped distribution pattern; in other embodiments however, the pattern of the first conductors 172 includes at least one of a line-shaped pattern, a mesh-shaped pattern and a spot-shaped pattern.
The first doped type semiconductor layer 130 of the embodiment includes a platform portion 132 and a sink portion 134, and the thickness of the platform portion 132 is greater than the thickness of the sink portion 134. The light-emitting layer 140 and the second doped type semiconductor layer 150 are disposed over the platform portion 132, while the first conductors 170 and the first electrical transmission layer 160 are disposed on the sink portion 134.
The semiconductor light-emitting structure 100 of the embodiment further includes a second electrical transmission layer 180 and a second conductor 190. The second electrical transmission layer 180 is disposed on the second doped type semiconductor layer 150 and the second conductor 190 passes through the second electrical transmission layer 180 to connect the second doped type semiconductor layer 150. In the embodiment, a third interface J3 is formed between the second electrical transmission layer 180 and the second doped type semiconductor layer 150, a fourth interface J4 is formed between the second conductor 190 and the second doped type semiconductor layer 150, and the resistance of the fourth interface J4 is greater than the resistance of the third interface J3.
In the embodiment, the second conductor 190 is, for example, a metallic conductor. Taking an example, the metallic conductor is, for example, clad metal layers, which are, for example, chrome layer and gold layer sequentially-stacked from the position close to an end of the fourth interface J4 to the position far away from another end of the fourth interface J4, or for example, chrome layer, platinum layer and gold layer sequentially-stacked from the position close to an end of the fourth interface J4 to the position far away from another end of the fourth interface J4, which the invention is not limited to.
In the embodiment, the second conductor 190 is an electrode connecting external power serving for connecting an external conductive path. For example, the second conductor 190 can be electrically connected to an external power through a bonding wire 54; in other embodiments, the second conductor 190 can be electrically connected to an external power through a conductive bump or other conductive structures.
The material of the first electrical transmission layer 160 and the second electrical transmission layer 180 of the embodiment includes transparent material or semi-transparent material. For example, the first electrically conductive layer 160 and the second electrically conductive layer 180 are respectively a transparent conductive layer, for example, respectively an indium tin oxide (ITO) layer after being annealed and the annealing processing temperature Ta meets the condition of 500° C.≦Ta≦600° C.
In the semiconductor light-emitting structure 100 of the embodiment, since the first electrical transmission layer 160 connected to the first conductors 170 is adopted for serving as an extension of the first conductors 170 to make the current more dispersed and the first electrical transmission layer 160 selects a transparent material or a semi-transparent material to allow light passing through, so that the semiconductor light-emitting structure 100 of the embodiment is advantageous in making the current more dispersed and not reducing the light extraction rate. In this way, the semiconductor light-emitting structure 100 of the embodiment can effectively advance the light efficiency and the light uniformity. In more details, holes C come from the second conductor 190 would dispersedly flow towards the first conductors 170 and the first electrical transmission layer 160, followed by flowing to the light-emitting layer 140 via the second doped type semiconductor layer 150. On the other hand, since the resistance of the second interface J2 is less than the resistance of the first interface J1, electrons C′ come from all the first conductors 170 (including the first conductor 172 serving as the electrode connecting external power and the other first conductors 174 except for the electrode connecting external power) are likely injected into the first doped type semiconductor layer 130 via the second interface J2. Thus, a part of the electrons C′ come from the first conductor 172 is injected into the first doped type semiconductor layer 130 via the second interface J2, while the other part would laterally flow to the first conductors 174 via the first electrical transmission layer 160, and then, the electrons C′ are injected into the first doped type semiconductor layer 130 via the second interface J2. After that, the electrons C′ injected into the first doped type semiconductor layer 130 would continuously flow to the light-emitting layer 140 to recombine with the holes C located in the light-emitting layer 140 to emit light. It can be seen the semiconductor light-emitting structure 100 of the embodiments certainly makes the current more dispersed. The dispersed current results in more dispersed distribution of the interface temperature of the semiconductor light-emitting structure 100 produced during operation in the embodiment, which thereby enables the semiconductor light-emitting structure 100 keeping higher light-emitting efficiency during operation and unlikely damaged so as to have longer lifetime.
In the embodiment, both the first electrical transmission layer 160 and the first conductors 170 can surround the platform portion 132 so as to further advance the dispersed extent of the current. However, the distribution positions of the first conductors 170 in the invention are not limited to the layout of
In the embodiment, an annealing processing is performed on the first electrical transmission layer 160, so that the resistances of the first electrical transmission layer 160 and the first interface J1 meet an expected value.
The resistance of the fourth interface J4 is greater than the resistance of the third interface J3, and therefore the fourth interface J4 can serve as a current-blocking structure to reduce the current passing through under the second conductor 190, that is because if the current formed above the second conductor 190 passes through the light-emitting layer 140 under the second conductor 190, the light-emitting layer 140 would emit light, but the light emitted from the light-emitting layer 140 under the second conductor 190 is easily blocked by the second conductor 190 so as to reduce the light efficiency. On the contrary, by using the fourth interface J4 to block the current formed under the second conductor 190 in the embodiment, the current passing through the third interface J3 is increased, which further reduces the proportion of the light emitted from the light-emitting layer 140 but blocked by the second conductor 190 so as to advance the light efficiency of the semiconductor light-emitting structure 100.
After that as shown by
In the fabrication method of semiconductor light-emitting structure 100 of the embodiment, since the first electrical transmission layer 160 is processed by annealing, so that the resistance of the second interface J2 is less than the resistance of the first interface J1.
In summary, in the semiconductor light-emitting structure of the embodiments of the invention, the first electrical transmission layer connected to the first conductors serves as an extension of the first conductors and the first electrical transmission layer is suitable to allow light passing through, so that the semiconductor light-emitting structure of the embodiments of the invention can make the current more dispersed, and meanwhile, the light extraction rate unlikely gets loss. In this way, the semiconductor light-emitting structure of the embodiments of the invention can effectively advance the light efficiency and the light uniformity. In addition, since the current is more dispersed, the heat of the semiconductor light-emitting structure of the embodiments of the invention produced during operation is more dispersed, so that the semiconductor light-emitting structure has better heat-dissipation effect, which enables the semiconductor light-emitting structure keeping higher light-emitting efficiency during operation and unlikely damaged so as to have longer lifetime.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Number | Date | Country | Kind |
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100117781 | May 2011 | TW | national |