JP2005268636A - Gallium nitride system light emitting element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simplified manufacturing method to form a light extracting layer which is suitably employed for various kinds of light emitting elements whereas ensuring the effect for reducing total reflection and improvement in the light extracting coefficient. <P>SOLUTION: A titanium nitride layer is formed on a current distributing layer (28), and a double-layer structure for extracting light beam is also formed through cooperation. Such double-layer structure is formed to a certain light emitting material, and the titanium nitride layer includes a microstructure (29). This microstructure (29) is constituted as a nano/net structure. Formation of such microstructure (29) effectively prevents generation of total-reflection of the light generated in a semiconductor active layer (24) in such light emitting material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a gallium nitride-based light-emitting element for improving the light-emitting efficiency of a gallium nitride-based light-emitting diode and a method for manufacturing the same, and in particular, to provide a light-emitting layer having a metal microstructure and to improve the light-emitting efficiency. The present invention relates to a gallium nitride light emitting device and a method for manufacturing the same.

  The development of semiconductor light emitting diodes (LEDs) has already had a decades of history, and improving their luminous efficiency has always been a factor in whether LEDs can be used as consumer light sources. In recent years, the direction of LED development has evolved in the direction of improving its luminous efficiency, and the improvement of its luminous efficiency is largely due to the design, transparency, and total reflection of the semiconductor materials and device structures that are selected and used. It is deeply and closely related to phenomena.

  Gallium nitride-based materials are commonly used materials for semiconductor light-emitting diodes, and it is important to apply voltage and current to the diodes in order to cause the gallium nitride-based materials to emit light. The diode element is always provided with a pair of positive and negative electrodes in order to apply a voltage or to pass a current therethrough.

  The positive electrode is a general so-called p-type electrode, and the negative electrode is a general so-called n-type electrode. The electricity of the p-type electrode first flows into the p-type semiconductor layer, and the electricity of the n-type electrode is This is because the p-type electrode is a location where a positive current flows, while the p-type electrode is a place where a positive current flows, and mobile carriers as a means of relying on the conduction are holes, and the n-type electrode is a negative current. The moving carrier as a means of relying on the conduction is an electron while becoming a flowing-in place. As is well known, the transition rate of successful migration is much lower than that of electrons, so that the conductivity efficiency of the p-type electrode location is much inferior to that of the n-type electrode. Usually, a current distribution layer is joined below the p-type electrode, thereby guiding the positive charge entering the p-type electrode to be uniformly distributed in the p-type semiconductor layer, thereby the p-type electrode and the n-type electrode. The power distribution with the mold electrode is made uniform, and the luminous efficiency of the excited light is then improved.

  Any suitable material can be used as the material for the current distribution layer, of which the Ni / Au bilayer structure is the most commonly used, and the overall LED structure is the light emitting diode structure disclosed in FIG. As shown in FIG. 10, the substrate 11, the buffer layer 12, the n-type gallium nitride-based layer 13, the semiconductor active layer 14, the p-type gallium nitride-based layer 15, the p-type semiconductor layer 16, and the current distribution layer 17 are included therein. The p-type electrode 18 and the manufacturing process thereof are as disclosed in Taiwan Patent Nos. 558848 and 419837. In the figure, a current distribution layer 17 is provided between the p-type semiconductor layer 16 and the p-type electrode 18, and the positive charge of the p-type electrode 18 is uniformly distributed in the current distribution layer 17 by such a design. The p-type semiconductor layer 16 is intended to be uniformly entered.

  However, this type of current distribution layer design has a much more severe problem with its total reflection, and because its surface is flat, the rays are totally reflected back into its configuration, which can interfere with its output, For this reason, an invention of a light emitting diode is proposed in which a roughened design structure is added above the current distribution layer. For example, by introducing a roughened structure at a light emitting portion above the light emitting element, a large number of emitted light beams The angle of injection is made smaller than the critical angle (according to Snell's law). Such a roughened structure is generally formed in a semi-circular shape or a pyramid shape that is rounded. However, this type of roughened structure has problems such that the number of processing steps is considerably complicated and the processing cost is considerably high.

