Light Emitting Diode

Abstract

The present invention discloses a light emitting diode. The light emitting diode disclosed in the embodiment of the present invention comprises an N-type semiconductor layer, a light emitting layer, a first P-type semiconductor layer, a hole dispersion layer and a second P-type semiconductor layer stacked in sequence. The hole dispersion layer comprises a first sublayer, a second sublayer and a third sublayer stacked in sequence from the first P-type semiconductor layer to the second P-type semiconductor layer; the first sublayer is an AlN layer; the second sublayer is an AlInGaN layer or an AlGaN layer; the third sublayer is an AlInGaN layer or an AlGaN layer. The present invention has the characteristics of alleviating the current crowding problem and improving the luminous efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of light-emitting semiconductors, and in particular to a light-emitting diode. Background Art

[0002] LED (Light Emitting Diode) has the advantages of small size and long life, so LED is widely used in various fields. With limited resources on the earth, how to spend less electricity to get higher brightness is necessary, so how to improve the light efficiency of LED has become a more important issue. The P-type semiconductor of LED is prone to current crowding, which causes the starting voltage to rise and the light efficiency to decrease. Therefore, how to make the P-type semiconductor get good current dispersion has become an urgent problem to be solved.

[0003] Therefore, there is an urgent need to provide a solution to the above-mentioned current congestion problem. Summary of the invention

[0004] Therefore, in order to overcome at least some of the defects in the prior art, an embodiment of the present invention provides a light emitting diode, which has the characteristics of alleviating the current crowding problem and improving the light emitting efficiency of the LED.

[0005] Specifically, on the one hand, an embodiment of the present invention provides a light-emitting diode, comprising: an N-type semiconductor layer, a light-emitting layer, a first P-type semiconductor layer, a hole dispersion layer and a second P-type semiconductor layer stacked in sequence; wherein the hole dispersion layer comprises a first sublayer, a second sublayer and a third sublayer stacked in sequence along a direction from the first P-type semiconductor layer to the second P-type semiconductor layer; wherein the first sublayer is an AlN layer; the second sublayer is an AlInGaN layer or an AlGaN layer; and the third sublayer is an AlInGaN layer or an AlGaN layer.

[0006] Another embodiment of the present invention provides another light-emitting diode, comprising an N-type semiconductor layer, a light-emitting layer, a P-type semiconductor layer stacked in sequence, and a hole dispersion layer located between the light-emitting layer and the P-type semiconductor layer; wherein the hole dispersion layer comprises a first sublayer, a second sublayer and a third sublayer stacked in sequence along a direction from the light-emitting layer to the P-type semiconductor layer; the first sublayer is an undoped AlN layer, the second sublayer is an undoped AlInGaN layer or an undoped AlGaN layer; and the third sublayer is an undoped AlGaN layer or an undoped AlGaN layer.

[0007] The above-mentioned embodiments of the present invention can achieve one or more of the following beneficial effects: by adding a hole dispersion layer between the light-emitting layer and the P-type layer, the unique structure of the hole dispersion layer can change the path of the holes and prevent the holes from concentrating at the same position, so as to disperse the current and thereby improve the luminous efficiency of the LED.

[0008] Other aspects and features of the present invention will become apparent from the following detailed description with reference to the accompanying drawings. It should be understood, however, that the drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. It should also be understood that, unless otherwise indicated, the drawings are not necessarily drawn to scale and are intended only to conceptually illustrate the structures and processes described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The specific implementation modes of the present invention will be described in detail below with reference to the accompanying drawings.

[0010] Figure 1 A schematic structural diagram of a light emitting diode provided by an embodiment of the present invention.

[0011] Figure 2 for Figure 1 A schematic diagram of the structure of a hole dispersion layer in a light-emitting diode is shown.

[0012] Figure 3 for Figure 1 A schematic diagram of the structure of another hole dispersion layer in a light-emitting diode is shown.

[0013] Figure 4 for Figure 2 Energy band diagram of the hole dispersion layer shown.

