CN114188454B - Ultraviolet light-emitting diode and light-emitting device - Google Patents

Abstract

The invention provides an ultraviolet light-emitting diode and a light-emitting device. The ultraviolet light-emitting diode includes: a semiconductor layer sequence, including a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence, and has one or more self-contained components. The second semiconductor layer extends a mesa of the first semiconductor layer that exposes the first semiconductor layer, wherein the first semiconductor layer has a first conductivity, the second semiconductor layer has a second conductivity, and the first conductivity is different from the second conductivity. Conductivity; a first ohmic contact electrode, located on the mesa, forming ohmic contact with the first semiconductor layer; a second ohmic contact electrode, located on the second semiconductor layer, forming ohmic contact with the second semiconductor layer; A connection electrode is formed on the second ohmic contact electrode, and is electrically connected to the second semiconductor layer through the ohmic contact electrode; the edge of the connection electrode is located inside the edge of the second ohmic contact electrode, and both There is a certain distance between them.

Description

Ultraviolet light-emitting diodes and light-emitting devices

Technical field

The present invention relates to the field of semiconductor technology, and in particular to an ultraviolet light-emitting diode and a light-emitting device.

Background technique

Light-emitting diodes that emit ultraviolet light with a wavelength in the range of 200 to 300 nm can be used in a variety of applications including sterilization devices, water or air purification devices, and high-density optical recording devices.

Figure 1 shows a schematic cross-sectional structural diagram of an existing ultraviolet light-emitting diode, including a substrate 110, a semiconductor layer sequence 120, a first ohmic contact electrode 131, a second ohmic contact electrode 132, a first connection electrode 133, a second connection The electrode 134, the first bonding pad 151 and the second bonding pad 152, wherein the semiconductor layer sequence 120 includes the first semiconductor layer 121, the active layer 122 and the second semiconductor layer 123 sequentially stacked on the surface of the substrate 110, and has from One or more mesas of the first semiconductor layer extend from the second semiconductor layer, and the mesa exposes the first semiconductor layer. The first ohmic contact electrode 131 forms ohmic contact with the first semiconductor layer on the mesa, and the second ohmic contact electrode is in contact with the first semiconductor layer. The second semiconductor layer forms an ohmic contact electrode.

Unlike near-ultraviolet light-emitting diodes or blue-light light-emitting diodes, light-emitting diodes that emit relatively deep ultraviolet light include Al-containing semiconductor layers such as AlGaN. The lateral expansion rate of carriers is relatively low, so it is easy to occur at the edge of the mesa. Current accumulation leads to local overheating and electrode burning, which leads to weakened reliability and shortened life of the LED chip. As shown in Figure 2, an ignition occurs at the edge of the ohmic contact electrode.

Contents of the invention

One object of the present invention is to provide an ultraviolet light-emitting diode that can effectively improve the reliability of the ultraviolet light-emitting diode.

An ultraviolet light-emitting diode according to the present invention includes: a semiconductor layer sequence, including a first semiconductor layer, an active layer and a second semiconductor layer stacked in sequence, and has one or more first semiconductor layers extending from the second semiconductor layer. a mesa of a semiconductor layer, the mesa exposing a first semiconductor layer, wherein the first semiconductor layer has a first conductivity, the second semiconductor layer has a second conductivity, the first conductivity is different from the second conductivity; a first ohmic contact An electrode is located on the mesa and forms ohmic contact with the first semiconductor layer; a second ohmic contact electrode is located on the second semiconductor layer and forms ohmic contact with the second semiconductor layer; a connecting electrode is formed on the On the second ohmic contact electrode, an electrical connection is formed between the ohmic contact electrode and the second semiconductor layer; the edge of the connecting electrode is located inside the edge of the second ohmic contact electrode, with a certain spacing between the two. .

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other beneficial effects of the present invention can be achieved and obtained by the structures particularly pointed out in the specification, claims, etc.

Description of the drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting creative efforts; in the following description, the positional relationships described in the drawings, Unless otherwise specified, the directions of the components in the illustrations are used as the basis.

Figure 1 is a schematic cross-sectional view of an existing ultraviolet light-emitting diode.

Figure 2 is a partial enlarged view of the light-emitting diode shown in Figure 1, showing the explosion point at the edge of the chip's mesa.