  In addition, other coarsening methods have been proposed. For example, by destroying a planar part on the element structure by an etching method, a plurality of small cut faces are formed on the planar part, and an emission angle of a plurality of emitted light beams is made smaller than a critical angle. Thus, the light beam is not totally reflected to the element structure. This type of roughening method has a step of randomly etching a plane, for example, first depositing particles on the plane and then using those particles as a random etch mask. However, the planar pattern formed in this way has at least two major problems, one of which is that the p-type electrode may form a part of an island-like structure. Since the lower part of the structure does not contact the p-type electrode, those parts do not emit light, and the overall light output efficiency may be reduced, and the second is in the structure of the element. Since the plane is quite close to the light emitting area below it, the etching method easily destroys the light emitting area, and this causes other light emission amounts to decrease.

  In light of the fact that conventional gallium nitride light-emitting diodes have the above-mentioned structural defects, it is necessary to propose a gallium nitride light-emitting diode having a high light extraction rate.

  It is an object of the present invention to provide a gallium nitride based light emitting diode device having high light extraction efficiency, and to provide a method for manufacturing the gallium nitride based light emitting diode device. Let's assume the problem to be solved.

  In order to achieve the above object, the GaN-based light emitting device according to the present invention forms a surface of a microstructure in the current distribution layer, and reduces the total light reflection phenomenon of the current distribution layer by the microstructure. The purpose is to improve the luminous efficiency.

  The structure of the light emitting device comprising the surface of the microstructure of the present invention mainly includes two main embodiments. In the first embodiment of the device structure of the present invention, the current distribution layer includes A titanium nitride layer is formed and jointly forms a light extraction two-layer structure, the two-layer structure is formed on a light emitter, and the titanium nitride layer has a microstructure, and the microstructure is nano- By forming the microstructure of the net structure, it is possible to ensure that the light generated in the semiconductor active layer in the light emitter does not effectively cause total reflection.

  Further, in the second light emitting device embodiment of the present invention, a Pt layer is formed in the current distribution layer, and a light extraction two-layer structure is jointly formed to form a light emitter having the two-layer structure. In addition, the Pt layer has a microstructure, and the microstructure is actually a metal cluster structure. By forming the microstructure, all the light rays generated in a certain semiconductor active layer in the light emitter are formed. It can be ensured that no reflection is generated.

  In the first device manufacturing method of the present invention, first, a gallium nitride-based light emitter structure is formed, then a current distribution layer is formed on the light emitter, and then a titanium layer is formed on the current distribution layer, Then, the titanium layer is subjected to nitriding treatment, thereby forming a surface having a microstructure made of titanium nitride having a nano-net structure.

  In an embodiment of the second light emitting device manufacturing method of the present invention, first, a gallium nitride based light emitting structure is formed, then a current distribution layer is formed on the light emitting body, and then Pt is formed on the current distribution layer. A layer is formed, and then the Pt layer is tempered, thereby having a microstructured surface of Pt having a metal cluster structure.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail and specifically with reference to the accompanying drawings. However, the specific structures according to the detailed descriptions are merely possible embodiments of the present invention. However, the claimed scope of the present invention is not strictly limited.

  The main object of the present invention is to eliminate the total reflection phenomenon by proposing a light extraction layer mainly having a microstructure surface, and to improve the efficiency for extracting the emitted light from the light extraction layer. Will be described in detail as will be described later.

