KR20080058722A - Fabrication method of light emitting device having scattering center laminated with a plurality of insulator layer and light emitting device thereby - Google Patents

Abstract

A fabrication method of a light emitting device having a scattering center laminated with a plurality of insulator layers and a light emitting device thereby are provided to reduce a light transmittance and to improve a reflectance by forming a scattering center. A first conductive type semiconductor layer(226) is grown on a substrate(100). Two or more insulating layers having different refractive indexes are alternately laminated on the first conductive type semiconductor layer. A scattering center is formed by patterning and etching the laminated insulating layers to expose a part of the first conductive type semiconductor layer. The first conductive type semiconductor layer is grown on the scattering center. An active layer(240) and a second conductive type semiconductor layer(260) are formed on the first conductive type semiconductor layer.

Description

TECHNICAL FIELD A light emitting device manufacturing method including a scattering center having a plurality of insulating layers stacked thereon, and a light emitting device therefor {FABRICATION METHOD OF LIGHT EMITTING DEVICE HAVING SCATTERING CENT

1 is a cross-sectional view schematically showing a light emitting diode according to an embodiment of the present invention.

2 to 6 are cross-sectional views illustrating a process of manufacturing the light emitting diode shown in FIG. 1.

<Description of the symbols for the main parts of the drawings>

100: substrate 210: buffer layer

220: N-type semiconductor layer 222: first N-type semiconductor layer

224: scattering center 226: second N-type semiconductor layer

240: active layer 260: P-type semiconductor layer

320: transparent electrode layer 330, 340: electrode pad

The present invention relates to a light emitting device manufacturing method including a scattering center in which a plurality of insulating layers are stacked, and a light emitting device.

A light emitting diode, which is a typical light emitting device, is a photoelectric conversion semiconductor device having a structure in which an N-type semiconductor and a P-type semiconductor are bonded to each other, and are configured to emit light by recombination of electrons and holes. As such a light emitting diode, a GaN-based light emitting diode is known. GaN-based light emitting diodes are manufactured by sequentially stacking GaN-based N-type semiconductor layers, active layers (or light-emitting layers), and P-type semiconductor layers on a substrate made of a material such as sapphire or SiC.

In light emitting diodes, when light is generated, a large amount of light is lost from the inside instead of being emitted outward. Therefore, in order to increase the light efficiency of the light emitting diode, it is necessary to allow the light generated by the light emitting diode to be emitted to the outside without being lost inside the semiconductor.

SUMMARY OF THE INVENTION The present invention has been made by such a necessity, and the technical problem to be achieved by the present invention is to stack a plurality of insulating layers in a semiconductor layer so that light generated in the light emitting diodes can be emitted to the outside by internal reflection without being lost inside. It is to increase the amount of light is emitted to the outside by scattering light through the light reflection at the scattering center having a scattering center made by.

According to an aspect of the present invention for achieving the above technical problem, in the method for manufacturing a light emitting device formed by forming a first conductive semiconductor layer, a second conductive semiconductor layer and an active layer therebetween on a substrate, Firstly growing a first conductive semiconductor layer, alternately stacking two or more insulating layers having different refractive indices on the first conductive semiconductor layer, and stacking the stacked insulating layers with the first conductive semiconductor layer Patterning etching to reveal a portion of the layer to form a scattering center, secondary growing the first conductive semiconductor layer on the scattering center, and forming an active layer and a second conductive type on the first conductive semiconductor layer. It provides a light emitting device manufacturing method comprising the step of forming a semiconductor layer.

Preferably, the laminating step may be alternately laminated to the SiO ₂ layer and Si ₃ N ₄ layer.

Preferably, the laminating step may be laminated in a plurality of layers by repeatedly alternating two or more different insulating layers.

Preferably, in the forming of the scattering center, the stacked insulating layers may be etched using a mask pattern in a mesh form using photolithography.

According to another aspect of the present invention, there is provided a light emitting device in which a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer therebetween are formed on a substrate, wherein the substrate and the first conductive semiconductor layer are formed on the substrate. A first scattering center, a plurality of scattering centers formed by alternately stacking two or more insulating layers having different refractive indices on the first layer, and the first conductivity-type semiconductor layer on the first layer on which the plurality of scattering centers is formed Provided is a light emitting device comprising a second layer formed of an active layer and a second conductive semiconductor layer formed on the second layer.