FIG. 3 is a top view of an ultraviolet light-emitting diode according to the first embodiment of the present invention.

FIG. 4 is a schematic longitudinal cross-sectional view taken along line A-A of FIG. 1 .

FIG. 5 is a top view of the n-type ohmic contact electrode of the ultraviolet light-emitting diode provided in the first embodiment of the present invention.

FIG. 6 is a top view of the connection electrode of the ultraviolet light-emitting diode provided by the first embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view of an ultraviolet light-emitting diode according to a second embodiment of the present invention.

Figures 8 and 9 show top views of the reflective layer of the ultraviolet light-emitting diode provided by the first embodiment of the present invention. Figure 8 shows the reflective area that overlaps the active layer, and Figure 9 shows the area that does not overlap the active layer. .

Figure 10 shows the absorption rate curve of ITO.

FIG. 11 is a top view of an ultraviolet light-emitting diode according to a third embodiment of the present invention.

FIG. 12 is a schematic longitudinal cross-sectional view taken along line B-B of FIG. 11 .

FIG. 13 is a top view of the connection electrode of the ultraviolet light-emitting diode provided by the third embodiment of the present invention.

Figure 14 shows the reflectance curve of the reflective layer of the ultraviolet light-emitting diode provided by the third embodiment of the present invention.

Figure 15 shows a brightness scatter diagram of the ultraviolet light-emitting diode provided by the second embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, not all of them; the technical features designed in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Please refer to FIGS. 3 and 4 . FIG. 3 is a schematic top structural view of the light-emitting diode disclosed in the first embodiment of the present invention. FIG. 4 is a schematic longitudinal cross-sectional view taken along line A-A in FIG. 1 . The light-emitting diode includes a substrate 110, a semiconductor layer sequence 120 formed on the upper surface of the substrate, a first ohmic contact electrode 131, a second ohmic contact electrode 132, a connecting electrode 134, a first bonding pad 151, a second bonding pad 152 and 160 layers of insulation. In this embodiment, the light emitting diode is a flip chip with a light extraction surface S12 on one side of the substrate.

Substrate 110 serves to support semiconductor layer sequence 110 . The substrate has a first surface S11 and a light extraction surface S12. The first surface S11 is a semiconductor layer forming surface. The light extraction surface S12 is a surface opposite to the first surface S11. The substrate 110 is, for example, a sapphire substrate, or may be a growth substrate capable of forming a group III nitride semiconductor film. Preferably, the substrate is a transparent material or a translucent material. In order to enhance the light extraction efficiency of the light S12, especially the effect of light extraction from the substrate surface, the substrate 110 is preferably thickened, and its thickness can be 250 μm to 900 μm.

Preferably, a layer of aluminum nitride is formed on the first surface S11 of the substrate 110 as the bottom layer 111. The bottom layer 111 is in contact with the first surface S11, and its thickness is preferably less than 1 μm. Furthermore, the aluminum nitride bottom layer 111 includes a low-temperature layer, an intermediate layer and a high-temperature layer in order from the side close to the substrate 110, enabling the growth of a semiconductor layer with excellent crystallinity. In other preferred embodiments, a series of hole structures are formed in the aluminum nitride bottom layer, which is beneficial to releasing the stress of the semiconductor layer sequence. The series of holes are preferably a series of elongated holes extending along the thickness of the aluminum nitride, and the depth thereof may be, for example, 0.5-1.5 μm.

The semiconductor layer sequence 120 is formed on the aluminum nitride bottom layer 111 and includes a first semiconductor layer 121, a second semiconductor layer 123 and an active layer 122 between them. For example, the first semiconductor layer 121 is an N-type layer. The second semiconductor layer 123 is a P-type layer, and they can also be inverted. The first semiconductor layer 121 is, for example, an n-type AlGaN layer. The active layer 122 is a layer that emits ultraviolet rays and has a well layer and a barrier layer. The number of repetitions of the well layer and the barrier layer is, for example, 1 or more and 10 or less. The well layer is, for example, an AlGaN layer, and the barrier layer is, for example, an AlGaN layer. However, the Al composition of the well layer is lower than that of the barrier layer. The second semiconductor layer 123 is, for example, a p-type AlGaN layer or a p-type GaN layer, or a layer in which a p-type AlGaN layer and a p-type GaN layer are sequentially stacked. In this embodiment, the second semiconductor layer 123 includes a p-type GaN surface layer. The p-type GaN surface layer has a thickness of 5 to 50 nm. By providing thin film GaN, both the internal quantum luminous efficiency and the external quantum luminous efficiency of the device can be taken into consideration. Specifically, the p-type GaN layer within this thickness range helps to conduct lateral current expansion of the p-side current without causing excessive light absorption.

