JPH09307140A - Semiconductor light emitting device - Google Patents
Semiconductor light emitting deviceInfo
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- JPH09307140A JPH09307140A JP11872296A JP11872296A JPH09307140A JP H09307140 A JPH09307140 A JP H09307140A JP 11872296 A JP11872296 A JP 11872296A JP 11872296 A JP11872296 A JP 11872296A JP H09307140 A JPH09307140 A JP H09307140A
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- layer
- current
- light emitting
- emitting device
- current diffusion
- Prior art date
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、化合物半導体材料
を用いた半導体発光装置に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device using a compound semiconductor material.
【０００２】[0002]
【従来の技術】以下、特に活性層にInGaAlP系材料を用
いた発光ダイオードについて説明する。近年、交通情報
表示板や広告表示板等、屋外で使用される可視発光ダイ
オードの需要は急速に高まっており、高輝度化と多色化
が強く要望されている。その中でInGaAlPを活性層とす
る発光ダイオードは、従来のGaPやGaAsP等の間接遷移型
の材料を用いたものに比べ、緑色，黄色，橙色の高輝度
発光が可能な光源として注目されている。2. Description of the Related Art A light emitting diode using an InGaAlP-based material for an active layer will be described below. In recent years, the demand for visible light emitting diodes used outdoors such as traffic information display boards and advertisement display boards is rapidly increasing, and there is a strong demand for higher brightness and multicolor. Among them, a light emitting diode using InGaAlP as an active layer is attracting attention as a light source capable of high-luminance green, yellow, and orange light emission as compared with a conventional one using an indirect transition type material such as GaP or GaAsP. .
【０００３】図９に第１の従来の技術を説明するInGaAl
P活性層を有する発光ダイオードの断面構造を示す。こ
れは特開平３−１７１６７９号公報に開示されている。
１はn-GaAs基板、２はn-InGaAlPクラッド層、３はInGaA
lP活性層、４はp-InGaAlPクラッド層、５はp-GaAlAs電
流拡散層、６はp-GaAsコンタクト層、７はAuZnからなる
ｐ側電極、８はAuGeからなるｎ側電極である。結晶成長
は有機金属気相成長(MOCVD)法が主に用いられている。p
-GaAlAs電流拡散層５の上面から光を取り出すので、ｐ
側電極７はp-GaAlAs電流拡散層５の上の一部に形成され
ている。また、InGaAlP活性層３のエネルギーギャップ
は、クラッド層２，４のそれより小さくなるように混晶
組成が設定されており、キャリアが活性層３に閉じ込め
られ高効率の発光が可能なダブルへテロ構造をなしてい
る。p-GaAlAs電流拡散層５はｐ側電極７から流入する電
流を拡散させるために、比抵抗は0.05Ωcm程度と低く
し、膜厚は5μm以上とする。また、Al組成はInGaAlP活
性層３からの発光波長に対してほぼ透明になるように設
定されている。FIG. 9 illustrates InGaAl for explaining the first conventional technique.
2 shows a cross-sectional structure of a light emitting diode having a P active layer. This is disclosed in Japanese Patent Laid-Open No. 3-171679.
1 is an n-GaAs substrate, 2 is an n-InGaAlP clad layer, 3 is InGaA
Ip active layer, 4 is a p-InGaAlP cladding layer, 5 is a p-GaAlAs current diffusion layer, 6 is a p-GaAs contact layer, 7 is a p-side electrode made of AuZn, and 8 is an n-side electrode made of AuGe. The metal organic chemical vapor deposition (MOCVD) method is mainly used for crystal growth. p
-Because light is extracted from the upper surface of the GaAlAs current diffusion layer 5, p
The side electrode 7 is formed on a part of the p-GaAlAs current diffusion layer 5. In addition, the mixed crystal composition is set so that the energy gap of the InGaAlP active layer 3 is smaller than that of the cladding layers 2 and 4, and the carriers are confined in the active layer 3 so that the double heterostructure capable of highly efficient light emission. It has a structure. The p-GaAlAs current diffusion layer 5 has a low specific resistance of about 0.05 Ωcm and a film thickness of 5 μm or more in order to diffuse the current flowing from the p-side electrode 7. The Al composition is set so as to be almost transparent to the emission wavelength from the InGaAlP active layer 3.
【０００４】図９において順方向に電圧をかけると、ｐ
側電極７から流入する電流が電流拡散層５を通る過程で
広げられ、活性層３に注入されることになり、発光領域
は活性層３のｐ側電極７の直下以外の領域にも広がる。
従って上面方向に光を取り出す場合、ｐ側電極７によっ
て遮られる割合が減少するので、光の取り出し効率は増
加し、内部量子効率の大きい橙色等の長波長領域では高
輝度化が実現されている。When a voltage is applied in the forward direction in FIG. 9, p
The current flowing from the side electrode 7 is spread in the process of passing through the current diffusion layer 5 and injected into the active layer 3, so that the light emitting region also spreads to a region other than directly below the p-side electrode 7 of the active layer 3.
Therefore, when the light is extracted in the upper surface direction, the ratio of being blocked by the p-side electrode 7 is reduced, so that the light extraction efficiency is increased, and high brightness is realized in a long wavelength region such as orange with a large internal quantum efficiency. .
