JP4957130B2 - Light emitting diode - Google Patents
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- JP4957130B2 JP4957130B2 JP2006241341A JP2006241341A JP4957130B2 JP 4957130 B2 JP4957130 B2 JP 4957130B2 JP 2006241341 A JP2006241341 A JP 2006241341A JP 2006241341 A JP2006241341 A JP 2006241341A JP 4957130 B2 JP4957130 B2 JP 4957130B2
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本発明は、高効率で低価格であることを特徴とする発光ダイオードに関する。 The present invention relates to a light emitting diode characterized by high efficiency and low cost.
発光ダイオードは、赤色から青色までフルカラーが揃ったことから、照明用への応用が積極的に試みられるようになってきた。発光ダイオードを照明用として使おうとすると、省エネルギーの面から発光効率が高いことが要求される。このため、発光効率を高くするための構造開発が積極的に行われている。 Since light emitting diodes are available in full colors from red to blue, attempts have been made to actively apply them for illumination. In order to use a light emitting diode for illumination, high luminous efficiency is required from the viewpoint of energy saving. For this reason, structure development for increasing luminous efficiency has been actively carried out.
一般的な発光ダイオードは、図５に示すように、基板１０６上にｐ型である上部クラッド層１０３とｎ型である下部クラッド層１０５で活性層１０４を挟み、電流分散層１０２の上部に上部電極１０１と基板１０６の下部に下部電極１０７を有する構造になっている。 As shown in FIG. 5, a general light emitting diode has an active layer 104 sandwiched between a p-type upper cladding layer 103 and an n-type lower cladding layer 105 on a substrate 106, and an upper portion above the current spreading layer 102. The lower electrode 107 is provided below the electrode 101 and the substrate 106.
この発光ダイオードでは、活性層１０４から表面側に向かった光の一部は取り出せるが、基板１０６側に向かった光は、基板１０６に吸収されてしまい、光取り出し効率の悪い発光ダイオードになってしまう。 In this light emitting diode, a part of the light traveling from the active layer 104 toward the surface side can be extracted, but the light traveling toward the substrate 106 side is absorbed by the substrate 106 and becomes a light emitting diode with poor light extraction efficiency. .
そこで従来の技術として、図６（ａ）に示すように、ｐコンタクト層１０９ｂ（上部電極１０１側にはｎコンタクト層１０９ａが有る）と基板１０６の間に半導体多層薄膜からなるＤＢＲ（Ｄｉｓｔｒｉｂｕｔｅｄ Ｂｒａｇｇ Ｒｅｆｌｅｃｔｏｒ）光反射層１０８を設けることによって、基板１０６側に向かった光の一部を反射させて、光取り出し効率を高め、さらに、下部電極１０７をＤＢＲ光反射層１０８上部の両脇に設けることによって発光ダイオード自体の抵抗を小さくすることを可能にした発光ダイオードが知られている（例えば、特許文献１参照）。 Therefore, as a conventional technique, as shown in FIG. 6A, a DBR (Distributed Bragg Reflector) formed of a semiconductor multilayer thin film between a p-contact layer 109b (the n-contact layer 109a is provided on the upper electrode 101 side) and the substrate 106 is used. ) By providing the light reflecting layer 108, part of the light directed toward the substrate 106 is reflected to increase the light extraction efficiency, and further, the lower electrode 107 is provided on both sides of the upper part of the DBR light reflecting layer 108. There is known a light-emitting diode that can reduce the resistance of the light-emitting diode itself (see, for example, Patent Document 1).
この発光ダイオードによると、基板１０６側に向かった光の一部をＤＢＲ光反射層１０８で反射させて、光取り出し効率を高めることが可能になる。 According to this light emitting diode, a part of the light directed to the substrate 106 side is reflected by the DBR light reflecting layer 108, and the light extraction efficiency can be increased.
