TW201508948A - Flip-chip light emitting diode structure - Google Patents

Abstract

The present invention provides a flip-chip light emitting diode structure, which comprises a semiconductor substrate, a buffer layer, an N-type semiconductor layer, a light emitting layer, a P-type semiconductor layer, a reflection electrode layer, an N-type ohmic contact electrode, and a P-type ohmic contact electrode which are sequentially stacked from bottom to top. The reflection electrode layer comprises a first metal layer, a second metal layer, and a graphene layer which are sequentially stacked from bottom to top, wherein the graphene layer comprises a plurality of layers of graphene. With the first metal layer, the second metal layer and the graphene layer, the present invention may achieve high reflection and thermal stability, and overcome the matching between semiconductor and conducting elements, so that the flip-chip light emitting diode structure may achieve excellent heat dissipating effect and thus improve the issue of semiconductor sapphire substrate with poor heat dissipation; moreover, utilizing both the first metal layer and the second metal layer as reflective electron layer to enhance the light output efficiency of light emitting diode.

Description

Flip chip light emitting diode structure

The invention relates to a light emitting diode structure, in particular to a reflective electrode layer comprising a first metal layer, a second metal layer and a graphene layer stack, wherein the nano metal particles in the first metal layer and the second metal layer are prone to high temperature After heat treatment, it agglomerates into a spherical shape. The graphene layer has good thermal stability and can be improved for the instability of contact resistance caused by discontinuous agglomeration to reduce the adverse effects of silver in thermal annealing and increase its heat. Stability effect.

Light Emitting Diode (LED), which has the advantages of energy saving, low driving voltage, short starting time, no heat radiation, etc. Its application fields include indoor and outdoor lighting, traffic lights, mobile phone backlight modules, and automobile fog. A variety of products such as lights and brake lights. Among the light-emitting diodes, gallium nitride-related materials are the most popular photovoltaic element materials. The III-nitride semiconductor materials have high direct energy gap, strong physical rigidity and high thermal stability. It is widely used in the development of blue-green light-emitting diodes, blue lasers and high-temperature components. With the development of today's solid-state lighting industry, the GaN LED is still the most representative.

Referring to the first figure, a schematic cross-sectional view of a conventional light-emitting diode structure. As shown in the first figure, the LED structure 100 includes a sapphire substrate 110, a buffer layer 120, an N-type semiconductor layer 130, a light-emitting layer 140, a P-type semiconductor layer 150, and an N-type ohmic contact electrode 160. And a P-type ohmic contact electrode 170.

The buffer layer 120 is formed on the sapphire substrate 110 as an intrinsic tri-five semiconductor, or a P-type tri-five semiconductor, and an N-type semiconductor layer 130. Formed on the buffer layer 120, an N-type three-five semiconductor, such as N-type GaN, includes a base region 131 and a protrusion region 133, the protrusion region 133 is protruded from the base region 131; the light-emitting layer 140 is formed in the N-type On the protrusion region 133 of the semiconductor layer 130, a multi-layer quantum well structure is formed. The P-type semiconductor layer 150 is formed on the light-emitting layer 140 as a P-type tri-five semiconductor, such as P-type GaN.

The N-type ohmic contact electrode 160 is formed on the base region 131 of the N-type semiconductor layer 130, and includes at least one of titanium (Ti) and aluminum (Al), and the P-type ohmic contact electrode 170 is formed on the P-type semiconductor layer 150. Containing at least one of gold (Au) and nickel (Ni).

The conventional light-emitting diode structure usually connects the N-type ohmic contact electrode 160 and the P-type ohmic contact electrode 170 in a wire bonding manner, and then the light-emitting diode structure is sealed by the encapsulant, and the heat after being energized is difficult to escape. The problem is that the temperature of the component is too high.

Graphene is a material with good electrical and thermal conductivity and heat stability and chemical stability at the same time, but directly replaces N-type ohmic contact electrode 160 or P-type ohmic contact electrode 170 with graphene, but because of the material The junction characteristics cause the resistance to be too high, and the overall performance is not good.

In addition, in the fabrication of conventional flip-chip devices of the prior art, the development of ohmic contact electrodes having high thermal stability and high reflectivity is still an important issue for improving light-emitting elements. The reflective electrode metal generally used in flip-chip components is mainly aluminum (Al) or silver (Ag). The work function of these two metals is quite different from that of P-type gallium nitride, which is not only impossible to nitride. The formation of a good ohmic contact electrode on the surface of the gallium further causes the deterioration of the reflective electrode, resulting in a decrease in light extraction efficiency and a shortened lifetime of the light-emitting diode.