In a preferred embodiment, there is a certain distance between the edge 121-1 of the first semiconductor layer and the edge 110-1 of the substrate. As shown in FIGS. 1 and 2, the sidewalls of the first semiconductor layer are located at the the inside of the sidewalls of the substrate. In the ultraviolet LED chip, increasing the thickness of the substrate 110 is beneficial to improving the luminous efficiency, but increasing the thickness of the substrate also increases the difficulty of cutting the substrate. Therefore, in this embodiment, by cutting the edge 121 of the first semiconductor layer A certain distance is maintained between -1 and the edge 110-1 of the substrate, so as to ensure that the semiconductor layer sequence will not be damaged when the substrate is cut, thereby improving the reliability of the light-emitting diode. Preferably, the distance is 2 μm or more, such as 4 to 10 μm.

The second semiconductor layer 123 and the active layer 122 are removed from part of the semiconductor layer sequence 120 to expose the first semiconductor layer 121 to form one or more mesas 120A, as shown in FIGS. 3 and 4 . In this embodiment, it is preferable to form multiple mesas 120A, which are used to form the first ohmic contact electrode 131. The distribution of the mesas 120A is not limited to that shown in Figure 4, and can be based on the actual chip size and shape. Design, the plurality of mesa 120A can be connected together or separated from each other. In ultraviolet light-emitting diodes, the Al content of the n-type semiconductor layer is usually high, which makes it difficult for current to diffuse. Therefore, the current cannot flow evenly in the active layer and the p-type semiconductor layer. The mesa 120A of the light-emitting diode in this embodiment The area is preferably set to be more than 20% and less than 70% of the area of the semiconductor layer sequence 120, and is relatively evenly distributed in the semiconductor layer sequence. Preferably, the closest distance between each area of the active layer 122 and the mesa is preferably 4 to 15 μm. This can protect the current expansion of the n-type semiconductor layer and help improve the internal quantum efficiency of the light-emitting diode, thus helping to reduce luminescence. The forward voltage of the diode. When the mesa area is too large, the area of the active area of the light-emitting diode will be too much lost, which is not conducive to improving the luminous efficiency of the light-emitting diode.

As shown in FIG. 5 and FIG. 3 , the first ohmic contact electrode 131 is formed in direct contact with the mesa 120A and forms ohmic contact with the first semiconductor layer 121 . The first ohmic contact electrode 131 is selected from one or more types of Cr, Pt, Au, Ni, Ti, and Al. Since the first semiconductor layer has a high Al composition, the first ohmic contact electrode 131 needs to be fused at high temperature to form an alloy after being deposited on the mesa, so as to form a good ohmic contact with the first semiconductor layer. For example, it can be Ti -Al-Au alloy, Ti-Al-Ni-Au alloy, Cr-Al-Ti-Au alloy, Ti-Al-Au-Pt alloy, etc.