しかし、この発光ダイオードにおいて、光取り出し効率を更に高くするためには、活性層１０４の発光効率を高くするしかないが、活性層１０４の内部量子効率（活性層に注入された電子が光に変わる効率）は、ほぼ限界に達しており、これ以上の大幅な特性向上は難しい。また、限界に達しつつあるとはいえ、光取り出し効率は１０％以下でしかない。また図６（ａ）に示すように、ＤＢＲ光反射層１０８上部の両脇に下部電極を移動させると、発光面積が小さくなり、効率が高くなったとしても効果が相殺されてしまう。 However, in this light emitting diode, in order to further increase the light extraction efficiency, the light emitting efficiency of the active layer 104 must be increased. However, the internal quantum efficiency of the active layer 104 (electrons injected into the active layer are changed to light). (Efficiency) has almost reached its limit, and it is difficult to further improve the characteristics. Moreover, although the limit is being reached, the light extraction efficiency is only 10% or less. Further, as shown in FIG. 6A, when the lower electrode is moved to both sides of the upper part of the DBR light reflection layer 108, the light emission area is reduced, and even if the efficiency is increased, the effect is offset.
そこで光取り出し効率を高めるものとして、図７に示すように（上下電極の図示省略）、バッファ層１１４と基板１０６との間に高効率の金属光反射層１１５を設けた発光ダイオードが知られている（例えば、特許文献２及び特許文献３参照）。 Therefore, as shown in FIG. 7 (upper and lower electrodes are not shown), a light emitting diode in which a highly efficient metal light reflecting layer 115 is provided between the buffer layer 114 and the substrate 106 is known as one that increases the light extraction efficiency. (For example, refer to Patent Document 2 and Patent Document 3).
この発光ダイオードによると、バッファ層１１４と基板１０６との間に高効率の金属光反射層１１５を設けることで、光取り出し効率を高めることが可能になる。 According to this light emitting diode, the light extraction efficiency can be increased by providing the highly efficient metal light reflection layer 115 between the buffer layer 114 and the substrate 106.
しかし、この発光ダイオードを製造するためには、ＡｌＧａＩｎＰ発光ダイオードを例に取ると、ＧａＡｓ基板上に発光部となるエピ層を成長させ、その後エピ層とＧａＰ基板上のバッファ層１１４を接合面として貼り付けた後、ＧａＡｓ基板を除去するという複雑な製造工程を採用している。その結果、発光ダイオードの価格が高価になってしまう。 However, in order to manufacture this light emitting diode, taking an AlGaInP light emitting diode as an example, an epi layer serving as a light emitting portion is grown on a GaAs substrate, and then the epi layer and the buffer layer 114 on the GaP substrate are used as a bonding surface. After pasting, a complicated manufacturing process of removing the GaAs substrate is adopted. As a result, the price of the light emitting diode becomes expensive.
また、図８に示すように、ＡｌＧａＩｎＰ発光ダイオードのエピ層と基板の間に金属光反射層１１６を設けることで、光取り出し効率を高めた発光ダイオードが知られている。 Further, as shown in FIG. 8, a light emitting diode is known in which the light extraction efficiency is improved by providing a metal light reflection layer 116 between the epitaxial layer of the AlGaInP light emitting diode and the substrate.
この発光ダイオードにおいても活性層１０４から基板側に向かった光が、金属光反射層１１６で反射され光取り出し効率を高めることができるが、この発光ダイオードを作るためには、図示しないＧａＡｓ基板上に発光部になるエピ層を成長させ、その表面に光反射と接合のために金属層を形成し、また、張替基板１１３にも接合用の金属層を形成し、それらを向かい合わせて接合した後に、ＧａＡｓ基板を除去しなければならない。
しかし、従来の発光ダイオードによると、活性層の発光効率を高くするためには、張替基板が必要となり、また、そのために製造工程が長くなる結果、発光ダイオードの価格が高くなる問題を有している。発光ダイオードは、多様な利用方法があり、そのためにも価格が安いことが強く要求されている。よって、発光ダイオードの価格を安くするためには、材料及び製造工程の簡略化が必要であり、図７や、図８の構造のように、１回のエピ成長ですませ、貼替等の工程を通さずに高輝度を達成できることが望ましい。 However, according to the conventional light emitting diodes, a replacement substrate is required to increase the luminous efficiency of the active layer, and the manufacturing process is lengthened for this reason, resulting in a problem that the price of the light emitting diodes is increased. ing. Light emitting diodes have various usage methods, and for that reason, it is strongly required that the price is low. Therefore, in order to reduce the price of the light emitting diode, it is necessary to simplify the material and the manufacturing process. As shown in FIG. 7 and FIG. 8, only one epitaxial growth is required. It is desirable to be able to achieve high brightness without passing through.