[0014] Figure 5 FIG. 4 is a schematic diagram of the energy band of the hole dispersion layer in one embodiment of the present invention.

[0015] [Description of Reference Numerals]

[0016] 10: light emitting diode; 20: substrate; 30: electrode; 11: N-type semiconductor layer; 12: light emitting layer; 13: electron blocking layer; 14: P-type semiconductor layer; 15: hole dispersion layer; 141: first P-type semiconductor layer; 142: second P-type semiconductor layer; 151: first sublayer; 152: second sublayer; 153: third sublayer; 154: fourth sublayer; 1541: AlGaN layer; 1542: GaN layer. DETAILED DESCRIPTION

[0017] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0018] It should also be noted that the division of multiple embodiments in the present invention is only for the convenience of description and should not constitute a special limitation. The features in various embodiments can be combined and referenced to each other without contradiction.

[0019] like Figure 1, which is a schematic diagram of the structure of a light emitting diode 10 provided by an embodiment of the present invention, the light emitting diode 10 includes an N-type semiconductor layer 11, a light emitting layer 12, a P-type semiconductor layer 14 stacked in sequence, and a hole dispersion layer 15 disposed between the light emitting layer 12 and the P-type semiconductor layer 14. Figure 2 , the hole dispersion layer 15 includes a first sublayer 151, a second sublayer 152 and a third sublayer 153 stacked in sequence along the direction from the light emitting layer 12 to the P-type semiconductor layer 14. Specifically, the first sublayer 151 is, for example, an AlN (aluminum nitride) layer. The second sublayer 152 may be an AlInGaN (aluminum indium gallium nitride) layer or an AlGaN (aluminum gallium nitride) layer. The third sublayer 153 may be an AlInGaN layer or an AlGaN layer. More specifically, for example, the first sublayer 151 is an AlN layer, and the second sublayer 152 and the third sublayer 153 are AlInGaN layers. Or the first sublayer 151 is an AlN layer, and the second sublayer 152 and the third sublayer 153 are AlGaN layers. Or the first sublayer 151 is an AlN layer, the second sublayer 152 is an AlInGaN layer, and the third sublayer 153 is an AlGaN layer. Alternatively, the first sublayer 151 is an AlN layer, the second sublayer is an AlGaN layer, and the third sublayer is an AlInGaN layer.

[0020] Among them, the N-type semiconductor layer 11 in the light-emitting diode 10 provided in this embodiment is generally an N-type GaN layer, and its material is generally Si-doped gallium nitride material. The light-emitting layer 12 is a multi-layer quantum well layer, generally including a plurality of groups of alternately stacked InGaN and GaN layers. In some embodiments, the N-type semiconductor layer 11 also includes, for example, a substrate layer, a low-temperature buffer layer, a u-type gallium nitride layer, a stress adjustment layer, etc. stacked in sequence, for example, also including an N electrode and a P electrode, the N electrode is electrically connected to the N-type semiconductor layer 11, and the P electrode is electrically connected to the P-type semiconductor layer 14. The specific settings can be made with reference to conventional light-emitting diodes, and will not be repeated here. The P-type semiconductor layer 14 is generally a P-type GaN layer, and its material is generally Mg-doped gallium nitride material. In some embodiments, the P-type semiconductor layer specifically includes, for example, a first P-type semiconductor layer 141 and a second P-type semiconductor layer 142. In order to obtain better crystal quality, the growth temperature of the P-type semiconductor layer is usually higher, but the higher growth temperature will affect the crystal structure of the light-emitting layer. Therefore, a layer of low-temperature P-GaN can be grown at a relatively low temperature on the side close to the light-emitting layer, that is, the first P-type semiconductor layer 141 in this embodiment. Although the growth temperatures of the first P-type semiconductor layer 141 and the second P-type semiconductor layer 142 are different, their materials are both Mg-doped GaN layers. The hole dispersion layer 15 is specifically located between the first P-type semiconductor layer 141 and the second P-type semiconductor layer 142, for example.