  The structure of the gallium nitride light emitting device of the present invention includes two main embodiments, and FIG. 2 shows an embodiment showing the structure 20 of the first device of the present invention. In FIG. First, a base material 21 is prepared for manufacture, and a material to be applied such as sapphire, gallium nitride, or SiC can be used as the base material. In addition, an n-type gallium nitride-based layer 23, a semiconductor active layer 24, and a p-type gallium nitride-based layer 25 are sequentially formed on the base material 21, and films 23, 24, and 25 of the respective layers are formed. On the other hand, when a voltage is applied or when electricity is applied, a light beam is generated. Here, the three-layer structures 23, 24, and 25 are referred to as light emitters. Among them, an AlGaInN layer or an InGaN / GaN layer can be used as the semiconductor active layer. Among them, a buffer layer 22 may be selectively formed between the base material 21 and the n-type gallium nitride layer 23, whereby excellent crystals are formed on both layers 21 and 23 on the buffer layer 22 side. Have a degree of lattice matching. Then, a p-type contact layer 26 is provided on the p-type gallium nitride-based layer 25, and a light extraction layer 27 is provided on the p-type contact layer 26. Among them, the contact layer 26 is a p-InGaN layer or p-AlInGaN. Layers can be adopted. In addition, the light extraction layer 27 employs a two-layer structure including a current distribution layer 28 and a microstructure layer 29. Among them, a current distribution layer 28 made of a transparent conductive material is used, and a conventional Ni / Au bilayer is used. Structures, Ni, Pt, Pd, Rh, Ru, Os, Ir, Zn, In, Sn, Mg, and other materials and oxides of those materials can be used appropriately. Can be doped thereby improving its conductivity, for example aluminum, the light transmission wavelength range of which varies depending on the material of the phosphor used, usually the phosphor The principle is to make it possible to transmit a large amount of the light rays emitted from.

  Further, the microstructure layer 29 is a film layer having a nano-net structure, and titanium nitride is used as a material thereof, and the actual surface pattern is disclosed in the figure in order to consider the readability of the figure. In addition, since the nano-net structure of titanium nitride is a coarse structure with very fine dimensions, most of the photons generated in the semiconductor active layer 24 pass through the nano-net microstructure layer 29. The light is emitted at an angle smaller than the critical angle, so that a large number of photons can be output from the device structure. Compared with a conventional light emitting device having a rough surface, the fine size structure of the present invention is formed more finely than the conventional rough structure, so that photons can be emitted from an angle formed much smaller than the critical angle, and more can be emitted. Therefore, since the degree of total reflection is greatly reduced, the light extraction efficiency is greatly increased.

  As shown in the figure, a p-type electrode 30 is provided on the microstructure layer 29, and an n-type electrode 31 is provided on the side where the n-type gallium nitride-based layer is provided. The current is set to flow into the light emitter of the element.

  Also shown in FIG. 3 is an embodiment showing a second device structure 40 of the present invention, which includes a substrate 41, a buffer layer 42, an n-type gallium nitride-based layer 43, and a semiconductor active And includes a layer 44, a p-type gallium nitride based layer 45, a p-type contact layer 46, a current distribution layer 48, a microstructure layer 49, and electrodes 50 and 51, and a first blocking embodiment. Although the structure of the multi-layer film is the same, the microstructure layer 49 of the light extraction layer 47 is different. In the present embodiment, a tempered Pt layer is used as the microstructure layer 49, and it has a metal cluster structure in it, and the pattern is difficult to disclose in the drawing. Not shown in detail. Similarly, the metal cluster structure has a size that is considerably smaller than the conventional coarse structure, so that photons can be emitted at an angle much smaller than the critical angle, and the emission amount can be greatly improved. Since the rate of total reflection of photons can be greatly reduced, the light extraction rate can be greatly improved.

  FIG. 4 shows a manufacturing method of an embodiment of the structure of the first element of the present invention. First, a substrate is manufactured and prepared (61). Then, a buffer layer is selectively formed on the substrate (62), and molecular beam crystal stacking method (MBE), metal organic chemical vapor deposition (MOCVD) or the like can be suitably employed as the forming method, An n-type gallium nitride-based layer is formed on the buffer layer (63), a semiconductor active layer is then formed on the n-type gallium nitride-based layer (64), and a p-type gallium nitride-based layer is formed on the semiconductor active layer (65). Then, a contact layer is formed on the p-type gallium nitride-based layer (66), a current distribution layer is formed on the contact layer (67), and then a titanium layer is formed on the current distribution layer (68). Thereafter, the titanium layer is nitrided to form a titanium nitride layer having a nano-net structure (69). In addition, a p-type electrode is formed in the microstructure layer, and an n-type electrode is formed on one side of the n-type gallium nitride material layer. Manufacturing is completed.

  FIG. 5 shows a method of manufacturing the second device embodiment of the present invention, in which steps (71) to (77) are the same as steps (61) to (67) shown in FIG. However, steps (78) and (79) are different from steps (68) and (69) shown in FIG. In the case of this embodiment, after the current distribution layer is formed, a Pt layer is formed on the current distribution layer (78), and the Pt layer is tempered to thereby form a Pt layer having a metal cluster structure. Is acquired (79). In addition, a p-type electrode is formed on the microstructure layer, and an n-type electrode is formed on the side of the n-type gallium nitride material layer, thereby completing the structure of the second device embodiment. .

