JP2003133585A - Light emitting diode and manufacturing method therefor - Google Patents
Light emitting diode and manufacturing method thereforInfo
- Publication number
- JP2003133585A JP2003133585A JP2001332238A JP2001332238A JP2003133585A JP 2003133585 A JP2003133585 A JP 2003133585A JP 2001332238 A JP2001332238 A JP 2001332238A JP 2001332238 A JP2001332238 A JP 2001332238A JP 2003133585 A JP2003133585 A JP 2003133585A
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- Japan
- Prior art keywords
- type layer
- light emitting
- emitting diode
- layer
- type
- Prior art date
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Abstract
Description
【発明の属する技術分野】本発明は、いろいろな色を組
み合わせて使用するディスプレーに使用する発光ダイオ
ードの構造及びその製造方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a light emitting diode used in a display using various colors in combination and a method of manufacturing the same.
【従来の技術】発光ダイオード（Light Emitting Diod
e：ＬＥＤ）は、その半導体の種類を選択することによ
りいろいろな色を発光することができる。最近ＧａＮや
ＡｌＧａＩｎＰの発光ダイオードが開発されたことか
ら、青色から緑色の高輝度の発光が可能となった。これ
により、すべての可視光の発光が可能となった。いろい
ろな色の発光が可能となったことから、フルカラーディ
スプレーの用途が広がり、屋外表示から装置の表示、そ
して最近では携帯電話用などと、その用途は広がってい
る。2. Description of the Related Art Light Emitting Diode
e: LED) can emit various colors by selecting the type of semiconductor. With the recent development of GaN and AlGaInP light emitting diodes, it has become possible to emit blue to green light with high brightness. This enabled the emission of all visible light. Since it is possible to emit light of various colors, the applications of full-color displays are expanding, and the applications are expanding from outdoor displays to device displays, and recently to mobile phones.
【発明が解決しようとする課題】しかしながら、フルカ
ラーの発光を行なうためには、複数の波長の光が必要で
あり、複数の発光ダイオードを用いる必要があった。発
光波長の異なる発光ダイオードでは、発光層のバンドギ
ャップエネルギーが異なるため、駆動電圧が異なってし
まう。例えば、緑色及び青色を高輝度発光するＬＥＤチ
ップとして発光色のバンドギャップなどとの関係から窒
化物半導体材料（ＩｎaＧａbＡｌ1-a-bＮ、０≦ａ、０
≦ｂ、ａ＋ｂ≦１）が実用化されている。他方、赤色を
高輝度に発光するＬＥＤチップの材料としては、ＧａＡ
ｓＰ、ＧａＡｌＡｓ、ＡｌＧａＩｎＰが実用化されてい
る。しかし、窒化物半導体材料はバンドギャップや結晶
性などとの関係上ＧａＡｓＰ、ＧａＡｌＡｓ、ＡｌＧａ
ＩｎＰなどの材料とは異なり駆動電圧が高い。この違い
に対応する方法としては、発光波長の異なる発光ダイオ
ードごとに駆動電圧の異なる電源を用いる方法がある。
この方法では、電源が異なるため、大規模なディスプレ
ーパネルなどでは、対応可能であるが、携帯電話などの
ように小型の光源として用いるには、電源の方が大きく
なり、実用的ではない。もう一つの方法として、電源は
同じ物を用い、発光波長が異なる発光ダイオードごとに
異なる抵抗を挿入して、実際に発光ダイオードそのもの
に印可される電圧を調整する方法がある。この方法は、
複数の電源を用いる方法に比べれば、小型で済む。しか
し、発光ダイオード１個ごとに１個の抵抗を用いること
になる。発光ダイオードが小さいことから、実際の抵抗
を実装するには場所も相当必要となる。またその実装の
手間も単純に考えて２倍になる。そこで、本発明の目的
は、上記課題を解決し、発光波長の異なる発光ダイオー
ドを同じ駆動電源で、且つ外部回路的に電圧抵抗を付加
すること無く使用できるようにすること、具体的には、
赤色発光ダイオードおよび緑色発光ダイオードを青色発
光ダイオードと同じ駆動電源で、且つ外部回路的に電圧
抵抗を付加すること無く使用できるようにすることにあ
る。However, in order to perform full-color light emission, it is necessary to use light of a plurality of wavelengths and to use a plurality of light emitting diodes. In a light emitting diode having a different emission wavelength, the bandgap energy of the light emitting layer is different, so that the driving voltage is different. For example, a nitride semiconductor material (In a Ga b Al 1-ab N, 0 ≦ a, 0 is used as an LED chip that emits green and blue light with high brightness in view of a band gap of emission colors.
≦ b, a + b ≦ 1) have been put to practical use. On the other hand, GaA is used as a material for LED chips that emit red light with high brightness.
sP, GaAlAs, and AlGaInP have been put to practical use. However, the nitride semiconductor material is GaAsP, GaAlAs, AlGa due to its band gap and crystallinity.
Unlike materials such as InP, the driving voltage is high. As a method of dealing with this difference, there is a method of using a power source having a different driving voltage for each light emitting diode having a different emission wavelength.