また、半導体多層膜構造であるＤＢＲ構造で高い効率が得られないのは、ＤＢＲ膜は、膜に対して垂直及び垂直に近い角度で入射した光に対しては高い反射率を示すが、斜めに入射した光に対しては、光を反射させることができない。このため、ＤＢＲ層に垂直及び垂直付近に向かった光のみが反射されることになり、高効率の光反射が達成できないことにあった。 Also, the high efficiency cannot be obtained with the DBR structure which is a semiconductor multilayer film structure. The DBR film exhibits high reflectivity with respect to light incident at an angle perpendicular to the film and an angle close to perpendicular to the film. The light that is incident on the light cannot be reflected. For this reason, only light directed vertically and near the DBR layer is reflected, and high-efficiency light reflection cannot be achieved.
従って、本発明の目的は、高い発光効率を低コストで実現することのできる発光ダイオードを提供することにある。 Accordingly, an object of the present invention is to provide a light emitting diode capable of realizing high luminous efficiency at low cost.
本発明によると、表面に多数の凹部または凸部を有する半導体基板と、前記半導体基板の表面一帯に半導体多層薄膜として形成されたＤＢＲ光反射層と、前記ＤＢＲ光反射層の表面一帯に形成され、活性層を第１の導電型の上部クラッド層と第２の導電型の下部クラッド層で挟んだ構造を有する発光部と、前記半導体基板の裏側と前記発光部の表面に形成された電極と、を有することを特徴とする発光ダイオードを提供する。 According to the present invention, a semiconductor substrate having a large number of recesses or protrusions on the surface, a DBR light reflection layer formed as a semiconductor multilayer thin film on the surface of the semiconductor substrate, and a surface of the DBR light reflection layer are formed. A light emitting part having a structure in which an active layer is sandwiched between an upper cladding layer of a first conductivity type and a lower cladding layer of a second conductivity type; an electrode formed on the back side of the semiconductor substrate and on the surface of the light emitting part; A light-emitting diode characterized by comprising:
このような構成によれば、高い発光効率を低コストで実現することのできる発光ダイオードを提供することができる。 According to such a configuration, it is possible to provide a light emitting diode capable of realizing high luminous efficiency at low cost.
以下に、本発明の第１の実施の形態にかかる発光ダイオードを図面を参考にして詳細に説明する。 Hereinafter, a light emitting diode according to a first embodiment of the present invention will be described in detail with reference to the drawings.
[第１の実施の形態]
（第１の実施の形態の構成）
図１は、本発明の第１の実施の形態に関する発光ダイオードの概略構成図である。
[First embodiment]
(Configuration of the first embodiment)
FIG. 1 is a schematic configuration diagram of a light-emitting diode according to the first embodiment of the present invention.
この発光ダイオードは、上部中央に設置された直径１２０μｍの配線接続用の上部電極１と、膜厚が１０μｍでｐ型のＧａＰ層からなる電流分散層２と、ダブルヘテロ構造を持つ発光層１０の上部部分でｐ型の上部クラッド層３と、発光層の中心部で量子井戸構造を有する活性層４と、発光層１０の下部部分でｎ型の下部クラッド層５と、半導体の多層薄膜で形成され発光層１０からＧａＡｓ基板７側に向かった光を上部に反射するＤＢＲ光反射層６と、表面に直径１０μｍのＧａＡｓ基板凹部８が６回対称で密に形成されたＧａＡｓ基板７と、ＧａＡｓ基板７の裏面側の全面に設けられた下部電極９を有する。 This light-emitting diode includes an upper electrode 1 for wiring connection having a diameter of 120 μm installed in the upper center, a current spreading layer 2 having a thickness of 10 μm and made of a p-type GaP layer, and a light-emitting layer 10 having a double heterostructure. Formed with a p-type upper cladding layer 3 at the upper part, an active layer 4 having a quantum well structure at the center of the light emitting layer, an n-type lower cladding layer 5 at the lower part of the light emitting layer 10, and a semiconductor multilayer thin film A DBR light reflecting layer 6 that reflects light directed from the light emitting layer 10 toward the GaAs substrate 7 upward, a GaAs substrate 7 having a GaAs substrate recess 8 having a diameter of 10 μm formed on the surface thereof in six-fold symmetry, and GaAs A lower electrode 9 is provided on the entire back surface of the substrate 7.
