JP2008084973A - Semiconductor light-emitting device - Google Patents

Semiconductor light-emitting device Download PDF

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JP2008084973A
JP2008084973A JP2006261217A JP2006261217A JP2008084973A JP 2008084973 A JP2008084973 A JP 2008084973A JP 2006261217 A JP2006261217 A JP 2006261217A JP 2006261217 A JP2006261217 A JP 2006261217A JP 2008084973 A JP2008084973 A JP 2008084973A
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layer
refractive index
periodic structure
active layer
dimensional periodic
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Toshihiko Baba
俊彦 馬場
Takuya Kazama
拓也 風間
Junichi Sonoda
純一 園田
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Stanley Electric Co Ltd
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Stanley Electric Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To efficiently extract light radiated into air by a phosphor. <P>SOLUTION: In a semiconductor light-emitting device, the surface of the device is in a two-dimensional periodic structure, and the refractive index of two layers for sandwiching an active layer is made asymmetrical, thus improving the extraction efficiency of light radiated by the phosphor into air. In the semiconductor light-emitting device, a substrate layer, a first layer, an active layer, and a second layer are laminated sequentially. In the first layer, a single layer or a plurality of layers containing a first-conductivity-type semiconductor cladding layer are provided at the upper portion of the substrate layer; the active layer is provided at the upper portion of the first layer; and further a second layer is provided at the upper portion. The first layer has a refractive index that is smaller than that of the active layer, and contains at least a layer having a refractive index that is smaller than that of a layer in contact with the active layer in the second layer. In the second layer, all layers for composing the second layer have a refractive index that is smaller than that of the active layer. With such a configuration, the refractive index of two layers for sandwiching the active layer is made asymmetrical. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、光取り出し効率の高い半導体発光デバイス（ＬＥＤ）に関し、二次元周期構造を有し、活性層を挟み非対称な屈折率分布を有するLEDに関する。   The present invention relates to a semiconductor light emitting device (LED) having high light extraction efficiency, and relates to an LED having a two-dimensional periodic structure and having an asymmetric refractive index distribution with an active layer interposed therebetween.

半導体発光デバイス（ＬＥＤ）は、表示、ディスプレイ、照明等の広い分野での利用が期待されている。しかし、一般に半導体材料は空気や樹脂などの周囲環境に対する屈折率が大きいため、ＬＥＤから放射された光は全反射によって外部への取り出しが制限される。よって、ＬＥＤで発光した光の利用効率が低いという問題が指摘されている。例えば半導体材料の屈折率は2.0〜3.5、空気や樹脂などの周囲の屈折率を1.0〜1.5とすると、半導体材料と周囲の媒質の間で全反射が生じるため、LEDから取り出される光の効率は数％に制限される。   Semiconductor light emitting devices (LEDs) are expected to be used in a wide range of fields such as displays, displays, and lighting. However, since the semiconductor material generally has a large refractive index with respect to the surrounding environment such as air and resin, extraction of the light emitted from the LED to the outside is limited by total reflection. Therefore, the problem that the utilization efficiency of the light emitted from the LED is low is pointed out. For example, if the refractive index of the semiconductor material is 2.0 to 3.5 and the surrounding refractive index of air or resin is 1.0 to 1.5, total reflection occurs between the semiconductor material and the surrounding medium, so the efficiency of the light extracted from the LED is Limited to a few percent.

したがって、上記したＬＥＤでは、放射する光を外部により効率良く取り出すことが求められている。   Therefore, the above-described LED is required to extract emitted light more efficiently from the outside.

この課題を解決するものとして、半導体表面に周期構造を形成する手法が提案されている（例えば、特許文献１，２，３，４参照）。半導体表面に形成した周期構造は、周期構造の波数変換作用によって半導体内部の光の方向を変化させ、全反射していた光を空気中に取り出すようにするもので、内部の光が大きな立体角を有することから、結果的に取り出し効率が向上する。   In order to solve this problem, a method of forming a periodic structure on a semiconductor surface has been proposed (see, for example, Patent Documents 1, 2, 3, and 4). The periodic structure formed on the semiconductor surface changes the direction of the light inside the semiconductor by the wave number conversion action of the periodic structure so that the totally reflected light is taken out into the air. As a result, the extraction efficiency is improved.

米国特許 第５７７９９２４号US Pat. No. 5,777,924 特開平１０−４２０９号公報Japanese Patent Laid-Open No. 10-4209 特開２００４−１２８４４５号公報JP 2004-128445 A 特開２００４−３１２２１号公報JP 2004-3221 A 特開２００５−６９７０９号公報JP 2005-69709 A

しかしながら、３次元光波シミュレーションによって前記した周期構造による取り出し効率を算出した結果、見込まれる取り出し効率の向上は、周期構造 による回折効率によって制限され、未だ多くの光がＬＥＤ内部にとどまりその光取り出し効果が十分に発揮できていないことを確認した。なお、３次元光波シミュレーションは、本出願の発明者が波動光学シミュレーション方法として出願している（特許文献５）。   However, as a result of calculating the extraction efficiency due to the periodic structure described above by three-dimensional light wave simulation, the expected improvement in extraction efficiency is limited by the diffraction efficiency due to the periodic structure, and a large amount of light still remains inside the LED, and the light extraction effect is not improved. It was confirmed that it was not fully demonstrated. The inventor of the present application has applied for a three-dimensional light wave simulation as a wave optical simulation method (Patent Document 5).

また、周期構造を形成する加工プロセスによっては、周期構造の周期性を完全なものとすることができず、十分な光の取り出し効率が得られないという問題があり、また、この周期構造の周期性を完全なものとするには、加工プロセスに大きな負担がかかるという問題がある。   Further, depending on the machining process for forming the periodic structure, there is a problem that the periodicity of the periodic structure cannot be perfected, and sufficient light extraction efficiency cannot be obtained. There is a problem that a large burden is imposed on the machining process in order to achieve completeness.

この効率を向上させるものとして、発光層（活性層）に二次元周期構造を直接に形成する構造が考えられ、この構造とすることによって、さらに大幅な効率向上が見込まれる。しかしながら、発光層に直接に二次元周期構造を形成する構造では、発光層自体の品質を著しく損傷させてしまうという問題があるため、現実にはこのような構造を採用することはできない。   In order to improve this efficiency, a structure in which a two-dimensional periodic structure is directly formed in the light emitting layer (active layer) is conceivable, and this structure is expected to further improve efficiency. However, in the structure in which the two-dimensional periodic structure is formed directly on the light emitting layer, there is a problem that the quality of the light emitting layer itself is remarkably damaged. Therefore, such a structure cannot be actually used.

一般に結合の切れた半導体表面には、バンドギャップ内に多くの表面状態や欠陥状態が存在する。そのため、半導体表面近くの多くのキャリアは、この表面状態や欠陥状態を通し再結合する（表面再結合）。活性層に二次元周期構造を形成した場合、加工された活性層には結晶の結合が切れた表面と同じ状態が生じることになり、活性層に注入されたキャリアは表面再結合によりが光ではなく熱に変換されてしまい効率が低下する。   In general, a semiconductor surface with broken bonds has many surface states and defect states in the band gap. Therefore, many carriers near the semiconductor surface recombine through this surface state and defect state (surface recombination). When a two-dimensional periodic structure is formed in the active layer, the processed active layer has the same state as the surface where the crystal bond is broken, and carriers injected into the active layer are not recombined by light due to surface recombination. Without being converted to heat, the efficiency decreases.

本発明は前記した従来の問題点を解決し、発光体が放射する光を空気中により効率よく取り出すことを目的とする。   An object of the present invention is to solve the above-described conventional problems and to more efficiently extract light emitted from a light emitter in the air.

また、加工プロセスに負担をかけることなく光の取り出し効率を向上させることを目的とする。   Another object of the present invention is to improve the light extraction efficiency without imposing a burden on the processing process.

また、周期構造の周期性が不十分な場合であっても、光の取り出し効率を向上させることを目的とする。   Another object of the present invention is to improve the light extraction efficiency even when the periodicity of the periodic structure is insufficient.

発明者は、前記した三次元光波シミュレーションによってＬＥＤからの光放射を解析した結果、光の取り出しに係わる要因として、二次元周期構造を有する半導体発光デバイスを構成する半導体層の各層の屈折率分布があることを見出した。   As a result of analyzing the light emission from the LED by the above-described three-dimensional light wave simulation, the inventor found that the refractive index distribution of each layer of the semiconductor layer constituting the semiconductor light emitting device having the two-dimensional periodic structure is a factor related to light extraction. I found out.

また、光取出しに関わる要因が、その二次元周期構造の形状、発光層と二次元周期構造との距離にあることも見出した。ここでいう二次元周期構造とは三角格子、正方格子、六角格子などの周期構造、または、ペンローズタイリングのパターン、１２回対称を有する正方形―三角形タイリングのパターンなどいずれかの並進対称性を持たない準結晶構造およびそれらの組み合わせをいう。   The present inventors also found that the factors related to light extraction are the shape of the two-dimensional periodic structure and the distance between the light emitting layer and the two-dimensional periodic structure. The two-dimensional periodic structure here refers to any translational symmetry such as a periodic structure such as a triangular lattice, a square lattice, a hexagonal lattice, a Penrose tiling pattern, or a square-triangular tiling pattern with 12-fold symmetry. It refers to a quasicrystalline structure that does not have any combination thereof.

さらに、半導体層が活性層を挟んで非対称な屈折率分布を有する構造に加え、二次元周期構造中、または近傍に活性層の屈折率以下の屈折率を有する中間層を設けることで中間層が方向性結合の役割を果たし活性層と二次元周期構造との結合を強め光取り出しの効果を改善することも見出した。   Furthermore, in addition to the structure in which the semiconductor layer has an asymmetric refractive index distribution across the active layer, an intermediate layer having a refractive index equal to or lower than the refractive index of the active layer is provided in or in the vicinity of the two-dimensional periodic structure. It has also been found that it plays a role of directional coupling and strengthens the coupling between the active layer and the two-dimensional periodic structure to improve the light extraction effect.

本発明の半導体発光デバイスは、デバイスの表面の構造を二次元周期構造とすると共に、活性層を挟む２つの層の屈折率を非対称とする構成とすることで、発光体が放射する光の外部への光の取り出し効率を向上させるものである。   The semiconductor light emitting device of the present invention has a two-dimensional periodic structure on the surface of the device, and a structure in which the refractive index of the two layers sandwiching the active layer is asymmetric so that the light emitted from the light emitter can be externally emitted. This improves the light extraction efficiency of the light.

本発明の半導体発光デバイスは、基板層と、この基板層の上方に、第１の層、活性層、および第２の層を順に積層した構成とする。   The semiconductor light emitting device of the present invention has a configuration in which a substrate layer and a first layer, an active layer, and a second layer are sequentially stacked above the substrate layer.

第１の層は、第１導電型半導体クラッド層を含む単数または複数からなる層であり、基板層の上方に設けられる。   The first layer is a single layer or a plurality of layers including the first conductivity type semiconductor clad layer, and is provided above the substrate layer.

活性層は、この第１の層の上方に設けられ、さらに上方には第２の層を設ける。   The active layer is provided above the first layer, and the second layer is provided above the active layer.

第２の層は、第２導電型半導体クラッド層を含み、表面に二次元周期構造を有する単数または複数からなる層であり、活性層の上方に設けられる。この構成によって、デバイスの表面に二次元周期構造を持たせる。   The second layer includes a second conductivity type semiconductor clad layer, and is a single or plural layer having a two-dimensional periodic structure on the surface, and is provided above the active layer. With this configuration, the surface of the device has a two-dimensional periodic structure.

また、本発明の半導体発光デバイスが備える第１の層は、活性層の屈折率より低く、かつ、第２の層の内で活性層に接する層の屈折率よりも低い屈折率の層を少なくとも一層を含む構成とし、第２の層は、この第２の層を構成する何れの層も活性層の屈折率より低い屈折率を有する構成とする。この構成によって、活性層を挟む２つの層の屈折率分布を非対称とする。   In addition, the first layer included in the semiconductor light emitting device of the present invention includes at least a layer having a refractive index lower than the refractive index of the active layer and lower than the refractive index of the layer in contact with the active layer in the second layer. The second layer is configured to include one layer, and the second layer has a refractive index lower than that of the active layer. With this configuration, the refractive index distribution of the two layers sandwiching the active layer is made asymmetric.

本発明の半導体発光デバイスは、上記した構成において、活性層を多重量子井戸構造とすることができる。活性層が多重量子井戸構造の場合、第１の層が備える少なくとも一つの層の屈折率は、活性層の屈折率の膜厚荷重平均値より低く、かつ、第２の層の活性層に接する層の屈折率よりも低い構成とし、さらに、第２の層を構成する何れの層の屈折率も活性層の屈折率の膜厚荷重平均値より低い構成とする。   In the semiconductor light emitting device of the present invention, the active layer can have a multiple quantum well structure in the above-described configuration. In the case where the active layer has a multiple quantum well structure, the refractive index of at least one layer included in the first layer is lower than the thickness load average value of the refractive index of the active layer and is in contact with the active layer of the second layer. The refractive index of the layer is lower than the refractive index of the layer, and the refractive index of any of the layers constituting the second layer is lower than the average thickness of the active layer.

また、第２の層において、二次元周期構造を形成する位置は、活性層で発光した光が通過する層の屈折率ｎと、光学波長λに基づいて定めることができ、二次元周期構造の底部を活性層の上部から距離が0.1nλ〜nλに位置とする。ここでnは二次元周期構造の底部と活性層の上部との間の層の屈折率であって、発光の真空波長（λ0）に対する屈折率である。また、λは媒質中の光学波長である。 In the second layer, the position where the two-dimensional periodic structure is formed can be determined based on the refractive index n of the layer through which the light emitted from the active layer passes and the optical wavelength λ. The bottom is located at a distance of 0.1 nλ to nλ from the top of the active layer. Here, n is the refractive index of the layer between the bottom of the two-dimensional periodic structure and the top of the active layer, and is the refractive index with respect to the vacuum wavelength (λ 0 ) of light emission. Λ is an optical wavelength in the medium.