Therefore, an improved light emitting diode structure is needed to achieve good thermal stability and heat dissipation.

The main object of the present invention is to provide a flip chip light emitting diode structure, The flip chip light emitting diode structure includes a semiconductor substrate, a buffer layer, an N-type semiconductor layer, a light emitting layer, a P-type semiconductor layer, and a reflective electrode layer which are sequentially stacked from bottom to top, and is formed on the N-type semiconductor layer. An N-type ohmic contact electrode, and a P-type ohmic contact electrode formed on the P-type semiconductor layer.

a reflective electrode layer comprising a first metal layer, a second metal layer, and a graphene layer sequentially pushed from bottom to top for achieving reflection, heat dissipation, and ohmic contact matching effects, the first metal layer, The thickness of the two metal layers and the graphene layer is 10 to 250 nm, the first metal layer is silver, the second metal layer is nickel, and the graphene layer contains a plurality of layers of graphene.

The invention is characterized in that the first metal layer, the second metal layer, and the reflective electrode layer formed by the graphene layer are used to control the first metal layer and the second metal layer during thermal annealing by the heat stable property of the graphene layer. The agglomeration effect, and the good heat conduction effect to enhance the heat dissipation effect of the flip-chip light-emitting diode, while the stacking of silver, nickel and graphene can overcome the matching effect between the semiconductor and the conductive element, The effect of low resistance and high reflectivity is achieved, and the resistance value and the reflectance can be adjusted by annealing, thereby increasing the light extraction efficiency and component reliability of the light emitting diode.

1‧‧‧Flip-chip light-emitting diode structure

100‧‧‧Lighting diode structure

110‧‧‧Sapphire substrate

120‧‧‧buffer layer

130‧‧‧N type semiconductor layer

131‧‧‧Base area

133‧‧‧ raised area

140‧‧‧Lighting layer

150‧‧‧P type semiconductor layer

160‧‧‧N type ohmic contact electrode

170‧‧‧P type ohmic contact electrode

210‧‧‧Semiconductor substrate

220‧‧‧buffer layer

230‧‧‧N type semiconductor layer

231‧‧‧Base area

233‧‧‧ protruding area

240‧‧‧Lighting layer

250‧‧‧P type semiconductor layer

260‧‧‧Reflective electrode layer

261‧‧‧First metal layer

263‧‧‧Second metal layer

265‧‧‧graphene layer

270‧‧‧N type ohmic contact electrode

280‧‧‧P type ohmic contact electrode

The first figure is a schematic cross-sectional view of a conventional light-emitting diode structure.

The second figure is a schematic cross-sectional view of the structure of the flip-chip light emitting diode of the present invention.

The embodiments of the present invention will be described in more detail below with reference to the drawings and the <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt;

Referring to the second figure, a schematic cross-sectional view of a flip-chip LED structure of the present invention is shown. As shown in the second figure, the flip-chip diode structure 1 of the present invention comprises a semiconductor substrate 210, a buffer layer 220, an N-type semiconductor layer 230, a light-emitting layer 240, a P-type semiconductor layer 250, and a reflective electrode. A layer 260, an N-type ohmic contact electrode 270, and a P-type ohmic contact electrode 280.

The semiconductor substrate 210 is a sapphire substrate, and the buffer layer 220 is formed on the semiconductor Above the substrate 210, an intrinsic tri-five semiconductor, or a P-type tri-five semiconductor, such as gallium arsenide (GaN), aluminum gallium arsenide (AlGaN), indium gallium arsenide (InGaN), or the like; The N-type semiconductor layer 230 is formed on the buffer layer 220, and is an N-type three-five semiconductor, such as N-type GaN, and includes a base region 231 and a protrusion region 233. The protrusion region 233 is protruded from the base region 231; 240 is formed on the protrusion region 233 of the N-type semiconductor layer 230, and is a multilayer quantum well structure, such as a multilayer stack structure of InGaN/GaN. The P-type semiconductor layer 250 is formed on the light-emitting layer 240, which is a P-type three-five. Group semiconductors, such as P-type GaN.

The reflective electrode layer 260 is formed on the P-type semiconductor layer 250, and includes a first metal layer 261, a second metal layer 263, and a graphene layer 265, which are sequentially pushed from bottom to top, and the first metal layer 261 is The silver and second metal layer 263 are nickel, and the graphene layer 265 includes a plurality of layers of graphene. The first metal layer 261, the second metal layer 263, and the graphene layer 265 have a thickness of 10 to 250 nm.