  FIG. 6 shows a light-emitting element structure 80 in which a p-type metal electrode 88 is formed on the current distribution layer 86 side and is not formed thereabove, and includes a base material 81 and an n-type gallium nitride system. A layer 82, a semiconductor active layer 83, a p-type gallium nitride-based layer 84, and a p-type contact layer 85, and a gallium nitride-based current distribution layer 86 is formed in the p-type contact layer 85, A p-type metal electrode 88 is formed on the gallium nitride-based current distribution layer 86 side and a part of the area, and the microstructure layer 87 of the present invention is finally formed above the gallium nitride-based current distribution layer 86 and the metal electrode. 88 is formed on the side. In the present embodiment, since the microstructure layer 87 does not need to participate in the conduction work of current distribution, it can be formed separately from the p-type metal electrode 88.

  As for the microstructure layer of the present invention, a structure of a light emitting element forming a tunnel junction surface will be described as an example. Among them, the above-described nano / net structure layer or metal layer is formed as a microstructure layer formed thereon. A cluster layer structure can be employed, and the structure 90 includes a base material 91, an n-type gallium nitride-based layer 92, and a semiconductor active layer 93, as shown in FIG. In the layer 94, p + and n + type gallium nitride based layers 95 and 96 are formed, in which the n + gallium nitride based layer 96 is located above the p + type layer 95, and is hereinafter referred to as p + / n + type gallium nitride. It is described as a system layer. Further, the microstructure layer 97 of the present invention is formed directly on the n + gallium nitride based layer 96, and there is no need to dispose a current distribution layer as in the previous embodiment, and directly below the microstructure layer 97. This is because it is a film layer that uses electrons as the main conductive carrier. Of course, a current distribution layer may be selectively disposed. A p-type electrode 98 is provided on the microstructure layer 97, and an n-type electrode 99 is provided on the n-type gallium nitride layer 92.

  Then, an example in which the microstructure layer of the present invention is used in a special light emitting device structure will be described, and the structure thereof is shown in a light emitting device structure 100 having a vertical structure shown in FIG. In the figure, a metal reflective layer 102 is formed on a substrate 101, and the light generated by a film layer (including a p-type gallium nitride layer 103, a semiconductor active layer 104, an n-type gallium nitride layer 105, etc.) is generated. It is localized so that it is located above it. This is because a metal conductive material is used as the substrate 101 and is used to supply power to the p-type gallium nitride-based layer 103, and the n-type electrode 107 is located on the upper surface portion of the structure 100. In such a structure 100, since there is no problem of a low transition rate for introducing holes of the electrode, it is not necessary to provide a current distribution layer, and of course, it may be selectively added. At this time, the microstructure layer 106 of the present invention may be formed directly above the n-type gallium nitride-based layer 105. Then, an n-type electrode 107 is formed on the microstructure layer 106.

  The structure of the light emitting device according to the present invention has an excellent effect of reducing the total reflection and the light extraction rate, and the structure of the device of the present invention as compared with the rough surface structure by the conventional etching method. Is easy to manufacture and not complicated, and the light extraction layer is suitable for use in various light emitting devices.

  Although the basic embodiments of the present invention have already been disclosed in detail as described above, engineers in the field can develop and develop various different embodiments based on the above embodiments, for example, electrodes at different locations. The light extraction layer having the two-layer structure of the present invention can also be introduced into the light emitting device disposed in the above structure, however, if the modified design can achieve the same effect as the present invention, the implementation change is also claimed in the present invention. Needless to say, it should be delivered within range.

It is a front view which shows the structure of the conventional gallium nitride type light emitting diode element. It is explanatory drawing which shows the structure of the 1st element of this invention. It is explanatory drawing which shows the structure of the 2nd element of this invention. It is explanatory drawing which shows the Example of the manufacturing method for manufacturing the structure of the 1st element of this invention. It is explanatory drawing which shows the Example of the manufacturing method for manufacturing the structure of the 2nd element of this invention. It is explanatory drawing which shows a mode in the case of using the microstructure of this invention for another light emitting element. It is explanatory drawing which shows a mode in the case of using the microstructure of this invention for the light emitting element which has a tunnel junction surface. It is explanatory drawing which shows a mode in the case of using the microstructure layer of this invention for the structure of a vertical light emitting element.

