TWI630730B - Light-emitting device - Google Patents

Abstract

A light emitting device comprising: a light emitting layer comprising a first surface and a second surface opposite to the first surface, the light emitting layer emitting a light having a wavelength between 365 nm and 550 nm; and a first The electrode is formed on the first surface and comprises a first metal layer and a second metal layer overlapping, wherein the first electrode has a relative light reflectance greater than 95%, and the first metal layer has higher thermal stability than The second metal layer, and the second metal layer has a higher reflectance for light than the first metal layer.

Description

Illuminating device

The present invention relates to a light emitting device, and more particularly to a light emitting device having a reflective layer.

The principle of illumination of a light-emitting diode (LED) is due to electrons moving between the n-type semiconductor and the p-type semiconductor to release energy. Since the principle of illumination of a light-emitting diode is different from that of an incandescent lamp that heats a filament, the light-emitting diode is also referred to as a cold light source. Furthermore, the better environmental tolerance, longer life, lighter and more portable, and lower power consumption of the LED make it an alternative to the light source in the lighting market. Light-emitting diodes have been used in various fields such as traffic signs, backlight modules, street lights, and medical equipment, and have gradually replaced traditional light sources.

The light emitting diode has a light emitting layer that is epitaxially grown on a conductive substrate or an insulating substrate. A light-emitting diode having a conductive substrate can form an electrode on top of the light-emitting layer, which is generally referred to as a vertical light-emitting diode. A light-emitting diode having an insulating substrate is required to expose two semiconductor layers of different polarities by an etching process, and to form electrodes on the two semiconductor layers, which are generally referred to as horizontal light-emitting diodes. The advantages of the vertical light-emitting diode are that the light-shielding area of the electrode is small, the heat-dissipating effect is good, and there is no additional etching and epitaxial process, but the conductive substrate used for growing epitaxial crystal has the problem of easily absorbing light, thus affecting the light-emitting diode. The luminous efficiency of the body. The advantage of the horizontal light-emitting diode is that the insulating substrate is usually also a transparent substrate, and the light can be emitted from the direction of the light-emitting diode. However, there are disadvantages such as poor heat dissipation, large light-shielding area of the electrode, and loss of light-emitting area by the epitaxial etching process.

The above-described light emitting diode can be further connected to other elements to form a light emitting device. The light emitting diode may be connected to the primary carrier by the side having the substrate, or formed between the secondary carrier and the light emitting diode by solder or glue to form a light emitting device. In addition, the secondary carrier may further include a circuit electrically connected to the electrode of the light emitting diode through a conductive structure such as a metal wire.

A light emitting device comprising: a light emitting layer comprising a first surface and a second surface opposite to the first surface, the light emitting layer emitting a light having a wavelength between 365 nm and 550 nm; and a first The electrode is formed on the first surface and includes a first metal layer and a second metal layer overlapping, wherein the first electrode has a relative light reflectance greater than 95% and the first metal layer has higher thermal stability than the first metal layer The second metal layer, and the second metal layer has a higher reflectance for light than the first metal layer.

A light emitting device comprising: a light emitting layer comprising a first surface and a second surface opposite to the first surface, the light emitting layer emitting a light having a wavelength between 365 nm and 550 nm, and the first surface The first electrode has a first electrical property and the second portion has a second electrical property; a first electrode comprising a first electrode pad and a reflective laminate comprising a first metal layer and a second metal layer Repeatingly overlapping and electrically guiding the first portion of the first surface, the reflective laminate having a relative light reflectance greater than 95%, wherein the first metal layer has a higher thermal stability than the second metal layer, and the second The metal layer has a higher reflectance for light than the first metal layer; a second electrode includes a second electrode pad and an ohmic contact layer formed on the second portion of the first surface; and a carrier includes a first conductive connection The pad is electrically connected to the first electrode and the second pad is electrically connected to the second electrode pad.

Referring to FIGS. 1A to 1E, there is shown a method of manufacturing a light-emitting device according to a first embodiment of the present invention.