図２は、本発明の第１の実施の形態に関するＧａＡｓ基板７上に形成したＧａＡｓ基板凹部８の配置図である。 FIG. 2 is a layout diagram of the GaAs substrate recess 8 formed on the GaAs substrate 7 according to the first embodiment of the present invention.
発光ダイオードを上方向から見ると、中央に図示しない上部電極１があり、その直下にはＧａＡｓ基板凹部８が規則正しく配列されている。発光ダイオードは一辺が３００μｍの正方形であり、ＧａＡｓ基板凹部８の直径ｄは１０μｍで深さは３μｍである。このＧａＡｓ基板７の裏面側には、図示しない下部電極９が形成されている。 When the light emitting diode is viewed from above, there is an upper electrode 1 (not shown) at the center, and GaAs substrate recesses 8 are regularly arranged immediately below. The light emitting diode is a square having a side of 300 μm, the diameter d of the GaAs substrate recess 8 is 10 μm, and the depth is 3 μm. A lower electrode 9 (not shown) is formed on the back side of the GaAs substrate 7.
ここで、ＧａＡｓ基板凹部８は、周期的に並んでいるのが最も好ましいが、必ずしも周期的でなくとも良い。 Here, it is most preferable that the GaAs substrate recesses 8 are arranged periodically, but it is not necessarily required to be periodic.
（第１の実施の形態の動作）
以下に、本発明の第１の実施の形態における発光ダイオードの動作を図１〜図８を参照しつつ説明する。
(Operation of the first embodiment)
The operation of the light emitting diode in the first embodiment of the present invention will be described below with reference to FIGS.
図３（ａ）は、本発明の発光ダイオードの量子井戸型活性層４を出た光がどのように反射を繰り返しながら外部に取り出せるのかを表した図である。 FIG. 3A is a diagram showing how the light emitted from the quantum well active layer 4 of the light emitting diode of the present invention can be extracted outside while repeating reflection.
従来のＤＢＲ構造では、図６（ｂ）に示すように、臨界角以上で表面に向かった光は、エピ表面で反射され、その後表面とＤＢＲ光反射層１０８との間で反射を繰り返し光を取り出すことができなかった。これを回避するために、図３（ａ）及び（ｂ）に示すように、ＤＢＲ光反射層１０８に凹凸が形成されているためＤＢＲ光反射層１０８で反射された光は、反射角が変わり、臨界角以下の方向に反射される可能性が生じ光を取り出すことができるようになる。また、この凹凸を形成したＧａＡｓ基板７上にエピ層が形成されているため、エピ層表面にも凹凸部が形成されることになり、表面に向かった光も光取り出し効率が高くなるとともに、また表面で反射する光も反射方向が変えられるという効果もある。 In the conventional DBR structure, as shown in FIG. 6B, light directed to the surface at a critical angle or more is reflected on the epi surface, and then repeatedly reflected between the surface and the DBR light reflecting layer 108 to emit light. I could not take it out. In order to avoid this, as shown in FIGS. 3 (a) and 3 (b), the DBR light reflecting layer 108 has irregularities, so that the light reflected by the DBR light reflecting layer 108 changes its reflection angle. Then, there is a possibility that the light is reflected in a direction below the critical angle, and light can be extracted. In addition, since the epi layer is formed on the GaAs substrate 7 on which the irregularities are formed, irregularities are also formed on the epi layer surface, and the light extraction efficiency of the light directed to the surface is increased. Also, there is an effect that the direction of reflection of light reflected from the surface can be changed.