【０００５】図１０に第２の従来の技術を説明するInGa
AlP活性層を有する発光ダイオードの断面構造を示す。
これは特開平７−１６９９９２号公報に開示されてい
る。なお、図９と同一部分には同一符号を付してその詳
しい説明は省略する。９はp-In 0.5(Ga0.14Al0.86)0.5P
第２電流拡散層である。図１０が図９と異なる点はp-In
0 .5(Ga0.14Al0.86)0.5P第２電流拡散層９が付加される
ことにより、p-GaAlAs電流拡散層５とp-In0.5(Ga0.14Al
0.86)0.5P第２電流拡散層９の界面の価電子帯にヘテロ
障壁による電流拡散の効果が有効になるような大きなヘ
テロ障壁が形成されていることである。ヘテロ障壁で電
流が広がるのは、そこで生じる過剰な電圧降下を低減す
るために、電流がヘテロ界面で拡散することで電流密度
を下げようとするからである。FIG. 10 illustrates InGa for explaining the second conventional technique.
3 shows a cross-sectional structure of a light emitting diode having an AlP active layer.
This is disclosed in JP-A-7-169992.
You. Note that the same parts as those in FIG.
A detailed description is omitted. 9 is p-In 0.5(Ga0.14Al0.86)0.5P
The second current spreading layer. The difference between FIG. 10 and FIG. 9 is p-In
0 .Five(Ga0.14Al0.86)0.5P second current spreading layer 9 is added
As a result, the p-GaAlAs current diffusion layer 5 and the p-In0.5(Ga0.14Al
0.86)0.5P Heterogeneous to the valence band at the interface of the second current diffusion layer 9
A large barrier where the effect of current spreading by the barrier is effective.
That is, the terror barrier has been formed. Electricity with a hetero barrier
Spreading the flow reduces the excessive voltage drop that occurs
Therefore, the current density is
Because it tries to lower.
【０００６】図１０において順方向に電圧をかけると、
図９と同様に電流はp-GaAlAs電流拡散層５により広げら
れるが、p-GaAlAs電流拡散層５とp-In0.5(Ga0.14A
l0.86)0.5P第２電流拡散層９の界面の価電子帯に大きな
ヘテロ障壁が形成されているため、さらに広げられる。
結果として図１０の構造においては、InGaAlP活性層３
全体に均一に電流が注入されるために、内部量子効率の
低下する黄色，緑色等の短波長領域でも高輝度化が実現
されている。When a voltage is applied in the forward direction in FIG. 10,
As in FIG. 9, the current is spread by the p-GaAlAs current diffusion layer 5, but the p-GaAlAs current diffusion layer 5 and p-In 0.5 (Ga 0.14 A
l 0.86 ) 0.5 P Since a large hetero barrier is formed in the valence band of the interface of the second current diffusion layer 9, it can be further expanded.
As a result, in the structure of FIG. 10, InGaAlP active layer 3
Since the current is uniformly injected into the whole, high brightness is realized even in the short wavelength region such as yellow and green where the internal quantum efficiency is lowered.
【０００７】[0007]
【発明が解決しようとする課題】しかしながら上記従来
の構成では、次のような問題点があった。第１の従来の
技術では、p-GaAlAs電流拡散層５によってのみ電流を活
性層全体に均一に広げるためには20μm以上の膜厚が必
要である。結晶成長に用いられるMOCVD法は、他の結晶
成長法に比べ成長速度が1〜3μm/hと低く、20μm以上の
膜厚を得るには長時間の成長が必要となるが、このこと
は生産性の低下や、活性層３への上部クラッド層４等か
らの不純物拡散による発光効率の低下という問題を引き
起こすため、p-GaAlAs電流拡散層５の膜厚をせいぜい5
〜10μm程度にしかできない。従って第１の従来の技術
では電流広がりの大きさは十分でなく、電流は活性層３
に均一に注入されていないため、内部量子効率の低下す
る黄色，緑色等の短波長領域では高輝度化の実現が困難
であった。However, the above conventional structure has the following problems. In the first conventional technique, a film thickness of 20 μm or more is required to uniformly spread the current over the entire active layer only by the p-GaAlAs current diffusion layer 5. The MOCVD method used for crystal growth has a low growth rate of 1 to 3 μm / h compared to other crystal growth methods, and long-term growth is required to obtain a film thickness of 20 μm or more. The p-GaAlAs current diffusion layer 5 has a thickness of at most
Can only be about 10 μm. Therefore, in the first conventional technique, the magnitude of the current spread is not sufficient, and the current flows in the active layer 3
Therefore, it was difficult to realize high brightness in the short wavelength region such as yellow and green where the internal quantum efficiency is lowered.