Explanation of symbols

20 First element structure 21, 41, 81, 91 Base material 22, 42 Buffer layer 23, 43, 82, 92, 105 n-type gallium nitride-based layer 24, 44, 83, 93, 104 Semiconductor active layer 25, 45, 84, 94, 103 p-type gallium nitride-based layers 26, 46, 85 p-type contact layers 27, 47 Light extraction layers 28, 48 Current distribution layers 29, 49, 87, 97, 106 Microstructure layers 30, 50, 98, 108 p-type electrodes 31, 51, 99, 107 n-type electrode 40 second element structure 80 light-emitting element structure 86 current distribution layer 88 p-type metal electrode 89 n-type metal electrode 90 tunnel junction surface light-emitting element structure 95 p + Type gallium nitride based layer 96 n + type gallium nitride based layer 100 vertical light emitting element structure 101 metal substrate 102 metal reflective layer

Claims (24)

A light emitter made of a gallium nitride-based material capable of emitting light;
It has at least a light extraction layer comprising at least a current distribution layer provided in the light emitter, and a microstructure layer made of a titanium nitride layer having a nano-net structure provided in the current distribution layer. A gallium nitride based light emitting device.   The light emitter includes an n-type gallium nitride-based layer, a semiconductor active layer, and a p-type gallium nitride-based layer, in which the semiconductor active layer is located above the n-type gallium nitride layer, and The gallium nitride-based light emitting device according to claim 1, wherein a p-type gallium nitride layer is located above the active layer.   The light emitting element includes a p-type electrode and an n-type electrode, and the p-type electrode is provided above the microstructure layer, or on the microstructure layer side and the current distribution layer side. The gallium nitride-based light emitting device according to claim 1, wherein the gallium nitride light emitting device is located.   A transparent conductive layer is used as the current distribution layer, and a material selected from a group consisting of materials described later is selectively used, that is, a Ni / Au bilayer structure, Ni, Pt, Pd, Rh, or Ru. 2. The gallium nitride based light-emitting element according to claim 1, wherein a gallium nitride-based light-emitting element is used which selectively uses Os, Os, Ir, Zn, In, Sn, Mg, and the like, and oxides of these substances.   The gallium nitride-based light-emitting element according to claim 1, wherein the titanium nitride nano-net includes a TiN layer. A light emitter made of a gallium nitride-based material capable of emitting light;
Nitriding characterized by comprising at least a current distribution layer provided in the luminous body and a light extraction layer provided in the current distribution layer and comprising at least a microstructure layer made of a Pt layer having a metal cluster structure Gallium-based light emitting device.   The light emitter includes an n-type gallium nitride-based layer, a semiconductor active layer, and a p-type gallium nitride-based layer, in which the semiconductor active layer is located above the n-type gallium nitride layer, and The gallium nitride-based light emitting device according to claim 6, wherein a p-type gallium nitride layer is located above the active layer.   The light emitting element includes a p-type electrode and an n-type electrode, and the p-type electrode is provided above the microstructure layer, or on the microstructure layer side and the current distribution layer side. The gallium nitride-based light emitting device according to claim 6, wherein the gallium nitride light emitting device is located.   A transparent conductive layer is used as the current distribution layer, and a material selected from a group consisting of materials described later is selectively used, that is, a Ni / Au bilayer structure, Ni, Pt, Pd, Rh, or Ru. 7. The gallium nitride-based light emitting device according to claim 6, wherein a gallium nitride-based light emitting device that employs selective use of Os, Ir, Zn, In, Sn, Mg, and the like, and oxides of these substances is used.   The gallium nitride based light emitting device according to claim 6 or 9, wherein the Pt layer metal cluster structure is formed by tempering a Pt layer. Step 1 to prepare the substrate for production,
Forming an n-type gallium nitride-based layer on the substrate;
Forming a semiconductor active layer on the n-type gallium nitride-based layer; and
Forming a p-type gallium nitride based layer on the semiconductor active layer; and
Forming a current distribution layer on the p-type gallium nitride based layer; and
And a step 6 of forming a microstructure layer on the current distribution layer. In the step of forming a microstructure layer in the current distribution layer,