量子井戸型活性層４から出た光１０は、ほぼ各層に対して垂直なため、反射して内部に止まること無く、外部に取り出すことができる。従来の発光ダイオードにおいても、図６（ｂ）で示すように、光１１０として外部に取り出すことが可能になる。 Since the light 10 emitted from the quantum well active layer 4 is substantially perpendicular to each layer, it can be extracted outside without reflecting and stopping inside. Also in the conventional light emitting diode, as shown in FIG. 6B, it is possible to extract the light 110 to the outside.
量子井戸型活性層４から出た光１１は、一度電流分散層２の内側で反射され、ＤＢＲ光反射層６の凹部で反射された後に、外部に取り出すことができる。従来の発光ダイオードでは、図６（ｂ）で示すように、光１１１は内部反射を繰り返して、例えばＤＢＲ光反射層６等に吸収されてしまい、取り出すことができない。 The light 11 emitted from the quantum well active layer 4 is once reflected inside the current dispersion layer 2, reflected by the concave portion of the DBR light reflecting layer 6, and then extracted to the outside. In the conventional light emitting diode, as shown in FIG. 6B, the light 111 is repeatedly internally reflected and absorbed by, for example, the DBR light reflecting layer 6 and cannot be extracted.
量子井戸型活性層４のＧａＡｓ基板７側に出た光１４及び１５は、従来であれば、図６（ｂ）の光１１２のようにＤＢＲ光反射層１０８に吸収されてしまうが、図３（ａ）、（ｂ）に示す、ＤＢＲ光反射層６のＧａＡｓ基板凹部８の効果で反射され取り出すことができるようになる。 Conventionally, the light 14 and 15 emitted to the GaAs substrate 7 side of the quantum well active layer 4 are absorbed by the DBR light reflecting layer 108 like the light 112 of FIG. Reflected by the effect of the GaAs substrate recess 8 of the DBR light reflection layer 6 shown in FIGS.
本発明の発光ダイオードを作るための手順を以下に説明する。まず、ウェハ状でｎ型のＧａＡｓ基板７にフォトリソグラフィのプロセス技術を用いてＧａＡｓ基板凹部８を形成する。ＧａＡｓ基板凹部８の直径は１０μｍで深さは３μｍである。このプロセスは、フォトリソグラフィとウエットエッチングで行うことができるため、多数枚処理が可能であり安価に形成することができる。このＧａＡｓ基板凹部８を形成後、軽くエッチングして、ＧａＡｓ基板凹部８の角を滑らかにすると角部でのエピ成長異常を回避でき、発光効率が高く信頼性の高い発光ダイオードを作ることができる。ＧａＡｓ基板凹部８の配置は、図２に示す通りである。 The procedure for making the light emitting diode of the present invention will be described below. First, a GaAs substrate recess 8 is formed on a wafer-like n-type GaAs substrate 7 by using a photolithography process technique. The GaAs substrate recess 8 has a diameter of 10 μm and a depth of 3 μm. Since this process can be performed by photolithography and wet etching, a large number of sheets can be processed and can be formed at low cost. After this GaAs substrate recess 8 is formed, light etching is performed to smooth the corners of the GaAs substrate recess 8, so that abnormal epi-growth at the corners can be avoided, and a light emitting diode with high luminous efficiency and high reliability can be manufactured. . The arrangement of the GaAs substrate recesses 8 is as shown in FIG.
ＧａＡｓ基板凹部８の構造は、斜面の部分が増えることが有効である。従って、ＧａＡｓ基板凹部８が形成されていない部分及びＧａＡｓ基板凹部８の底の平坦な部分ができるだけ少ない構造が良い。また、ＧａＡｓ基板凹部８を円形状にしたが、斜面の面積を増やすためには、円形では無く六角形など全面を斜面で覆うような構造にすると良い。 The structure of the GaAs substrate recess 8 is effective in that the slope portion is increased. Therefore, a structure in which the portion where the GaAs substrate recess 8 is not formed and the flat portion at the bottom of the GaAs substrate recess 8 is as small as possible is preferable. In addition, although the GaAs substrate recess 8 has a circular shape, in order to increase the area of the inclined surface, it is preferable to have a structure in which the entire surface is covered with an inclined surface such as a hexagon instead of a circle.