また、本発明の半導体発光デバイスは、上述した構成において、第２の層中に中間層を備える構成とすることが好ましい。第２の層が備える中間層の屈折率は、活性層の屈折率以下であり、第２の層の他の層の屈折率より高く設定する。つまり、中間層は、第２導電型半導体クラッド層の屈折率より高い。活性層が複数の井戸層および障壁層から構成される多重量子井戸構造を有する場合には、中間層は、その井戸層の屈折率以下の屈折率を有するように設定することが好ましい。この中間層により、発光の外部への取り出し効率をさらに高めることができる。中間層は、第２の層を構成する各層のいずれの層内に導入してもよく、また、いずれの層との間に導入してもよいが、活性層には隣接させないで構成するものとする。   The semiconductor light-emitting device of the present invention preferably has a configuration in which the intermediate layer is provided in the second layer in the above-described configuration. The refractive index of the intermediate layer provided in the second layer is set to be lower than the refractive index of the active layer and higher than the refractive indexes of the other layers of the second layer. That is, the intermediate layer is higher than the refractive index of the second conductivity type semiconductor clad layer. When the active layer has a multiple quantum well structure composed of a plurality of well layers and barrier layers, the intermediate layer is preferably set to have a refractive index equal to or lower than the refractive index of the well layer. By this intermediate layer, the efficiency of taking out emitted light to the outside can be further increased. The intermediate layer may be introduced into any of the layers constituting the second layer, or may be introduced between any of the layers, but is not adjacent to the active layer. And

基板層には、第１の層と接するように、高い反射率の層（低い屈折率の層）を設けることが好ましく、さらに光取出し効率を高めることができる。また、一時的な成長基板上で成長した半導体積層構造を、金属層や反射層を介して別途用意した支持基板へ貼り合わせる方法を用いることにより容易に製造することができる。   The substrate layer is preferably provided with a high reflectance layer (a low refractive index layer) so as to be in contact with the first layer, and the light extraction efficiency can be further increased. Further, it can be easily manufactured by using a method in which a semiconductor stacked structure grown on a temporary growth substrate is bonded to a separately prepared support substrate via a metal layer or a reflective layer.

また、基板上に直接半導体積層構造を成長して非対称な屈折率分布を形成することの難しいＧａＮ系等の材料系においては、一時的な成長基板上で成長した半導体層を、別途用意した支持基板へ貼り合わせる方法を用いることにより、電気特性および発光効率を維持して非対称な屈折率分布を有する半導体発光デバイスを作製することができる。   In addition, in a material system such as a GaN system in which it is difficult to form an asymmetric refractive index distribution by directly growing a semiconductor multilayer structure on a substrate, a semiconductor layer grown on a temporary growth substrate is provided separately. By using a method of bonding to a substrate, it is possible to manufacture a semiconductor light emitting device having an asymmetric refractive index distribution while maintaining electrical characteristics and light emission efficiency.

また、本発明の半導体発光デバイスは、上述した構成において、基板層は、基板に加えて、この基板と第１の層とを接合する接合層を含む構成としてもよく、第１の層および第２の層は、適宜、バッファ層、コンタクト層、電流拡散層を設けた構成としてもよい。第２の層にコンタクト層、電流拡散層を設ける場合には、中間層は、コンタクト層および電流拡散層の各層の屈折率よりも大きいものとする。   In the semiconductor light-emitting device of the present invention, in the above-described configuration, the substrate layer may include a bonding layer that bonds the substrate and the first layer in addition to the substrate. The layer 2 may have a structure in which a buffer layer, a contact layer, and a current diffusion layer are provided as appropriate. When the contact layer and the current diffusion layer are provided in the second layer, the intermediate layer is assumed to have a refractive index higher than that of each of the contact layer and the current diffusion layer.

また、第２の層の二次元周期構造の凸部上に透明導電膜（ZnO（n=2）、TiO2、Ta2O5、ITO（n=1.8〜1.9））、高屈折率樹脂層等を形成した構成としてもよい。 The transparent conductive film on the convex portion of the two-dimensional periodic structure of the second layer (ZnO (n = 2), TiO 2, Ta 2 O 5, ITO (n = 1.8~1.9)), the high-refractive index resin layer It is good also as a structure which formed etc.

本発明の半導体発光デバイスは、シミュレーションから得られる知見に基づくものであり、以下、ある屈折率媒質を想定した場合の検証結果を示す。   The semiconductor light-emitting device of the present invention is based on the knowledge obtained from the simulation, and the following shows the verification results when a certain refractive index medium is assumed.

また、実施例としてAlGaInP系デバイスとGaN系デバイスを、シミュレーション結果に基づいて構成した場合の具体的な作製方法とその光取り出し効果を示す。   Further, as an example, a specific manufacturing method and its light extraction effect when an AlGaInP-based device and a GaN-based device are configured based on simulation results will be shown.

以上説明したように、本発明によれば、発光体が放射する光をＬＥＤの外部により効率よく取り出すことができる。また、加工プロセスに負担をかけることなく光の取り出し効率を向上させることができる。   As described above, according to the present invention, the light emitted from the light emitter can be efficiently extracted outside the LED. Further, the light extraction efficiency can be improved without imposing a burden on the processing process.

また、周期構造の周期性が不十分な場合であっても、光の取り出し効率を向上させることができる。   Even if the periodicity of the periodic structure is insufficient, the light extraction efficiency can be improved.

本発明のＬＥＤは、活性層を挟んで上下に積層される第１の層と第２の層において第２の層が第１の層より高い屈折率を有する非対称な屈折率分布を備え、かつ、その第２の層の表面に二次元周期構造を設けることで光取り出しの効果を向上したものである。   The LED of the present invention has an asymmetric refractive index distribution in which the second layer has a higher refractive index than the first layer in the first layer and the second layer stacked up and down across the active layer, and The effect of light extraction is improved by providing a two-dimensional periodic structure on the surface of the second layer.

また、本発明のＬＥＤは、さらに、二次元周期構造内、あるいは、二次元周期構造の近傍に、活性層の屈折率以下で第２の他の層より高い屈折率を有する中間層を備えることで、中間層が方向性結合の役割を果たし、活性層と二次元周期構造との結合を強め光取り出しの効果を向上したものである。   The LED of the present invention further includes an intermediate layer having a refractive index lower than that of the active layer and higher than that of the second other layer in the two-dimensional periodic structure or in the vicinity of the two-dimensional periodic structure. Thus, the intermediate layer plays a role of directional coupling, strengthening the coupling between the active layer and the two-dimensional periodic structure, and improving the light extraction effect.

以下、本発明の実施の形態について、図を参照しながら詳細に説明する。   Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

本発明の半導体発光デバイスの構成例を図１を用いて説明する。なお、図１は断面構成を示している。   A configuration example of the semiconductor light emitting device of the present invention will be described with reference to FIG. FIG. 1 shows a cross-sectional configuration.

図１において、半導体発光デバイス１は、半導体発光デバイスの光取出し面側に二次元周期構造を備える構成において、第１の層２と、この第１の層２上に重なる活性層３と、この活性層３上に重なる第２の層４とを備え、第２の層４の表面、又は第２の層４上に重なる層の表面に二次元周期構造１０を備え、第２の層４の屈折率を第１の層２の屈折率よりも高い構成とする。   In FIG. 1, a semiconductor light emitting device 1 includes a first layer 2, an active layer 3 overlying the first layer 2, and a structure including a two-dimensional periodic structure on the light extraction surface side of the semiconductor light emitting device. A second layer 4 overlying the active layer 3, and a two-dimensional periodic structure 10 on the surface of the second layer 4 or the surface of the layer overlying the second layer 4. The refractive index is higher than that of the first layer 2.

また、活性層３と二次元周期構造１０との距離は、活性層３の上部と二次元周期構造１０の底部との距離を0.1λ0〜λ0（0.1nλ〜nλ）とし、かつ、この距離は、消失領域の浸透深さと同程度、あるいはそれよりも長い距離である。なお、ここで、λ0を真空中波長とし、ｎを活性層３と二次元周期構造１０との間の半導体層の屈折率である。 The distance between the active layer 3 and the two-dimensional periodic structure 10 is such that the distance between the top of the active layer 3 and the bottom of the two-dimensional periodic structure 10 is 0.1λ 0 to λ 0 (0.1nλ to nλ). The distance is the same as or longer than the penetration depth of the disappearing region. Here, λ 0 is the wavelength in vacuum, and n is the refractive index of the semiconductor layer between the active layer 3 and the two-dimensional periodic structure 10.

この構成は、MOCVD（有機金属気相成長法）などによる半導体発光デバイス作製時に、第１の層２と第２の層４を構成する層の組成を調整することで実現可能である。   This configuration can be realized by adjusting the composition of the layers constituting the first layer 2 and the second layer 4 when fabricating a semiconductor light emitting device by MOCVD (metal organic chemical vapor deposition) or the like.

このように第２の層の屈折率を第１の層の屈折率より高い構成とすることによって、半導体発光デバイスを構成する各層内における光の存在分布を、屈折率分布が活性層を挟んで対称である構成による光分布と異ならせ、この光分布によって発光層内に閉じ込められていた光を発光層外に取り出し易くすることが可能である。これは、第２の層４の屈折率を第１の層２の屈折率よりも高くすることによって、発光層から取り出した光を、屈折率が高い第２の層４側に導き、二次元周期構造５と活性層３から発光した光が強く結合し、二次元周期構造５がより効果的に光取り出しに寄与するためである。   Thus, by setting the refractive index of the second layer to be higher than the refractive index of the first layer, the distribution of light in each layer constituting the semiconductor light-emitting device can be determined with the refractive index distribution sandwiching the active layer. It is possible to make it easy to take out the light confined in the light emitting layer by this light distribution to the outside of the light emitting layer. This is because, by making the refractive index of the second layer 4 higher than that of the first layer 2, the light extracted from the light emitting layer is guided to the second layer 4 side having a high refractive index, and two-dimensional. This is because the light emitted from the periodic structure 5 and the active layer 3 is strongly coupled, and the two-dimensional periodic structure 5 contributes to light extraction more effectively.

また、この効果は半導体発光デバイス１の周囲が空気(n=1.00)だけでなく、樹脂(n=1.45)などの媒質で覆われている場合でも効果があり、LEDの実用上効果的である。   This effect is also effective when the periphery of the semiconductor light emitting device 1 is covered not only with air (n = 1.00) but also with a medium such as resin (n = 1.45), which is practically effective for LEDs. .

本発明の半導体発光デバイス１が備える二次元周期構造１０は、例えば円孔最密配列又は錐状突起最密配列により構成することができ、フォトニック結晶あるいはフォトニック準結晶により形成することができる。錐状突起最密配列は、錐状体の突起物を最密配列するものであり、錐状体は任意の形状とすることができ、例えば、円錐状突 起最密配列や角錐状突起最密配列とすることができる。   The two-dimensional periodic structure 10 included in the semiconductor light emitting device 1 of the present invention can be configured by, for example, a close-packed array of circular holes or a close-packed array of conical protrusions, and can be formed of a photonic crystal or a photonic quasicrystal. . The close-packed array of conical protrusions is a close-packed array of conical protrusions, and the conical body can have any shape, for example, the close-conical array of conical protrusions or the closest pyramid-shaped protrusion. It can be a dense array.

なお、フォトニック結晶は、屈折率を異にする領域を光の波長程度の周期で繰り返して並べることで構成され、フォトニック準結晶は、２つの異なる屈折率領域を光の波長程度の周期で繰り返すフォトニック結晶において配列パターンを準結晶のパターンに従って構成するものであり、屈折率について並進対称性を持たず、長距離秩序及び回転対称性を有する屈折率の準周期構造を備える。準結晶を形成するパターンとしては、例えば、ペンローズタイリング(Penrose-type) のパターンや正方形−三角形タイリング（12-fold Symmetric）のパターンを用いることができる。   A photonic crystal is formed by repeatedly arranging regions having different refractive indices at a period of about the wavelength of light, and a photonic quasicrystal has two different refractive index regions at a period of about the wavelength of light. In a repeating photonic crystal, an arrangement pattern is formed in accordance with a quasi-crystal pattern, and has a refractive index quasi-periodic structure having a long-range order and a rotational symmetry without having a translational symmetry with respect to a refractive index. As a pattern for forming the quasicrystal, for example, a Penrose tiling pattern or a 12-fold Symmetric pattern can be used.

フォトニック準結晶による格子構造を備えた発光取出し面を適用することによって、光の取り出し効率を高めることができ、また、視野角依存性を低減して高い立体角を得ることができる。   By applying a light emission extraction surface having a lattice structure of a photonic quasicrystal, light extraction efficiency can be increased, and viewing angle dependency can be reduced to obtain a high solid angle.

図２（ａ）は円孔最密配列による二次元周期構造１０の平面を示し、図２（ｂ）は半導体発光デバイス１及び二次元周期構造１０の側面を示している。   FIG. 2A shows a plane of the two-dimensional periodic structure 10 with a circular hole close-packed arrangement, and FIG. 2B shows side surfaces of the semiconductor light emitting device 1 and the two-dimensional periodic structure 10.

この円孔最密配列の二次元周期構造を備える半導体発光デバイス１では、第２の半導体層４に孔径２ｒ、孔の深さｄhを有する円孔１１ａが周期的に配列され、円孔１１ａの底部１２と活性層３の上部との間の距離をｄsとしている。二次元周期構造を定めるパラメータとして格子常数ａ（孔間のピッチ）を備える。   In the semiconductor light emitting device 1 having the two-dimensional periodic structure with the circular hole close-packed arrangement, the circular holes 11a having the hole diameter 2r and the hole depth dh are periodically arranged in the second semiconductor layer 4, and the circular holes 11a The distance between the bottom 12 and the top of the active layer 3 is ds. A lattice constant a (pitch between holes) is provided as a parameter for determining the two-dimensional periodic structure.