[0021] As mentioned above, the P electrode is electrically connected to the P-type semiconductor layer 14. When the light-emitting diode is powered on, current flows from the P electrode into the P-type semiconductor layer 14. As holes move from the P-type semiconductor layer toward the light-emitting layer 12, the P-type semiconductor layer may have a problem of uneven impedance distribution due to different distances from the electrode or problems with the quality of the internal crystal. The flow of current (i.e., the movement of holes) has a characteristic that it is usually concentrated on a path with lower impedance. Therefore, current crowding is prone to occur, causing the starting voltage to rise, and then the luminous efficiency to decrease. In this embodiment, a hole dispersion layer 15 is provided in the P-type semiconductor layer 14. The hole dispersion layer 15 contains multiple sub-layers with Al components and has a higher energy barrier. When the light-emitting diode 10 provided by this embodiment is used, holes can be injected from the second P-type semiconductor layer 142, and the current is dispersed through the hole dispersion layer 15. After passing through the first P-type semiconductor layer 141 more evenly, it enters the light-emitting layer 12 to participate in luminescence. The movement of holes forms a certain energy barrier in the middle of the P-type semiconductor layer 14 through the high-component Al, which can change the movement path of the holes, so that the holes are dispersed instead of being concentrated in a certain path, thereby reducing the occurrence of current crowding problems.

[0022] More specifically, the first sublayer 151, the second sublayer 152 and the third sublayer 153 are all non-doped layers, that is, the first sublayer 151 is a non-doped AlN layer, and the second sublayer 152 and the third sublayer 153 are non-doped AlInGaN or non-doped AlGaN layers. The prior art believes that all semiconductor layers on the side of the P-type semiconductor layer 14 should be P-type doped materials to facilitate the transmission of holes. However, the present invention accidentally discovered during the experiment that setting up a hole dispersion layer 15 and using non-doped materials can not only improve the brightness, but also reduce the voltage and improve the overall luminous efficiency. Please refer to Table 1:

[0023] Table 1. Differences in chip voltage and brightness with or without hole dispersion layer doping

[0024]

[0025] The reason may be that Mg-doped materials are easy to combine with H2 during the growth process to form high-impedance Mg-H materials. It is difficult to ensure that all Mg-H bonds are broken during the existing annealing process, so there will be a problem of voltage rise, and Mg itself has some light absorption characteristics, which will also have some impact on the brightness. Among them, when the first sublayer 151, the second sublayer 152 and the third sublayer 153 are non-doped layers, the chance of Mg-H (magnesium hydrogen bond) high impedance can be reduced, and the light absorption problem can be reduced, thereby effectively reducing the startup voltage of the light-emitting diode and improving the brightness.

[0026] In some embodiments, the Al (aluminum) content in the first sublayer 151, the second sublayer 152, and the third sublayer 153 decreases in sequence. The concentration in the first sublayer 151 is the highest, for example, 1×10E+19 to 1×10E+21 atom / cm 3 . Reference Figure 4 , which is Figure 2 Schematic diagram of the energy band of the light-emitting diode 10 shown. From the P-type semiconductor layer 14 to the light-emitting layer 12, the concentration of the Al component increases, the energy band gradually becomes larger, and the concentration gradient structure of the hole dispersion layer 15 matches the energy band of the P-type semiconductor layer 14 while further realizing the hole acceleration effect. Among them, when the second sublayer 152 and the third sublayer 153 are AlInGaN (aluminum indium gallium nitride) layers, the concentration of In (indium) in the second sublayer 152 and the third sublayer 153 is equal. Compared with the use of AlGaN, the use of AlInGaN in the second sublayer 152 and the third sublayer 153 increases the In component. The doping of the In component can reduce material defects and improve the quality of the material.