The first metal layer 261, a second metal layer 263, and a graphene layer 265 are epitaxially prepared by a magnetron sputtering system, and then formed by a high temperature heat treatment, for example, 500 ° C, wherein the first metal layer 261 is a structure. Observed, it is composed of a plurality of nano silver particles, and the nano silver particles in the first metal layer 261 are aggregated into a spherical shape by thermal annealing, and can be used as a light reflecting layer, thereby increasing the light of the light emitting diode. The extraction efficiency; and because the graphene layer 265 has good thermal stability, it can be improved for the instability of the contact resistance caused by the discontinuous agglomeration of the silver nanoparticles to reduce the agglomeration of the silver nanoparticles in the thermal annealing. The effect and increase its thermal stability effect.

The N-type ohmic contact electrode 270 is formed on the base region 231 of the N-type semiconductor layer 230, and includes at least one of titanium (Ti) and aluminum (Al), and the P-type ohmic contact electrode 280 is formed on the reflective electrode layer 260, including At least one of gold (Au), silver (Ag), aluminum (Al), nickel (Ni), platinum (Pt), and palladium (Pd).

The invention is characterized in that the first metal layer and the second metal layer are utilized And the reflective electrode layer formed by the graphene layer, by the thermal stability property of the graphene layer, can control the agglomeration effect of the nano particles in the first metal layer and the second metal layer during thermal annealing, and utilize the good heat conduction thereof The effect is to improve the heat dissipation effect of the flip-chip light-emitting diode, and further utilize the stacking of the first metal layer, the second metal layer and the graphene layer to overcome the matching effect between the semiconductor and the conductive element, and at the same time achieve low resistance and high reflectivity. The effect, and the resistance value and the reflectance, can be adjusted by annealing, thereby increasing the light-emitting efficiency and component reliability of the light-emitting diode.

The above is only a preferred embodiment for explaining the present invention, and is not intended to limit the present invention in any way, so that any modifications or alterations to the present invention made in the same spirit of creation are made. , should still be included in the scope of protection of this creative intent.

1‧‧‧Flip-chip light-emitting diode structure

210‧‧‧Semiconductor substrate

220‧‧‧buffer layer

230‧‧‧N type semiconductor layer

231‧‧‧Base area

233‧‧‧ protruding area

240‧‧‧Lighting layer

250‧‧‧P type semiconductor layer

260‧‧‧Reflective electrode layer

261‧‧‧First metal layer

263‧‧‧Second metal layer

265‧‧‧graphene layer

270‧‧‧N type ohmic contact electrode

280‧‧‧P type ohmic contact electrode

Claims (7)

A flip-chip light emitting diode structure comprising: a semiconductor substrate; a buffer layer formed on the semiconductor substrate as an intrinsic three-five semiconductor, or a P-type three-five semiconductor; an N-type semiconductor a layer formed on the buffer layer as an N-type three-five semiconductor, and comprising a base region and a protrusion region protruding from the base region; a light emitting layer formed on the N-type semiconductor The protrusion region of the layer is a multi-layer quantum well structure; a P-type semiconductor layer is formed on the light-emitting layer as a P-type tri-five semiconductor; and a reflective electrode layer is formed on the P-type semiconductor layer. a first metal layer, a second metal layer, and a graphene layer, and an N-type ohmic contact electrode formed on the base region of the N-type semiconductor layer; A P-type ohmic contact electrode is formed on the reflective electrode layer, wherein the graphene layer comprises a plurality of layers of graphene, and the first metal layer, the second metal layer and the graphene layer have a thickness of 10 to 250 nm. The flip-chip light emitting diode structure of claim 1, wherein the first metal layer is silver and the second metal layer is nickel. The flip-chip light emitting diode structure according to claim 1, wherein the semiconductor substrate is a sapphire substrate. The flip-chip light emitting diode structure according to claim 1, wherein the essential three-five semiconductor, the P-type three-five semiconductor, and the three-five of the N-type three-five semiconductor Group semiconductors are GaAs, AlGaN, and InGaN. one of them. The flip-chip light emitting diode structure according to claim 1, wherein the N-type ohmic contact electrode comprises at least one of titanium (Ti) and aluminum (Al), and the P-type ohmic contact electrode comprises gold ( At least one of Au), silver (Ag), aluminum (Al), nickel (Ni), platinum (Pt), and palladium (Pd). The flip-chip light emitting diode structure according to claim 2, wherein the first metal layer, the second metal layer, and the graphene layer are prepared by epitaxy using a magnetron sputtering system, and then It is formed by thermal annealing at a high temperature of 500 °C. The flip-chip light emitting diode structure according to claim 1, wherein the light emitting layer is a multilayer quantum well structure of a multilayer stacked structure of InGaN/GaN.