３次元光波シミュレーションの結果によれば、これらのパラメータａ，２ｒ，及びｄhによって光の取り出し効率が変化し、
ａ＝nλ〜n1.5λ
2ｒ＝0.5ａ〜0.6ａ
ｄh＝0.5nλ〜nλ
において、光の取り出し効率が最大となる。 According to the result of the three-dimensional lightwave simulation, the light extraction efficiency varies depending on these parameters a, 2r, and dh,
a = nλ to n1.5λ
2r = 0.5a-0.6a
dh = 0.5 nλ to nλ
In this case, the light extraction efficiency is maximized.

また、図３（ａ）は円錐突起最密配列による二次元周期構造１０の平面を示し、図３（ｂ）は半導体発光デバイス１及び二次元周期構造１０の側面を示している。   FIG. 3A shows a plane of the two-dimensional periodic structure 10 having a conical projection close-packed arrangement, and FIG. 3B shows side surfaces of the semiconductor light emitting device 1 and the two-dimensional periodic structure 10.

この円錐突起最密配列の二次元周期構造を備える半導体発光デバイス１（発光面は円錐突起によって完全に満たされているものとする）では、第２の半導体層４に角度θを有する円錐突起１３が周期的に配列され、円錐突起１３の底部１４と活性層３の上部との間の距離をｄsとしている。二次元周期構造を定めるパラメータとして格子常数ａ（円錐突起間のピッチ）、及び角度θを備える。   In the semiconductor light emitting device 1 having the two-dimensional periodic structure with the conical protrusions closely packed (the light emitting surface is completely filled with the conical protrusions), the conical protrusions 13 having an angle θ in the second semiconductor layer 4 are used. Are periodically arranged, and the distance between the bottom 14 of the conical protrusion 13 and the top of the active layer 3 is ds. As parameters for determining the two-dimensional periodic structure, a lattice constant a (a pitch between conical protrusions) and an angle θ are provided.

３次元光波シミュレーションの結果によれば、これらのパラメータａ，θによって光の取り出し効率が変化し、
ａ＝0.5nλ〜nλ
θ＝60°〜65°
において、光の取り出し効率が最大となる。 According to the results of the three-dimensional lightwave simulation, the light extraction efficiency varies depending on these parameters a and θ.
a = 0.5 nλ to nλ
θ = 60 ° -65 °
In this case, the light extraction efficiency is maximized.

格子常数ａの依存性が小さいことから、要素のサイズと最密配列の程度が、最適な最密配列から大きくずれていない程度に適正化されていれば、他の表面構造であっても同様の効果を得ることを期待することができる。   Since the dependence of the lattice constant a is small, the same applies to other surface structures as long as the element size and the close-packed arrangement are optimized so as not to deviate significantly from the optimum close-packed arrangement. You can expect to get the effect.

以上より、二次元周期構造の加工精度は低くてもよいため、加工プロセスも容易であることがわかる。   From the above, it can be seen that the machining process is easy because the machining accuracy of the two-dimensional periodic structure may be low.

なお、上記光の取り出し効率は、後述するように、二次元周期構造を備えない平面構造の自発光デバイスの光取り出し量を基準とした比較によって得ている。   The light extraction efficiency is obtained by comparison based on the light extraction amount of a self-luminous device having a planar structure that does not have a two-dimensional periodic structure, as will be described later.

また、３次元光波シミュレーションの結果によれば、活性層３の上部と二次元周期構造１０の底部（図２（ｂ）に示す円孔最密配列の底部１２、図３（ｂ）に示す円錐突起最密配列の底部１４）との距離ｄsを0.1nλ〜0.3nλ、又は0.3nλ〜nλとすることによって、光の取り出し効率が向上する。   Further, according to the result of the three-dimensional light wave simulation, the upper part of the active layer 3 and the bottom part of the two-dimensional periodic structure 10 (the bottom part 12 of the close-packed circular holes shown in FIG. 2B, the cone shown in FIG. 3B). The light extraction efficiency is improved by setting the distance ds from the bottom 14) of the close-packed projections to 0.1 nλ to 0.3 nλ or 0.3 nλ to nλ.

距離ｄsを0.3nλ〜nλとして、活性層の上部と二次元周期構造の底部との距離を厚い構成とした場合には、活性層３で自由発光する光の活性層からの取り出しを高め、また、距離ｄsを0.1nλ〜0.3nλとして、活性層の上部と二次元周期構造の底部との距離を薄い構成とした場合には、光放射及び光の取り出しを、より高めるように変化させることで取り出し効率を向上させる。   When the distance ds is set to 0.3 nλ to nλ and the distance between the upper part of the active layer and the bottom part of the two-dimensional periodic structure is thick, the active layer 3 increases the extraction of light emitted freely from the active layer, When the distance ds is 0.1 nλ to 0.3 nλ and the distance between the upper part of the active layer and the bottom part of the two-dimensional periodic structure is thin, the light emission and the light extraction can be changed to be higher. Improve extraction efficiency.

この二次元周期構造は、モールドや鋳型によって予め二次元周期構造の突起を形成しておき、この突起構造を半導体基板に転写することで形成するほか、エピタキシャル等のエッチング処理等によって形成することができる。   This two-dimensional periodic structure can be formed by forming protrusions of a two-dimensional periodic structure in advance with a mold or mold and transferring the protrusion structure to a semiconductor substrate, or by etching such as epitaxial. it can.

この二次元周期構造の形成では半導体層を削る工程を含むため、底部では活性層の近傍まで半導体層を削ることになり、その距離は前記したｄsで定まる。そのため、活性層の上部と二次元周期構造の底部との距離ｄsが薄い構成では、製造プロセス中に活性層を損傷する可能性が高くなるという問題がある。   Since the formation of the two-dimensional periodic structure includes a step of cutting the semiconductor layer, the semiconductor layer is cut to the vicinity of the active layer at the bottom, and the distance is determined by ds described above. For this reason, in a configuration in which the distance ds between the upper portion of the active layer and the bottom portion of the two-dimensional periodic structure is thin, there is a problem that there is a high possibility that the active layer is damaged during the manufacturing process.

この場合には、前記した距離ｄsを0.3nλ〜nλの二次元周期構造を形成し、本発明の構成のように、活性層を挟み非対称な屈折率分布を形成すること、または、さらに中間層を導入することにより、高い光取出し効率を維持しつつ、この製造プロセス中の活性層の損傷の問題を解決することができる。   In this case, a two-dimensional periodic structure having the above-mentioned distance ds of 0.3 nλ to nλ is formed, and an asymmetric refractive index distribution is formed with the active layer sandwiched as in the configuration of the present invention, or further, an intermediate layer In this case, it is possible to solve the problem of damage to the active layer during the manufacturing process while maintaining high light extraction efficiency.

以下、上記した半導体発光デバイスの光の取り出し効率について、二次元周期構造を備えない平面構造の半導体発光デバイスの光強度を基準として３次元光波シミュレーションにより求めた結果を、図４〜図７を用いて示す。   Hereinafter, with respect to the light extraction efficiency of the semiconductor light-emitting device described above, the results obtained by three-dimensional light wave simulation with reference to the light intensity of the planar light-emitting semiconductor light-emitting device not having the two-dimensional periodic structure are shown in FIGS. Show.

なお、活性層の屈折率は２．８、第１の層の屈折率は２．８または２．５、第２の層の屈折率は２．８、２．７８、２．５、および中間層の屈折率を２．７８として演算を行った。また、光の光学波長λとするとき、活性層３の厚さを０．２nλとする。発光面が面する空気の屈折率を1.0（図４、５）、樹脂の屈折率を１．４５とした。   The refractive index of the active layer is 2.8, the refractive index of the first layer is 2.8 or 2.5, the refractive index of the second layer is 2.8, 2.78, 2.5, and the middle. The calculation was performed with the refractive index of the layer being 2.78. Further, when the optical wavelength of light is λ, the thickness of the active layer 3 is 0.2 nλ. The refractive index of air facing the light emitting surface was 1.0 (FIGS. 4 and 5), and the refractive index of the resin was 1.45.

図４，５に、二次元周期構造を備える半導体発光デバイスについて、各構造の光取り出し効率（Ｆ）を、二次元周期構造を備えない平面構造の半導体発光デバイスの場合を基準（１．００）として示す。３次元光波シミュレーションの結果により得られた最適なパラメータ範囲に基づいて、図４に示す円孔最密配列の二次元周期構造を備える半導体発光デバイスでは、ａ＝1.5nλ、2ｒ＝0.6ａ，ｄh＝nλとし、図５に示す円錐突起最密配列の二次元周期構造を備える半導体発光デバイスではａ＝0.5nλ、θ＝63°とした結果である。   4 and 5, the light extraction efficiency (F) of each structure of a semiconductor light emitting device having a two-dimensional periodic structure is based on the case of a semiconductor light emitting device having a planar structure not having a two-dimensional periodic structure (1.00). As shown. In the semiconductor light emitting device having the two-dimensional periodic structure with the close-packed circular holes shown in FIG. 4 based on the optimum parameter range obtained from the result of the three-dimensional light wave simulation, a = 1.5 nλ, 2r = 0.6 a, dh In the semiconductor light emitting device having the two-dimensional periodic structure with the conical protrusion close-packed arrangement shown in FIG. 5, a = 0.5nλ and θ = 63 °.

図４、５には、シミュレーションを行った、単一層の構造（（ｂ），（ｆ））、屈折率を異ならせる非対称構造（（ｃ），（ｇ））、屈折率を等しくする対称構造（（ｄ），（ｈ））、第２の半導体層に中間層を備える中間層構造（（ｅ），（ｉ））、の各構造の模式図を各層の屈折率と共に示す。また、二次元周期構造の底部と活性層との距離ｄsを0.3nλ〜nλとした場合（（ｂ）〜（ｅ））、0.1nλ〜0.3nλとした場合（（ｆ）〜（ｉ））についてそれぞれ示した。   4 and 5 show a simulation of a single layer structure ((b), (f)), an asymmetric structure with different refractive indexes ((c), (g)), and a symmetrical structure with equal refractive indexes. The schematic diagram of each structure of ((d), (h)) and intermediate | middle layer structure ((e), (i)) provided with an intermediate | middle layer in a 2nd semiconductor layer is shown with the refractive index of each layer. Further, when the distance ds between the bottom of the two-dimensional periodic structure and the active layer is 0.3 nλ to nλ ((b) to (e)), and 0.1 nλ to 0.3 nλ ((f) to (i)) For each.

上記図４，５に示したシミュレーション結果をまとめると、以下の表１となる。   The simulation results shown in FIGS. 4 and 5 are summarized in Table 1 below.

二次元周期構造の形状を円孔最密配列とした場合においても、円錐突起最密配列とした場合においても同様の光取出し効率向上の傾向が見られた。また、二次元周期構造を設けた場合において、半導体発光デバイスの層構成が非対称構造の場合に、最も高い光取出し効率が得られ、続いて、中間層構造の場合に高い光取出し効率が得られた。また、いずれの構造においても、二次元周期構造の底部と活性層との距離ｄsは、小さい方（0.1nλ〜0.3nλ）が光取出し効率が高いことが確認できた。   The same tendency of improving the light extraction efficiency was observed when the shape of the two-dimensional periodic structure was a close-packed array of circular holes and a close-packed array of conical protrusions. In addition, when a two-dimensional periodic structure is provided, the highest light extraction efficiency can be obtained when the layer structure of the semiconductor light emitting device is an asymmetric structure, and subsequently, a high light extraction efficiency can be obtained when the intermediate layer structure is used. It was. Further, in any structure, it was confirmed that the light extraction efficiency is higher when the distance ds between the bottom of the two-dimensional periodic structure and the active layer is smaller (0.1 nλ to 0.3 nλ).

図６，７に、二次元周期構造を備え、かつ光取出し面を樹脂により覆った被覆構造の半導体発光デバイスについて、各構造の光取り出し効率（Ｆ）を、二次元周期構造を備えない平面構造の半導体発光デバイスの場合（樹脂被覆あり）を基準（１．００）として示す。３次元光波シミュレーションの結果により得られた最適なパラメータ範囲に基づいて、図６に示す円孔最密配列の二次元周期構造を備える半導体発光デバイスでは、ａ＝1.5nλ、2ｒ＝0.6ａ，ｄh＝nλとし、図７に示す円錐突起最密配列の二次元周期構造を備える半導体発光デバイスではａ＝0.5nλ、θ＝63°とした結果である。   FIGS. 6 and 7 show the light extraction efficiency (F) of each structure for a semiconductor light emitting device having a two-dimensional periodic structure and having a light extraction surface covered with resin, and a planar structure without a two-dimensional periodic structure. The case of the semiconductor light emitting device (with resin coating) is shown as a reference (1.00). Based on the optimum parameter range obtained from the result of the three-dimensional light wave simulation, in the semiconductor light emitting device having the two-dimensional periodic structure with the close-packed circular holes shown in FIG. 6, a = 1.5nλ, 2r = 0.6a, dh In the semiconductor light emitting device having the two-dimensional periodic structure with the conical protrusions close-packed as shown in FIG. 7, a = 0.5nλ and θ = 63 °.

図６、７には、シミュレーションを行った、屈折率を異ならせる非対称構造（（ａ），（ｃ））、屈折率を等しくする対称構造（（ｂ），（ｄ））の各構造の模式図を各層の屈折率と共に示す。二次元周期構造の底部と活性層との距離ｄsを0.3nλ〜nλとした場合（（ａ）〜（ｂ））、0.1nλ〜0.3nλとした場合（（ｃ）〜（ｄ））についてそれぞれ示した。   FIGS. 6 and 7 schematically show the structures of the asymmetric structure ((a), (c)) that makes the refractive index different and the symmetrical structure ((b), (d)) that make the refractive index equal. The figure is shown together with the refractive index of each layer. When the distance ds between the bottom of the two-dimensional periodic structure and the active layer is 0.3 nλ to nλ ((a) to (b)) and 0.1 nλ to 0.3 nλ ((c) to (d)), respectively. Indicated.