このＧａＡｓ基板凹部８を形成したＧａＡｓ基板７の上に、ＭＯＣＶＤ（Ｍｅｔａｌ Ｏｒｇａｎｉｃ Ｃｈｅｍｉｃａｌ Ｖａｐｏｒ Ｄｅｐｏｓｉｔｉｏｎ；有機金属気相成長法）を用いて、ＤＢＲ光反射層６を２０ペア重ね、更にその上にＡｌＧａＩｎＰからなる発光層を形成する。発光層は、３層からなるダブルヘテロ構造で、基板側からｎ型のＡｌＧａＩｎＰの下部クラッド層５、その上に活性層となる量子井戸型活性層４、更にその上にｐ型のＡｌＧａＩｎＰの上部クラッド層３を形成する。この活性層としては、量子井戸構造でもよいし、また、バルク型の通常のダブルヘテロ構造でも良い。この上部クラッド層３の上にｐ型のＧａＰからなる電流分散層２を形成する。この電流分散層２の上に蒸着法とリソグラフィーを用いて直径１２０μｍの円形状をなす上部電極１を形成する。この上部電極１はこれまでの発光ダイオードに用いられた電極と同じである。またウェハの裏面側全面に下部電極９を形成する。 On the GaAs substrate 7 in which the GaAs substrate recess 8 is formed, 20 pairs of DBR light reflecting layers 6 are stacked using MOCVD (Metal Organic Chemical Vapor Deposition), and AlGaInP is further stacked thereon. A light emitting layer is formed. The light-emitting layer has a double heterostructure consisting of three layers. From the substrate side, an n-type AlGaInP lower cladding layer 5, a quantum well active layer 4 serving as an active layer thereon, and a p-type AlGaInP upper layer thereon. The clad layer 3 is formed. The active layer may have a quantum well structure or a bulk type normal double hetero structure. A current spreading layer 2 made of p-type GaP is formed on the upper cladding layer 3. An upper electrode 1 having a circular shape with a diameter of 120 μm is formed on the current spreading layer 2 by vapor deposition and lithography. The upper electrode 1 is the same as the electrode used in the conventional light emitting diode. A lower electrode 9 is formed on the entire back surface of the wafer.
このウェハをダイサーにセットし、３００μｍ角のチップに切断し、その断面をエッチングにより処理して、破砕層除去と汚染を取り除いて発光ダイオードチップを製作した。この発光ダイオードチップを金属ステムにダイボンディングして実装し、更にワイヤボンディングにより配線して、特性評価用サンプルとしての発光ダイオードを製作した。 This wafer was set on a dicer, cut into 300 μm square chips, and the cross section was processed by etching to remove the crushing layer and remove contamination, thereby producing a light emitting diode chip. This light emitting diode chip was mounted by die bonding to a metal stem, and further wired by wire bonding to produce a light emitting diode as a sample for characteristic evaluation.
この発光ダイオードに電流を流して発光出力を測定した。発光波長は６３０ｎｍの赤色であり、電流２０ｍＡを通電しその発光出力を測定したところ、３．９ｍＷであった。上記したＧａＡｓ基板凹部８を形成しない従来の基板上に同様の材料で発光層を形成した場合は、２．１ｍＷで有り、これに比べると１．８６倍の発光出力を得られることが分かった。 The light emission output was measured by passing a current through the light emitting diode. The emission wavelength was red at 630 nm, and when the current output was measured by applying a current of 20 mA, it was 3.9 mW. When the light emitting layer is formed of the same material on the conventional substrate in which the GaAs substrate recess 8 is not formed, it is 2.1 mW, and it is found that a light emission output of 1.86 times can be obtained compared to this. .
（第１の実施の形態の効果）
上記した第１の実施の形態によると、発光ダイオードの光取り出し効率を大幅に改善し、取り出し効率が向上したことで、金属層を界面に挟んだ貼替構造に比べると取り出し効率は低くなるが、コスト的には大幅に安くなり、その結果、非常に安価で高効率な発光ダイオードを提供することができる。
(Effects of the first embodiment)
According to the first embodiment described above, the light extraction efficiency of the light emitting diode is greatly improved, and the extraction efficiency is improved. However, the extraction efficiency is lower than that of the repositioning structure in which the metal layer is sandwiched between the interfaces. As a result, the cost is significantly reduced, and as a result, a very inexpensive and highly efficient light emitting diode can be provided.