【０００８】また第２の従来の技術では、電流を第１の
従来の技術よりも広げ活性層全体に均一に注入するため
に、p-GaAlAs電流拡散層５とp-InGaAlPクラッド層４の
間にp-In0.5(Ga0.14Al0.86)0.5P第２電流拡散層９を付
加し、p-GaAlAs電流拡散層５とp-In0.5(Ga0.14Al0.86)
0.5P第２電流拡散層９の界面の価電子帯に大きなヘテロ
障壁を形成している。しかし、ヘテロ障壁により電流を
広げる場合、その電流拡散の効果とへテロ障壁での電圧
降下、結果として素子の発光効率と動作電圧はへテロ障
壁の大きさに強く依存する。図１１と図１２に図１０の
構造において第２電流拡散層９をp-In0.5(Ga1-XAlX)0.5
Pとした場合の発光効率と動作電圧のAl混晶比Xに対する
依存性を示す。また横軸には各混晶比に対応するp-GaAl
As電流拡散層５とp-In0.5(Ga1-XAlX)0.5Pとの間のヘテ
ロ障壁の大きさも併せて示している。ただし、黄緑色の
発光(波長570nm)を得るために、各層の組成を活性層３
はIn0.5(Ga0.6Al0.4)0.5P、nとp型クラッド層２、４は
何れもIn0.5(Ga0.3Al0.7)0.5P、電流拡散層５はGa0.15A
l0.85Asとした。図１１と図１２からわかるように、発
光効率はへテロ障壁の大きさが 0.20eVと0.22eVの間で
急激に増大し、それ以上で飽和しているのに対して、動
作電圧は0.22eV以上で急激に増加する。動作電圧を発光
ダイオードとして実用的な2.0V以下にし、かつへテロ障
壁による電流拡散の効果を有効にし、発光効率を顕著に
増加させるためには、へテロ障壁の大きさを0.21eVから
0.22eVの範囲と非常に制限された範囲に設定する必要が
ある。第２電流拡散層９の組成がわずかに変化してヘテ
ロ障壁の大きさがこの範囲から外れると、発光効率及び
動作電圧が大きく変動する。従って第２の従来の技術で
は、素子間の輝度や動作電圧のばらつきが大きく、製造
歩留りが低下する。Further, in the second conventional technique, in order to spread the current more uniformly than in the first conventional technique and to inject it uniformly into the entire active layer, the current between the p-GaAlAs current diffusion layer 5 and the p-InGaAlP cladding layer 4 is increased. p-in 0.5 (Ga 0.14 Al 0.86) 0.5 by adding P second current diffusion layer 9, p-GaAlAs current diffusing layer 5 and the p-an in 0.5 in (Ga 0.14 Al 0.86)
A large hetero barrier is formed in the valence band at the interface of the 0.5 P second current diffusion layer 9. However, when the current is spread by the hetero barrier, the effect of the current diffusion and the voltage drop at the hetero barrier, and as a result, the luminous efficiency of the device and the operating voltage strongly depend on the size of the hetero barrier. 11 and 12, the second current diffusion layer 9 in the structure of FIG. 10 is formed by p-In 0.5 (Ga 1-X Al X ) 0.5.
The dependence of the luminous efficiency and the operating voltage on the Al mixed crystal ratio X is shown. The horizontal axis shows p-GaAl corresponding to each mixed crystal ratio.
The size of the hetero barrier between the As current diffusion layer 5 and p-In 0.5 (Ga 1-X Al X ) 0.5 P is also shown. However, in order to obtain yellow-green light emission (wavelength: 570 nm), the composition of each layer should be the same as that of the active layer 3.
Is In 0.5 (Ga 0.6 Al 0.4 ) 0.5 P, the n and p-type cladding layers 2 and 4 are both In 0.5 (Ga 0.3 Al 0.7 ) 0.5 P, and the current spreading layer 5 is Ga 0.15 A
l 0.85 As. As can be seen from FIGS. 11 and 12, the luminous efficiency sharply increases between the hetero barrier sizes of 0.20 eV and 0.22 eV and saturates above that, while the operating voltage is 0.22 eV. With the above, it increases rapidly. To reduce the operating voltage to 2.0V or lower, which is practical for a light-emitting diode, and to enable the effect of current diffusion due to the hetero barrier and to significantly increase the luminous efficiency, the size of the hetero barrier should be 0.21 eV or less.
It should be set to a very limited range of 0.22 eV. When the composition of the second current diffusion layer 9 is slightly changed and the size of the hetero barrier is out of this range, the light emission efficiency and the operating voltage are greatly changed. Therefore, in the second conventional technique, variations in luminance and operating voltage between elements are large, and the manufacturing yield is reduced.
【０００９】本発明は上記事情を考慮してなされたもの
で、その目的とするところは、電流が活性層に均一に注
入されることにより、黄色，緑色等の短波長領域でも高
輝度の発光が可能であり、かつ輝度や動作電圧のばらつ
きが小さく製造歩留りの高い半導体発光装置を提供する
ことにある。The present invention has been made in view of the above circumstances, and an object thereof is to uniformly inject an electric current into an active layer, thereby emitting light with high brightness even in a short wavelength region such as yellow and green. It is possible to provide a semiconductor light emitting device that is capable of achieving high manufacturing yield with small variations in brightness and operating voltage.
【００１０】[0010]
【課題を解決するための手段】この目的を達成するため
に本発明の半導体発光装置は、半導体基板と、活性層
と、クラッド層と、第１の電流拡散層と、第２の電流拡
散層と、電極とを少なくとも具備し、前記第１の電流拡
散層と前記第２の電流拡散層が前記活性層と前記電極と
の間にあり、前記第２の電流拡散層がヘテロ障壁を有す
るバンドギャップの異なる２つの層からなる対を複数含
んでいることを特徴とする。In order to achieve this object, a semiconductor light emitting device of the present invention comprises a semiconductor substrate, an active layer, a clad layer, a first current spreading layer, and a second current spreading layer. And a electrode, the first current spreading layer and the second current spreading layer are between the active layer and the electrode, and the second current spreading layer has a hetero barrier. It is characterized in that it includes a plurality of pairs of two layers having different gaps.
