JPH0634409B2 - Light emitting diode - Google Patents
Light emitting diodeInfo
- Publication number
- JPH0634409B2 JPH0634409B2 JP919984A JP919984A JPH0634409B2 JP H0634409 B2 JPH0634409 B2 JP H0634409B2 JP 919984 A JP919984 A JP 919984A JP 919984 A JP919984 A JP 919984A JP H0634409 B2 JPH0634409 B2 JP H0634409B2
- Authority
- JP
- Japan
- Prior art keywords
- layer
- contact
- window
- light emitting
- emitting diode
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000000605 extraction Methods 0.000 claims description 10
- 229910000980 Aluminium gallium arsenide Inorganic materials 0.000 claims description 7
- 238000005530 etching Methods 0.000 description 11
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 9
- 239000000758 substrate Substances 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 238000004943 liquid phase epitaxy Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/005—Processes
- H01L33/0062—Processes for devices with an active region comprising only III-V compounds
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Led Devices (AREA)
Description
【発明の詳細な説明】 (イ) 発明の技術分野 本発明は近赤外および可視発光ダイオードにおける電極
のオーミック・コンタクト性の改善に関するものであ
る。TECHNICAL FIELD OF THE INVENTION The present invention relates to improvement of ohmic contact property of electrodes in near infrared and visible light emitting diodes.
(ロ) 従来技術と問題点 第１図は従来の発光ダイオードの一例を示す構造断面で
ある。その製造の際はｎ型ＧaＡs基板(図示せず)上に、
先ず光取出し窓層とするｎ型Ａｌ0.5Ｇa0.5Ａs層１を厚
さ５０μに、活性層とするｎ型又はｐ型のＡl0.2Ｇa0.8
Ａs層２を厚さ１μに、閉じ込め層とするｐ型Ａl0.4Ｇa
0.6Ａs層３を厚さ１μに、コンタクト層兼電流路を制限
する逆バイアス層）とする成長時は全体にｎ型のＡl0.3
Ｇa0.7Ａs層４の厚さ１μに、順次液相成長したウエハ
を使用している。尚、窓層１のＡl含有比の０．５は成
長開始部での値である。これにコンタクト抵抗を低減す
るためにＺn（ｐ型不純物）を１〜３μｍ拡散してｐ型
領域５を形成し、電極(通常はＡuＺn)６が3000Åの厚さ
に形成される。その上にはＡuのＰＨＳ電極７が形成さ
れる。他方Ｎ側電極８のワイヤをボンデングする場所は
広くとられる。窓層１のような厚いＡlＧaＡs層を液相
成長させる場合、液相エピ成長時のＡlの編析係数が大
きい為、成長方向に向ってＡl含有比が下っていく。発
光波長λ0は活性層のエネルギーギャップＥg で制御さ
れ、ＥgはＡl含有比に依存する。一方、基板として使用
されるＧaＡsは、発光波長λ0＜950ｎｍでは吸収層とな
る為、光通信用光源用等の場合除去される。基板除去は
エッチングによるが、エッチング液はＡlの含有比ｘに
対して依存成を持っているものが使われる。たとえばNH
4OH+H2O2（1:30）液はＧaＡsのみをエッチングし、ｘ＞
0.2のＡlxＧa1−xＡsに対しては全くエッチングしな
い。この様な選択エッチングによって吸収層となるＧa
Ａs基板を除去した構造が得られる。この露出した結晶
面に電極が形成されるが、先述したように所望膜厚を得
る為に初期のＡlx値を高く（0.3〜0.6）する必要があ
る。コンタクト抵抗はＧaＡs中のＡlが少ない方が低
く、ＧaＡs層に対し電極を形成するのが低いコンタクト
抵抗を得るためには望ましい。しかし、結晶界面（基板
との）上に精度良く数μｍのコンタクト用ＧaＡs層を均
一に残すようなエッチングは困難であり、又、光取出し
窓部分のみかかるコンタクト層による光吸収を避ける為
更にエッチング加工等でこのコンタクト用ＧaＡs層を除
去しなければならないので、工程も著しく煩雑になる。(B) Conventional Technology and Problems FIG. 1 is a structural cross section showing an example of a conventional light emitting diode. At the time of manufacturing, on an n-type GaAs substrate (not shown),
First, the n-type Al0.5Ga0.5As layer 1 serving as the light extraction window layer is made to have a thickness of 50 μ, and the n-type or p-type Al0.2Ga0.8 serving as the active layer is formed.