Since this method uses different power supplies, it can be applied to a large-scale display panel or the like, but the power supply is larger and not practical for use as a small light source such as a mobile phone. Another method is to use the same power source and insert a different resistor for each light emitting diode having a different light emission wavelength to adjust the voltage actually applied to the light emitting diode itself. This method
It is smaller than the method using multiple power supplies. However, one resistor is used for each light emitting diode. Since the light emitting diode is small, a lot of space is required to mount the actual resistance. In addition, the time and effort required for its implementation are doubled by simply considering it. Therefore, an object of the present invention is to solve the above-mentioned problems, to allow light emitting diodes having different emission wavelengths to be used with the same driving power supply, and without adding a voltage resistance to an external circuit, specifically,
A red light emitting diode and a green light emitting diode can be used with the same driving power source as the blue light emitting diode and without adding a voltage resistance to an external circuit.
【課題を解決するための手段】上記目的を達成するた
め、本発明は、次のように構成したものである。請求項
１の発明に係る発光ダイオードは、結晶基板上に半導体
のｐ型層とｎ型層を形成して、そのｐ型層側とｎ型層側
に金属電極を形成した発光ダイオードにおいて、ｐ型層
中またはｎ型層中またはｐ型層とｎ型層の界面、または
ｐ型層と金属電極界面、またはｎ型層と金属電極界面に
発光ダイオードの駆動電圧を高めるための高抵抗層を挿
入したことを特徴とする。請求項２の発明に係る発光ダ
イオードは、結晶基板上に半導体のｐ型層とｎ型層を形
成して、そのｐ型層側とｎ型層側に金属電極を形成した
発光ダイオードにおいて、ｐ型層中またはｎ型層中また
はｐ型層とｎ型層の界面、またはｐ型層と金属電極界
面、またはｎ型層と金属電極界面に発光ダイオードの駆
動電圧を高めるためのヘテロ障壁を挿入したことを特徴
とする。請求項３の発明に係る発光ダイオードは、結晶
基板上に半導体のｐ型層とｎ型層を形成して、活性層を
含むヘテロ構造の発光領域を形成し、そのｐ型層側とｎ
型層側に金属電極を形成した発光ダイオードにおいて、
活性層の表面または活性層と基板の間に導電型が異なる
エピタキシャル層を部分的に挿入することにより電流狭
窄効果を起こす構造を形成し、これにより電流分散抵抗
を高くして発光ダイオードの駆動電圧を高めたことを特
徴とする。請求項４の発明に係る発光ダイオードは、結
晶基板上に半導体のｐ型層とｎ型層を形成して、そのｐ
型層側とｎ型層側に金属電極を形成した発光ダイオード
において、ｐｎ接合の上で金属電極の下に導電型が基板
と同じエピタキシャル層を形成し、これにより発光ダイ
オードの駆動電圧を高めたことを特徴とする。請求項５
の発明は、請求項１〜４のいずれかに記載の構造を持
ち、且つ同時に使用される赤色発光ダイオードおよび緑
色発光ダイオードにおいて、赤色発光ダイオードの駆動
電圧が緑色発光ダイオードの駆動電圧と同じであること
を特徴とする。請求項６の発明は、請求項１〜４のいず
れかに記載の構造を持ち、且つ青色発光ダイオードと同
時に使用される赤色発光ダイオードおよび緑色発光ダイ
オードにおいて、赤色発光ダイオードと緑色発光ダイオ
ードの駆動電圧を青色発光ダイオードと同じにしたこと
を特徴とする。請求項７の発明に係る発光ダイオードの
製造方法は、結晶基板上にＭＯＶＰＥ法により半導体の
ｐ型層とｎ型層を形成して、そのｐ型層側とｎ型層側に
金属電極を形成する発光ダイオードの製造方法におい
て、ｐ型層中またはｎ型層中またはｐ型層とｎ型層の界
面、またはｐ型層と金属電極界面、またはｎ型層と金属
電極界面に、ＭＯＶＰＥ法（metal organic vapor phas
e epitaxy）によりＭｇドーパントを用いて高抵抗のエ
ピタキシャル層を形成し、発光ダイオードの駆動電圧を
高めるための高抵抗層とすることを特徴とする。＜発明
の要点＞本発明では、結晶基板上に半導体のｐ型層とｎ
型層を形成して、そのｐ型層側とｎ型層側に金属電極を
形成した発光ダイオードを前提とし、ｐ型層中またはｎ
型層中またはｐ型層とｎ型層の界面、またはｐ型層と金
属電極界面、またはｎ型層と金属電極界面に、高抵抗層
又はヘテロ障壁を挿入して、発光ダイオードの駆動電圧
を高める（請求項１、２）。また本発明の他の形態で
は、ｐｎ接合の上で金属電極の下に導電型が基板と同じ
エピタキシャル層を形成し、これにより発光ダイオード
の駆動電圧を高める（請求項４）。さらに本発明の別の
形態では、結晶基板上に半導体のｐ型層とｎ型層を形成
して、活性層を含むヘテロ構造の発光領域を形成し、そ
のｐ型層側とｎ型層側に金属電極を形成した発光ダイオ
ードを前提とし、活性層の表面または活性層と基板の間
に導電型が異なるエピタキシャル層を部分的に挿入して
電流狭窄構造を形成し、これにより電流分散抵抗を高く
して発光ダイオードの駆動電圧を高める（請求項３）。
このように、ＬＥＤのエピタキシャル層内、または表面
電極の界面に、高抵抗層となるエピタキシャル層または
ヘテロ障壁層となるエピタキシャル層を挿入することに
より、外部回路的に電圧抵抗を付加する必要なしに、赤
色発光ダイオードの駆動電圧を緑色発光ダイオードの駆
動電圧と同じとし、又は赤色発光ダイオードと緑色発光
ダイオードの駆動電圧を青色発光ダイオードと同じにす
ることができる（請求項５、６）。従って、赤色、青
色、緑色の三種のＬＥＤを用いた白色光源を容易に構築
することができ、また、これらのＬＥＤチップをそれぞ
れドットマトリックス状に配置して同一電圧で駆動する
ことにより、屋内外でも使用できる高輝度フルカラーデ
ィスプレイ（ＬＥＤドットマトリックス表示器）を構成
することができる。また、上記発光ダイオードの製造方
法としては、ＭＯＶＰＥ法（有機金属気相成長法）によ
りＭｇドーパントを用いて高抵抗のエピタキシャル層を
形成し、発光ダイオードの駆動電圧を高めるための高抵
抗層とする（請求請７）ことにより高抵抗層を薄く形成
することができる。In order to achieve the above object, the present invention is configured as follows. A light emitting diode according to the invention of claim 1 is a light emitting diode in which a p-type layer and an n-type layer of a semiconductor are formed on a crystal substrate, and metal electrodes are formed on the p-type layer side and the n-type layer side, respectively. A high resistance layer for increasing the driving voltage of the light emitting diode is formed in the mold layer or in the n-type layer, the interface between the p-type layer and the n-type layer, the interface between the p-type layer and the metal electrode, or the interface between the n-type layer and the metal electrode. It is characterized by being inserted. A light emitting diode according to a second aspect of the present invention is a light emitting diode in which a p-type layer and an n-type layer of a semiconductor are formed on a crystal substrate, and metal electrodes are formed on the p-type layer side and the n-type layer side, respectively. A heterobarrier for increasing the driving voltage of the light emitting diode is inserted in the type layer or in the n-type layer, at the interface between the p-type layer and the n-type layer, at the interface between the p-type layer and the metal electrode, or at the interface between the n-type layer and the metal electrode. It is characterized by having done. In the light emitting diode according to the invention of claim 3, a semiconductor p-type layer and an n-type layer are formed on a crystal substrate to form a heterostructure light emitting region including an active layer, and the p-type layer side and the n-type layer are formed.