上記図６および図７の結果より、光取出し面を樹脂で被覆した場合においても、二次元周期構造を有する構造、二次元周期構造および非対称な屈折率分布を有する構造で光取出し効率の向上の効果を確認できる。また、二次元周期構造の形状は、円孔最密配列および円錐突起最密配列のいずれの形状においても光取出し向上の効果が確認できた。   From the results shown in FIGS. 6 and 7, even when the light extraction surface is covered with resin, the light extraction efficiency is improved by the structure having a two-dimensional periodic structure, the two-dimensional periodic structure, and the structure having an asymmetric refractive index distribution. The effect can be confirmed. In addition, it was confirmed that the two-dimensional periodic structure had the effect of improving the light extraction in both the circular hole close-packed array and the conical protrusion close-packed array.

また、半導体部分に孔（開口部）あるいは凹部を形成する手法は、光照射による凹部の生成するレーザー加工技術や、マスクを用いて半導体層をエッチングする等の半導体生成技術を用いることができる。   As a method of forming a hole (opening) or a recess in a semiconductor portion, a laser processing technique for generating a recess by light irradiation or a semiconductor generation technique such as etching a semiconductor layer using a mask can be used.

シミュレーション結果によれば、円錐突起周期構造において、半導体発光デバイスのサイズが固定であり、格子定数ａが６λまで可変である場合には、光の取り出し効率は最大値の半分まで低下する。このことは、各要素での光散乱、及びフォトニック結晶の周期性による光の回折は、光の取り出し効率に対して同程度に寄与していることを表している。   According to the simulation result, in the conical protrusion periodic structure, when the size of the semiconductor light emitting device is fixed and the lattice constant a is variable up to 6λ, the light extraction efficiency decreases to half of the maximum value. This indicates that light scattering at each element and light diffraction due to the periodicity of the photonic crystal contribute to the same extent on the light extraction efficiency.

また、格子常数ａの依存性が小さいことから、フォトニック結晶は光の取り出し効率に大きく寄与している。また、要素のサイズと最密配列の程度が、構造がローカルで周期的で最適な最密配列から大きくずれていない程度に適正化されていれば、他の表面構造であっても同様の効果を得ることを期待することができる。   In addition, since the dependence of the lattice constant a is small, the photonic crystal greatly contributes to the light extraction efficiency. In addition, if the size of elements and the degree of close-packed arrangement are optimized to such an extent that the structure is local, periodic, and not significantly deviated from the optimal close-packed arrangement, the same effect can be obtained with other surface structures. You can expect to get

なお、上述した構成は、第1の層、第２の層および活性層を単層で示したが、複数層であってもよい。実際の半導体発光デバイスは、一般的に種々の機能を有する複数の層から構成されるため、後述する実施例のように第1の層および第2の層は、適宜、バッファ層、コンタクト層、電流拡散層を設けた構成としてもよく活性層は多重量子井戸構造としてもよい。また、中間層は、第2の層を構成する各層のいずれの層内に導入してもよく、いずれの層との間に導入してもよい。ただし、中間層は活性層には隣接させない。   In the above-described configuration, the first layer, the second layer, and the active layer are shown as a single layer, but a plurality of layers may be used. Since an actual semiconductor light emitting device is generally composed of a plurality of layers having various functions, the first layer and the second layer are appropriately formed as a buffer layer, a contact layer, The current diffusion layer may be provided, and the active layer may have a multiple quantum well structure. Further, the intermediate layer may be introduced into any of the layers constituting the second layer, or may be introduced between any of the layers. However, the intermediate layer is not adjacent to the active layer.

ここで、第２の層を複数の層で構成する場合には、第１の層は、第2の層の活性層に接する層の屈折率よりも低い屈折率の層を有するように設計され、中間層は、活性層に隣接させないよう設計すればよい。また、活性層を複数の層で構成する場合には、非対称屈折率分布は、各層の屈折率の膜厚荷重平均値を活性層の屈折率とみなし、それより低い屈折率を有する層で第1の層および第2の層を構成するよう設計される。このことは、多重量子井戸構造の場合、井戸層および障壁層の膜厚(数nm)は、発光波長の１０分の１以下であるため、発光は、それぞれの層の屈折率に対し影響を受けるのではなく、その平均屈折率の影響を受けるためである。   Here, when the second layer is composed of a plurality of layers, the first layer is designed to have a layer having a refractive index lower than that of the layer in contact with the active layer of the second layer. The intermediate layer may be designed not to be adjacent to the active layer. In addition, when the active layer is composed of a plurality of layers, the asymmetric refractive index distribution assumes that the film thickness load average value of the refractive index of each layer is regarded as the refractive index of the active layer, and the layer having a refractive index lower than that is the first. Designed to compose one layer and second layer. This is because, in the case of a multiple quantum well structure, the film thickness (several nm) of the well layer and the barrier layer is 1/10 or less of the emission wavelength, so that the emission has an influence on the refractive index of each layer. This is because it is not affected by the average refractive index.

また、活性層を多重量子井戸構造で構成する場合には、中間層は、活性層の井戸層の屈折率以下となるよう設計する。さらに、中間層は、活性層（多重量子井戸構造の場合は、中でも井戸層）の屈折率に近いことが望ましい。このことは、中間層としては、屈折率が大きい方が２次元周期構造との結合効果の点で有効と考えられる一方、発光波長の吸収損失を少なくする観点から、活性層よりバンドギャップの小さい材料、すなわち活性層（多重量子井戸構造の場合は、中でも井戸層）の屈折率以下とすることが望ましいためである。   Further, when the active layer has a multiple quantum well structure, the intermediate layer is designed to have a refractive index lower than that of the well layer of the active layer. Further, it is desirable that the intermediate layer has a refractive index close to that of the active layer (in particular, the well layer in the case of a multiple quantum well structure). This is because, as the intermediate layer, a higher refractive index is considered to be effective in terms of the coupling effect with the two-dimensional periodic structure, while a band gap is smaller than that of the active layer from the viewpoint of reducing absorption loss of the emission wavelength. This is because the refractive index of the material, that is, the active layer (in the case of a multiple quantum well structure, the well layer, in particular) is desirable.

また、第2の層の二次元周期構造の凸部上に透明導電膜（ZnO（n=2）、TiO2、Ta2O5、ITO（n=1.8〜1.9））、高屈折率樹脂層等を形成した構成としてもよい。 The transparent conductive film on the convex portion of the two-dimensional periodic structure of the second layer (ZnO (n = 2), TiO 2, Ta 2 O 5, ITO (n = 1.8~1.9)), the high-refractive index resin layer It is good also as a structure which formed etc.

次に、本発明の半導体発光デバイスの実施例として、ＡｌＧａＩｎＰ系とＧａＮ系の２つの材料系について、構成、作製方法、および光取り出し効果のシミュレーション結果について説明する。   Next, as an example of the semiconductor light emitting device of the present invention, the structure, manufacturing method, and simulation result of the light extraction effect will be described for two material systems of AlGaInP and GaN.

図８に、二次元周期構造および半導体層が活性層を挟んで非対称な屈折率分布を有する半導体発光デバイスの構成を示す。基板層６Ａ上に第１の層である第１導電型半導体クラッド層２Ａ、活性層３Ａ，第２の層である第２導電型半導体クラッド層４Ａａおよび電流拡散層４ｂを積層して形成し、電流拡散層４ｂの表面に二次元周期構造１０を形成する。また、基板層６Ａの下方には電極７Ａを設ける。   FIG. 8 shows a configuration of a semiconductor light emitting device having a two-dimensional periodic structure and a semiconductor layer having an asymmetric refractive index distribution with an active layer interposed therebetween. A first conductive type semiconductor clad layer 2A, which is a first layer, an active layer 3A, a second conductive type semiconductor clad layer 4Aa, which is a second layer, and a current diffusion layer 4b are stacked on the substrate layer 6A. A two-dimensional periodic structure 10 is formed on the surface of the current diffusion layer 4b. An electrode 7A is provided below the substrate layer 6A.

図９に、二次元周期構造、半導体層が活性層を挟んで非対称な屈折率分布、および中間層を有する半導体発光デバイスの構成を示す。上述した図８の構成において、第２の層４Ａ中に中間層５Ａを備える。この中間層５Ａの屈折率は、活性層３Ａの屈折率以下とするとともに、第２の層４Ａの他の層の屈折率より高くする。なお、第２の層４Ａ中において、中間層５Ａは、二次元周期構造１０の部分に設ける他、二次元周期構造１０以外の部分に設けても良い。   FIG. 9 shows a structure of a semiconductor light emitting device having a two-dimensional periodic structure, a semiconductor layer having an asymmetric refractive index distribution with an active layer interposed therebetween, and an intermediate layer. In the configuration of FIG. 8 described above, the intermediate layer 5A is provided in the second layer 4A. The refractive index of the intermediate layer 5A is set to be equal to or lower than the refractive index of the active layer 3A and higher than the refractive indexes of the other layers of the second layer 4A. In the second layer 4 </ b> A, the intermediate layer 5 </ b> A may be provided in a portion other than the two-dimensional periodic structure 10 in addition to the portion of the two-dimensional periodic structure 10.

図１０に、図８と同様、二次元周期構造および半導体層が活性層を挟んで非対称な屈折率分布を有する半導体発光デバイスの構成を示す。図８とは、基板と半導体層間の構成が異なり、基板と半導体層間に電極８Ｂｃおよび結合層８Ｂａが設けられている。基板と半導体層間の構成が異なるのは、その製造方法が、基板上に直接半導体層を成長して作製するのではく、一時成長基板（最終的に除去される）で形成した半導体層を別途用意した永久基板に貼り合わせて作製されることによる。一時成長基板（図示なし）上に、第２の層（第２導電型半導体クラッド層４Ｂ、中間層５Ａ、第２導電型半導体クラッド層４Ｂ）、活性層３Ｂ、第１の層２Ｂ（電流拡散層２Ｂｂおよび第１導電型半導体クラッド層２Ｂａ）を成長した後、電極８Ｂｂ、結合層８Ｂａの一部を形成する。一方、基板６Ｂ上に、電極８Ｂｃ、結合層８Ｂａの一部を形成する。結合層８Ｂａを向かい合わせて熱圧着した後、一時成長基板を除去し、露出した第２導電型半導体クラッド層４Ｂの表面に二次元周期構造１０を形成する。電極８Ｂｂは、半導体層とオーミック接合をとると共に、活性層から基板側へ向かう光を基板へ到達する前に反射する機能を有する。   FIG. 10 shows a structure of a semiconductor light emitting device having a two-dimensional periodic structure and a semiconductor layer having an asymmetric refractive index distribution with an active layer interposed therebetween, as in FIG. 8 is different in structure between the substrate and the semiconductor layer, and an electrode 8Bc and a coupling layer 8Ba are provided between the substrate and the semiconductor layer. The difference between the structure of the substrate and the semiconductor layer is that the manufacturing method does not produce the semiconductor layer directly on the substrate, but the semiconductor layer formed on the temporary growth substrate (which is finally removed) is separately provided. By being bonded to a prepared permanent substrate. On a temporary growth substrate (not shown), a second layer (second conductivity type semiconductor clad layer 4B, intermediate layer 5A, second conductivity type semiconductor clad layer 4B), active layer 3B, first layer 2B (current diffusion) After the layer 2Bb and the first conductivity type semiconductor clad layer 2Ba) are grown, the electrode 8Bb and a part of the coupling layer 8Ba are formed. On the other hand, an electrode 8Bc and a part of the coupling layer 8Ba are formed on the substrate 6B. After bonding layer 8Ba face to face and thermocompression bonded, the temporary growth substrate is removed, and two-dimensional periodic structure 10 is formed on the exposed surface of second conductivity type semiconductor clad layer 4B. The electrode 8Bb has an ohmic junction with the semiconductor layer and has a function of reflecting light traveling from the active layer toward the substrate before reaching the substrate.

図１１に、図９と同様、二次元周期構造、半導体層が活性層を挟んで非対称な屈折率分布、および中間層を有する半導体発光デバイスの構成を示す。図９とは、基板と半導体層間の構成が異なる。   FIG. 11 shows a structure of a semiconductor light emitting device having a two-dimensional periodic structure, a semiconductor layer having an asymmetric refractive index distribution with an active layer interposed therebetween, and an intermediate layer, as in FIG. 9 differs from FIG. 9 in the configuration between the substrate and the semiconductor layer.

また、上述した図１１の構成において、第２の層４Ｂ中に中間層５Ｂを備える。この中間層５Ｂの屈折率は、活性層３Ｂの屈折率以下とするとともに、第２の層４Ｂの他の層の屈折率より高くする。なお、第２の層４Ｂ中において、中間層５Ｂは、二次元周期構造１０の部分に設ける他、二次元周期構造１０以外の部分に設けても良い。   In the configuration of FIG. 11 described above, the intermediate layer 5B is provided in the second layer 4B. The refractive index of the intermediate layer 5B is set to be equal to or lower than the refractive index of the active layer 3B and higher than the refractive indexes of the other layers of the second layer 4B. In the second layer 4B, the intermediate layer 5B may be provided in a portion other than the two-dimensional periodic structure 10 in addition to the portion of the two-dimensional periodic structure 10.