As shown in FIG. 1A, a buffer layer 103 and a light-emitting layer 108 are sequentially epitaxially grown on a growth substrate 101. The growth substrate 101 may be a transparent substrate such as sapphire, or the conductive substrate may be, for example, tantalum carbide. The buffer layer 103 may include an unintentionally doped aluminum nitride, aluminum gallium nitride or gallium nitride, the light emitting layer 108 may include gallium nitride, and the buffer layer 103 may reduce the crystal growth between the growth substrate 101 and the light emitting layer 108. Defects caused by mismatches. The light emitting stack 108 can include a first semiconductor layer 102, a light emitting layer 104, and a second semiconductor layer 106. The first semiconductor layer 102 and the second semiconductor layer 106 can be, for example, a cladding layer or a confinement layer, and can respectively provide electrons and holes to combine electrons and holes in the light-emitting layer 104 to emit light. . The material of the first semiconductor layer 102, the light emitting layer 104, and the second semiconductor layer 106 may comprise a III-V semiconductor material, such as AlxInyGa(1-xy)N, where 0≦x, y≦1; (x+y)≦ 1. According to the material of the light-emitting layer 104, the light-emitting body can emit green light with a wavelength between 530 nm and 570 nm, blue light with a wavelength between 450 nm and 490 nm, or a wavelength of 365 nm to 405 nm of ultraviolet light. The first semiconductor layer 102 can be an n-type semiconductor layer, and the second semiconductor layer 106 can be a p-type semiconductor layer.

As shown in FIG. 1B, a patterned current blocking layer 110 is formed on a first surface 108a of the light emitting stack 108, i.e., the second semiconductor layer 106. The current blocking layer 110 may be an insulating oxide such as hafnium oxide or titanium oxide; or may be tantalum nitride.

As shown in FIG. 1C, a first electrode 112 is formed on the first surface 108a of the light emitting layer 108 and covers the current blocking layer 110, and then can be covered on the uncovered surface of the first surface 108a and the first electrode 112. A barrier layer 114 can include a first barrier layer 114a and a second barrier layer 114b. The current blocking layer 110 is entirely covered by the first electrode 112, and the first electrode 112 is internally contracted to the barrier layer 114 on the first surface 108a. The first electrode 112 may be a reflective laminate comprising a first metal layer 112a and a second metal layer 112b overlapping, wherein the first metal layer 112a has higher thermal stability than the second metal layer 112b. The second metal layer 112b has a higher reflectivity than the first metal layer 112a. For example, the first metal layer 112a may be aluminum, and the second metal layer 112b may be silver. Referring to FIG. 1F, the first metal layer 112a and the first The two metal layers 112b may overlap over 2 to 12 times. In this embodiment, the first electrode 112 has a first metal layer 112a that is in direct contact with the first surface 108a. The material of the barrier layer 114 may comprise an alloy or a laminate of titanium, tungsten, platinum, nickel. The thickness of the first metal layer 112a may be between 1 and 10 A, and the thickness of the second metal layer 112b may be between 100 and 700 A. In particular, the thickness of the first metal layer 112a may be approximately 3 A, and the first electrode 112 The total thickness can be between about 1400A and 1500A or above 1500A. In order to make the first electrode 112 ohmically contact the second semiconductor layer 106 of the light emitting layer 108, after the first electrode 112 is formed, the second metal layer 112b may be mainly performed at a temperature of 500 ° C for 40 minutes. One of the second semiconductor layers 106 is annealed at a high temperature. For example, when the first metal layer 112b is silver and the second semiconductor layer 106 is p-type GaN, high temperature annealing of a silver and p-type GaN is performed, and the first metal layer 112a can be made of The second metal layer 112b remains stable during high temperature annealing. The first metal layer 112a may comprise, besides pure aluminum, an alloy or laminate of aluminum, titanium, tungsten, platinum, nickel, to enhance the stability of the first electrode 112.

Referring to FIG. 1D, a conductive substrate 118 is bonded to the light emitting layer 108 through a conductive bonding layer 116. The conductive bonding layer 116 is interposed between the conductive substrate 118 and the barrier layer 114, and may include gold, indium, nickel, etc. Metal or its alloy. At this time, the light-emitting layer stack 108 includes the first semiconductor layer 102, the light-emitting layer 104, and the second semiconductor layer 106 interposed between the growth substrate 101 and the conductive substrate 118. A buffer (not shown) may be used to decompose the buffer layer 103 to remove the growth substrate 101, and the residual buffer layer 103 may be removed by dry etching and wet etching.