【００１１】[0011]
【発明の実施の形態】図１は本発明の第１の実施の形態
に関する半導体発光装置の概略構造を示す断面図であ
る。１１はn-GaAs基板であり、この基板１１上にはn-In
GaAlPクラッド層１２、InGaAlP活性層１３及びp-InGaAl
Pクラッド層１４からなるダブルヘテロ構造部が形成さ
れている。ダブルヘテロ構造部上には、p-InGaAlP広バ
ンドギャップ層１５とp-GaAlAs狭バンドギャップ層１６
の複数の対からなる第２電流拡散層１7が形成されてい
る。ここで層１５と層１６の界面の価電子帯にヘテロ障
壁が生じるように、層１５のバンドギャップは層１６の
それよりも大きくなっている。そこで層１５を広バンド
ギャップ層、層１６を狭バンドギャップ層と記述した。
この第２電流拡散層１7上にはp-GaAlAs第１電流拡散層
１８が形成され、この第１電流拡散層１８上の一部にp-
GaAsコンタクト層１9が形成されている。そしてコンタ
クト層１9上にAuZnからなるｐ側電極２０が形成され、
基板１１の下面にAuGeからなるｎ側電極２１が形成され
ている。1 is a sectional view showing a schematic structure of a semiconductor light emitting device according to a first embodiment of the present invention. 11 is an n-GaAs substrate, on which n-In
GaAlP clad layer 12, InGaAlP active layer 13 and p-InGaAl
A double heterostructure portion composed of the P clad layer 14 is formed. A p-InGaAlP wide bandgap layer 15 and a p-GaAlAs narrow bandgap layer 16 are formed on the double heterostructure.
The second current spreading layer 17 is formed of a plurality of pairs. Here, the band gap of the layer 15 is larger than that of the layer 16 so that a hetero barrier is generated in the valence band at the interface between the layers 15 and 16. Therefore, the layer 15 is described as a wide bandgap layer and the layer 16 is described as a narrow bandgap layer.
A p-GaAlAs first current diffusion layer 18 is formed on the second current diffusion layer 17, and a p-GaAlAs first current diffusion layer 18 is formed on a part of the first current diffusion layer 18.
A GaAs contact layer 19 is formed. Then, the p-side electrode 20 made of AuZn is formed on the contact layer 19 and
An n-side electrode 21 made of AuGe is formed on the lower surface of the substrate 11.
【００１２】図１に示した構造において、各層の膜厚は
以下のように設定されている。即ち、n-GaAs基板１１(1
10μm)、n-InGaAlPクラッド層１２(1μm)、InGaAlP活性
層１３(0.5μm)、p-InGaAlPクラッド層１４(1μm)、p-I
nGaAlP広バンドギャップ層１５(0.05μm)、p-GaAlAs狭
バンドギャップ層１６(0.05μm)、p-GaAlAs第１電流拡
散層１８(7μm)、p-GaAsコンタクト層１９(0.2μm)であ
る。広バンドギャップ層１５と狭バンドギャップ層１６
の膜厚は、抵抗を下げるために、広バンドギャップ層１
５と狭バンドギャップ層１６の間をトンネル効果により
正孔が移動することがない範囲で薄くすることが望まし
い。In the structure shown in FIG. 1, the film thickness of each layer is set as follows. That is, the n-GaAs substrate 11 (1
10 μm), n-InGaAlP clad layer 12 (1 μm), InGaAlP active layer 13 (0.5 μm), p-InGaAlP clad layer 14 (1 μm), pI
The nGaAlP wide band gap layer 15 (0.05 μm), the p-GaAlAs narrow band gap layer 16 (0.05 μm), the p-GaAlAs first current diffusion layer 18 (7 μm), and the p-GaAs contact layer 19 (0.2 μm). Wide band gap layer 15 and narrow band gap layer 16
The thickness of the wide bandgap layer 1 is set to reduce the resistance.
5 and the narrow bandgap layer 16 are preferably thinned within a range in which holes do not move due to a tunnel effect.
【００１３】各層の組成は以下のように設定されてい
る。即ち、活性層１３は黄緑色の発光(570nm)を得るた
めにIn0.5(Ga0.6Al0.4)0.5P、ｎとｐ型クラッド層１
２、１４は活性層１３に注入されたキャリアを閉じこめ
るために何れもIn0.5(Ga0.3Al0.7)0 .5P、狭バンドギャ
ップ層１６と第１電流拡散層１８は活性層１３からの発
光に対して透明になるようにGa0.15Al0.85Asとした。The composition of each layer is set as follows. That is, the active layer 13 is made of In 0.5 (Ga 0.6 Al 0.4 ) 0.5 P, n and p-type cladding layer 1 in order to obtain yellow-green light emission (570 nm).
2, 14 the emission from the active layer 13 both In 0.5 to confine the injected carriers in the (Ga 0.3 Al 0.7) 0 .5 P, a narrow band gap layer 16 is the first current spreading layer 18 active layer 13 Ga 0.15 Al 0.85 As was used so as to be transparent to.