And a step of forming a p-type electrode and an n-type electrode on the light-emitting element, and the p-type electrode is located above the microstructure layer or on the side of the microstructure layer and the current distribution layer. The method of manufacturing a gallium nitride based light emitting device according to claim 11, wherein the method is formed.   A transparent conductive layer is used as the current distribution layer, and a material selected from a group consisting of materials described later is selectively used, that is, a Ni / Au bilayer structure, Ni, Pt, Pd, Rh, or Ru. 12. The gallium nitride based light-emitting element according to claim 11, wherein the gallium nitride-based light-emitting element according to claim 11, wherein a material that selectively uses Os, Os, Ir, Zn, In, Sn, Mg, and the like and oxides of these substances is employed. Production method. In the step of forming a microstructure layer in the current distribution layer,
12. The method of manufacturing a gallium nitride based light emitting device according to claim 11, further comprising a process of forming a titanium layer on the p-type gallium nitride layer and then performing a nitriding process on the titanium layer. In the step of forming a microstructure layer in the current distribution layer,
12. The method of manufacturing a gallium nitride light emitting device according to claim 11, further comprising a process of performing a tempering process on the Pt layer after forming a Pt layer on the p-type gallium nitride layer. A light emitter made of a gallium nitride-based material capable of emitting light;
A gallium nitride based p + / n + tunnel junction layer located above the light emitter;
A gallium nitride based light emission comprising a light extraction layer located above the p + / n + tunnel junction surface layer and comprising a titanium nitride layer having a nano-net structure or a Pt layer having a metal cluster structure element.   The light emitter includes an n-type gallium nitride-based layer, a semiconductor active layer, and a p-type gallium nitride-based layer, in which the semiconductor active layer is located above the n-type gallium nitride layer, and The gallium nitride-based light emitting device according to claim 16, wherein a p-type gallium nitride layer is located above the active layer.   The gallium nitride according to claim 16 or 17, wherein the light emitting element has a p-type electrode and an n-type electrode, and the p-type electrode is provided above the microstructure layer. System light emitting element.   The titanium nitride nano-net is formed of a titanium nitride layer, and the metal cluster structure of the Pt layer is formed by tempering the Pt layer. 2. A gallium nitride based light emitting device according to 1.   The light extraction layer has a current distribution layer, and uses a transparent conductive layer as the current distribution layer and selectively uses one selected from the group consisting of the materials described later, that is, Ni / Features that adopt Au double layer structure, Ni, Pt, Pd, Rh, Ru, Os, Ir, Zn, In, Sn, Mg, etc. and oxides of those substances selectively The gallium nitride-based light emitting device according to claim 16. A conductive metal substrate;
A conductive metal reflective layer located above the substrate;
A p-type gallium nitride-based layer located above the metal reflective layer;
A semiconductor active layer located above the p-type gallium nitride-based layer;
An n-type gallium nitride-based layer located above the semiconductor active layer;
A gallium nitride-based light emitting device having at least a titanium nitride layer having a nano-net structure or a microstructure layer made of a Pt layer having a metal cluster structure, located above the n-type gallium nitride-based layer .   The gallium nitride according to claim 21, wherein a p-type electrode is formed below the conductive metal substrate of the light emitting device, and an n-type electrode is formed above the microstructure layer. System light emitting element.   The nitriding according to claim 21, wherein the titanium nitride nano-net comprises a titanium nitride layer, and the metal cluster structure of the Pt layer is formed by tempering the Pt layer. Gallium-based light emitting device.   A transparent conductive layer is used as the current distribution layer, and a material selected from a group consisting of materials described later is selectively used, that is, a Ni / Au bilayer structure, Ni, Pt, Pd, Rh, or Ru. 24. The gallium nitride according to claim 21 or 23, wherein a material that selectively uses Al, Os, Ir, Zn, In, Sn, Mg, and the like, and oxides of these substances is used. System light emitting element.

Images