The As layer 2 has a thickness of 1 μ and is a p-type Al0.4 Ga layer that serves as a confinement layer.
When the 0.6As layer 3 is grown to a thickness of 1μ and is used as a contact layer and a reverse bias layer that limits the current path, n-type Al0.3
A wafer having a thickness of 1 μm of the Ga0.7As layer 4 and sequentially subjected to liquid phase growth is used. The Al content ratio of 0.5 in the window layer 1 is a value at the growth start portion. To reduce the contact resistance, Zn (p-type impurity) is diffused by 1 to 3 μm to form a p-type region 5, and an electrode (usually AuZn) 6 is formed with a thickness of 3000 Å. An Au PHS electrode 7 is formed thereon. On the other hand, there is a wide space for bonding the wire of the N-side electrode 8. When a thick AlGaAs layer such as the window layer 1 is grown in liquid phase, the Al content ratio decreases in the growth direction because the Al segregation coefficient during liquid phase epitaxy is large. The emission wavelength λ 0 is controlled by the energy gap Eg of the active layer, and Eg depends on the Al content ratio. On the other hand, GaAs used as a substrate becomes an absorption layer at an emission wavelength λ 0 <950 nm, and is therefore removed in the case of a light source for optical communication. Although the substrate is removed by etching, an etching solution having a dependency on the Al content ratio x is used. For example NH
4 OH + H 2 O 2 (1:30) solution etches only GaAs, x>
No etching is performed for 0.2 AlxGa1-xAs. Ga which becomes an absorption layer by such selective etching
A structure with the As substrate removed is obtained. An electrode is formed on this exposed crystal face, but as described above, it is necessary to increase the initial Alx value (0.3 to 0.6) in order to obtain the desired film thickness. The smaller the Al content in GaAs, the lower the contact resistance. It is desirable to form an electrode on the GaAs layer in order to obtain a low contact resistance. However, it is difficult to perform etching so that a contact GaAs layer of several μm is uniformly left on the crystal interface (with the substrate) with high accuracy, and further etching is performed in order to avoid light absorption by the contact layer only on the light extraction window portion. Since the contact GaAs layer must be removed by processing or the like, the process becomes extremely complicated.
(ハ) 発明の目的 本発明は以上の従来技術における欠点を解消し、ＡlＧa
Ａs窓層側のコンタクト抵抗を低減することが可能で製
造も容易な発光ダイオード構造を提供することを目的と
する。(C) Purpose of the Invention The present invention solves the above-mentioned drawbacks of the prior art, and provides AlGa
It is an object of the present invention to provide a light emitting diode structure that can reduce the contact resistance on the As window layer side and is easy to manufacture.
(ニ) 発明の構成 上記目的は本発明により、活性層に隣接して、該活性層
から離れるに従い次第にＡｌ含有比が増大するＡｌＧａ
Ａｓ層からなる窓層を有し、該窓層の前記活性層と反対
側の全面上に、Ａｌ含有比が該面における窓層より小
で、活性層より発せられる発光波長を吸収しない値に選
ばれたＡｌＧａＡｓ層からなるコンタクト層が設けら
れ、光取出し窓部分のコンタクト層以外のコンタクト層
上にオーミック・コンタクト電極が設けられ、活性層か
らの出力光が光取出し窓部分のコンタクト層を通して出
射することを特徴とする発光ダイオードによって達成さ
れる。(D) Structure of the Invention According to the present invention, the AlGa content is adjacent to the active layer and has an Al content ratio that gradually increases as the distance from the active layer increases.