【００１４】また広バンドギャップ層１５の組成は以下
のようにして決めた。図１１と図１２が示すように、狭
バンドギャップ層１６とのヘテロ障壁の大きさが0.20eV
以下であれば、発光効率と動作電圧の変動は顕著でな
い。従ってヘテロ障壁の大きさが多少変化しても第２の
従来例のように発光効率と動作電圧が大きく変動するこ
とはない。そこで広バンドギャップ層１５の組成をヘテ
ロ障壁が0.20eV以下の0.17eVとなるIn0.5(Ga0.3Al0.7)
0.5Pとした。The composition of the wide band gap layer 15 was determined as follows. As shown in FIGS. 11 and 12, the size of the hetero barrier with the narrow band gap layer 16 is 0.20 eV.
If it is below, the fluctuations of the luminous efficiency and the operating voltage are not significant. Therefore, even if the size of the hetero barrier is changed to some extent, the light emission efficiency and the operating voltage do not greatly change as in the second conventional example. Therefore, the composition of the wide bandgap layer 15 is In 0.5 (Ga 0.3 Al 0.7 ) where the hetero barrier becomes 0.17 eV which is less than 0.20 eV.
It was set to 0.5 P.
【００１５】上記構造が従来の構造と異なる点は、p-In
GaAlPクラッド層１４とp-GaAlAs第１電流拡散層１８の
間に、ヘテロ障壁の大きさが多少変化しても発光効率と
動作電圧の変動が顕著でないヘテロ障壁を有する広バン
ドギャップ層１５と狭バンドギャップ層１６の複数の対
からなる第２電流拡散層１７を形成したことである。The above structure is different from the conventional structure in that p-In
Between the GaAlP cladding layer 14 and the p-GaAlAs first current diffusion layer 18, the wide bandgap layer 15 and the narrow bandgap layer 15 having a heterobarrier in which the luminous efficiency and the operating voltage do not change remarkably even if the size of the heterobarrier changes a little. That is, the second current spreading layer 17 including a plurality of pairs of the band gap layers 16 is formed.
【００１６】以上のような構成の半導体発光装置につい
てその動作を説明する。順方向に電流を流すと電流はp-
GaAlAs電流拡散層１８により広げられ、第２電流拡散層
１７を通る。第２電流拡散層１７に含まれる広バンドギ
ャップ層１５と狭バンドギャップ層１６の界面に形成さ
れているへテロ障壁は、顕著な電圧降下を生じるほど大
きくないので、単独では電流拡散の効果は小さい。しか
し、第２電流拡散層１７中には広バンドギャップ層１５
と狭バンドギャップ層１６の界面に形成されるへテロ障
壁が複数あるので、電流拡散の効果が積算され、電流は
十分に広がり活性層全体に均一に注入される。The operation of the semiconductor light emitting device having the above structure will be described. When a current is applied in the forward direction, the current is p-
It is widened by the GaAlAs current spreading layer 18 and passes through the second current spreading layer 17. The hetero barrier formed at the interface between the wide bandgap layer 15 and the narrow bandgap layer 16 included in the second current diffusion layer 17 is not so large as to cause a significant voltage drop. small. However, the wide bandgap layer 15 is included in the second current spreading layer 17.
Since there are a plurality of hetero barriers formed at the interface between the narrow band gap layer 16 and the narrow band gap layer 16, the effect of current diffusion is integrated, and the current is sufficiently spread and uniformly injected into the entire active layer.
【００１７】図１に示した構造に順方向に20mAの電流を
流した場合の、発光効率と動作電圧の広バンドギャップ
層１５と狭バンドギャップ層１６の対数依存性をそれぞ
れ図２と図３に表す。図２からわかるように発光効率は
対数とともに増加し、３対以上でほぼ飽和する。対数を
３にしたときこの素子の発光効率は図９に示した第１の
従来構造の約１．５倍また図１０に示した第２の従来構
造とほぼ同じであった。図４と図５は、同一円形状のｐ
側電極を用いたそれぞれ図１と図９の素子構造でのp-Ga
AlAs電流拡散層１８、５の上面における発光強度の分布
を、ｐ側電極の中心を通る直線(図中AB)に沿って表わし
たものである(ニアフィールドパターン)。図５では発光
強度がチップの中心から離れるにつれて大きく低下する
のに対して、図４ではチップ周辺部の発光強度はｐ側電
極周辺部とほぼ等しくなっている。従って、図１の素子
構造では図９のそれに比べてｐ側電極の直下以外の活性
層で発光する割合が大幅に増加しており、第１電流拡散
層１８とｐ型クラッド１４の間に設けた広バンドギャッ
プ層１５と狭バンドギャップ層１６の界面の価電子帯に
生じる３箇所のヘテロ障壁により、電流広がりが大きく
改善されていると言える。一方、図３に示すように動作
電圧は対数とともに漸増し、３対で2.0Vであった。ま
た、図６と図７にそれぞれ図１と図９の素子構造におけ
る動作電圧の分布を示す。測定は100個のチップについ
て行った。本発明では電流を拡散させるヘテロ障壁を小
さくしたために、第２の従来の技術と比較して大幅に動
作電圧の分布が低減していることがわかる。2 and 3 show the logarithmic dependence of the luminous efficiency and the operating voltage of the wide bandgap layer 15 and the narrow bandgap layer 16 when a current of 20 mA is applied to the structure shown in FIG. 1 in the forward direction. Represent. As can be seen from FIG. 2, the luminous efficiency increases with the logarithm, and is saturated at 3 pairs or more. When the logarithm was set to 3, the luminous efficiency of this device was about 1.5 times that of the first conventional structure shown in FIG. 9 and almost the same as that of the second conventional structure shown in FIG. 4 and 5 show the same circular shape p
P-Ga in the device structure of FIG. 1 and FIG. 9 using the side electrode, respectively.