Preferably, the plurality of scattering centers may be formed by alternately stacking an SiO ₂ layer and an Si ₃ N ₄ layer.

Preferably, the plurality of scattering centers may be stacked in a plurality of layers by repeatedly alternating two or more different insulating layers.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so that the spirit of the invention to those skilled in the art can fully convey. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And, in the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 1, a light emitting diode 1 according to an embodiment of the present invention includes a substrate 100 as a base, and an N-type semiconductor layer 220, an active layer 240, and a P on the substrate 100. The light emitting cell 200 including the type semiconductor layer 260 is formed.

Although the light emitting diode 1 of this embodiment includes one light emitting cell but includes a plurality of light emitting cells, the light emitting diode which can be operated by an AC power supply is also within the scope of the present invention. Meanwhile, a portion of the N-type semiconductor layer 220 is exposed upward by the formation of mesas, and an N-type electrode pad 330 is formed at the exposed portion of the light emitting cell. The substrate 100 is preferably made of sapphire material, but may be made of another material such as SiC having a higher thermal conductivity than the sapphire material.

As shown, the active layer 240 is limitedly formed on a portion of the N-type semiconductor layer 220 by mesa formation, and the P-type semiconductor layer 260 is formed on the active layer 240. Therefore, a portion of the upper surface of the N-type semiconductor layer 220 is bonded to the active layer 240, and the remaining portion of the upper surface is exposed to the outside. In the present embodiment, a portion of the N-type semiconductor layer 220 is formed to be partially removed to form the N-type electrode pad, but the vertical light emitting diode from which the substrate under the N-type semiconductor layer 220 is removed is also present invention. Is in the range of.

N-type semiconductor layer 220 may include an N-type cladding layer _{Al x In y Ga 1 -x- y} N may have a (0≤x, y, x + y≤1 ), N -type. In addition, the P-type semiconductor layer 260 may be formed of P-type Al _x In _y Ga _{1- xy} N (0 ≦ x, y, x + y ≦ 1), and may include a P-type cladding layer. The N-type semiconductor layer 220 is formed by adding silicon (Si) as a dopant. The P-type semiconductor layer 260 may be formed by adding dopants such as zinc (Zn) or magnesium (Mg).

In particular, the N-type semiconductor layer 220 includes a scattering center 224. The scattering center 224 is formed by stacking two or more insulating layers having different refractive indices alternately. The scattering center 224 may maximize the scattering effect inside the N-type semiconductor layer 220. The configuration of the N-type semiconductor layer 220 will be described in more detail below.

In addition, a transparent electrode layer 320 formed of a metal or metal oxide such as Ni / Au, ITO, or ZnO is formed on an upper surface of the P-type semiconductor layer 260, and a P-type electrode pad is formed in a portion of the upper surface of the transparent electrode layer 320. 340 may be formed.

The active layer 240 is an area where electrons and holes are recombined and includes InGaN. The emission wavelength extracted from the light emitting cell 200 is determined according to the type of material constituting the active layer 240. The active layer 240 may be a multilayer film in which a quantum well layer and a barrier layer are repeatedly formed. Barrier layer and the well layer may be a semiconductor layer 2-to 4 won the compounds represented by the general formula _{Al x In y Ga 1 -x- y} N (0≤x, y, x + y≤1).

In addition, a buffer layer 210 may be interposed between the substrate 100 and the N-type semiconductor layer 220. The buffer layer 210 is used to mitigate the lattice mismatch between the semiconductor layers to be formed thereon and the substrate 100. In addition, when the substrate 100 is conductive, the buffer layer 210 is formed of an insulating material or a semi-insulating material to electrically insulate the substrate 100 from the light emitting cell 200. The buffer layer 210 may be formed of nitride such as AlN, GaN, or the like. On the other hand, when the substrate 100 is insulating, such as sapphire, the buffer layer 210 may be formed of a conductive material.

As briefly mentioned above, part of the N-type semiconductor layer 220 is formed by lateral growth by a lateral epitaxial overgrowth (LEO) method. An N-type semiconductor layer 222 and a second N-type semiconductor layer 226 thereon. In addition, a scattering center 224 is formed between the first N-type semiconductor layer 222 and the second N-type semiconductor layer 226 to cause lateral growth of the second semiconductor layer 226.

The scattering center 224 grows the first N-type semiconductor layer 222 and alternately stacks two or more insulating layers having different refractive indices into a plurality of layers, and then patternes the stacked insulating layers using photolithography technology. It forms by etching. The pattern may be a mesh structure or a stripe structure.