[0027] In some implementations, the thickness of the first sublayer 151 is less than the thickness of the second sublayer 152. The thickness of the first sublayer 151 is less than the thickness of the third sublayer 153. Specifically, the thickness of the first sublayer 151 ranges from 0.5 to 2 nm, the thickness of the second sublayer 152 ranges from 5 to 20 nm, and the thickness of the third sublayer 153 ranges from 5 to 30 nm. The Al component concentration of the first sublayer 151 is relatively high, which can disperse the current passing through the second sublayer 152 again. Designing the thickness of the first sublayer 151 to be relatively thin can ensure that the holes can tunnel through the first sublayer 151 while achieving the hole dispersion effect, thereby preventing the problem of causing the startup voltage to rise.

[0028] In one embodiment of the present invention, referring to Figure 3 The hole dispersion layer 15 further includes, for example, at least one fourth sublayer 154, which is disposed on a side of the third sublayer 153 away from the second sublayer 152. The fourth sublayer 154 includes, for example, a stacked AlGaN layer 1541 and a GaN layer 1542. Figure 3, the fourth sublayer 154 is located above the third sublayer 153, and the fourth sublayer 154 includes, for example, a stacked AlGaN layer 1541 and a GaN layer 1542, wherein the AlGaN layer 1541 is adjacent to the third sublayer 153. In some embodiments, the thickness of the AlGaN layer 1541 is, for example, less than the thickness of the GaN layer 1542. In some embodiments, the Al component content in the fourth sublayer 154 is lower than the Al component content in the third sublayer 153. In the fourth sublayer 154, the current dispersion function can be achieved through the AlGaN layer 1541, and the GaN layer 1542 can prevent the startup voltage from being too high. Similar to the first sublayer 151, the second sublayer 152, and the third sublayer 153, the fourth sublayer 154 is, for example, a non-doped layer, that is, the AlGaN layer 1541 is a non-doped AlGaN layer, and the GaN layer 1542 is a non-doped GaN layer. Non-doping, for example, means that Mg is not doped, which can prevent the startup voltage from rising.

[0029] In some embodiments, reference Figure 3 The hole dispersion layer 15 includes, for example, multiple groups of fourth sublayers 154, such as two, three or more groups of fourth sublayers 154. It can be understood that the multiple groups of fourth sublayers 154 are all AlGaN / GaN superlattice structures. Since the AlGaN layer 1541 and the GaN layer 1542 are different layers of materials, the holes are easily dispersed into different paths when passing through different layers. Therefore, the arrangement of multiple groups of fourth sublayers 154 can make the holes dispersed multiple times to increase the current dispersion effect. For example Figure 3 The two groups of fourth sublayers 154 shown can be understood as a double-periodic AlGaN / GaN superlattice structure. In some embodiments, the Al component content in the multiple groups of fourth sublayers 154 is the same. Or in some embodiments, along the direction from the second sublayer 152 to the third sublayer 153, the Al component content of the multiple groups of fourth sublayers 154 decreases in sequence. Figure 5 As shown, it is a schematic diagram of the energy band of a light-emitting diode 10 with three groups of fourth sublayers 154 provided by an embodiment of the present invention, wherein from the first sublayer 151 to the second P-type semiconductor layer 142, the concentration of Al in the layer containing Al components in the hole dispersion layer 15 gradually decreases, and the energy band also becomes lower and lower, so that better hole dispersion can be achieved and it is beneficial to hole acceleration.

[0030] In some embodiments, the thickness of the GaN layer 1541 in the fourth sublayer 154 is greater than the thickness of the AlGaN layer 1542. The thinner AlGaN layer 1542 can ensure that holes can be dispersed while ensuring the passage of holes. The overall thickness of the fourth sublayer 154 is, for example, no more than 100 nm. Because the thickness of the fourth sublayer 154 is positively correlated with the impedance, in order to reduce the impedance, increase the brightness, and reduce the light absorption effect of Mg-H (magnesium hydrogen bond), the thickness of the fourth sublayer is designed to be as thin as possible.