In a light emitting diode having a metal electrode formed on the mold layer side,
By partially inserting an epitaxial layer with a different conductivity type between the surface of the active layer or between the active layer and the substrate, a structure that causes a current constriction effect is formed, which increases the current dispersion resistance and increases the drive voltage of the light emitting diode. It is characterized by increasing. In the light emitting diode according to the invention of claim 4, a p-type layer and an n-type layer of a semiconductor are formed on a crystal substrate,
In a light emitting diode in which a metal electrode is formed on the type layer side and the n type layer side, an epitaxial layer having the same conductivity type as the substrate is formed below the metal electrode on the pn junction, thereby increasing the drive voltage of the light emitting diode. It is characterized by Claim 5
In the red light emitting diode and the green light emitting diode which have the structure according to any one of claims 1 to 4 and are used at the same time, the driving voltage of the red light emitting diode is the same as the driving voltage of the green light emitting diode. It is characterized by A sixth aspect of the present invention is a red light emitting diode and a green light emitting diode which have the structure according to any one of the first to fourth aspects and are used simultaneously with a blue light emitting diode. Is the same as the blue light emitting diode. In the method for manufacturing a light emitting diode according to the invention of claim 7, a p-type layer and an n-type layer of a semiconductor are formed on a crystal substrate by a MOVPE method, and metal electrodes are formed on the p-type layer side and the n-type layer side. In the method for manufacturing a light-emitting diode according to the above, the MOVPE method (in the p-type layer, the n-type layer, the interface between the p-type layer and the n-type layer, the interface between the p-type layer and the metal electrode or the interface between the n-type layer and the metal electrode metal organic vapor phas
Epitaxial) is used to form a high resistance epitaxial layer using a Mg dopant to form a high resistance layer for increasing the driving voltage of the light emitting diode. <Points of Invention> In the present invention, a semiconductor p-type layer and an n
Assuming a light emitting diode in which a p-type layer is formed and metal electrodes are formed on the p-type layer side and the n-type layer side of the p-type layer
By inserting a high resistance layer or a hetero barrier into the interface of the p-type layer or the interface of the p-type layer and the n-type layer, the interface of the p-type layer and the metal electrode, or the interface of the n-type layer and the metal electrode, the drive voltage of the light emitting diode is increased. Increase (claims 1 and 2). According to another aspect of the present invention, an epitaxial layer having the same conductivity type as the substrate is formed above the pn junction and below the metal electrode, thereby increasing the driving voltage of the light emitting diode (claim 4). According to another aspect of the present invention, a semiconductor p-type layer and an n-type layer are formed on a crystal substrate to form a heterostructure light emitting region including an active layer, and the p-type layer side and the n-type layer side thereof are formed. Assuming a light-emitting diode with a metal electrode formed on the substrate, an epitaxial layer with a different conductivity type is partially inserted between the surface of the active layer or between the active layer and the substrate to form a current confinement structure. The driving voltage of the light emitting diode is increased by increasing the voltage (Claim 3).