図１２に、図１０と同様、二次元周期構造、および半導体層が活性層を挟んで非対称な屈折率分布を有する半導体発光デバイスの構成を示す。図１０とは、基板と半導体層間の構成が異なり、基板と半導体層との間に高反射率層８Ｂｄを備えた構成を有する。図１０における電極８Ｂｂより高い反射率の層を導入することができるため、高い光取出し効率を得ることができる。   FIG. 12 shows a structure of a semiconductor light emitting device having a two-dimensional periodic structure and a semiconductor layer having an asymmetric refractive index distribution with an active layer interposed therebetween, as in FIG. FIG. 10 differs from FIG. 10 in that the structure between the substrate and the semiconductor layer is different, and the high reflectivity layer 8Bd is provided between the substrate and the semiconductor layer. Since a layer having a higher reflectance than the electrode 8Bb in FIG. 10 can be introduced, high light extraction efficiency can be obtained.

上述した図８、図９に示す構成のＡｌＧａＩｎＰ系材料における実施例について、各層の材料例、屈折率を以下の表２に示し、図１０，図１１，図１２に示す構成の実施例について、各層の材料例、屈折率を以下の表３に示す。   For the examples of the AlGaInP-based material having the configuration shown in FIGS. 8 and 9, the material examples of each layer and the refractive index are shown in Table 2 below, and the examples of the configurations shown in FIGS. Table 3 below shows examples of materials and refractive indexes of the respective layers.

なお、活性層を多重量子井戸で構成しており、このときの屈折率は井戸層（AlGaInP、z =0.15、膜厚20nm、n=3.46）とバリア層（AlGaInP、z =0.56、膜厚10nm、n=3.30）の荷重平均値（3.41）を使用している。   The active layer is composed of multiple quantum wells, and the refractive index at this time is a well layer (AlGaInP, z = 0.15, film thickness 20 nm, n = 3.46) and a barrier layer (AlGaInP, z = 0.56, film thickness 10 nm). , N = 3.30), the load average value (3.41) is used.

上記表２の実施例では第１の層と第２の層の屈折率差はΔn=0.09であり、上記表３の実施例では第１の層と第２の層の屈折率差はΔn=0.1である。なお、上記表２において、zは(AlzGa1-z)0.5In0.5PのAl組成の比率を示し、活性層の組成範囲はｚ=0〜0.7であり、第１の層および第２の層の組成範囲はz=0.5〜1.0（ただし、屈折率は、第２の層＞第１の層、ｚは、第２の層＜第１の層）であり、中間層の組成範囲はz=0〜0.6（ただし、屈折率は、活性層＞中間層、ｚは、活性層＜中間層）である。 In the example of Table 2, the refractive index difference between the first layer and the second layer is Δn = 0.09. In the example of Table 3, the refractive index difference between the first layer and the second layer is Δn = 0.1. In Table 2, z represents the Al composition ratio of (Al z Ga 1-z ) 0.5 In 0.5 P, the composition range of the active layer is z = 0 to 0.7, the first layer and the second layer The composition range of the layer is z = 0.5 to 1.0 (where the refractive index is the second layer> the first layer, z is the second layer <the first layer), and the composition range of the intermediate layer is z = 0 to 0.6 (where the refractive index is active layer> intermediate layer, z is active layer <intermediate layer).

本発明の半導体発光デバイスの作製方法の実施例について説明する。以下では、基板上に直接半導体層を成長することで図８、９に示すような構成の半導体発光デバイスを作製する方法と、永久基板と半導体層とをメタルボンディング等により貼り合わせることで図１０〜１２のような構成の半導体発光デバイスを作製する方法の２つの作製方法を説明する。   Examples of a method for manufacturing a semiconductor light emitting device of the present invention will be described. In the following, a method for manufacturing a semiconductor light emitting device having a structure as shown in FIGS. 8 and 9 by growing a semiconductor layer directly on a substrate, and a permanent substrate and a semiconductor layer are bonded together by metal bonding or the like. Two manufacturing methods of manufacturing a semiconductor light emitting device having a configuration as described above to 12 will be described.

はじめに、二次元周期構造を有する、GaAs成長基板上にAlGaInP系半導体層を形成して半導体発光デバイスを作製する方法について説明する。   First, a method for manufacturing a semiconductor light emitting device by forming an AlGaInP-based semiconductor layer on a GaAs growth substrate having a two-dimensional periodic structure will be described.

ｎ型GaAs成長基板上にAlGaInPから成るn-Clad層、活性層、p-Clad層、さらに、及び、電極とオーミック接触を確保するためのGaPから成る電流拡散層（CSL）をMOCVD法（（有機金属気相成長法）により順次成長する。本実施例では活性層の(AlzGa1-z) 0.5In0.5Pの組成を井戸層（z=0.15,20nm)、バリア層（z=0.56,10nm）とした。ただし、井戸層とバリア層のAl組成(z)は発光波長に合わせ0＜z＜0.7の範囲で調整可能であり、本実施例の組成で限定するものではない。 On the n-type GaAs growth substrate, an n-Clad layer made of AlGaInP, an active layer, a p-Clad layer, and a current diffusion layer (CSL) made of GaP to ensure ohmic contact with the electrode are formed by MOCVD (( In this embodiment, the composition of (Al z Ga 1-z ) 0.5 In 0.5 P in the active layer is changed to a well layer (z = 0.15, 20 nm) and a barrier layer (z = 0.56). However, the Al composition (z) of the well layer and the barrier layer can be adjusted in the range of 0 <z <0.7 in accordance with the emission wavelength, and is not limited by the composition of this example.

AlGaInP系材料の場合、(AlzGa1-z)1-ｘInxPの組成をx=0.5に調整し、Al組成(z)を変化させることで、GaAs成長基板に格子整合させて屈折率を変化させることが可能である。 In the case of an AlGaInP-based material, the composition of (Al z Ga 1-z ) 1-x In x P is adjusted to x = 0.5, and the Al composition (z) is changed to lattice match with the GaAs growth substrate and refract. It is possible to change the rate.

この実施例では、バンドオフセットによる電子・ホールの閉じ込めと屈折率を考慮し、n-Clad(z =1.0)、p-Clad（z =0.7）、CSLをGaPとした。この時、n-Clad層を第１の層、p-Clad層+CSLを第２の層とし、それぞれ屈折率は3.17と3.26となる。   In this example, n-Clad (z = 1.0), p-Clad (z = 0.7), and CSL were GaP in consideration of electron / hole confinement and refractive index due to band offset. At this time, the n-Clad layer is the first layer, the p-Clad layer + CSL is the second layer, and the refractive indexes are 3.17 and 3.26, respectively.

なお、中間層を導入する場合は、p-Clad層とCSLの間にAl組成を調整したAlGaInP(z=0.3)からなる層を挿入した。このAl組成の調整は、中間層の屈折率が、CSL層の屈折率より大きくなるように、また、活性層の光を吸収しないように行う。   When an intermediate layer was introduced, a layer made of AlGaInP (z = 0.3) with an Al composition adjusted was inserted between the p-Clad layer and the CSL. The adjustment of the Al composition is performed so that the refractive index of the intermediate layer is larger than the refractive index of the CSL layer and does not absorb the light of the active layer.

電流拡散層であるGaPは、その格子定数はGaAsの格子定数と3％程度異なるため、格子不整合により結晶性の良い単結晶は積層できない。しかし、電流拡散層は、すでに活性層を積層した後の成長であるため、発光色に対し透明で、かつ、電気的に導電性を有し、金系の合金によりオーミック接触が可能であれば良く、結晶性は問題にならない。実際の製造では、この電流拡散層の積層には、AlGaInPの成長温度よりも、50〜100℃程度高温に成長すれば、十分要求に応える結晶が製造できる。また、金系の合金によりオーミック接触が可能であれば良いことから、AlGaAsを選択することも可能である。   Since the lattice constant of GaP, which is a current diffusion layer, differs from the lattice constant of GaAs by about 3%, single crystals with good crystallinity cannot be stacked due to lattice mismatch. However, since the current spreading layer is already grown after laminating the active layer, it should be transparent to the emission color, electrically conductive, and capable of ohmic contact with a gold alloy. Good, crystallinity is not a problem. In actual production, if the current diffusion layer is laminated at a temperature higher by about 50 to 100 ° C. than the growth temperature of AlGaInP, a crystal satisfying sufficient requirements can be produced. In addition, AlGaAs can be selected because it is sufficient if ohmic contact is possible with a gold-based alloy.

MOCVD法で成長させた後、CSL表面に二次元周期構造を形成する。ここでいう二次元周期構造とは三角格子、正方格子、六角格子などいずれかの周期構造、または、ペンローズタイリングのパターン、１２回対称を有する正方形―三角形タイリングのパターンなどいずれかの並進対称性を持たない準結晶構造をいう。   After growing by MOCVD method, a two-dimensional periodic structure is formed on the CSL surface. The two-dimensional periodic structure here means any one of periodic structures such as triangular lattice, square lattice, hexagonal lattice, Penrose tiling pattern, square-triangular tiling pattern having 12-fold symmetry, and so on. It refers to a quasicrystalline structure that has no properties.

実施例では、円孔で構成された三角格子配列の二次元周期構造を、第２の層であるCSL層の表面に形成した。二次元周期構造の周期a=1000nm、円孔半径r=300nm、深さｄ=600nm、活性層との距離ｈ=600ｎｍとした。   In the example, a two-dimensional periodic structure of a triangular lattice arrangement composed of circular holes was formed on the surface of the CSL layer as the second layer. The period of the two-dimensional periodic structure was a = 1000 nm, the hole radius r = 300 nm, the depth d = 600 nm, and the distance h from the active layer was 600 nm.

その二次元周期構造の形成方法は、CSL層の表面にフォトリソグラフィー、電子線描画、ナノインプリント、干渉露光などの手法により二次元周期構造のレジストパターンを形成し、ウェットエッチング、または、ドライエッチングにより所望の二次元周期構造を作成する。また、SiO2のパターンを上記方法で形成し、MOCVD法で再成長させることで二次元周期構造を形成することも可能である。 The two-dimensional periodic structure is formed by forming a resist pattern having a two-dimensional periodic structure on the surface of the CSL layer by a technique such as photolithography, electron beam drawing, nanoimprint, or interference exposure, and then performing desired etching by wet etching or dry etching. Create a two-dimensional periodic structure. It is also possible to form a two-dimensional periodic structure by forming a SiO 2 pattern by the above method and re-growing by the MOCVD method.

電流を供給するための電極は、GaAs基板裏面とCSL層の表面に真空蒸着法、スパッタ法、電子ビーム蒸着法などにより形成することができる。具体的には、GaAs基板裏面の電極は金、ゲルマニウム、ニッケルの合金を用いて形成し、CSL層の表面の電極は、金、亜鉛の合金を用いて形成した。LEDに電流を注入するための電極は、二次元周期構造作成前に形成しても、または、二次元周期構造後に形成しても構わない。   The electrode for supplying current can be formed on the back surface of the GaAs substrate and the surface of the CSL layer by vacuum deposition, sputtering, electron beam deposition, or the like. Specifically, the electrode on the back surface of the GaAs substrate was formed using an alloy of gold, germanium, and nickel, and the electrode on the surface of the CSL layer was formed using an alloy of gold and zinc. The electrode for injecting current into the LED may be formed before the creation of the two-dimensional periodic structure or may be formed after the two-dimensional periodic structure.

次に、永久基板（Si層）上のAlGaInP系LEDをメタルボンディングすることによって、半導体発光デバイスを作製する方法について説明する。   Next, a method for manufacturing a semiconductor light emitting device by metal bonding an AlGaInP LED on a permanent substrate (Si layer) will be described.

GaAs基板を一時基板とし、AlGaInP系の材料による半導体層を成長した後に、その半導体層を別途用意したSiからなる基板に貼り付け、しかる後にGaAsを除去した。   Using a GaAs substrate as a temporary substrate and growing a semiconductor layer made of an AlGaInP-based material, the semiconductor layer was attached to a separately prepared Si substrate, and then the GaAs was removed.

なお、手順の概略を図１３を用いて説明する。   The outline of the procedure will be described with reference to FIG.

半導体層と基板層とを個別に形成しておき、これらの層を結合層を挟んで、メタルボンディングによって結合することで行われる。図１３（ａ）〜（ｄ）は半導体層を形成する手順であり、図１３（ｅ）〜（ｇ）は基板層を形成する手順であり、図１３（ｈ）〜（ｊ）は半導体層と基板層とを結合する手順を示している。   A semiconductor layer and a substrate layer are formed separately, and these layers are bonded by metal bonding with a bonding layer interposed therebetween. FIGS. 13A to 13D are procedures for forming a semiconductor layer, FIGS. 13E to 13G are procedures for forming a substrate layer, and FIGS. 13H to 13J are semiconductor layers. Shows a procedure for bonding the substrate layer to the substrate layer.

半導体層を形成する手順では、GaAs基板上に半導体層を形成し（図１３（ａ））、半導体層に上に反射電極層を形成し（図１３（ｂ））、さらにその上にバリア層とAuの金属層を形成した後（図１３（ｃ））、反転させる（図１３（ｄ））。この半導体層に、上述した第１の層、活性層、第２の層を含むものであり、ｎ形GaAs成長基板（図１３（ａ）に相当）上にAlGaInPから成るn-Clad層、活性層、p-Clad層、さらに、GaPから成る電流拡散層（CSL）をMOCVD法により順次成長する（図１３（ｂ）に相当）。本実施例ではn-Clad層が光取り出し面側になるため、n-Clad層の屈折率を3.26(z=0.7)、p-Clad層の屈折率を3.17（z=1.0）、とした。本実施例では活性層の(AlzGa1-z)0.5In0.5Pの組成を井戸層（z=0.15,20nm)、バリア層（z=0.56,10nm）とした。ただし、井戸層とバリア層のAl組成(z)は発光波長に合わせ0＜z＜0.7の範囲で調整可能であり、本実施例の組成で限定するものではない。 In the procedure for forming a semiconductor layer, a semiconductor layer is formed on a GaAs substrate (FIG. 13A), a reflective electrode layer is formed on the semiconductor layer (FIG. 13B), and a barrier layer is further formed thereon. And Au are formed (FIG. 13 (c)) and then inverted (FIG. 13 (d)). This semiconductor layer includes the above-described first layer, active layer, and second layer, and an n-Clad layer made of AlGaInP on the n-type GaAs growth substrate (corresponding to FIG. 13A), active A layer, a p-Clad layer, and a current spreading layer (CSL) made of GaP are sequentially grown by MOCVD (corresponding to FIG. 13B). In this example, since the n-Clad layer is on the light extraction surface side, the refractive index of the n-Clad layer was 3.26 (z = 0.7), and the refractive index of the p-Clad layer was 3.17 (z = 1.0). In this example, the composition of (Al z Ga 1 -z) 0.5 In 0.5 P in the active layer was a well layer (z = 0.15, 20 nm) and a barrier layer (z = 0.56, 10 nm). However, the Al composition (z) of the well layer and the barrier layer can be adjusted in the range of 0 <z <0.7 in accordance with the emission wavelength, and is not limited by the composition of this example.