The distribution of emission intensity on the upper surfaces of the AlAs current diffusion layers 18 and 5 is represented along a straight line (AB in the figure) passing through the center of the p-side electrode (near field pattern). In FIG. 5, the emission intensity drops significantly as the distance from the center of the chip increases, whereas in FIG. 4, the emission intensity in the peripheral portion of the chip is almost equal to that in the peripheral portion of the p-side electrode. Therefore, in the device structure of FIG. 1, the ratio of light emission in the active layers other than directly under the p-side electrode is significantly increased as compared with that of FIG. It can be said that the current spread is greatly improved by the three hetero barriers generated in the valence band at the interface between the wide band gap layer 15 and the narrow band gap layer 16. On the other hand, as shown in FIG. 3, the operating voltage gradually increased with the logarithm, and was 2.0V in 3 pairs. 6 and 7 show distributions of operating voltages in the device structures of FIGS. 1 and 9, respectively. The measurement was performed on 100 chips. In the present invention, it is understood that the distribution of the operating voltage is significantly reduced as compared with the second conventional technique because the hetero barrier for diffusing the current is reduced.
【００１８】以上のように本発明によれば、図１０とほ
ぼ同じ輝度と動作電圧を有する発光ダイオードを、図１
０のように0.22eVの大きなへテロ障壁を形成することな
く、0.17eVの小さなへテロ障壁を３箇所形成することで
製造することができる。従って、In0.5(Ga0.3Al0.7)0.5
Pからなる広バンドギャップ層１５のAl組成が変動し、
へテロ障壁が0.17eVから多少ずれても、図１１と図１２
が示すように発光効率と動作電圧の変動は図１０の構造
に比べて小さくなる。よって電流が活性層全体に均一に
注入されることで、黄色，緑色等の短波長領域でも高輝
度化を実現し、かつ輝度や動作電圧のばらつきを抑制し
製造歩留りを高くすることができる。As described above, according to the present invention, a light emitting diode having substantially the same brightness and operating voltage as in FIG.
It can be manufactured by forming three small hetero barriers of 0.17 eV without forming a large hetero barrier of 0.22 eV like 0. Therefore, In 0.5 (Ga 0.3 Al 0.7 ) 0.5
The Al composition of the wide band gap layer 15 made of P changes,
11 and 12 even if the hetero barrier is slightly different from 0.17 eV
As shown in FIG. 10, fluctuations in light emission efficiency and operating voltage are smaller than those in the structure of FIG. Therefore, by uniformly injecting a current into the entire active layer, it is possible to realize high brightness even in a short wavelength region such as yellow and green, suppress variations in brightness and operating voltage, and increase the manufacturing yield.
【００１９】図８は本発明の第２の実施の形態に関する
半導体発光装置の概略構造を示す断面図である。なお、
図１と同一部分には同一符号を付してその詳しい説明は
省略する。２２はp-GaAs基板、２３はn-GaAsコンタクト
層である。この実施の形態が先に説明した第１の実施の
形態と異なる点は、基板の導電型と第１電流拡散層１８
と第２電流拡散層１７が活性層１３の下にあることであ
る。しかし、本質的な差異はなく第１電流拡散層１８と
p-InGaAlPクラッド層１４の間に0.17eVの小さなへテロ
障壁を３箇所形成することで電流広がりを改善し、外部
への光の取り出し効率を向上しているため、輝度や動作
電圧のばらつきが小さく製造歩留りを高くすることがで
きるのは第１の実施の形態と同じである。FIG. 8 is a sectional view showing a schematic structure of a semiconductor light emitting device according to the second embodiment of the present invention. In addition,
The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. 22 is a p-GaAs substrate, and 23 is an n-GaAs contact layer. This embodiment differs from the first embodiment described above in that the conductivity type of the substrate and the first current spreading layer 18 are different.
And the second current spreading layer 17 is under the active layer 13. However, there is no essential difference with the first current spreading layer 18.
By forming three small hetero barriers of 0.17 eV between the p-InGaAlP cladding layers 14 to improve the current spread and improve the efficiency of extracting light to the outside, there are variations in brightness and operating voltage. As in the first embodiment, the manufacturing yield can be made small and high.