Thus, by inserting the epitaxial layer that becomes the high resistance layer or the epitaxial layer that becomes the hetero barrier layer in the epitaxial layer of the LED or at the interface of the surface electrode, it is possible to add a voltage resistance to the external circuit. The driving voltage of the red light emitting diode may be the same as that of the green light emitting diode, or the driving voltage of the red light emitting diode and the green light emitting diode may be the same as that of the blue light emitting diode (claims 5 and 6). Therefore, it is possible to easily construct a white light source using three types of LEDs of red, blue, and green. Also, by arranging these LED chips in a dot matrix and driving them at the same voltage, However, a high brightness full color display (LED dot matrix display) that can be used can be configured. As a method for manufacturing the light emitting diode, a high resistance epitaxial layer is formed by using a Mg dopant by MOVPE method (metal organic chemical vapor deposition method) to form a high resistance layer for increasing a driving voltage of the light emitting diode. (Claim 7) makes it possible to form the high resistance layer thinly.
【発明の実施の形態】以下、本発明を図示の実施形態に
基づいて説明する。本発明の一実施形態を説明するため
の発光ダイオードの構造を図１に示す。この発光ダイオ
ードの構造は、第一導電型基板としてのｎ型のＧａＡｓ
基板２上に、第一導電型クラッド層であるｎ型のＡｌＧ
ａＩｎＰ下部クラッド層３と、ｐ型のＡｌＧａＩｎＰ活
性層４と、第二導電型クラッド層であるｐ型のＡｌＧａ
ＩｎＰ上部クラッド層５とから成るダブルヘテロ構造の
発光領域層（発光部）を有する。なお、ｎ型ＧａＡｓ基
板２とｎ型ＡｌＧａＩｎＰ下部クラッド層３との間に
は、ｎ型ＧａＡｓバッファ層を設けてもよい。さらに、
上記した発光部の上、正確には上部クラッド層５上に
は、第二導電型電流分散層であるｐ型ＧａＰ電流分散層
６、第二導電型高抵抗層であるｐ型ＧａＰ高抵抗層７、
第二導電型電流分散層であるｐ型ＧａＰ表面側電流分散
層８の各エピタキシャル層が形成されている。チップ表
面には、その中央に円形の部分電極（ｐ側金属電極）か
ら成る表面側電極９が形成され、また裏面には、その一
部分または全面にｎ側用金属電極から成る基板側電極１
が形成されている。この発光ダイオードの構造は、従来
のＬＥＤに比べて、高抵抗層７がｐ型層中に挿入されて
いることに特徴があり、その高抵抗層７が２０ｍＡ程度
の低い駆動電流時に２．０Ｖ以上に駆動電圧を上昇させ
ることにある。この発光ダイオードを製作するために
は、ＭＯＶＰＥ法により、ＧａＡｓ基板２上に、ｎ型Ａ
ｌＧａＩｎＰ下部クラッド層３、ｐ型ＡｌＧａＩｎＰ活
性層４、ｐ型ＡｌＧａＩｎＰ上部クラッド層５、ｐ型Ｇ
ａＰ電流分散層６、ｐ型ＧａＰ高抵抗層７、ｐ型ＧａＰ
表面側電流分散層８の各エピタキシャル層を成長させ
る。このエピタキシャル層の成長は通常の成長とほとん
ど同じであり、高抵抗のＧａＰ層（高抵抗層７）を挿入
する点でのみ相違する。このＧａＰ高抵抗層７は、キャ
リア濃度を低く、且つ厚くして挿入するだけであり特に
問題はない。ただし、この実施形態では、ドーパント拡
散等によりキャリア濃度が高くなってしまうことを抑止
するために、拡散の起こりにくいＭｇドーパントを用い
る。その理由は、Ｍｇドーパントを用いることにより、
高抵抗のエピタキシャル層（高抵抗層７）を薄く形成す
れば済むためである。この高抵抗層７の厚さを制御する
ことにより、発光ダイオードの駆動電圧を高くすること
ができた。６５０ｎｍの発光波長の発光ダイオードで、
駆動電圧は２．２Ｖであった。これにより同じ電源か
ら、２．２Ｖの電圧を印可することにより、緑色ＬＥＤ
と赤色ＬＥＤの両方に２０ｍＡの電流を流すことができ
た。電源スイッチを切りかえることにより、赤色、橙
色、緑色の発光ができた。またＧａＰ高抵抗層７の膜厚
を厚くすることにより、赤色ＬＥＤと緑色ＬＥＤの駆動
電圧を青色発光ダイオードと同じ２．８Ｖまで高くする
ことができた。これにより、青色ＬＥＤと緑色ＬＥＤそ
して赤色ＬＥＤの三種の発光ダイオードを、同じ駆動電
圧で動作させることができた。３色そろった場合には、
スイッチを切りかえるだけで、赤色、橙色、緑色、青緑
色、青色、白色の６色を発光させることができた。もち
ろんＬＥＤへの駆動電流を制御することにより、フルカ
ラーの表示が可能となる。通常発光ダイオードにおいて
は、駆動電圧を如何に低くできるかが課題である。また
同じ発光色なら、駆動電圧が同じでないと回路上置き換
えができないため、同じ駆動電圧が要求され、許容誤差