A window layer made of an As layer is provided, and the Al content ratio on the entire surface of the window layer opposite to the active layer is smaller than that of the window layer on the surface and does not absorb the emission wavelength emitted from the active layer. A contact layer made of a selected AlGaAs layer is provided, an ohmic contact electrode is provided on the contact layers other than the contact layer in the light extraction window portion, and the output light from the active layer is emitted through the contact layer in the light extraction window portion. It is achieved by a light emitting diode.
(ホ) 発明の実施例 第２図は本発明実施例の発光ダイオードの構造断面を示
し、第１図従来例と同一部分については同一参照番号を
付してある。従来例とは、厚さ2〜３μのｎ型Ａl0.3Ｇa
0.7Ａsから成るコンタクト層９をＮ側電極８（ＡuＧe−
Ａu）下に設けてある点で構造上相違している。本実施
例の発光ダイオードの製造工程について次に説明する
と、エピ成長の段階に於いて、所望発光波長λ0を吸収
せず且つ選択エッチ可能な範囲のＡlx値を有するｎ型の
コンタクト用ＡlＧaＡs層９を数μｍＧaＡs基板上に第
１層として成長する。連続して窓層１，活性層２，閉じ
込め層３，コンタクト層４を成長する。エピ工程なので
膜厚精度は良い。その後は、従来同様ｐ型領域５，電極
６，７を形成する。しかる後ＧaＡs基板を前述のエッチ
ング液を用いる等して選択的にエッチング除去する。第
３図に厚さ方向に対するＡlx値分布を示す。第１層目と
してコンタクト用の低抵抗層９を設ける本方法により、
順方向電圧は従来品に比べ0.4〜0.6Ｖ低くなり発熱も押
えられる効果を持った。本実施例では光取出し窓の電極
形成面に設けたコンタクト用のＡlＧaＡs層９のエッチ
ング除去不要としたが、このように光取出し窓部分に窓
層よりＡｌ含有比の小なるコンタクト層が設けられてい
ることによって窓層面は保護される。それはＡｌが多量
に含まれる窓層部分が直接外部に露出していると大気中
の酸素とＡｌが反応し半導体の特性が劣化するからであ
る。又５層構造に限定されるものではなく、光取出し窓
層上に活性層のみ設けて全体に３層構造にすることも可
能である。(E) Embodiment of the Invention FIG. 2 shows a structural cross section of a light emitting diode of an embodiment of the present invention, and the same parts as those of the conventional example of FIG. 1 are designated by the same reference numerals. The conventional example is an n-type Al0.3Ga with a thickness of 2-3μ.
The contact layer 9 made of 0.7 As is applied to the N-side electrode 8 (AuGe-
It is structurally different in that it is provided under Au). The manufacturing process of the light emitting diode of this embodiment will be described below. At the stage of epitaxial growth, an AlGaAs layer for n-type contact which does not absorb a desired emission wavelength λ 0 and has an Alx value within a range in which selective etching is possible. 9 is grown as a first layer on a several μm GaAs substrate. A window layer 1, an active layer 2, a confinement layer 3 and a contact layer 4 are continuously grown. The film thickness accuracy is good because it is an epi process. After that, the p-type region 5, electrodes 6 and 7 are formed as in the conventional case. Thereafter, the GaAs substrate is selectively removed by etching using the above-mentioned etching solution. FIG. 3 shows the Alx value distribution in the thickness direction. By this method of providing the low resistance layer 9 for contact as the first layer,
The forward voltage is 0.4 to 0.6 V lower than the conventional product, and it has the effect of suppressing heat generation. In this embodiment, the AlGaAs layer 9 for contact provided on the electrode forming surface of the light extraction window is not required to be removed by etching, but the contact layer having a smaller Al content ratio than the window layer is provided in the light extraction window portion in this way. The window layer surface is protected by this. This is because if the window layer portion containing a large amount of Al is directly exposed to the outside, oxygen in the atmosphere reacts with Al and the characteristics of the semiconductor deteriorate. The structure is not limited to the five-layer structure, and it is also possible to provide only the active layer on the light extraction window layer to form the three-layer structure as a whole.