The second ohmic contact electrode 132 is formed in contact with the surface of the second semiconductor layer 123 to form ohmic contact with the second semiconductor layer. Preferably, the material of the ohmic contact electrode 132 may be an oxide transparent conductive material or a metal alloy such as NiAu, NiAg, NiRh, etc. In a specific embodiment, the distance D1 between the edge of the second ohmic contact electrode 132 and the edge of the second semiconductor layer 123 is preferably 2 to 15 μm, for example, 5 to 10 μm. This arrangement can reduce the cost of the light emitting diode 1 The risk of leakage (also called reverse leakage current; IR for short) and electrostatic discharge (ESD) anomalies. Furthermore, the distance between the end point or edge of the upper surface of the second ohmic contact electrode 132 and the edge of the first ohmic contact electrode 131 is greater than or equal to 4 μm. When the distance is too small, leakage may easily occur. In some embodiments, the distance between the end point or edge of the upper surface of the second ohmic contact electrode 132 and the edge of the first ohmic contact electrode is greater than or equal to 4 μm and less than or equal to 10 μm. The distance between the end point or edge of the upper surface of the second ohmic contact electrode 132 and the edge of the first ohmic contact electrode 131 includes the distance between the edge of the first ohmic contact electrode 131 and the upper surface of the second conductive type semiconductor layer 123 and is greater than or equal to 2 μm, and the distance between the second ohmic contact electrode 132 and the edge of the upper surface of the second conductive type semiconductor layer 123 is greater than or equal to 2 μm. Such a setting can ensure a certain distance between the second ohmic contact electrode 132 and the mesa on the epitaxial structure 20 to prevent leakage and ESD abnormalities of the light emitting diode. At the same time, a certain distance between the second insulating layer 33 and the mesa on the epitaxial structure 20 can be ensured, so that the side walls of the etched epitaxial structure 20 have a sufficiently thick insulating layer to ensure that the light-emitting diode 1 has better insulation protection and anti-leakage performance. .

The second connection electrode 134 is formed on the second ohmic contact electrode 132 for spreading the current to the entire light emitting area. The connection electrode 134 is preferably a multi-layer metal stack, for example, an adhesion layer and a conductive layer are sequentially deposited on the ohmic contact electrode 132 . The adhesion layer can be a Cr metal layer, and its thickness is usually 1 to 10nm. The conductive layer can be an Al metal layer, and its thickness can be more than 100nm, for example, 200nm to 500nm. On the one hand, Al has a good conductive layer, and on the other hand, Al has a good conductive layer. On the one hand, Al has a high reflectivity for ultraviolet light. Preferably, the conductive layer has a reflectivity of more than 70% for light emitted by the active layer 122 . Further, it is preferable to insert a stress buffer layer inside the conductive layer, which may be an Al/Ti alternating layer, for example. Furthermore, an etching stop layer Pt, an adhesion layer Ti, etc. can also be formed on the conductive layer. Preferably, the first metal flow expansion layer 133 is formed on the first ohmic contact electrode 131, as shown in FIG. 4 . The first metal extension layer 133 and the second metal extension layer 134 can be formed in the same process and have the same metal stack structure. Preferably, the first metal extension layer 133 completely covers the first ohmic contact electrode 131, which can increase the height of the mesa area and protect the first ohmic contact electrode 131.

In the deep ultraviolet light-emitting diode structure, the lateral expansion rate of carriers in the semiconductor layer is relatively low, so current accumulation is prone to occur at the edge of the second ohmic contact electrode (near the mesa), which in turn leads to local overheating and electrode burn. phenomenon, resulting in weakened reliability and shortened life of the LED chip. Therefore, in a preferred embodiment, the connection electrode 134 is retracted compared to the second ohmic contact electrode 132, that is, the edge 134-1 of the connection electrode 134 is located inside the edge 132-1 of the second ohmic contact electrode 132. There is a distance D5 between them, which on the one hand plays the role of regulating the current expansion, and on the other hand reduces the failure ratio of the product caused by excessive accumulation of edge current. Preferably, the distance D5 is greater than or equal to 3 μm, more preferably 5 to 15 μm, ensuring a sufficiently large distance between the second ohmic contact electrode 132 and the connecting electrode 134 at the edge of the mesa, and improving the performance of the deep ultraviolet light-emitting diode near the mesa. The phenomenon of burnt ohmic contact electrodes reduces the burn rate of products during the aging process and improves the aging reliability of deep ultraviolet products.

The insulating layer 160 is formed on the connection electrode 134 and on the side surface of the semiconductor layer sequence and the side surface S13 of the mesa 120A to insulate the first connection electrode 133 and the second connection electrode 134 . The insulating layer 160 has a first opening 171 and a second opening 172 , exposing the first connection electrode 133 and the second connection electrode 134 . The material of the insulating layer 160 includes non-conductive material. The non-conductive material is preferably an inorganic material or a dielectric material. Inorganic materials include silica gel or glass, and dielectric materials include aluminum oxide, silicon nitride, silicon oxide, titanium oxide, or magnesium fluoride. For example, the insulating layer 160 may be silicon dioxide, silicon nitride, titanium oxide, tantalum oxide, niobium oxide, barium titanate, or a combination thereof. The combination may be, for example, a Bragg reflector (DBR) formed by repeated stacking of two materials.