Referring to FIG. 1E, after the process of removing the buffer layer 103 by the 1D image, the light emitting laminate 108 may expose a second surface 108b. The second surface 108b serves as a main light-emitting surface and is also a surface of the first semiconductor layer 102. The second surface 108b may be a roughened surface to increase light extraction efficiency. A second electrode 120 can be formed on the second surface 108b and corresponding to the location of the current blocking layer 110. When a driving current is injected into the light emitting layer 108 through the second electrode 120 and the conductive substrate 118, the light emitting layer 104 emits light L due to the combination of the electron holes, and the light L can be reflected by the first electrode 112 by the second surface. 108b shot. In this embodiment, when the wavelength of the light L is between 365 nm and 550 nm, the first electrode 112 may have a reflectance greater than 95%, and may even have a reflectance of 98% to 100%. In this embodiment, the first electrode 112 formed by the first metal layer 112a having high thermal stability and the second metal layer 112b having high reflectivity can improve the high temperature of the high reflectivity metal (for example, silver) and the semiconductor layer in the prior art. The phenomenon that the reflectance is significantly reduced after annealing, and such a phenomenon is because a high reflectivity metal such as silver is unstable after high temperature annealing, and a high reflectivity metal when a conventional light emitting laminate receives a high current of more than 350 mA It will be more unstable and further reduce the reflectivity. In this embodiment, the first metal layer 112a has a high reflectivity close to the second metal layer 112b and also has good ohmic contact with the second semiconductor layer 106, and the first metal layer 112a has a better contrast than the second metal layer 112b. The high thermal stability allows the second metal layer 112b to remain stable in the high temperature annealing of the second semiconductor layer 106 in the first metal layer 112a without causing a large attenuation of the reflectance after annealing at a high temperature. Further, in the actual test, even if a current slightly higher than 350 mA was input to the light-emitting layer 108, the reflectance of the first electrode 112 did not significantly decrease.

Referring to Fig. 2, there is shown a light-emitting device according to a second embodiment of the present invention. The light emitting device 200 includes a light emitting layer 210 including a first surface 210a and a second surface 210d opposite to the first surface 210a. The light emitting layer 210 emits a light L1 having the same wavelength as the light L in the first embodiment. The first surface 210a includes a first portion 210b having a first electrical property and a second portion 210c having a second electrical property. A first electrode 217 includes a first electrode pad 226 and a first metal layer 214a. A second metal layer 214b alternately forms a reflective layer electrically conductively connected to the first portion 210b of the first surface 210a, and has a relative light ray L1 having a reflectance greater than 95%, so that the light ray L1 is emitted from the second surface 210d. The second electrode 250 includes a second electrode pad 224 and an ohmic contact layer 231 formed on the second portion 210c of the first surface 210a; and a carrier 218 includes a first conductive pad 222. The first electrode 217 and the second conductive pad 220 are electrically connected to the second electrode pad 224. The light emitting layer 210 may include a second portion 210c and a second surface 210d of the first surface 210a on both sides of the first semiconductor layer 204, a light emitting layer 206, and a first semiconductor layer 208 having a first surface 210a. Part 210b. The second portion 210c of the first surface 210a is formed by removing portions of the second semiconductor layer 208 and the light emitting layer 206. An insulating layer 203 is formed on the first surface 210a of the light emitting layer 210, and a trench is formed by an etching process, and a metal can be filled in the subsequent process to form a conductive path. The first electrode 217 may further include a barrier layer 216 covering the reflective layer formed by the first metal layer 214a and the second metal layer 214b, and a first conductive via 228 penetrating the insulating layer 203 and connecting the two ends to the barrier layer respectively. Layer 216 is coupled to first electrode pad 226. The materials of the first metal layer 214a and the second metal layer 214b may be the same as those of the first embodiment. The first metal layer 214a can be directly contacted with the second semiconductor layer 208, and in the embodiment, the first metal layer 214a and the second metal layer 214b can overlap overlap 2~12 times, which can further enhance the light L1. The reflectance is above 95%, even between 98% and 100%. In other embodiments, a metal oxide layer (not shown) may be formed between the first electrode 217 and the second semiconductor layer 208 to facilitate current distribution. The second electrode 250 may further have a second conductive path 230, and the two ends thereof are respectively connected with the ohmic contact layer 231 and the second electrode pad 224. A transparent substrate 202 may be formed on the second surface 210d of the light emitting layer 210. The transparent substrate 202 may be a growth substrate of the epitaxial growth light emitting layer 210, such as a sapphire substrate, but in other embodiments, the transparent substrate 202 is also The second surface 210d may be formed as a roughened surface via an etching process as in the first embodiment. The first electrode pad 226, the second electrode pad 224, the first conductive via 228, and the second conductive via 230 may comprise a stack of metals such as nickel, gold, and/or titanium. The ohmic contact layer 231 of the first electrode 250 may comprise a stack of metals such as chromium, platinum, and/or gold. The area of the first electrode pad 226 and the second electrode pad 224 may be larger than the cross-sectional areas of the first conductive path 228 and the second conductive path 230, respectively, and extend on the surface of the insulating layer 203 to facilitate receiving a high current from the carrier 218.