【００２０】なお、本発明は上述した実施の形態に限定
されるものではない。実施の形態ではp-InGaAlPクラッ
ド層１４とp-GaAlAs第１電流拡散層１８の間に第２電流
拡散層１７を形成したが、p-GaAlAs第１電流拡散層１８
中に第２電流拡散層１７を形成しても同様の効果を得る
ことができる。また本実施の形態では第２電流拡散層１
８を構成する広バンドギャップ層１５にIn0.5(Ga0.3Al
0.7)0.5P、狭バンドギャップ層１６にGa0.15Al0.85Asを
用いたが、広バンドギャップ層１５と狭バンドギャップ
層１６の間のへテロ障壁が顕著な電圧降下を生じないよ
うな材料であれば同様の効果が期待できる。例えば広バ
ンドギャップ層１５にIn0.5(Ga0.3Al0.6)0.5P、狭バン
ドギャップ層１６にGa0.15Al0.85Asを用いた場合、へテ
ロ障壁は小さくなるので対数を増やせばよい。また、本
実施の形態では第２電流拡散層１７に含まれる複数のへ
テロ障壁の大きさは全て同じであるが、顕著な電圧降下
を生じなければそれぞれ異なっていてもよい。また、本
実施の形態では第２電流拡散層１７を構成する広バンド
ギャップ層１５と狭バンドギャップ層１６の膜厚は全て
同じであるが異なっていてもよい。また、第１の実施の
形態ではｎ型、第２の実施の形態ではｐ型の基板を用い
たが導電型が逆でもかまわない。このときは各半導体層
の導電型を逆にすればよい。また、本実施の形態ではダ
ブルへテロ構造部にInGaAlP系材料を用いた発光ダイオ
ードについて述べたが、GaAlAs系材料等他の材料を用い
た発光ダイオードにも本発明を適用することができる。
その他本発明の要旨を逸脱しない範囲で種々変形して用
いることができる。The present invention is not limited to the above embodiment. In the embodiment, the second current spreading layer 17 is formed between the p-InGaAlP cladding layer 14 and the p-GaAlAs first current spreading layer 18, but the p-GaAlAs first current spreading layer 18 is used.
The same effect can be obtained by forming the second current diffusion layer 17 therein. Further, in the present embodiment, the second current spreading layer 1
In 0.5 (Ga 0.3 Al) in the wide bandgap layer 15 constituting
0.7 ) 0.5 P, Ga 0.15 Al 0.85 As was used for the narrow bandgap layer 16, but with a material such that the hetero barrier between the wide bandgap layer 15 and the narrow bandgap layer 16 does not cause a significant voltage drop. If so, the same effect can be expected. For example, when In 0.5 (Ga 0.3 Al 0.6 ) 0.5 P is used for the wide bandgap layer 15 and Ga 0.15 Al 0.85 As is used for the narrow bandgap layer 16, the hetero barrier is reduced, so that the logarithm may be increased. Further, in the present embodiment, the plurality of hetero barriers included in the second current diffusion layer 17 have the same size, but may be different as long as no significant voltage drop occurs. In the present embodiment, the wide bandgap layer 15 and the narrow bandgap layer 16 forming the second current diffusion layer 17 have the same film thickness, but may have different film thicknesses. Further, although the n-type substrate is used in the first embodiment and the p-type substrate is used in the second embodiment, the conductivity types may be reversed. At this time, the conductivity type of each semiconductor layer may be reversed. Further, although the light emitting diode using the InGaAlP-based material for the double hetero structure is described in the present embodiment, the present invention can be applied to the light emitting diode using other material such as GaAlAs-based material.
Other various modifications can be used without departing from the scope of the present invention.
【００２１】[0021]
【発明の効果】以上のように本発明は、電極と活性層の
間にヘテロ障壁を有するバンドギャップの異なる２つの
層からなる対を複数含む第２の電流拡散層を設けること
により、このへテロ障壁を電圧降下が顕著でない程度に
小さくしても、電流は十分に広がり、活性層全体に均一
に注入される。従って、活性層の電極の直下以外の領域
で発光する割合が増大し、光の取り出し効率を向上させ
ることができるので、黄色，緑色等の短波長領域でも高
輝度の発光が可能であり、かつ輝度や動作電圧のばらつ
きが小さく製造歩留りの高い半導体発光装置を実現する
ことができる。As described above, according to the present invention, the second current spreading layer including a plurality of pairs of two layers having a hetero barrier and having different band gaps is provided between the electrode and the active layer. Even if the terror barrier is reduced to such an extent that the voltage drop is not remarkable, the current is sufficiently spread and is uniformly injected into the entire active layer. Therefore, the ratio of light emission in regions other than directly below the electrode of the active layer is increased, and the light extraction efficiency can be improved, so that high-luminance light emission is possible even in a short wavelength region such as yellow and green, and It is possible to realize a semiconductor light emitting device with a small variation in brightness and operating voltage and a high manufacturing yield.
【図１】本発明の第１の実施の形態における半導体発光
装置の素子構造を示す断面図FIG. 1 is a sectional view showing an element structure of a semiconductor light emitting device according to a first embodiment of the present invention.
【図２】本発明の第１の実施の形態における半導体発光
装置の広バンドギャップ層と狭バンドギャップ層の対数
と発光効率との関係を示す特性図FIG. 2 is a characteristic diagram showing a relationship between the logarithm of the wide band gap layer and the narrow band gap layer of the semiconductor light emitting device according to the first embodiment of the present invention and the light emission efficiency.
【図３】本発明の第１の実施の形態における半導体発光
装置の広バンドギャップ層と狭バンドギャップ層の対数
と動作電圧との関係を示す特性図FIG. 3 is a characteristic diagram showing the relationship between the operating voltage and the logarithm of the wide band gap layer and the narrow band gap layer of the semiconductor light emitting device according to the first embodiment of the present invention.