The first bonding pad 151 and the second bonding pad 152 are located on the insulating layer 160 . The first bonding pad 151 is electrically connected to the first connection electrode 133 through the first opening 171 , and the second bonding pad 152 is electrically connected through the second opening 172 The second connection electrode 134. The first bonding pad 41 and the second bonding pad 42 may be formed together using the same material in the same process, and thus may have the same layer configuration. The materials of the first and second pads may be selected from one or more of Cr, Pt, Au, Ni, Ti, Al, and AuSn.

Figure 4 shows a simple schematic diagram of the current flow after the light-emitting diode is powered on. When the light-emitting diode shown in Figure 4 is powered on, the current L1 injected through the first pad preferentially flows from the shortest distance to the active layer, so it is close to the mesa. The current density is the strongest in the edge area of At this time, only part of the current L23 will reach the edge area of the second semiconductor layer after passing through the lateral expansion of the second ohmic contact electrode, thus avoiding the accumulation of current in the edge area of the second ohmic contact electrode close to the mesa, effectively solving the problem of deep ultraviolet luminescence. The problem of the diode's ohmic contact electrode being burned near the mesa has improved the reliability of deep UV products due to aging.

FIG. 7 is a schematic cross-sectional view of the second embodiment of the present invention, and the corresponding top view can be referred to FIG. 3 . The light-emitting diode of this embodiment is similar to the light-emitting diode disclosed in the first embodiment. The difference is that the ultraviolet light-emitting diode disclosed in this embodiment further improves the light extraction efficiency of the light-emitting diode by providing a highly reflective structure. Specifically, the thickness of the second ohmic contact electrode 132 is preferably 30 nm or less to reduce the light absorption rate of this layer as much as possible. By arranging a thin-film transparent or semi-transparent conductive layer as a contact electrode, on the one hand, a good ohmic contact can be formed with the second semiconductor layer, and on the other hand, an excessive thickness can be avoided, which may lead to a significant decrease in the light absorption effect. In a preferred implementation, the wavelength emitted by the active layer is below 280 nm, and the ohmic contact electrode 132 is ITO with a thickness of 5 to 20 nm, for example, 10 to 15 nm. At this time, the ITO layer is The absorption rate of emitted light can be reduced to within 40%.

Furthermore, the insulating layer 160 of this embodiment is preferably a reflectivity insulating layer. As shown in the figure, the light-emitting diode has a mesa structure with a large area, and the second connection electrode 134 is only partially formed on the second ohmic contact electrode 132. Therefore, by setting the insulating layer 160 to a highly reflective structure, it can effectively Improve the light extraction efficiency of light-emitting diodes. Figures 8 and 9 show the reflective area of the ultraviolet light-emitting diode according to this embodiment. The diagonally shaded portion in Figure 8 represents the reflective area overlapping the active layer, specifically the edge 123-1 to the second semiconductor layer. In the area between the edges 134-1 of the second connection electrode, the light emitted by the corresponding active layer toward the electrode side can be directly reflected by the reflective layer to avoid being absorbed by the electrode below. Preferably, this area accounts for 5% to 20% of the area of the upper surface of the substrate, for example, it may be 10%. The hatched area in Figure 9 represents the area that does not overlap with the active layer, including the area between the outer edge 134-1 of the second connection electrode and the edge 110-1 of the substrate, and the inner area of the second connection electrode. The area between the edge 134-2 and the edge 123-1 of the second semiconductor layer is the area near the mesa. Preferably, this area accounts for 15% to 40% of the area of the upper surface of the substrate, for example, it may be 25%.

Figure 10 shows the absorptivity of ITO with different thicknesses. When ITO is used as a current expansion layer, a sufficient thickness is required, generally above 100nm, such as 110nm. The light yield for ultraviolet wavelengths is very high, so the luminous efficiency of the light-emitting diode is difficult. promote. The ohmic contact electrode 132 in this embodiment adopts a thin film structure with a thickness of less than 30 nm, and is only used to form an ohmic contact with the second semiconductor layer, reducing the absorption of the active layer emission by the ohmic contact electrode 133. For example, when using ITO with a thickness of 11 nm , for ultraviolet light below 310nm, the absorption rate is below 30%. At the same time, a connecting electrode with high reflectivity is used as the current expansion layer, taking into account the expansion and reflection of the current. Furthermore, the insulating layer 260 is set to a highly reflective structure, so that the area not covered by the connecting electrode can be reflected by the insulating layer, further improving the luminous efficiency of the light-emitting diode.