Although the invention has been described above, it is not intended to limit the scope of the invention, the order of implementation, or the materials and process methods used. Various modifications and variations of the present invention are possible without departing from the spirit and scope of the invention.

100‧‧‧Lighting device

101‧‧‧ Growth substrate

102‧‧‧First semiconductor layer

104‧‧‧Lighting layer

106‧‧‧Second semiconductor layer

108‧‧‧Lighting laminate

108a‧‧‧ first surface

108b‧‧‧second surface

110‧‧‧current barrier

112‧‧‧First electrode

112a‧‧‧First metal layer

112b‧‧‧Second metal layer

114‧‧‧Barrier layer

114a‧‧‧First barrier layer

114b‧‧‧second barrier layer

116‧‧‧ Conductive bonding layer

118‧‧‧Electrical substrate

L‧‧‧Light

120‧‧‧second electrode

200‧‧‧Lighting device

202‧‧‧Transparent substrate

203‧‧‧Insulation

204‧‧‧First semiconductor layer

206‧‧‧Lighting layer

208‧‧‧second semiconductor layer

210‧‧‧Lighting laminate

210a‧‧‧ first surface

210b‧‧‧Part I

210c‧‧‧Part II

210d‧‧‧second surface

214a‧‧‧First metal layer

214b‧‧‧Second metal layer

216‧‧‧ barrier layer

218‧‧‧ Carrier

220‧‧‧Second guide pad

222‧‧‧First lead pad

224‧‧‧Second electrode pad

226‧‧‧First electrode pad

228‧‧‧First conductive channel

230‧‧‧Second conductive channel

231‧‧‧Ohm contact layer

L1‧‧‧Light

1A to 1E are views showing a manufacturing method of a light-emitting device according to a first embodiment of the present invention.

Fig. 1F shows a reflective laminate in the first embodiment of the present invention.

Fig. 2 is a view showing a light-emitting device of a second embodiment of the present invention.

Claims (10)

A light emitting device comprising: a light emitting layer comprising a first surface and a second surface opposite to the first surface; a first electrode formed on the second surface of the light emitting layer; a current blocking layer Forming on the first surface of the light emitting layer and corresponding to a position of the first electrode; and a second electrode covering the current blocking layer and including the plurality of first metal layers and the plurality of second metal layers Stack. The illuminating device of claim 1, wherein the plurality of second metal layers and the plurality of first metal layers overlap each other 2 to 12 times. The illuminating device of claim 1, wherein the plurality of first metal layers comprise aluminum, titanium, tungsten, platinum or nickel. The illuminating device of claim 1, wherein the plurality of second metal layers have a thickness between 100 Å and 700 Å. The illuminating device of claim 1, wherein the illuminating laminate comprises a first semiconductor layer having the second surface, a second semiconductor layer having the first surface, and the first semiconductor layer And an active layer between the second semiconductor layer, the first electrode is formed on a portion of the second surface, and light generated by the active layer is emitted from the light emitting layer via the second surface. The illuminating device of claim 1, wherein one of the plurality of first metal layers directly contacts the first surface of the luminescent laminate. The illuminating device of claim 1, further comprising a conductive substrate and a conductive bonding layer formed between the conductive substrate and the second electrode. The illuminating device of claim 1, wherein one of the plurality of first metal layers is discontinuous from a cross-sectional view. A light emitting device comprising: a light emitting layer comprising a first surface and a second surface opposite to the first surface; a first electrode formed on the second surface of the light emitting layer; a current blocking layer Formed on the first surface of the light emitting layer and corresponding to a position of the first electrode; and a second electrode formed on the current blocking layer, the second electrode comprising a first metal layer and a a second metal layer, wherein the current blocking layer is interposed between the first metal layers and the first metal layer is discontinuous. The illuminating device of claim 9, further comprising a barrier layer covering the second electrode and a conductive substrate; and a conductive bonding layer formed between the conductive substrate and the barrier layer.