の範囲はせいぜい高くても０．１Ｖ程度が限界である。
これに対して本実施形態のＬＥＤは同じ発光色の従来の
ＬＥＤに対して、駆動電圧が０．２Ｖ以上高いため、従
来のＬＥＤの置き換えには使用できないが、新たな用途
として有利な特性を有している。上記実施形態では、ｐ
型層中に発光ダイオードの駆動電圧を高めるための高抵
抗層を挿入したが、ｎ型層中またはｐ型層とｎ型層の界
面、またはｐ型層と金属電極の界面、またはｎ型層と金
属電極の界面に発光ダイオードの駆動電圧を高めるため
の高抵抗層を挿入してもよい。本発明の第二実施形態に
係る発光ダイオードの構造を図２に示す。この発光ダイ
オードの構造は、第一導電型基板としてのｎ型のＧａＡ
ｓ基板２上に、第一導電型クラッド層であるｎ型のＡｌ
ＧａＩｎＰ下部クラッド層３、ｐ型のＡｌＧａＩｎＰ活
性層４、第二導電型クラッド層であるｐ型のＡｌＧａＩ
ｎＰ上部クラッド層５とから成るダブルヘテロ構造の発
光領域層（発光部）を設けている。さらに、上記した発
光部の上、正確には上部クラッド層５上には、第二導電
型電流分散層であるｐ型ＧａＰ電流分散層６、第二導電
型ヘテロ障壁層であるｐ型ＡｌＧａＩｎＰヘテロ障壁層
１０、第二導電型電流分散層であるｐ型ＧａＰ表面側電
流分散層８の各エピタキシャル層が形成されている。そ
して、チップ裏面のＧａＡｓ基板側にはｎ側金属電極か
ら成る基板側電極１が、表面中央には円形のｐ側金属電
極から成る表面側電極９が形成されている。この発光ダ
イオードの構造は、従来のＬＥＤに比べて、ｐ型ＡｌＧ
ａＩｎＰヘテロ障壁層１０から成るヘテロ障壁層が挿入
されていることに特徴があり、このヘテロ障壁層が２０
ｍＡ程度の低い駆動電流時に２．０Ｖ以上に駆動電圧を
上昇させることにある。すなわち、この構造の特徴は、
図１の実施形態の高抵抗層７の代わりにＡｌＧａＩｎＰ
のヘテロ障壁層１０を用いていることにある。この場合
に、電流を流れにくくする要因が高抵抗ではなくヘテロ
障壁にあるため、薄いヘテロ障壁層で駆動電圧を高くす
ることができた。この発光ダイオードに抵抗を入れる方
法としては、電流狭窄型などにして、電流分散させるた
めに抵抗を高くする方法が適用できる。すなわち、活性
層４の表面または活性層４と基板２の間に導電型が異な
るエピタキシャル層を部分的に挿入することにより電流
狭窄効果を起こす構造とし、これにより電流分散抵抗を
高くして発光ダイオードの駆動電圧を高めることができ
る。また発光ダイオードの構造中にｐｎ逆接合を挿入す
ることにより、駆動電圧を高くすることもできる。すな
わち、基板２上に形成した半導体のｐ型層とｎ型層によ
るｐｎ接合の上で金属電極の下に、導電型が基板２と同
じエピタキシャル層を形成し、これにより発光ダイオー
ドの駆動電圧を高めることができる。BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the illustrated embodiments. A structure of a light emitting diode for explaining an embodiment of the present invention is shown in FIG. The structure of this light emitting diode is as follows: n-type GaAs as the first conductivity type substrate.
On the substrate 2, n-type AlG that is the first conductivity type cladding layer is formed.
aInP lower clad layer 3, p-type AlGaInP active layer 4, and p-type AlGa that is the second conductivity type clad layer.
It has a light emitting region layer (light emitting portion) of a double hetero structure composed of the InP upper clad layer 5. An n-type GaAs buffer layer may be provided between the n-type GaAs substrate 2 and the n-type AlGaInP lower cladding layer 3. further,
A p-type GaP current spreading layer 6, which is a second conductivity type current spreading layer, and a p-type GaP high resistance layer, which is a second conductivity type high resistance layer, are provided on the light emitting portion described above, more precisely, on the upper cladding layer 5. 7,
Each epitaxial layer of the p-type GaP front surface side current spreading layer 8 which is the second conductivity type current spreading layer is formed. A front surface side electrode 9 composed of a circular partial electrode (p side metal electrode) is formed in the center on the front surface of the chip, and a substrate side electrode 1 composed of an n side metal electrode is formed on a part or the whole surface on the back surface.