Please refer to FIGS. 11 and 12 . FIG. 11 is a schematic top structural view of a light-emitting diode disclosed in a second embodiment of the present invention. FIG. 12 is a schematic longitudinal cross-sectional view taken along line B-B of FIG. 11 . This embodiment discloses an ultraviolet light-emitting diode. The difference from the second embodiment is that the connecting electrode 134 adopts a dense dot-like structure and cooperates with a metal reflective layer to further improve the luminous efficiency of the light-emitting diode.

In the structure of deep ultraviolet light-emitting diodes, aluminum has the best reflection effect among metals. However, the contact between pure aluminum Al and ITO has poor adhesion and high contact resistance. Therefore, the industry sets Cr as an adhesion layer between ITO and Al. The reflection effect will become worse. To address this problem, this embodiment discloses an ultraviolet light-emitting diode that uses Al as the reflective layer 143 and provides a transparent adhesion layer 163 between the ohmic contact electrode and the Al reflective layer.

Specifically, the ultraviolet light-emitting diode includes: a substrate 110, a semiconductor layer sequence 120 made on the upper surface of the substrate, ohmic contact electrodes 131\132, connecting electrodes 134, a transparent adhesion layer 163, an Al reflective layer 143, and a bonding pad. Electrodes 151\152, insulation layer 164. The first ohmic contact electrode 131 and the second ohmic contact electrode 132 can be arranged with reference to the first embodiment. This embodiment will be more advantageous when applied to medium and large-sized light-emitting diode chips, for example, one side of the chip is more than 20 mil. In this embodiment, the semiconductor layer sequence 120 has a plurality of mesas 120A that are open to each other and distributed inside the semiconductor layer sequence. Preferably, the second semiconductor layer is rectangular or square along the length direction, the mesas are arranged parallel to each other in a direction perpendicular to the length direction of the chip, and the first ohmic contact electrode 131 is formed on the plurality of mesas. , and forms ohmic contact with the first semiconductor layer. The second ohmic contact electrode 132 is formed on the second semiconductor and forms ohmic contact with the second semiconductor layer.

As shown in FIGS. 12 and 13 , the connection electrode 134 is formed on the second ohmic contact electrode 132 and includes a series of densely distributed dot-shaped metal blocks. The diameter D2 of each point-shaped metal block can be 10 to 50 μm, and the distance D3 between adjacent metal blocks is 10 to 100 μm, so that the metal can play a role in current expansion. When the value of D2 is less than 10 μm, it may cause the contact resistance between the metal block and the ohmic contact electrode 132 to increase, thereby causing the forward voltage to increase; when the value of D3 is less than 10 μm, it is difficult to reserve a large reflection area; When the value of D2 exceeds 50 μm or the value of D3 exceeds 100 μm, it will be difficult for the point-shaped metal blocks to be densely distributed, resulting in poor uniform current expansion and difficulty in achieving the effect of current expansion. In a preferred embodiment, the diameter D3 of the point-shaped metal blocks is preferably 15-35 μm, and the distance D3 between adjacent metal blocks is preferably 15-35 μm. Within this range, on the one hand, the point-shaped metal blocks can achieve current expansion. On the other hand, it can reserve enough reflection windows to reduce the light absorption effect of the metal block. In this embodiment, the forward voltage of the light-emitting diode is ensured by controlling the spacing of the metal blocks. The stacked structure of the metal blocks can be configured with reference to the connection electrodes of the first embodiment. Further, the first connection electrode 133 can be formed on the first ohmic contact electrode 131, which can protect the first ohmic contact electrode on the one hand, and the height of the mesa area on the other hand.