中間層を導入する場合は、n-Clad層の間にn-Clad層より屈折率が大きくなるように、また、活性層の光を吸収しないようにAl組成を調整したAlGaInP(z=0.3)からなる層を挿入した。   In the case of introducing an intermediate layer, AlGaInP (z = 0.3) in which the Al composition is adjusted so that the refractive index is higher than that of the n-Clad layer between the n-Clad layers and so as not to absorb the light of the active layer. A layer consisting of was inserted.

MOCVD法で半導体層の各層を成長させた後、電流拡散層（CSL層）の表面に半導体結晶との電気的接触を確保するためのAuZn合金（図１３（ｂ）の反射電極層に相当）をスパッタなどで形成し（厚み3000Å）、電気的接合とAuSnとの密着性を確保するためTa、Au（厚み3000Å）を形成する（図１３（ｃ）のバリア層およびAuに相当）。また、図１２に示す構成のように、半導体層と基板層に反射層を有する半導体発光デバイスを作製する場合には、例えば電流拡散層上にＳｉＯ2等からなる高い反射率の得られる層を部分的に形成した後、ＡｕＺｎ電極層、バリア層、密着層等を形成する。 After each layer of the semiconductor layer is grown by the MOCVD method, an AuZn alloy for securing electrical contact with the semiconductor crystal on the surface of the current diffusion layer (CSL layer) (corresponding to the reflective electrode layer in FIG. 13B) Is formed by sputtering or the like (thickness: 3000 mm), and Ta and Au (thickness: 3000 mm) are formed in order to ensure the adhesion between the electrical bonding and AuSn (corresponding to the barrier layer and Au in FIG. 13C). Also, as in the configuration shown in FIG. 12, a layer in the case, the resulting high reflectance of SiO 2 or the like on the example, the current spreading layer for producing a semiconductor light-emitting device having a reflective layer on the semiconductor layer and the substrate layer After partial formation, an AuZn electrode layer, a barrier layer, an adhesion layer, and the like are formed.

一方、例えばSiの永久基板にAuSnを形成し（図１３（ｆ）、（ｇ）の金属層、結合層に相当）、この永久基板のAuSn上に、前記した半導体層側のAuを載せて加熱・圧着してAuSnを溶解し、MOCVD法で形成した層と永久基板を結合する（図１３（ｈ）に相当）。この構成によれば、永久基板は成長基板を除去したあとのLED構造の機械的強度を保ち、電極との電気的接合を提供する。   On the other hand, for example, AuSn is formed on a permanent Si substrate (corresponding to the metal layers and bonding layers in FIGS. 13F and 13G), and Au on the semiconductor layer side is placed on the AuSn of the permanent substrate. The AuSn is dissolved by heating and pressure bonding, and the layer formed by the MOCVD method is bonded to the permanent substrate (corresponding to FIG. 13 (h)). According to this configuration, the permanent substrate maintains the mechanical strength of the LED structure after removal of the growth substrate and provides electrical bonding with the electrodes.

GaAs成長基板は永久基板に接着した後、アンモニアと過酸化水素から成るエッチャントにより除去される（図１３（ｉ）に相当）。成長基板を除去した後、n-Clad層に二次元周期構造を形成する。なお、二次元周期構造の構造、作製方法は前記した実施例と同様である。   After the GaAs growth substrate is bonded to the permanent substrate, it is removed by an etchant composed of ammonia and hydrogen peroxide (corresponding to FIG. 13 (i)). After removing the growth substrate, a two-dimensional periodic structure is formed in the n-Clad layer. The structure and manufacturing method of the two-dimensional periodic structure are the same as those in the above-described embodiment.

上記したメタルボンディングの手順は一例であり、反転させずに形成する方法、金属層や結合層を介さずに貼り合わせる方法など種々の方法をとり得る。   The above-described metal bonding procedure is an example, and various methods such as a method of forming without inversion and a method of bonding without using a metal layer or a bonding layer can be used.

次に、上述した、AlGaInP系LEDについてのシミュレーション結果について説明する。表４にAlGaInP系LEDの波動光学シミュレーションにおける二次元周期構造の設定条件を示す。シミュレーションの設定項目は図１４に示される。また、波動光学シミュレーションにおける発光波長（真空中）は、λ0＝６４０ｎｍ、励振方法はインコヒーレント、時間ステップは０．０３ｆｓ、セルサイズは２０ｎｍ×２０ｎｍ×２０ｎｍとした。 Next, simulation results for the AlGaInP-based LED described above will be described. Table 4 shows the setting conditions of the two-dimensional periodic structure in the wave optical simulation of the AlGaInP-based LED. The setting items of the simulation are shown in FIG. The emission wavelength (in vacuum) in the wave optical simulation was λ 0 = 640 nm, the excitation method was incoherent, the time step was 0.03 fs, and the cell size was 20 nm × 20 nm × 20 nm.

図１５に示す各構成について光取り出し効果について比較した。比較を行う構成は、二次元周期構造を有さず活性層を挟み対称な屈折率分布を有する構成（以下、基本構造、あるいは「平面対称」）、二次元周期構造を有さず活性層を挟み非対称な屈折率分布を有する構成（以下、「平面非対称」）、二次元周期構造および活性層を挟み対称な屈折率分布を有する構成（以下、「二次元周期×対称」）、二次元周期構造、活性層を挟み対称な屈折率分布および中間層を有する構成（以下、「二次元周期×対称×中間層」）、二次元周期構造および活性層を挟み非対称な屈折率分布を有する構成（以下、「二次元周期×非対称」）、二次元周期構造、活性層を挟み非対称な屈折率分布および中間層を有する構成（以下、「二次元周期×非対称×中間層」）である。なお、活性層を挟み非対称な屈折率分布を有する構造については、各層の屈折率を、第１の層3.26、活性層3.4）、第２の層屈折率3.17、中間層3.39で計算した。なお、λ0＝640nmとしている。 The light extraction effect of each configuration shown in FIG. 15 was compared. The configuration for comparison is a configuration having a symmetrical refractive index distribution with no active two-dimensional periodic structure and sandwiching the active layer (hereinafter referred to as a basic structure or “planar symmetry”), an active layer having no two-dimensional periodic structure. A structure having an asymmetric refractive index distribution (hereinafter referred to as “planar asymmetric”), a structure having a two-dimensional periodic structure and a symmetrical refractive index distribution across the active layer (hereinafter “two-dimensional period × symmetric”), a two-dimensional period Structure having a refractive index distribution and an intermediate layer sandwiched between the active layer and the active layer (hereinafter referred to as “two-dimensional period × symmetry × intermediate layer”), a structure having a two-dimensional periodic structure and an asymmetric refractive index distribution sandwiching the active layer ( Hereinafter, “two-dimensional period × asymmetric”), a structure having a two-dimensional periodic structure, an asymmetric refractive index distribution and an intermediate layer sandwiching the active layer (hereinafter, “two-dimensional period × asymmetric × intermediate layer”). For the structure having an asymmetric refractive index distribution across the active layer, the refractive index of each layer was calculated for the first layer 3.26, the active layer 3.4), the second layer refractive index 3.17, and the intermediate layer 3.39. Note that λ 0 = 640 nm.

図１５，図１６に、AlGaInP系LEDにおける光取り出し効果を示す。   15 and 16 show the light extraction effect in the AlGaInP-based LED.

図１５は、AlGaInP系LEDの各構成における光取り出し効果を「平面対称」の光強度を基準（１.００）として一覧で示したものである。   FIG. 15 shows a list of light extraction effects in each configuration of the AlGaInP-based LED, with “plane symmetry” light intensity as a reference (1.00).

図１６は、基本構造で得られる光強度を基準としたときの各構成で得られる光強度の比率と、二次元周期構造の底部と活性層との間の距離ｈとの関係について示している。   FIG. 16 shows the relationship between the ratio of the light intensity obtained in each configuration based on the light intensity obtained in the basic structure, and the distance h between the bottom of the two-dimensional periodic structure and the active layer. .

図１６中の符号Ａは「二次元周期×対称」を、符号Ｂは「二次元周期×対称×中間層」を、符号Ｃは「二次元周期×非対称」を、符号Ｄは二次元周期×非対称×中間層」を示している。   16, “A” is “two-dimensional period × symmetric”, “B” is “two-dimensional period × symmetric × intermediate layer”, “C” is “two-dimensional period × asymmetric”, and “D” is two-dimensional period × Asymmetric × intermediate layer ”is shown.

図１５，図１６に示すシミュレーション結果から、距離ｈと波長λ0との比率ｈ／λ0が小さい場合には、ＡとＣの比較から二次元周期構造と非対称な屈折率分布を有する構成とすることで光の取り出し効果が高まることが確認される。また、光の取り出し効果はｈ／λ0が小さいほど増加することが確認される。 15, from the simulation results shown in FIG. 16, when the distance h and the ratio h / lambda 0 the wavelength lambda 0 is small, a configuration having a two-dimensional periodic structure and an asymmetric refractive index distribution from a comparison of the A and C It is confirmed that the light extraction effect is enhanced. Further, it is confirmed that the light extraction effect increases as h / λ 0 decreases.

また、二次元周期構造、非対称な屈折率分布および中間層を有する構成とすることで、さらに光りの取り出し効果を向上させることができることが確認できた。   In addition, it was confirmed that the light extraction effect can be further improved by using a structure having a two-dimensional periodic structure, an asymmetric refractive index distribution, and an intermediate layer.

また、活性層と二次元周期構造底部の距離ｈがλ0より小さい場合に、「二次元周期×対称」、「二次元周期×対称×中間層」、「二次元周期×非対称」、「二次元周期×非対称×中間層」のいずれの構成も「平面対称」より光取出し効果が改善している。ここで、ｈ/λ0の値が１であるときのｈはｎλであるため、活性層から二次元周期構造の底部までの距離は、ｎλ以下において光取出し効率が向上すると言える。なかでも、「二次元周期×対称×中間層」、「二次元周期×非対称×中間層」は高い光取出し効果が得られることが確認できた。このことは、中間層が方向性結合の役割を果たし活性層と二次元周期構造との結合を強めることによるものと考えられる。特に「二次元周期×非対称×中間層」は、光取出し効果が高いことが確認できた。「二次元周期×非対称×中間層」の光取出し効率が、「二次元周期×対称×中間層」や「二次元周期×非対称」の効果から予測される以上に高い結果が得られた理由としては、非対称な屈折率分布の形成により、光取出し面側および活性層中を導波した光のうち、光取出し面側へ導波する光が２次元周期構造へと結合し取り出され、活性層中を導波する光が中間層を介して２次元周期構造へと結合し取り出されたことによると考えられる。 When the distance h between the active layer and the bottom of the two-dimensional periodic structure is smaller than λ 0 , “two-dimensional period × symmetric”, “two-dimensional period × symmetric × intermediate layer”, “two-dimensional period × asymmetric”, “two In any configuration of “dimensional period × asymmetric × intermediate layer”, the light extraction effect is improved from “plane symmetry”. Here, since h is nλ when the value of h / λ 0 is 1, it can be said that the light extraction efficiency is improved when the distance from the active layer to the bottom of the two-dimensional periodic structure is nλ or less. In particular, it was confirmed that “two-dimensional period × symmetry × intermediate layer” and “two-dimensional period × asymmetric × intermediate layer” provide a high light extraction effect. This is presumably because the intermediate layer plays a role of directional coupling and strengthens the coupling between the active layer and the two-dimensional periodic structure. In particular, it was confirmed that “two-dimensional period × asymmetric × intermediate layer” has a high light extraction effect. The reason why the light extraction efficiency of "two-dimensional period x asymmetric x intermediate layer" was higher than expected from the effect of "two-dimensional period x symmetrical x intermediate layer" and "two-dimensional period x asymmetric" The light guided to the light extraction surface side and the light extraction surface side out of the light guided to the light extraction surface side in the active layer due to the formation of an asymmetric refractive index profile is coupled to the two-dimensional periodic structure and extracted. This is considered to be due to the fact that the light guided inside is coupled to the two-dimensional periodic structure via the intermediate layer and extracted.

「二次元周期×非対称×中間層」の光取出し効率が、「二次元周期×対称×中間層」や「二次元周期×非対称」の効果から予測される以上に高い結果が得られた理由としては、非対称な屈折率分布の形成により、光取出し面側および活性層中を導波した光のうち、光取出し面側へ導波する光が２次元周期構造へと結合し取り出され、活性層中を導波する光が中間層を介して２次元周期構造へと結合し取り出されたことによると考えられる。   The reason why the light extraction efficiency of "two-dimensional period x asymmetric x intermediate layer" was higher than expected from the effect of "two-dimensional period x symmetrical x intermediate layer" and "two-dimensional period x asymmetric" The light guided to the light extraction surface side and the light extraction surface side out of the light guided to the light extraction surface side in the active layer due to the formation of an asymmetric refractive index profile is coupled to the two-dimensional periodic structure and extracted. This is considered to be due to the fact that the light guided inside is coupled to the two-dimensional periodic structure via the intermediate layer and extracted.