更に、本発明の発光ダイオードは、従来に比べて１．８倍の高い変換効率を再現性よく達成することができる。このため、高輝度が必要とされるところ及び省エネが必要とされる用途に使用すると有効である。例えば、携帯電話等のようにバッテリーの消耗の少ないことが望ましい場合に効果を発揮する。 Furthermore, the light emitting diode of the present invention can achieve a conversion efficiency 1.8 times higher than the conventional one with good reproducibility. For this reason, it is effective when used in applications where high brightness is required and where energy saving is required. For example, it is effective when it is desirable that battery consumption is low, such as a cellular phone.
また、従来の貼合せで作成した発光ダイオードに比べると、貼合せ部分が無いことから、信頼性等の面でも非常に有利である。 In addition, compared with a light emitting diode produced by conventional bonding, there is no bonding portion, which is very advantageous in terms of reliability.
（第２の実施の形態）
図４は、本発明の第２の実施の形態に関する発光ダイオードの概略構成図である。ＧａＡｓ基板凹部１６は、異方性エッチングで形成されて凹部の斜面が一定角をなす凹部形状を有する。
(Second Embodiment)
FIG. 4 is a schematic configuration diagram of a light emitting diode according to the second embodiment of the present invention. The GaAs substrate recess 16 is formed by anisotropic etching and has a recess shape in which the slope of the recess forms a certain angle.
（第２の実施の形態の効果）
上記した第２の実施の形態によると、異方性エッチングを利用して形成したＧａＡｓ基板凹部１６の方が、斜めに入射してきた光を反射する効率が高いことから、より高い光取り出し効率が得られる。
(Effect of the second embodiment)
According to the second embodiment described above, the GaAs substrate recess 16 formed by using anisotropic etching has a higher efficiency of reflecting obliquely incident light, and therefore has a higher light extraction efficiency. can get.
なお、ＤＢＲ光反射層６は、垂直及び垂直に近い角度で入射した光を反射する構造であるが、それ以外に斜めに入射した光も反射するような膜厚構造のＤＢＲ光反射層６を組み合わせた複数種類の組み合わせの構造の方がより光取り出し効率が高くなる。 The DBR light reflection layer 6 has a structure that reflects light incident at an angle close to vertical and near vertical, but the DBR light reflection layer 6 having a film thickness structure that reflects light incident at an angle is also used. The light extraction efficiency is higher in the structure of a combination of a plurality of types.
本発明の発光ダイオードにおいて、エピ成長前に基板に凹部又は凸部（又は両方）が形成されているということは重要である。従って、この凹部又は凸部の形状は、周期的に並んでいるのが最も効率的であるが、必ずしも周期的でなくとも良い。 In the light-emitting diode of the present invention, it is important that a concave portion or a convex portion (or both) are formed on the substrate before epi growth. Therefore, it is most efficient that the concave or convex shapes are arranged periodically, but it is not always necessary.
また、本発明の発光ダイオードにおいて、従来の発光ダイオードの構造で採用されている、電流分散層の有無や、活性層がダブルヘテロ構造か量子井戸構造かなどという選択は適宜対応可能である。 In the light emitting diode of the present invention, the selection of the presence / absence of a current spreading layer and whether the active layer is a double hetero structure or a quantum well structure, which is employed in the structure of a conventional light emitting diode, can be appropriately handled.
更に、半導体基板に凹部又は凸部（又は両方）を形成するとその高さにより、その直上部分にある表面電極に凹部又は凸部が形成され、ワイヤボンディング時に不良等が発生する可能性もある。このため、上部電極の部分の下部のみは、半導体基板表面に凹部又は凸部を形成しないようにする構造が有効であり、電極形成のフォトリソグラフィ工程時に平坦部分に合わせて中央電極を形成すれば良いことになる。 Furthermore, if a concave or convex portion (or both) is formed on the semiconductor substrate, the height or height may cause the concave portion or convex portion to be formed on the surface electrode located immediately above the concave portion, which may cause defects during wire bonding. For this reason, it is effective that only the lower portion of the upper electrode portion has a structure in which no concave portion or convex portion is formed on the surface of the semiconductor substrate. If the central electrode is formed in accordance with the flat portion in the photolithography process of electrode formation, It will be good.