(ハ) 発明の効果 本発明によれば、発光ダイオードのＡlＧaＡs窓層側オ
ーミック・コンタクト電極のコンタクト抵抗を低減する
ことができ、且つそのために製造工程に制御困難なエッ
チング工程を導入する必要もないという効果が得られ
る。(C) Effect of the Invention According to the present invention, the contact resistance of the AlGaAs window layer side ohmic contact electrode of the light emitting diode can be reduced, and therefore it is not necessary to introduce an etching step that is difficult to control into the manufacturing process. The effect is obtained.
第１図は従来の発光ダイオードの構造断面例を示し、第
２図は本発明実施例の発光ダイオードを示し、第３図は
その各層のＡl含有比分布を表す図である。 １……ＡlＧaＡs光取出し窓層 ２……活性層 ３……閉じ込め層 ４，９……オーミック・コンタクト層 ６，８……電極FIG. 1 shows a structural cross-sectional example of a conventional light emitting diode, FIG. 2 shows a light emitting diode of an embodiment of the present invention, and FIG. 3 is a diagram showing the Al content ratio distribution of each layer. 1 ... AlGaAs light extraction window layer 2 ... Active layer 3 ... Confinement layer 4, 9 ... Ohmic contact layer 6, 8 ... Electrode
Claims (1)
従い次第にＡｌ含有比が増大するＡｌＧａＡｓ層からな
る窓層を有し、該窓層の前記活性層と反対側の全面上
に、Ａｌ含有比が該面における窓層より小で、活性層よ
り発せられる発光波長を吸収しない値に選ばれたＡｌＧ
ａＡｓ層からなるコンタクト層が設けられ、光取出し窓
部分のコンタクト層以外のコンタクト層上にオーミック
・コンタクト電極が設けられ、活性層からの出力光が光
取出し窓部分のコンタクト層を通して出射することを特
徴とする発光ダイオード。1. A window layer comprising an AlGaAs layer adjacent to the active layer, the Al content ratio of which gradually increases as the distance from the active layer increases, and the window layer is formed on the entire surface of the window layer opposite to the active layer. AlG having an Al content ratio smaller than that of the window layer on the surface and not absorbing the emission wavelength emitted from the active layer
A contact layer composed of an aAs layer is provided, and an ohmic contact electrode is provided on a contact layer other than the contact layer in the light extraction window portion, so that output light from the active layer is emitted through the contact layer in the light extraction window portion. Characteristic light emitting diode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP919984A JPH0634409B2 (en) | 1984-01-20 | 1984-01-20 | Light emitting diode |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP919984A JPH0634409B2 (en) | 1984-01-20 | 1984-01-20 | Light emitting diode |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60153186A JPS60153186A (en) | 1985-08-12 |
| JPH0634409B2 true JPH0634409B2 (en) | 1994-05-02 |
Family
ID=11713823
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP919984A Expired - Lifetime JPH0634409B2 (en) | 1984-01-20 | 1984-01-20 | Light emitting diode |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0634409B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6415913A (en) * | 1987-07-09 | 1989-01-19 | Mitsubishi Monsanto Chem | Epitaxial growth method of substrate for high-brightness led |
| JPH0770755B2 (en) * | 1988-01-21 | 1995-07-31 | 三菱化学株式会社 | High brightness LED epitaxial substrate and method of manufacturing the same |
| JP4646166B2 (en) | 2000-11-08 | 2011-03-09 | 古河電気工業株式会社 | Light source consisting of a laser diode module |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58137274A (en) * | 1982-02-09 | 1983-08-15 | Sumitomo Electric Ind Ltd | Manufacture of surface luminescence type semiconductor light-emitting element |
-
1984
- 1984-01-20 JP JP919984A patent/JPH0634409B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60153186A (en) | 1985-08-12 |
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