The insulating layers constituting the scattering center 224 are alternately stacked in the form of a reflective film. For example, the SiO ₄ layer and the Si ₃ N ₄ layer may be repeatedly alternately stacked.

Another N-type semiconductor layer is epitaxially grown on the N-type semiconductor layer on which the scattering centers 224 in the pattern form are formed.

In the present embodiment, the first N-type semiconductor layer 222 is formed by growing in a vertical direction on the substrate 100 on which the low temperature buffer layer and / or the high temperature buffer layer are formed. In addition, between the pattern of the second N-type semiconductor layer 226 and the scattering center 224 is formed by both the vertical growth and the lateral growth, which is represented by an imaginary line in the enlarged view of FIG.

As the scattering center 224 is formed by alternately stacking two or more insulating layers having different refractive indices into a plurality of layers, light scattered from the active layer 240 is scattered by performing a function of a distributed bragg reflector (DBR) to increase reflectance. Loss in the semiconductor layer through the center 224 can be reduced, and scattering can be efficiently caused by the scattering center 224 to be emitted to the outside of the light emitting diode.

Distributed Bragg Reflectors (DBRs) are used when high reflectivity is required in various light emitting devices including light emitting functions, light detection functions, light modulation functions, and the like.

DBR is a reflecting mirror which laminates | stacks two types of media from which refractive indices differ, and reflects light using the difference in refractive index.

In addition, the lateral growth of the second N-type semiconductor layer 226 suppresses lattice defects such as dislocations caused by thermal expansion and / or lattice mismatch between the substrate 100 and the N-type semiconductor layer 220. In addition, the scattering center 224 is used for the lateral growth of the second N-type semiconductor layer 226 described above, and serves as a backbone of the N-type semiconductor layer 220, and thus, on the substrate 100. The light emitting cell including the N-type semiconductor layer 220 is prevented from distortion.

Hereinafter, a light emitting diode manufacturing method according to an exemplary embodiment of the present invention will be described with reference to FIGS. 2 to 6.

Referring to FIG. 2, a buffer layer 210 is formed on a substrate 100, and a first N-type semiconductor layer 222 is formed on the buffer layer 210. The buffer layer 210 and the first N-type semiconductor layer 222 are preferably formed by metal organic chemical vapor deposition (MOCVD), but may be formed using a molecular beam growth (MBE) or a hydride vapor deposition (HVPE) method. Can be. The buffer layer 210 and the first N-type semiconductor layer 222 are continuously formed in the same process chamber.

In particular, the first N-type semiconductor layer 222 is a layer formed by adding Si dopant, and is formed by growing in a vertical direction on the substrate 100 on which the buffer layer 210 is formed. An N-type semiconductor layer is grown on the substrate via organometallic chemical vapor deposition (MOCVD).

Next, as shown in FIG. 3, the scattering center 224 is formed on the top surface of the first N-type semiconductor layer 222. In this embodiment, the SiO ₂ layer is laminated as the first insulating layer on the first N-type semiconductor layer 222 to form the scattering center 224. The thickness of the SiO ₂ layer to be laminated is preferably 10 GPa or more.

When the SiO ₂ layer is laminated on the first N-type semiconductor layer 222 as the first insulating layer, the Si ₃ N ₄ layer is laminated as the second insulating layer on the SiO ₄ layer. The thickness of the SiO ₂ layer to be laminated is preferably 10 GPa or more.

When a Si ₃ N ₄ layer is laminated as the _second insulating layer, SiO ₂ and Si ₃ N ₄ are alternately stacked as a plurality of layers as the insulating layer.

The number of alternating stacks of SiO ₂ and Si ₃ N ₄ forming the scattering center 224 may be determined in consideration of the thickness of each insulation layer.

After the SiO ₂ layer and the Si ₃ N ₄ layer are alternately stacked, the stacked insulating layers are patterned and etched using photolithography to form a scattering center 224 having a mesh pattern.

4 and 5, the second N-type semiconductor layer 226 is formed on the first N-type semiconductor layer 222 on which the scattering center 224 is formed. The growth of the second N-type semiconductor layer 226 is performed in the above-described process chamber by MOCVD, and at this time, Si dopant is added. According to a preferred embodiment of the present invention, since the second N-type semiconductor layer 226 is made of GaN, GaN is not grown on the scattering center 224 made of an insulating layer, so that the scattering center 224 The second N-type semiconductor layer 226 growing in the vertical direction between the stripe patterns is laterally grown as shown in FIG. 4 above the scattering center 224.