なお、本発明は、上記した各実施の形態に限定されず、本発明の技術思想を逸脱あるいは変更しない範囲内で種々の変形が可能である。 The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from or changing the technical idea of the present invention.
１・・・上部電極、２・・・電流分散層、３・・・上部クラッド層、４・・・量子井戸型活性層、５・・・下部クラッド層、６・・・ＤＢＲ光反射層、７・・・ＧａＡｓ基板、８・・・ＧａＡｓ基板凹部、９・・・下部電極、１０・・・光、１１・・・光、１２・・・光、１３・・・光、１４・・・ＧａＡｓ基板凹部、１０１・・・上部電極、１０２・・・電流分散層、１０３・・・上部クラッド層、１０４・・・活性層、１０５・・・下部クラッド層、１０６・・・基板、１０７・・・下部電極、１０８・・・ＤＢＲ光反射層、１０９ａ・・・ｎコンタクト層、１０９ｂ・・・ｐコンタクト層、１１０・・・光、１１１・・・光、１１２・・・光、１１３・・・張替基板、１１４・・・バッファ層、１１５・・・金属光反射層、１１６ａ・・・接合用金属、１１６ｂ・・・接合用金属、１１６・・・金属光反射層、ｄ・・・ＧａＡｓ基板凹部８の直径 DESCRIPTION OF SYMBOLS 1 ... Upper electrode, 2 ... Current dispersion layer, 3 ... Upper clad layer, 4 ... Quantum well type active layer, 5 ... Lower clad layer, 6 ... DBR light reflection layer, 7 ... GaAs substrate, 8 ... GaAs substrate recess, 9 ... lower electrode, 10 ... light, 11 ... light, 12 ... light, 13 ... light, 14 ... GaAs substrate recess, 101 ... upper electrode, 102 ... current spreading layer, 103 ... upper clad layer, 104 ... active layer, 105 ... lower clad layer, 106 ... substrate, 107 ... ..Lower electrode, 108... DBR light reflection layer, 109a... N contact layer, 109b... P contact layer, 110. .. Replacement substrate, 114 ... buffer layer, 115 ... metal light reflection layer, 116a - bonding metal, 116 b ... bonding metal, 116 ... metal light reflective layer, the diameter of d ... GaAs substrate recess 8
Claims (7)
前記半導体基板の表面一帯に半導体多層薄膜として前記基板表面の前記凹部または凸部を引き継ぎ形成され、凹部または凸部を有するＤＢＲ（Ｄｉｓｔｒｉｂｕｔｅｄ Ｂｒａｇｇ Ｒｅｆｌｅｃｔｏｒ）光反射層と、
前記ＤＢＲ光反射層の表面一帯に形成され、活性層を第１の導電型の上部クラッド層と第２の導電型の下部クラッド層で挟んだ構造を有する発光部と、
前記半導体基板の裏側と前記発光部の表面に形成された電極とを有し、
前記基板表面の前記凹部または凸部の角部は滑らかに形成されることを特徴とする発光ダイオード。 A semiconductor substrate having a large number of recesses or protrusions on the surface;
A DBR (Distributed Bragg Reflector) light reflecting layer formed by inheriting the concave or convex portion of the substrate surface as a semiconductor multilayer thin film over the entire surface of the semiconductor substrate, and having a concave or convex portion ;
A light emitting part formed over the surface of the DBR light reflecting layer and having a structure in which an active layer is sandwiched between a first conductive type upper cladding layer and a second conductive type lower cladding layer;
Having a back side of the semiconductor substrate and an electrode formed on the surface of the light emitting part ;
The recess or the convex corner portion is formed smoothly emitting diode, wherein Rukoto of the substrate surface.
The light emitting diode according to claim 1 , wherein the active layer is formed using any one of AlGaInP, AlGaAs, GaAsP, InGaN, GaN, and AlGaN.
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