ここで、中間層は、屈折率を活性層以下とし、第２の層の他の層の屈折率より高く設定するが、活性層とほぼ同等の屈折率を有することが好ましい。活性層に二次元周期構造を加工した場合、表面再結合により半導体発光デバイスの効率が大幅に低下するが、活性層の屈折率とほぼ等しい中間層を二次元周期構造中、または、近傍に設けることで中間層が方向性結合の役割を果たし活性層と二次元周期構造との結合を強め光取り出しの効果が向上する。中間層を備えた場合、表面再結合による効率低下が生じない。さらに、活性層まで二次元周期構造を加工する必要がないため、加工プロセスも容易になるメリットがある。   Here, the intermediate layer has a refractive index lower than that of the active layer and is set higher than that of the other layers of the second layer, but preferably has a refractive index substantially equal to that of the active layer. When a two-dimensional periodic structure is processed in the active layer, the efficiency of the semiconductor light-emitting device is greatly reduced due to surface recombination. Thus, the intermediate layer plays a role of directional coupling, strengthening the coupling between the active layer and the two-dimensional periodic structure, and improving the light extraction effect. When the intermediate layer is provided, efficiency reduction due to surface recombination does not occur. Furthermore, since it is not necessary to process the two-dimensional periodic structure up to the active layer, there is a merit that the processing process becomes easy.

次に、GaN系LED の構成について、説明する。なお、上述したＡｌＧａＩｎＰ系ＬＥＤと材料は異なるものの基本的な構成（屈折率の大小関係を含む）は同じであるので、図１０〜１２を用いて構成例を説明する。   Next, the configuration of the GaN LED will be described. Although the basic configuration (including the refractive index magnitude relationship) is the same, although the material is different from the AlGaInP-based LED described above, a configuration example will be described with reference to FIGS.

基板６ＢをSiで形成し、第１の層２Ｂの電流拡散層（CSL層）２ＢｂをGaNで形成し、第１導電型半導体クラッド層（p−Clad層）２Ｂａを（AlGaN）で形成し、活性層３Ｂを（InGaN）で形成し、第２導電型半導体クラッド層（n−Clad層）４Ｂを（GaN）で形成する。   The substrate 6B is formed of Si, the current diffusion layer (CSL layer) 2Bb of the first layer 2B is formed of GaN, the first conductivity type semiconductor clad layer (p-Clad layer) 2Ba is formed of (AlGaN), The active layer 3B is formed of (InGaN), and the second conductivity type semiconductor clad layer (n-Clad layer) 4B is formed of (GaN).

ＧａＮ系ＬＥＤ構成の実施例について、各層の材料例、屈折率を表５に示す。   Table 5 shows material examples and refractive indexes of the respective layers for the examples of the GaN-based LED configuration.

なお、ここでは、活性層を多重量子井戸で構成しており、このときの屈折率は井戸層（InxGa1-xN、ｘ=0.4,2nm、n=2.75）とバリア層（GaN、14nm、n=2.50）の荷重平均値（n=2.53）を使用している。 Here, the active layer is composed of multiple quantum wells, and the refractive index at this time is such that the well layer (In x Ga 1-x N, x = 0.4,2 nm, n = 2.75) and the barrier layer (GaN, The load average value (n = 2.53) of 14nm, n = 2.50) is used.

表５の実施例では第１の層と第２の層の屈折率差はΔn=0.１である。なお、ｘはＩｎxＧａ1-xＮのＩｎ組成の比率を示し、活性層の組成範囲はｘ=0〜0.４（井戸とバリアの平均）であり、第２の層の組成範囲はｘ=0〜0.5であり、中間層の組成範囲はｘ=0〜0.4（ただし、活性層＞中間層）である。 In the example of Table 5, the refractive index difference between the first layer and the second layer is Δn = 0.l. X represents the ratio of In composition of In x Ga 1-x N, the composition range of the active layer is x = 0 to 0.4 (average of well and barrier), and the composition range of the second layer is x = 0 to 0.5, and the composition range of the intermediate layer is x = 0 to 0.4 (where active layer> intermediate layer).

以下に上記ＧａＮ系ＬＥＤの実施例の作製方法について示す。   Hereinafter, a method for producing an example of the GaN-based LED will be described.

はじめに、非対称な屈折率分布をもつGaN系LEDを、MOCVD法によりサファイア成長基板上に作製する。成長基板上に膜厚数nm〜10nm程度のGaN、またはAlNからなるバッファ層を形成した後、膜厚１〜６um程度のSiドープGaNから成るn-Clad層を作製する。   First, a GaN LED with an asymmetric refractive index profile is fabricated on a sapphire growth substrate by MOCVD. After forming a buffer layer made of GaN or AlN having a film thickness of several nm to 10 nm on the growth substrate, an n-Clad layer made of Si-doped GaN having a film thickness of about 1 to 6 μm is formed.

次に、InGaNから成る活性層を形成する。本実施例では活性層のInxGa1-xNからなる井戸層（ｘ=0.2,2nm)とGaNからなるバリア層（14nm）で構成される多重量子井戸構造とした。ただし、井戸層のIn組成(x)は発光波長に合わせ調整可能であり、本実施例の組成で限定するものではない。 Next, an active layer made of InGaN is formed. In the present embodiment, a multi-quantum well structure including an active layer In x Ga 1-x N well layer (x = 0.2, 2 nm) and a GaN barrier layer (14 nm) is used. However, the In composition (x) of the well layer can be adjusted according to the emission wavelength, and is not limited by the composition of this example.

その後、屈折率を非対称にするためにMgドープp-AlGaN層、次にp-GaNからなるp-Clad層を成長する。   Thereafter, in order to make the refractive index asymmetric, an Mg-doped p-AlGaN layer and then a p-Clad layer made of p-GaN are grown.

実施例では、n-Clad層 GaNの屈折率を2.50、活性層InGaNの屈折率を2.53、n-AlGaNの屈折率を結晶の品質低が生じない領域でAl組成を調整し2.40（Al組成40％）とした。この組成における屈折率差Δnは0.1である。   In the example, the refractive index of n-Clad layer GaN is 2.50, the refractive index of active layer InGaN is 2.53, and the refractive index of n-AlGaN is adjusted to 2.40 (Al composition 40 %). The refractive index difference Δn in this composition is 0.1.

中間層を導入する場合は、n-Clad層の間にn-Clad層より屈折率が大きくなるようにIn組成を調整したInGaNから成る層を挿入した。実施例では中間層の屈折率を2.55とした。   In the case of introducing the intermediate layer, a layer made of InGaN having an In composition adjusted so as to have a refractive index higher than that of the n-Clad layer was inserted between the n-Clad layers. In the example, the refractive index of the intermediate layer was 2.55.

MOCVD法で成長させた後、p-Clad層表面に半導体結晶との電気的接触を確保するためのPt/Ag合金をスパッタなどで形成し（厚み3000Å）、電気的接合とAuSnとの密着性を確保するためTa、Au（厚み3000Å）を形成し、AuSnが形成された永久基板（例えばSi）に加熱・圧着によりAuSnを溶解し、MOCVD法で形成した層と永久基板を結合する。   After growing by MOCVD method, a Pt / Ag alloy to ensure electrical contact with the semiconductor crystal is formed on the surface of the p-Clad layer by sputtering (thickness 3000 mm), and adhesion between the electrical junction and AuSn Ta and Au (thickness 3000 mm) are formed, AuSn is dissolved in a permanent substrate (eg, Si) on which AuSn is formed by heating and pressure bonding, and the layer formed by the MOCVD method is bonded to the permanent substrate.

成長基板の除去は、サファイアの場合、成長基板裏面からのパルスレーザ照射により除去可能である。   In the case of sapphire, the growth substrate can be removed by pulse laser irradiation from the back surface of the growth substrate.

MOCVD法での成長させた後、n-Clad層GaN表面に二次元周期構造を形成する。   After the growth by the MOCVD method, a two-dimensional periodic structure is formed on the n-Clad layer GaN surface.

実施例では、円孔で構成された三角格子配列の二次元周期構造を、第２の層であるn-GaN表面に形成した。本実施例においては、二次元周期構造を、周期a=700nm、円孔半径r=200nm、深さｄ=400nm、活性層との距離をｈ＝１２０ｎｍとした。   In the example, a two-dimensional periodic structure of a triangular lattice arrangement composed of circular holes was formed on the surface of the second layer, n-GaN. In this embodiment, the two-dimensional periodic structure has a period a = 700 nm, a circular hole radius r = 200 nm, a depth d = 400 nm, and a distance from the active layer h = 120 nm.

その形成手法は、n-Clad層GaN表面にフォトリソグラフィー、電子線描画、電子線転写、ナノインプリント、干渉露光などの手法により二次元周期構造のレジストパターンを形成し、ウェットエッチング、または、ドライエッチングにより所望の二次元周期構造を作成する。また、SiO2のパターンを上記方法で形成し、MOCVD法で再成長させることで二次元周期構造を形成することも可能である。 The formation method is to form a resist pattern with a two-dimensional periodic structure on the n-Clad layer GaN surface by techniques such as photolithography, electron beam drawing, electron beam transfer, nanoimprint, interference exposure, etc., and then wet etching or dry etching. A desired two-dimensional periodic structure is created. It is also possible to form a two-dimensional periodic structure by forming a SiO 2 pattern by the above method and re-growing by the MOCVD method.

LEDに電流を注入するための電極は、永久基板が導電性の場合、永久基板裏面とn-Clad GaN表面に形成する。   When the permanent substrate is conductive, electrodes for injecting current into the LED are formed on the back surface of the permanent substrate and the n-Clad GaN surface.

ここで、ＧａＮ系ＬＥＤにおいて、ｐ側領域に加工を行う場合、ドライエッチングなどが結晶に損傷を与えｐ型層が高抵抗化を引き起こす可能性がある。しかし、本実施例のような製法を用いることにより、ｎ側層を加工することで高抵抗化が回避できる。また、ＧａＮ系ＬＥＤでは、本発明特有の活性層を挟み非対称（第２の層の屈折率＞第１の層の屈折率）な屈折率分布を有する半導体発光デバイスは、成長基板上に直接半導体層を積層してＬＥＤを作製する方法によっては屈折率の低い第１の層を形成するためにＡｌ組成の高いＡｌＧａＮからなるｎ型クラッド層を形成する必要があるが、一方で、ｎ型側に電子の障壁となるＡｌＧａＮ層の形成により電子注入能力が低下するという問題があるため作製困難であるが、本実施例のように基板の貼り合わせ工程を用いることにより作製することができる。   Here, in the GaN-based LED, when processing is performed on the p-side region, dry etching or the like may damage the crystal and cause the p-type layer to increase in resistance. However, by using the manufacturing method as in this embodiment, it is possible to avoid an increase in resistance by processing the n-side layer. In addition, in a GaN-based LED, a semiconductor light-emitting device having an asymmetric refractive index distribution (a refractive index of the second layer> a refractive index of the first layer) sandwiching an active layer peculiar to the present invention is formed directly on the growth substrate. Depending on the method of fabricating the LED by laminating the layers, it is necessary to form an n-type cladding layer made of AlGaN having a high Al composition in order to form the first layer having a low refractive index. However, the formation of an AlGaN layer serving as an electron barrier has a problem in that the electron injection capability is reduced, which makes it difficult to produce, but it can be produced by using a substrate bonding step as in this embodiment.

次に、GaN系LED についてのシミュレーションについて説明する。表６はGaN系LEDの波動光学シミュレーションにおける二次元周期構造の設定条件であり、各設定項目は、ＡｌＧａＩｎＰ系ＬＥＤのシミュレーション同様、図１４に示される。また、波動光学シミュレーションにおける発光波長（真空中）は、λ0＝４５５ｎｍ、励振方法はインコヒーレント、時間ステップは０．０３ｆｓ、セルサイズは２０ｎｍ×２０ｎｍ×２０ｎｍとした。 Next, a simulation for a GaN LED will be described. Table 6 shows the setting conditions of the two-dimensional periodic structure in the wave optical simulation of the GaN-based LED. Each setting item is shown in FIG. 14 as in the simulation of the AlGaInP-based LED. The emission wavelength (in vacuum) in the wave optical simulation was λ 0 = 455 nm, the excitation method was incoherent, the time step was 0.03 fs, and the cell size was 20 nm × 20 nm × 20 nm.

図１７，図１８に、GaN系LEDにおけるシミュレーション結果として得られた光取り出し効果を示す。   17 and 18 show the light extraction effect obtained as a simulation result in the GaN-based LED.

図１７は、GaN系LEDの各構成における光取り出し効果を一覧で示したものである。比較を行う構成は、二次元周期構造を有さず活性層を挟み対称な屈折率分布を有する構成（以下、基本構造、あるいは「平面対称」）、二次元周期構造を有さず活性層を挟み非対称な屈折率分布を有する構成（以下、「平面非対称」）、二次元周期構造および活性層を挟み対称な屈折率分布を有する構成（以下、「二次元周期×対称」）、二次元周期構造、活性層を挟み対称な屈折率分布および中間層を有する構成（以下、「二次元周期×対称×中間層」）、二次元周期構造および活性層を挟み非対称な屈折率分布を有する構成（以下、「二次元周期×非対称」）、二次元周期構造、活性層を挟み非対称な屈折率分布および中間層を有する構成（以下、「二次元周期×非対称×中間層」）である。   FIG. 17 shows a list of light extraction effects in each configuration of the GaN-based LED. The configuration for comparison is a configuration having a symmetrical refractive index distribution with no active two-dimensional periodic structure and sandwiching the active layer (hereinafter referred to as a basic structure or “planar symmetry”), an active layer having no two-dimensional periodic structure. A structure having an asymmetric refractive index distribution (hereinafter referred to as “planar asymmetric”), a structure having a two-dimensional periodic structure and a symmetrical refractive index distribution across the active layer (hereinafter “two-dimensional period × symmetric”), a two-dimensional period Structure having a refractive index distribution and an intermediate layer sandwiched between the active layer and the active layer (hereinafter referred to as “two-dimensional period × symmetry × intermediate layer”), a structure having a two-dimensional periodic structure and an asymmetric refractive index distribution sandwiching the active layer ( Hereinafter, “two-dimensional period × asymmetric”), a structure having a two-dimensional periodic structure, an asymmetric refractive index distribution and an intermediate layer sandwiching the active layer (hereinafter, “two-dimensional period × asymmetric × intermediate layer”).