The transparent adhesive layer 163 covers the second ohmic contact electrode 134, the connecting electrode 134 and the semiconductor layer sequence. In this embodiment, the transparent adhesive layer 163 is preferably made of an insulating material, so that the first connection electrode 133 and the second connection electrode 134 can be insulated from each other at the same time. The transparent adhesive layer 163 has a first opening 171 and a third opening 173, wherein the first opening 171 exposes the first connection electrode 133, and the second opening corresponds to the metal block of the second connection electrode 134. Specifically, each metal Each block has a third opening 173 above it. The material of the transparent adhesion layer 163 may include aluminum oxide, silicon nitride, silicon oxide, titanium oxide, or magnesium fluoride. In a specific implementation, the transparent adhesion layer 163 is made of silicon dioxide, and its thickness is less than 100 nm. The Al metal reflective layer 143 is formed on the transparent adhesion layer 163 and is connected to the connection electrode 134 through the third opening 173, thereby connecting all the metal blocks into a surface and at the same time playing a role in current expansion. In some embodiments, an Al metal reflective layer (not shown in the figure) can also be formed on the first connection electrode 133, which can reduce the height difference between different electrodes and facilitate the subsequent placement of pad electrodes. In this embodiment, the thickness of the Al metal reflective layer 143 is preferably more than 80 nm, for example, 100 to 300 nm. On the one hand, it can have good reflection ability, and on the other hand, it can achieve good conductive performance.

In the light-emitting diode structure described in this embodiment, a thin film structure is first used as the ohmic contact of the second semiconductor layer, which can effectively reduce the light absorption problem of the ohmic contact electrode; dense dot-shaped metal blocks are used, and the second ohmic contact electrode, The surface of the dot-shaped metal blocks is covered with a transparent adhesive layer, and an Al metal reflective layer 143 is formed on the transparent adhesion layer. On the one hand, it connects the dot-shaped metal blocks into a surface to play an expansion role, and on the other hand, it interacts with the transparent adhesive layer. The attached layer forms an omnidirectional reflector. On the one hand, the point-like metal block structure 132 can reserve sufficient reflection area for the Al reflective layer, especially the area overlapping with the active layer, which effectively improves the reflectivity. On the other hand, the point-like metal block and ITO can form a good ohmic The contact solves the problem of high contact resistance between Al and ITO, and the transparent adhesion layer solves the problem of adhesion between ITO and the Al metal layer.

Figure 14 shows the reflectance curves of light-emitting diodes with different structures. The dot curve corresponds to the reflectivity of the Al metal reflective layer, the triangle curve corresponds to the reflectance of an existing light-emitting diode using CrAl alloy as the second electrode, and the x-curve corresponds to the existing light-emitting diode using CrAl alloy as the second electrode. Reflectivity of light-emitting diodes using NiAu alloy as second electrode. It can be seen from the figure that the reflectivity of the light-emitting diode structure described in this embodiment is greater than 80% when the wavelength is 260 to 300 nm, which is much higher than the reflectivity of the existing NiAu electrode or CrAl electrode.

Figure 15 shows the brightness scatter diagram of different light-emitting diode chip structures with the same epitaxial structure when the input current is 40mA. The dot curve represents the brightness of the light-emitting diode of this embodiment at different wavelengths, and the x-curve represents the existing The brightness of a light-emitting diode using CrAl as the second electrode. It can be seen from the figure that under the same epitaxial structure and the same input current, the brightness of the light-emitting diode described in this embodiment is greatly improved compared to the existing light-emitting diode with CrAl electrode structure.

This embodiment discloses a light-emitting device. The light-emitting device adopts the light-emitting diode structure provided in any of the above embodiments. Its specific structure and technical effects will not be described again. The lighting device may be a lighting device for UV products or UVC products.

In addition, those skilled in the art should understand that although there are many problems in the prior art, each embodiment or technical solution of the present invention can only be improved in one or several aspects, without having to simultaneously solve the problems in the prior art or All technical issues listed in the background art. Those skilled in the art will understand that content not mentioned in a claim shall not be used as a limitation on the claim.