【図４】本発明の第１の実施の形態における半導体発光
装置のニアフィールドパターンを示す模式図FIG. 4 is a schematic diagram showing a near-field pattern of the semiconductor light emitting device according to the first embodiment of the invention.
【図５】第１の従来の半導体発光装置のニアフィールド
パターンを示す模式図FIG. 5 is a schematic diagram showing a near-field pattern of a first conventional semiconductor light emitting device.
【図６】本発明の第１の実施の形態における半導体発光
装置の動作電圧の分布を示す特性図FIG. 6 is a characteristic diagram showing a distribution of operating voltage of the semiconductor light emitting device according to the first embodiment of the invention.
【図７】第２の従来の半導体発光装置の動作電圧の分布
を示す特性図FIG. 7 is a characteristic diagram showing a distribution of operating voltage of a second conventional semiconductor light emitting device.
【図８】本発明の第２の実施の形態における半導体発光
装置の素子構造を示す断面図FIG. 8 is a sectional view showing an element structure of a semiconductor light emitting device according to a second embodiment of the present invention.
【図９】第１の従来の半導体発光装置の素子構造を示す
断面図FIG. 9 is a sectional view showing an element structure of a first conventional semiconductor light emitting device.
【図１０】第２の従来の半導体発光装置の素子構造を示
す断面図FIG. 10 is a sectional view showing an element structure of a second conventional semiconductor light emitting device.
【図１１】第２の従来の半導体発光装置の素子構造にお
ける第２電流拡散層のAl混晶比と発光効率との関係を示
す特性図FIG. 11 is a characteristic diagram showing the relationship between the Al mixed crystal ratio of the second current diffusion layer and the luminous efficiency in the element structure of the second conventional semiconductor light emitting device.
【図１２】第２の従来の半導体発光装置の素子構造にお
ける第２電流拡散層９のAl混晶比と動作電圧との関係を
示す特性図FIG. 12 is a characteristic diagram showing the relationship between the Al mixed crystal ratio of the second current diffusion layer 9 and the operating voltage in the element structure of the second conventional semiconductor light emitting device.
１，１１ n-GaAs基板 ２，１２ n-InGaAlPクラッド層 ３，１３ InGaAlP活性層 ４，１４ p-InGaAlPクラッド層 ５ p-GaAlAs電流拡散層 ６，１９ p-GaAsコンタクト層 ７，２０ ｐ側電極 ８，２１ ｎ側電極 １５ p-InGaAlP広バンドギャップ層 １６ p-GaAlAs狭バンドギャップ層 ２２ p-GaAs基板 ２３ n-GaAsコンタクト層 1, 11 n-GaAs substrate 2, 12 n-InGaAlP clad layer 3, 13 InGaAlP active layer 4, 14 p-InGaAlP clad layer 5 p-GaAlAs current diffusion layer 6, 19 p-GaAs contact layer 7, 20 p-side electrode 8, 21 n-side electrode 15 p-InGaAlP wide bandgap layer 16 p-GaAlAs narrow bandgap layer 22 p-GaAs substrate 23 n-GaAs contact layer
Claims (4)
と、第１の電流拡散層と、第２の電流拡散層と、電極と
を少なくとも具備し、前記第１の電流拡散層と前記第２
の電流拡散層が前記活性層と前記電極との間にあり、前
記第２の電流拡散層がヘテロ障壁を有するバンドギャッ
プの異なる２つの層からなる対を複数含んでいることを
特徴とする半導体発光装置。1. A semiconductor substrate, an active layer, a clad layer, a first current spreading layer, a second current spreading layer, and an electrode, and at least the first current spreading layer and the first current spreading layer. Two
A current spreading layer between the active layer and the electrode, and the second current spreading layer includes a plurality of pairs of two layers having different band gaps and having a hetero barrier. Light emitting device.
ヘテロ障壁を発光効率及び動作電圧の変動の少ない大き
さにした請求項１記載の半導体発光装置。2. The semiconductor light emitting device according to claim 1, wherein the hetero barriers of the two layers having different band gaps are sized so as to have a small variation in luminous efficiency and operating voltage.
ヘテロ障壁を0.2eV以下にした請求項１記載の半導体発
光装置。3. The semiconductor light emitting device according to claim 1, wherein the hetero barriers of the two layers having different band gaps are 0.2 eV or less.
第１の電流拡散層がGaAlAsであることを特徴とする請求
項１記載の半導体発光装置。4. The semiconductor light emitting device according to claim 1, wherein the active layer is InGaAlP and the first current spreading layer is GaAlAs.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11872296A JPH09307140A (en) | 1996-05-14 | 1996-05-14 | Semiconductor light emitting device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11872296A JPH09307140A (en) | 1996-05-14 | 1996-05-14 | Semiconductor light emitting device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09307140A true JPH09307140A (en) | 1997-11-28 |
Family
ID=14743472
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11872296A Pending JPH09307140A (en) | 1996-05-14 | 1996-05-14 | Semiconductor light emitting device |
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| Country | Link |
|---|---|
| JP (1) | JPH09307140A (en) |
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| US9025235B2 (en) * | 2002-12-25 | 2015-05-05 | Qualcomm Mems Technologies, Inc. | Optical interference type of color display having optical diffusion layer between substrate and electrode |
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