Are formed. The structure of this light emitting diode is characterized in that the high resistance layer 7 is inserted in the p-type layer as compared with the conventional LED, and the high resistance layer 7 is 2.0 V at a low drive current of about 20 mA. Above is to increase the drive voltage. In order to manufacture this light emitting diode, an n-type A is formed on the GaAs substrate 2 by the MOVPE method.
lGaInP lower clad layer 3, p-type AlGaInP active layer 4, p-type AlGaInP upper clad layer 5, p-type G
aP current distribution layer 6, p-type GaP high resistance layer 7, p-type GaP
Each epitaxial layer of the surface side current distribution layer 8 is grown. The growth of this epitaxial layer is almost the same as the normal growth, and is different only in that a high resistance GaP layer (high resistance layer 7) is inserted. The GaP high-resistance layer 7 is inserted with a low carrier concentration and a large thickness, and there is no particular problem. However, in this embodiment, in order to prevent the carrier concentration from increasing due to dopant diffusion or the like, a Mg dopant that hardly diffuses is used. The reason is that by using the Mg dopant,
This is because the high-resistance epitaxial layer (high-resistance layer 7) may be thinly formed. By controlling the thickness of the high resistance layer 7, the drive voltage of the light emitting diode could be increased. A light emitting diode with an emission wavelength of 650 nm,
The driving voltage was 2.2V. By applying a voltage of 2.2V from the same power source, the green LED
It was possible to pass a current of 20 mA to both the red LED and the red LED. By switching the power switch, red, orange, and green light was emitted. By increasing the thickness of the GaP high resistance layer 7, the driving voltage of the red LED and the green LED could be increased to 2.8V, which is the same as that of the blue light emitting diode. As a result, it was possible to operate the three types of light emitting diodes of the blue LED, the green LED and the red LED with the same drive voltage. If you have 3 colors,
Only by switching the switch, six colors of red, orange, green, turquoise, blue and white could be emitted. Of course, full-color display is possible by controlling the drive current to the LED. In a normal light emitting diode, how to reduce the driving voltage is a problem. Further, if the emission colors are the same, the circuit cannot be replaced unless the drive voltages are the same. Therefore, the same drive voltage is required, and the allowable error range is at most about 0.1 V at the maximum.
On the other hand, the LED of the present embodiment has a driving voltage higher than that of the conventional LED of the same emission color by 0.2 V or more, and thus cannot be used to replace the conventional LED, but has advantageous characteristics as a new application. Have In the above embodiment, p
A high resistance layer for increasing the driving voltage of the light emitting diode is inserted in the mold layer, but the n-type layer or the interface between the p-type layer and the n-type layer, or the interface between the p-type layer and the metal electrode, or the n-type layer A high resistance layer for increasing the driving voltage of the light emitting diode may be inserted at the interface between the metal electrode and the metal electrode. The structure of the light emitting diode according to the second embodiment of the present invention is shown in FIG. The structure of this light emitting diode is such that n-type GaA as the first conductivity type substrate is used.
On the substrate 2, n-type Al that is the first conductivity type cladding layer
GaInP lower clad layer 3, p-type AlGaInP active layer 4, and p-type AlGaI which is the second conductivity type clad layer.
A light emitting region layer (light emitting portion) having a double hetero structure including the nP upper cladding layer 5 is provided. Further, on the light emitting portion described above, more precisely on the upper cladding layer 5, a p-type GaP current spreading layer 6 which is a second conductivity type current spreading layer, and a p-type AlGaInP hetero layer which is a second conductivity type hetero barrier layer. Each epitaxial layer of the barrier layer 10 and the p-type GaP front surface side current spreading layer 8 which is the second conductivity type current spreading layer is formed. A substrate-side electrode 1 made of an n-side metal electrode is formed on the GaAs substrate side on the back surface of the chip, and a surface-side electrode 9 made of a circular p-side metal electrode is formed at the center of the surface. The structure of this light emitting diode is p-type AlG compared to the conventional LED.
It is characterized in that a hetero barrier layer consisting of aInP hetero barrier layer 10 is inserted.
The purpose is to increase the drive voltage to 2.0 V or more when the drive current is as low as mA. That is, the features of this structure are
Instead of the high resistance layer 7 of the embodiment of FIG. 1, AlGaInP is used.
This is because the hetero barrier layer 10 is used. In this case, since the factor that makes the current difficult to flow is not the high resistance but the hetero barrier, the drive voltage could be increased with the thin hetero barrier layer. As a method of adding a resistance to the light emitting diode, a method of increasing the resistance for current dispersion by applying a current constriction type or the like can be applied. That is, a structure for causing a current constriction effect by partially inserting an epitaxial layer having a different conductivity type on the surface of the active layer 4 or between the active layer 4 and the substrate 2, thereby increasing the current dispersion resistance and increasing the light emitting diode. Driving voltage can be increased. Also, the driving voltage can be increased by inserting a pn reverse junction in the structure of the light emitting diode. That is, an epitaxial layer having the same conductivity type as that of the substrate 2 is formed under the metal electrode on the pn junction of the semiconductor p-type layer and the n-type layer formed on the substrate 2, and thereby the driving voltage of the light emitting diode is increased. Can be increased.