[0031] In one embodiment, the light emitting diode 10 further includes an electron blocking layer 13, which is located between the light emitting layer 12 and the P-type semiconductor layer 14, specifically between the light emitting layer 12 and the first P-type semiconductor layer 141. The light emitting layer 12 includes multiple groups of alternately stacked InGaN and GaN layers, wherein the side of the light emitting layer 12 adjacent to the electron blocking layer 13 is an undoped GaN layer, and the electron blocking layer 13 is specifically located between the undoped GaN layer and the first P-type semiconductor 141. The undoped GaN layer can be understood as the last layer of the light emitting layer 12. The electron blocking layer 13, for example, includes an AlInGaN / InGaN superlattice structure layer and an AlN layer stacked in sequence from the light emitting layer 12 to the first P-type semiconductor layer 142. Or in some embodiments, the electron blocking layer 13, for example, includes a GaN layer and an AlN layer stacked in sequence from the light emitting layer 12 to the first P-type semiconductor layer 142. The structure of the electron blocking layer 13 is not limited to this in this embodiment. The electron blocking layer 13 usually contains a relatively high concentration of Al and has a relatively high energy barrier, so that electrons are not easy to pass through. The electron blocking layer 13 can block electrons and will not excessively block the flow of holes into the light-emitting layer.

[0032] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A light emitting diode (10), characterized in that: The invention comprises an N-type semiconductor layer (11), a light-emitting layer (12), a first P-type semiconductor layer (141), a hole dispersion layer (15) and a second P-type semiconductor layer (142) which are stacked in sequence; wherein the hole dispersion layer (15) comprises a first sublayer (151), a second sublayer (152) and a third sublayer (153) which are stacked in sequence along a direction from the first P-type semiconductor layer (141) to the second P-type semiconductor layer (142); wherein the first sublayer (151) is an AlN layer; the second sublayer (152) is an AlInGaN layer or an AlGaN layer; and the third sublayer (153) is an AlInGaN layer or an AlGaN layer.

2. The light emitting diode (10) according to claim 1, characterized in that The first P-type semiconductor layer (141) and the second P-type semiconductor layer (142) are both Mg-doped GaN layers.

3. The light emitting diode (10) according to claim 1, characterized in that The first sublayer (151), the second sublayer (152) and the third sublayer (153) are all non-doped layers.

4. The light emitting diode (10) according to claim 1, characterized in that The Al component contents in the first sub-layer (151), the second sub-layer (152) and the third sub-layer (153) decrease sequentially.

5. The light emitting diode (10) according to claim 1, characterized in that The thickness of the first sublayer (151) ranges from 0.5 to 2 nm; the thickness of the second sublayer (152) ranges from 5 to 20 nm; and the thickness of the third sublayer (153) ranges from 5 to 30 nm.

6. The light emitting diode (10) according to claim 1, characterized in that The hole dispersion layer (15) further comprises at least one group of fourth sublayers (154), which are arranged on a side of the third sublayer (153) away from the second sublayer (152); the fourth sublayer (154) comprises a stacked AlGaN layer (1541) and a GaN layer (1542).

7. The light emitting diode (10) according to claim 6, characterized in that The hole dispersion layer (15) comprises a plurality of fourth sublayers (154); in a direction from the second sublayer (152) to the third sublayer (153), the Al component contents of the plurality of fourth sublayers (154) decrease sequentially.

8. The light emitting diode (10) according to claim 1, characterized in that It also includes an electron blocking layer (13) located between the light-emitting layer (12) and the first P-type semiconductor layer (141), the electron blocking layer (13) including an AlInGaN / InGaN superlattice structure layer and an AlN layer stacked in sequence in a direction from the light-emitting layer (12) to the first P-type semiconductor layer (141).

9. The light emitting diode according to claim 8, characterized in that The light-emitting layer (12) comprises a plurality of groups of alternately stacked InGaN and GaN layers, wherein a side of the light-emitting layer (12) adjacent to the electron blocking layer (13) is a non-doped GaN layer.

Images