Next, in the same process chamber, the active layer 240 and the P-type semiconductor layer 260 are sequentially formed on the upper surface of the second N-type semiconductor layer 226 to form a stacked structure as shown in FIG. 6. At this time, a P-type dopant such as zinc (Zn) or magnesium (Mg) is added to the P-type semiconductor layer 260.

Next, although not shown, a process of forming a transparent electrode layer 320 (see FIG. 1) selected from Ni / Au, ITO, ZnO, and the like on the upper surface of the P-type semiconductor layer 260 and a part of the N-type semiconductor layer 220 A process of forming a mesa and a process of forming a P-type electrode pad 340 and an N-type electrode pad 330 in the exposed regions of the transparent electrode layer 320 and the N-type semiconductor layer 220 may be performed. As a result, a light emitting diode having a structure as shown in FIG. 1 can be manufactured.

Alternatively, a vertical light emitting diode in which a P-type electrode and an N-type electrode are provided up and down may be manufactured by taking a process of removing the substrate 100 from the light emitting cell.

The present invention is not limited to the above described embodiments, and various modifications and changes can be made by those skilled in the art, which are included in the spirit and scope of the present invention as defined in the appended claims.

For example, in one embodiment of the present invention, a scattering center formed by patterning and forming a plurality of layers by alternately stacking SiO ₂ and Si ₃ N ₄ as an insulating layer on the GaN-based first N-type semiconductor layer 222. The method of transversely growing the second N-type semiconductor layer 226 by the LEO method using the scattering center 224 and the light emitting diode manufactured by the method have been mainly described.

However, in addition to SiO ₂ and Si ₃ N ₄ , the scattering center pattern may be formed using an insulating layer having different refractive indices as the insulating layer.

According to the present invention, an insulating layer having different refractive indices is stacked between a substrate and an active layer in a light emitting device to form a scattering center for forming a DBR, thereby reducing light transmittance at the scattering center and improving reflectance. As a result, light generated by the active layer is transmitted through the scattering center and is not extinct in the light emitting device, but is scattered by the scattering center and can be efficiently emitted to the outside, thereby improving light efficiency.

 According to the present invention, lattice defects such as dislocations caused by lattice mismatch and / or difference in heat transfer rate between the substrate and the semiconductor layer can be suppressed through the lateral growth of the semiconductor layer by the LEO method using the scattering center. have.

Claims (7)

In the method of manufacturing a light emitting device formed by forming a first conductive semiconductor layer, a second conductive semiconductor layer and an active layer therebetween on a substrate, Firstly growing a first conductivity type semiconductor layer on the substrate, Alternately stacking two or more insulating layers having different refractive indices on the first conductive semiconductor layer; Patterning the stacked insulating layers to expose a portion of the first conductive semiconductor layer to form scattering centers; Secondarily growing the first conductivity type semiconductor layer on the scattering center; And forming an active layer and a second conductive semiconductor layer on the first conductive semiconductor layer. The method of claim 1, wherein the laminating step, A method of manufacturing a light emitting device, in which an SiO ₂ layer and an Si ₃ N ₄ layer are alternately laminated. The method of claim 1, wherein the laminating step, A method of manufacturing a light emitting device in which two or more different insulating layers are alternately repeatedly stacked in a plurality of layers. The method of claim 1, wherein the scattering center forming step, Method of manufacturing a light emitting device for etching the laminated insulating layer by a mask pattern of a mesh form using photolithography. In a light emitting device formed by forming a first conductive semiconductor layer, a second conductive semiconductor layer and an active layer therebetween on a substrate, Substrate, A first layer formed of a first conductivity type semiconductor layer on the substrate, A plurality of scattering centers formed by alternately stacking two or more insulating layers having different refractive indices on the first layer, A second layer formed of the first conductivity type semiconductor layer on the first layer on which the plurality of scattering centers are formed; A light emitting device comprising an active layer and a second conductivity type semiconductor layer formed on the second layer. The method of claim 5, wherein the plurality of scattering centers are A light emitting device in which an SiO ₂ layer and an Si ₃ N ₄ layer are alternately stacked. The method of claim 5, wherein the plurality of scattering centers are A light emitting device stacked in a plurality of layers by repeatedly alternating two or more different insulating layers.

Images