【発明の効果】以上説明したように本発明の発光ダイオ
ードによれば、結晶基板上に形成したｐ型層中またはｎ
型層中またはｐ型層とｎ型層の界面、またはｐ型層と金
属電極界面、またはｎ型層と金属電極界面に、高抵抗層
又はヘテロ障壁を挿入するか、ｐｎ接合の上で金属電極
の下に基板と同じ導電型のエピタキシャル層を形成する
か、又は活性層の表面または活性層と基板の間に導電型
が異なるエピタキシャル層を部分的に挿入して電流狭窄
構造を形成したので、外部回路的に電圧抵抗を付加する
必要なしに、発光ダイオードの駆動電圧を高めることが
できる。このため、赤色発光ダイオードの駆動電圧を緑
色発光ダイオードの駆動電圧と同じとし、又は赤色発光
ダイオードと緑色発光ダイオードの駆動電圧を青色発光
ダイオードと同じにすることが容易にできる。本発明の
発光ダイオードは、通常販売されているＬＥＤに対し
て、駆動電圧が高くなる。同じ駆動電源で、２色または
それ以上のＬＥＤに同じ電流を流すことができるように
なることから、ＬＥＤの駆動電源及び回路が従来に比べ
大幅に低減できる。このため、廉価なフルカラー表示装
置を生産できるようになった。As described above, according to the light emitting diode of the present invention, in the p-type layer formed on the crystal substrate or in the n-type layer.
A high resistance layer or a hetero barrier is inserted into the interface between the p-type layer and the interface between the p-type layer and the n-type layer, the interface between the p-type layer and the metal electrode, or the interface between the n-type layer and the metal electrode, or the metal is formed on the pn junction. Since the epitaxial layer having the same conductivity type as the substrate is formed under the electrode, or the epitaxial layer having a different conductivity type is partially inserted between the surface of the active layer or the active layer and the substrate to form the current confinement structure. The drive voltage of the light emitting diode can be increased without adding a voltage resistor to the external circuit. Therefore, it is possible to easily make the driving voltage of the red light emitting diode the same as the driving voltage of the green light emitting diode, or make the driving voltage of the red light emitting diode and the green light emitting diode the same as that of the blue light emitting diode. The light emitting diode of the present invention has a higher driving voltage than that of an LED that is normally sold. Since the same current can be supplied to the LEDs of two colors or more with the same driving power source, the driving power source and circuit of the LED can be significantly reduced as compared with the conventional one. Therefore, it has become possible to produce an inexpensive full-color display device.
【図１】本発明の一実施形態に係る発光ダイオードの構
造を示す断面である。FIG. 1 is a cross-sectional view showing a structure of a light emitting diode according to an exemplary embodiment of the present invention.
【図２】本発明の第二実施形態に係る発光ダイオードの
構造を示す断面である。FIG. 2 is a cross-sectional view showing a structure of a light emitting diode according to a second embodiment of the present invention.
１ 基板側電極 ２ ｎ型ＧａＡｓ基板 ３ ｎ型ＡｌＧａＩｎＰ下部クラッド層 ４ ｐ型ＡｌＧａＩｎＰ活性層 ５ ｐ型ＡｌＧａＩｎＰ上部クラッド層 ６ ｐ型ＧａＰ電流分散層 ７ ｐ型ＧａＰ高抵抗層 ８ ｐ型ＧａＰ表面側電流分散層 ９ 表面側電極 １０ ｐ型ＡｌＧａＩｎＰヘテロ障壁層 1 Substrate side electrode 2 n-type GaAs substrate 3 n-type AlGaInP lower cladding layer 4 p-type AlGaInP active layer 5 p-type AlGaInP upper cladding layer 6 p-type GaP current spreading layer 7 p-type GaP high resistance layer 8 p-type GaP surface side current distribution layer 9 Front side electrode 10 p-type AlGaInP hetero barrier layer
Claims (7)
成して、そのｐ型層側とｎ型層側に金属電極を形成した
発光ダイオードにおいて、 ｐ型層中またはｎ型層中またはｐ型層とｎ型層の界面、
またはｐ型層と金属電極界面、またはｎ型層と金属電極
界面に発光ダイオードの駆動電圧を高めるための高抵抗
層を挿入したことを特徴とする発光ダイオード。1. A light emitting diode in which a p-type layer and an n-type layer of a semiconductor are formed on a crystal substrate, and metal electrodes are formed on the p-type layer side and the n-type layer side of the p-type layer or the n-type layer. In the layer or at the interface between the p-type layer and the n-type layer,
Alternatively, a high resistance layer for increasing the driving voltage of the light emitting diode is inserted at the interface between the p-type layer and the metal electrode or at the interface between the n-type layer and the metal electrode.