図１８は、基本構造で得られる光強度を基準としたときの各構成で得られる光強度の比率と、二次元周期構造の底部と活性層との間の距離ｈとの関係について示している。   FIG. 18 shows the relationship between the ratio of the light intensity obtained in each configuration based on the light intensity obtained in the basic structure and the distance h between the bottom of the two-dimensional periodic structure and the active layer. .

図１７中の符号Ｅは「二次元周期×対称」、符号Ｆは「二次元周期×対称×中間層」、符号Ｇは「二次元周期×非対称」、符号Ｈは「二次元周期×非対称×中間層」を示している。   In FIG. 17, the symbol E is “two-dimensional cycle × symmetric”, the symbol F is “two-dimensional cycle × symmetric × intermediate layer”, the symbol G is “two-dimensional cycle × asymmetric”, and the symbol H is “two-dimensional cycle × asymmetric ×”. "Intermediate layer".

非対称な屈折率分布を有する「二次元周期×非対称」（Ｇ）および「二次元周期×非対称×中間層」（Ｈ）の光取出し効率が顕著に高く、中でも中間層を有する「二次元周期×非対称×中間層」（Ｈ）の光取出し効率が高い。また、構成「二次元周期×対称×中間層」（Ｆ）、「二次元周期×非対称」（Ｇ）、「二次元周期×非対称×中間層」（Ｈ）においては、距離ｈと波長λ0との比率ｈ／λ0が小さいほうが、光取出し効果が高まることが確認できた。ここで、中間層を導入した効果については、非対称の屈折率分布を有する場合には、活性層と二次元周期構造底部の距離ｈが１．５ｎλ（ｈ/λ0＝１．５）以下において、対称の屈折率分布を有する場合には、０．７ｎλ（ｈ/λ0＝０．７）以下において、光取出し向上の効果が確認できた。 The light extraction efficiency of “two-dimensional period × asymmetric” (G) and “two-dimensional period × asymmetric × intermediate layer” (H) having an asymmetric refractive index profile is remarkably high. The light extraction efficiency of “asymmetric × intermediate layer” (H) is high. In the configuration “two-dimensional period × symmetric × intermediate layer” (F), “two-dimensional period × asymmetric” (G), and “two-dimensional period × asymmetric × intermediate layer” (H), the distance h and the wavelength λ 0 It was confirmed that the light extraction effect is enhanced when the ratio h / λ 0 is smaller. Here, as for the effect of introducing the intermediate layer, when the refractive index profile is asymmetric, the distance h between the active layer and the bottom of the two-dimensional periodic structure is 1.5 nλ (h / λ 0 = 1.5) or less. In the case of having a symmetric refractive index distribution, the effect of improving the light extraction was confirmed at 0.7 nλ (h / λ 0 = 0.7) or less.

図１７，図１８に示すGaN系LEDのシミュレーション結果は光の取り出し効果はAlGaInP系LEDよりも小さいが、AlGaInP系LEDのシミュレーション結果とほぼ同様の傾向を示しており、異なる材料系においても同様の傾向を示すことが確認できた。   The simulation results of the GaN-based LEDs shown in FIGS. 17 and 18 show a tendency similar to that of the simulation results of the AlGaInP-based LEDs, although the light extraction effect is smaller than that of the AlGaInP-based LEDs. It was confirmed that the trend was shown.

本発明は、半導体ＬＥＤ、およびそれを用いた白色照明、ライト、インジケータ、ＬＥＤ通信等に適用することができる。   The present invention can be applied to semiconductor LEDs and white illumination, lights, indicators, LED communications, and the like using the same.

本発明の半導体発光デバイスの構成例を説明するための図である。It is a figure for demonstrating the structural example of the semiconductor light-emitting device of this invention. 本発明の二次元周期構造の円孔最密配列の平面図および側面図である。It is the top view and side view of a circular hole close-packed arrangement of the two-dimensional periodic structure of this invention. 本発明の二次元周期構造の円錐突起最密配列の平面図および側面図である。It is the top view and side view of a conical protrusion close-packed array of the two-dimensional periodic structure of this invention. 本発明の二次元周期構造（円孔最密配列）を備える半導体発光デバイスの光取り出し効率を示す図である。It is a figure which shows the light extraction efficiency of a semiconductor light-emitting device provided with the two-dimensional periodic structure (circular hole close-packed arrangement) of this invention. 本発明の二次元周期構造（円錐突起最密配列）を備える半導体発光デバイスの光取り出し効率を示す図である。It is a figure which shows the light extraction efficiency of a semiconductor light-emitting device provided with the two-dimensional periodic structure (cone-projection close-packed arrangement) of this invention. 本発明の二次元周期構造（円孔最密配列）を備える半導体発光デバイスの光取り出し効率を示す図である。It is a figure which shows the light extraction efficiency of a semiconductor light-emitting device provided with the two-dimensional periodic structure (circular hole close-packed arrangement) of this invention. 本発明の二次元周期構造（円錐突起最密配列）を備える半導体発光デバイスの光取り出し効率を示す図である。It is a figure which shows the light extraction efficiency of a semiconductor light-emitting device provided with the two-dimensional periodic structure (cone-projection close-packed arrangement) of this invention. 本発明のAlGaInP系LEDの二次元周期構造と非対称屈折率構成との構成を説明するための構成図である。It is a block diagram for demonstrating the structure of the two-dimensional periodic structure and asymmetrical refractive index structure of AlGaInP-type LED of this invention. 本発明のAlGaInP系LEDの二次元周期構造と非対称屈折率構成と中間層の構成を説明するための構成図である。It is a block diagram for demonstrating the two-dimensional periodic structure of the AlGaInP-type LED of this invention, an asymmetrical refractive index structure, and the structure of an intermediate | middle layer. 本発明のAlGaInP系LEDの二次元周期構造と非対称屈折率構成との構成を説明するための図である。It is a figure for demonstrating the structure of the two-dimensional periodic structure and asymmetrical refractive index structure of AlGaInP-type LED of this invention. 本発明のAlGaInP系LEDの二次元周期構造と非対称屈折率構成と中間層の構成を説明するための構成図である。It is a block diagram for demonstrating the two-dimensional periodic structure of the AlGaInP-type LED of this invention, an asymmetrical refractive index structure, and the structure of an intermediate | middle layer. 本発明のAlGaInP系LEDの二次元周期構造と非対称屈折率構成との構成を説明するための図である。It is a figure for demonstrating the structure of the two-dimensional periodic structure and asymmetrical refractive index structure of AlGaInP-type LED of this invention. メタルボンディングによって永久基板層上に半導体層を形成する手順の概略を説明するための図である。It is a figure for demonstrating the outline of the procedure which forms a semiconductor layer on a permanent substrate layer by metal bonding. 本発明のAlGaInP系LEDのシミュレーションにおける二次元周期構造の設定条件を説明するための図である。It is a figure for demonstrating the setting conditions of the two-dimensional periodic structure in the simulation of AlGaInP type LED of this invention. 本発明のAlGaInP系LEDにおける光り取り出し効果を示す図である。It is a figure which shows the light extraction effect in AlGaInP type LED of this invention. 本発明のAlGaInP系LEDにおける光り取り出し効果を示す図である。It is a figure which shows the light extraction effect in AlGaInP type LED of this invention. 本発明のGaN系LEDにおける光り取り出し効果を示す図である。It is a figure which shows the light extraction effect in GaN-type LED of this invention. 本発明のGaN系LEDにおける光り取り出し効果を示す図である。It is a figure which shows the light extraction effect in GaN-type LED of this invention.

符号の説明Explanation of symbols

１…半導体発光デバイス
２…第１の層
２Ａ…n-Clad層
２Ｂａ…ｐ-Clad層
２Ｂｂ…ＣＳＬ（電流拡散層）
２Ｃａ…ｐ-Clad層
２Ｃｂ…ＣＳＬ（電流拡散層）
３…活性層
３Ａ，３Ｂ，３Ｃ…活性層
４…第２の層
４Ａａ…ｐ-Clad層
４Ａｂ…ＣＳＬ（電流拡散層）
４Ｂ…n-Clad層
５…中間層
５Ａ，５Ｂ，５Ｃ…中間層
６…基板層
６Ａ…成長基板
６Ｂ，６Ｃ…永久基板
７Ａ，７Ｂ…電極
１０…二次元周期構造
１１…孔
１１ａ…円孔
１２…底部
１３…突起
１３ａ…円錐突起
１４…底部 DESCRIPTION OF SYMBOLS 1 ... Semiconductor light-emitting device 2 ... 1st layer 2A ... n-Clad layer 2Ba ... p-Clad layer 2Bb ... CSL (current diffusion layer)
2Ca ... p-Clad layer 2Cb ... CSL (current diffusion layer)
DESCRIPTION OF SYMBOLS 3 ... Active layer 3A, 3B, 3C ... Active layer 4 ... 2nd layer 4Aa ... p-Clad layer 4Ab ... CSL (current spreading layer)
4B ... n-Clad layer 5 ... Intermediate layer 5A, 5B, 5C ... Intermediate layer 6 ... Substrate layer 6A ... Growth substrate 6B, 6C ... Permanent substrate 7A, 7B ... Electrode 10 ... Two-dimensional periodic structure 11 ... Hole 11a ... Circular hole 12 ... Bottom 13 ... Projection 13a ... Conical projection
14 ... Bottom

Claims (5)

基板層と、
前記基板層の上方に設けた第１導電型半導体クラッド層を含む単数または複数からなる第１の層と、
前記第１の層の上方に設けた活性層と、
前記活性層の上方に設けた、第２導電型半導体クラッド層を含み、表面に二次元周期構造を有する単数または複数からなる第２の層と、を備えた半導体発光デバイスであって、
前記第１の層は、前記活性層の屈折率より低く、かつ、前記第２の層の活性層に接する層の屈折率よりも低い屈折率の層を少なくとも一層を含み、
前記第２の層を構成する何れの層も前記活性層の屈折率より低い屈折率を有することを特徴とする半導体発光デバイス。 A substrate layer;
A first layer composed of one or a plurality of layers including a first conductivity type semiconductor clad layer provided above the substrate layer;
An active layer provided above the first layer;
A semiconductor light emitting device including a second conductive layer including a second conductivity type semiconductor clad layer provided on the active layer and having a two-dimensional periodic structure on a surface thereof;
The first layer includes at least one layer having a refractive index lower than the refractive index of the active layer and lower than the refractive index of the layer in contact with the active layer of the second layer,
Any of the layers constituting the second layer has a refractive index lower than that of the active layer. 基板層と、
前記基板層の上方に設けた単数または複数からなる第１の層と、
前記第１の層の上方に設けた多重量子井戸構造を有する活性層と、
前記活性層の上方に設けた、表面に二次元周期構造を有する単数または複数からなる第２の層と、を備えた半導体発光デバイスであって、
前記第１の層は、前記活性層の屈折率の膜厚荷重平均値より低く、かつ、前記第２の層の活性層に接する層の屈折率よりも低い屈折率の層を少なくとも一層含み、
前記第２の層を構成する何れの層も前記活性層の屈折率の膜厚荷重平均値より低い屈折率を有することを特徴とする半導体発光デバイス。 A substrate layer;
A single layer or a plurality of first layers provided above the substrate layer;
An active layer having a multiple quantum well structure provided above the first layer;
A semiconductor light emitting device comprising a second layer formed of one or more having a two-dimensional periodic structure on a surface provided above the active layer,
The first layer includes at least one layer having a refractive index lower than the refractive index of the active layer of the second layer and lower than the refractive index of the layer in contact with the active layer of the second layer,
Any one of the layers constituting the second layer has a refractive index lower than the film thickness load average value of the refractive index of the active layer. 前記二次元周期構造の底部と前記活性層の上部の距離が、0.1nλ〜nλ（n：前記二次元周期構造の底部と前記活性層の上部との間の層の屈折率、λ：光学波長）であることを特徴とする請求項１または２に記載の半導体発光デバイス。   The distance between the bottom of the two-dimensional periodic structure and the top of the active layer is 0.1 nλ to nλ (n: refractive index of the layer between the bottom of the two-dimensional periodic structure and the top of the active layer, λ: optical wavelength The semiconductor light-emitting device according to claim 1, wherein 前記第２の層は、前記活性層の屈折率以下の屈折率を有する中間層を含み、
前記中間層は、前記第２の層の他の層の屈折率より高いことを特徴とする請求項1または３の何れか一つに記載の半導体発光デバイス。 The second layer includes an intermediate layer having a refractive index lower than that of the active layer,
4. The semiconductor light emitting device according to claim 1, wherein the intermediate layer has a refractive index higher than that of other layers of the second layer. 前記第２の層は、前記多重量子井戸構造を構成する井戸層の屈折率以下の屈折率を有する中間層を含み、
前記中間層は、前記第２の層の他の層の屈折率より高いことを特徴とする請求項２または３のいずれか一つに記載の半導体発光デバイス。 The second layer includes an intermediate layer having a refractive index equal to or lower than the refractive index of the well layer constituting the multiple quantum well structure,
4. The semiconductor light emitting device according to claim 2, wherein the intermediate layer has a refractive index higher than that of other layers of the second layer.
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