Claims (20)

1. An ultraviolet light emitting diode comprising:

a semiconductor layer sequence comprising a first semiconductor layer, an active layer and a second semiconductor layer stacked in this order and having a mesa extending the first semiconductor layer from one or more of the second semiconductor layers, the mesa exposing the first semiconductor layer, wherein the first semiconductor layer has a first conductivity and the second semiconductor layer has a second conductivity, the first conductivity being different from the second conductivity;

the first ohmic contact electrode is positioned on the table top and forms ohmic contact with the first semiconductor layer;

a second ohmic contact electrode on the second semiconductor layer and forming ohmic contact with the second semiconductor layer;

a connection electrode formed on the second ohmic contact electrode and electrically connected to the second semiconductor layer through the ohmic contact electrode;

the method is characterized in that: the semiconductor layer sequence has a semiconductor layer containing Al, the edge of the connection electrode is positioned inside the edge of the second ohmic contact electrode, and a certain interval is arranged between the connection electrode and the second ohmic contact electrode, and the interval is 3-15 mu m.

2. The ultraviolet light emitting diode of claim 1, wherein: the second semiconductor layer includes an AlGaN layer and a GaN layer having a thickness of 50nm or less.

3. The ultraviolet light emitting diode of claim 1, wherein: the edge of the second ohmic contact electrode is positioned at the inner side of the edge of the second semiconductor layer, and the edge have a distance of 2-15 mu m.

4. The ultraviolet light emitting diode of claim 1, wherein: the thickness of the second ohmic contact electrode is 150nm or less.

5. The ultraviolet light emitting diode of claim 1, wherein: and the distance between the edge of the connecting electrode and the edge of the second ohmic contact electrode is more than or equal to 5 mu m.

6. The ultraviolet light emitting diode of claim 1, wherein: the connection electrode comprises a multi-metal lamination layer, and comprises an adhesion layer, a conductive layer and an etching stop layer in sequence from the second ohmic contact electrode.

7. The ultraviolet light emitting diode of claim 6, wherein: the conductive layer has a reflectivity of 70% or more for light emitted from the active layer.

8. The ultraviolet light emitting diode of claim 1, wherein: the semiconductor device further comprises an insulating layer which is formed on the connecting electrode, the side surface of the semiconductor layer sequence and the side surface of the table top, and the first ohmic contact electrode and the second connecting electrode are insulated.

9. The ultraviolet light emitting diode of claim 8, wherein: the insulating layer is an insulating reflecting layer.

10. The ultraviolet light emitting diode of claim 1, wherein: the connection electrode comprises a series of metal block arrays and a metal reflecting layer, and the metal blocks form ohmic contact with the second ohmic contact electrode.

11. The ultraviolet light emitting diode of claim 10, wherein: the metal blocks are uniformly distributed on the second ohmic contact electrode, and the distance between the metal blocks is 10-100 mu m.

12. The ultraviolet light emitting diode of claim 10, wherein: the transparent adhesion layer is formed on the second ohmic contact electrode and the metal block array and is provided with a first opening and a second opening, the second opening is positioned above the metal block, and the metal reflection layer is electrically connected to the metal block through the second opening.

13. An ultraviolet light emitting diode according to claim 12 wherein: the transparent adhesive layer is made of silicon dioxide, hafnium oxide, aluminum oxide, magnesium fluoride, silicon nitride and titanium oxide.

14. The ultraviolet light emitting diode of claim 10, wherein: the metal reflective layer has a reflectivity of 75% or more for light emitted from the active layer.

15. The ultraviolet light emitting diode of claim 1, wherein: the center wavelength emitted by the active layer is 220-400 nm, and the first semiconductor layer is an n-type AlGaN semiconductor layer.

16. The ultraviolet light emitting diode of claim 1, wherein: the material of the first ohmic contact electrode is selected from one or more of Cr, pt, au, ni, ti, al.

17. The ultraviolet light emitting diode of claim 1, wherein: the material of the connection electrode is selected from one or more of Cr, pt, au, ni, ti, al.

18. The ultraviolet light emitting diode of claim 1, wherein: the semiconductor device further comprises a substrate for supporting the semiconductor layer sequence, wherein the thickness of the substrate is 250-900 mu m, and a gap is reserved between the edge of the first semiconductor layer and the edge of the substrate, and the gap is larger than or equal to 2 mu m.

19. The ultraviolet light emitting diode of claim 1, wherein: the semiconductor device further comprises a substrate for supporting the semiconductor layer sequence, the thickness of the substrate is 250-900 mu m, and the nearest distance between the second semiconductor layer and the side wall of the substrate is more than or equal to 30 mu m.

20. A light-emitting device, characterized in that the ultraviolet light-emitting diode according to any one of claims 1 to 19 is employed.