成して、そのｐ型層側とｎ型層側に金属電極を形成した
発光ダイオードにおいて、 ｐ型層中またはｎ型層中またはｐ型層とｎ型層の界面、
またはｐ型層と金属電極界面、またはｎ型層と金属電極
界面に発光ダイオードの駆動電圧を高めるためのヘテロ
障壁を挿入したことを特徴とする発光ダイオード。2. A light emitting diode in which a p-type layer and an n-type layer of a semiconductor are formed on a crystal substrate, and metal electrodes are formed on the p-type layer side and the n-type layer side of the p-type layer or the n-type layer. In the layer or at the interface between the p-type layer and the n-type layer,
Alternatively, a light emitting diode is characterized in that a hetero barrier for increasing a driving voltage of the light emitting diode is inserted at an interface between the p-type layer and the metal electrode or at an interface between the n-type layer and the metal electrode.
成して、活性層を含むヘテロ構造の発光領域を形成し、
そのｐ型層側とｎ型層側に金属電極を形成した発光ダイ
オードにおいて、 活性層の表面または活性層と基板の間に導電型が異なる
エピタキシャル層を部分的に挿入することにより電流狭
窄効果を起こす構造を形成し、これにより電流分散抵抗
を高くして発光ダイオードの駆動電圧を高めたことを特
徴とする発光ダイオード。3. A semiconductor p-type layer and an n-type layer are formed on a crystal substrate to form a heterostructure light emitting region including an active layer,
In a light emitting diode in which metal electrodes are formed on the p-type layer side and the n-type layer side, the current confinement effect can be obtained by partially inserting an epitaxial layer having a different conductivity type on the surface of the active layer or between the active layer and the substrate. A light emitting diode characterized by forming a structure for causing a current spreading resistance to thereby increase a driving voltage of the light emitting diode.
成して、そのｐ型層側とｎ型層側に金属電極を形成した
発光ダイオードにおいて、 ｐｎ接合の上で金属電極の下に導電型が基板と同じエピ
タキシャル層を形成し、これにより発光ダイオードの駆
動電圧を高めたことを特徴とする発光ダイオード。4. A light emitting diode in which a semiconductor p-type layer and an n-type layer are formed on a crystal substrate, and metal electrodes are formed on the p-type layer side and the n-type layer side of the semiconductor substrate. A light emitting diode characterized in that an epitaxial layer having the same conductivity type as that of the substrate is formed underneath to increase the driving voltage of the light emitting diode.
ち、且つ同時に使用される赤色発光ダイオードおよび緑
色発光ダイオードにおいて、 赤色発光ダイオードの駆動電圧が緑色発光ダイオードの
駆動電圧と同じであることを特徴とする発光ダイオー
ド。5. A red light emitting diode and a green light emitting diode having the structure according to any one of claims 1 to 4 and used at the same time, wherein the driving voltage of the red light emitting diode is the same as that of the green light emitting diode. A light-emitting diode characterized by being present.
ち、且つ青色発光ダイオードと同時に使用される赤色発
光ダイオードおよび緑色発光ダイオードにおいて、 赤色発光ダイオードと緑色発光ダイオードの駆動電圧を
青色発光ダイオードと同じにしたことを特徴とする発光
ダイオード。6. A red light emitting diode and a green light emitting diode, which have the structure according to any one of claims 1 to 4 and are used simultaneously with a blue light emitting diode, wherein the driving voltage for the red light emitting diode and the green light emitting diode is blue. A light emitting diode having the same structure as the light emitting diode.
ｐ型層とｎ型層を形成して、そのｐ型層側とｎ型層側に
金属電極を形成する発光ダイオードの製造方法におい
て、 ｐ型層中またはｎ型層中またはｐ型層とｎ型層の界面、
またはｐ型層と金属電極界面、またはｎ型層と金属電極
界面に、ＭＯＶＰＥ法によりＭｇドーパントを用いて高
抵抗のエピタキシャル層を形成し、発光ダイオードの駆
動電圧を高めるための高抵抗層とすることを特徴とする
発光ダイオードの製造方法。7. A method for manufacturing a light-emitting diode, comprising forming a p-type layer and an n-type layer of a semiconductor on a crystal substrate by MOVPE method, and forming metal electrodes on the p-type layer side and the n-type layer side thereof. In the mold layer or in the n-type layer or at the interface between the p-type layer and the n-type layer,
Alternatively, a high resistance epitaxial layer is formed at the interface between the p-type layer and the metal electrode or at the interface between the n-type layer and the metal electrode by using the Mg dopant by the MOVPE method to form a high resistance layer for increasing the driving voltage of the light emitting diode. A method of manufacturing a light-emitting diode, comprising:
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001332238A JP4000821B2 (en) | 2001-10-30 | 2001-10-30 | Light emitting device |
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|---|---|---|---|
| JP2001332238A JP4000821B2 (en) | 2001-10-30 | 2001-10-30 | Light emitting device |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2007059386A Division JP4544253B2 (en) | 2007-03-09 | 2007-03-09 | Light emitting device |
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| Publication Number | Publication Date |
|---|---|
| JP2003133585A true JP2003133585A (en) | 2003-05-09 |
| JP4000821B2 JP4000821B2 (en) | 2007-10-31 |
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ID=19147683
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| Country | Link |
|---|---|
| JP (1) | JP4000821B2 (en) |
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