JP2004228506A - Metal oxide film forming method and semiconductor light emitting device manufactured by the film forming method - Google Patents
Metal oxide film forming method and semiconductor light emitting device manufactured by the film forming method Download PDFInfo
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- 229910044991 metal oxide Inorganic materials 0.000 title claims abstract description 63
- 150000004706 metal oxides Chemical class 0.000 title claims abstract description 63
- 238000000034 method Methods 0.000 title claims abstract description 48
- 239000004065 semiconductor Substances 0.000 title claims abstract description 44
- 239000000758 substrate Substances 0.000 claims abstract description 34
- 229910001218 Gallium arsenide Inorganic materials 0.000 claims abstract description 22
- 238000010438 heat treatment Methods 0.000 claims abstract description 19
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 9
- 239000001301 oxygen Substances 0.000 claims abstract description 9
- 239000010408 film Substances 0.000 claims description 62
- 239000010409 thin film Substances 0.000 claims description 8
- 239000007921 spray Substances 0.000 claims description 6
- 229910006404 SnO 2 Inorganic materials 0.000 claims description 4
- 238000000576 coating method Methods 0.000 claims description 3
- 238000004544 sputter deposition Methods 0.000 claims description 3
- 238000007740 vapor deposition Methods 0.000 claims description 3
- 238000010586 diagram Methods 0.000 abstract 1
- 230000015572 biosynthetic process Effects 0.000 description 16
- 235000012431 wafers Nutrition 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 7
- 239000000523 sample Substances 0.000 description 7
- 238000000151 deposition Methods 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 238000002488 metal-organic chemical vapour deposition Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 2
- 229910000980 Aluminium gallium arsenide Inorganic materials 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 125000005842 heteroatom Chemical group 0.000 description 1
- 229910003437 indium oxide Inorganic materials 0.000 description 1
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 description 1
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Abstract
【課題】最表面エピタキシャル層としてＡｌＸＧａ１−ＸＡｓ（Ｘ≦０．５）を用いると、その上に低抵抗な金属酸化物膜を形成することが困難であった。
【解決手段】酸素を含む雰囲気において４５０℃以上の温度で金属酸化物を成膜する工程を含む金属酸化物の成膜方法、または、酸素を含む雰囲気において４５０℃以上の温度で基板または最表面エピタキシャル層を熱処理する工程と、該熱処理工程の後、基板または最表面エピタキシャル層上に金属酸化物を成膜する工程を含む金属酸化物の成膜方法により、ＧａＡｓ半導体基板またはＡｌＸＧａ１−ＸＡｓ（但し、０≦Ｘ≦０．５）からなる最表面エピタキシャル層上に金属酸化物を成膜する。
【選択図】図１A With Al X Ga 1-X As ( X ≦ 0.5) as the outermost epitaxial layer, it is difficult to form a low-resistance metal oxide film thereon.
A metal oxide film forming method includes a step of forming a metal oxide film at a temperature of 450 ° C. or more in an atmosphere containing oxygen, or a substrate or the outermost surface at a temperature of 450 ° C. or more in an oxygen containing atmosphere. A GaAs semiconductor substrate or Al x Ga 1− by a metal oxide film forming method including a step of heat-treating the epitaxial layer and a step of forming a metal oxide on the substrate or the uppermost surface epitaxial layer after the heat treatment step. A metal oxide is formed on the outermost surface epitaxial layer made of XAs (where 0 ≦ X ≦ 0.5).
[Selection diagram] Fig. 1
Description
【０００１】
【発明の属する技術分野】
本発明は、半導体基板または半導体エピタキシャル層上、特にＧａＡｓ系基板またはＡｌＧａＡｓ系エピタキシャル層上に低抵抗な金属酸化物を成膜する方法に関する。また、本発明は、上記方法により形成される低抵抗な金属酸化物からなる薄膜を、ＧａＡｓ半導体基板またはＡｌＸＧａ１−ＸＡｓ（但し、０≦Ｘ≦０．５）からなる最表面エピタキシャル層上に有した半導体発光素子及び半導体発光素子用エピタキシャルウエハに関する。
【０００２】
【従来の技術】
従来、ＩＴＯ（錫添加インジウム酸化物）等の金属酸化物はガラス基板に使用されることが殆どであったが、近年、例えばＩＴＯは、３ｅＶ程度の禁止帯幅を有するため、発光した光を良好に透過したり、非常に低抵抗な膜が形成できる等の理由から、半導体発光素子である発光ダイオード等の窓層または電流分散層として用いる研究が行われている。特に、ＭＯＶＰＥ法により窓層または電流分散層を厚く形成するｐｎ接合型ダブルへテロ構造の高輝度ＡｌＧａＩｎＰ系ＬＥＤにおいて、ＩＴＯ膜を用いる研究が盛んに行われている。
【０００３】
例えば、下記特許文献１には、ｐ型オーミックコンタクト層上にＩＴＯからなる窓層を形成したＡｌＧａＩｎＰ系ＬＥＤが開示されている。
【特許文献１】米国特許第５，４８１，１２２号公報
また、下記特許文献２には、ｐ型オーミックコンタクト層上にＩＴＯからなる電流分散層を形成したＡｌＧａＩｎＰ系ＬＥＤが開示されている。
【特許文献２】特開平１１−４０２０号公報
【０００４】
【発明が解決しようとする課題】
一般的に、ＡｌＧａＩｎＰ系ＬＥＤの最表面エピタキシャル層（窓層、コンタクト層、電流分散層）はｐ−ＧａＰ、ｐ−ＡｌＧａＩｎＰ、ｐ−ＡｌＸＧａ１−ＸＡｓ（Ｘ≦０．７）から成り、該最表面エピタキシャル層上に形成するＩＴＯ膜はｎ型である。このため、これらの層に電流を流すために、最表面エピタキシャル層として、キャリア濃度が高く、移動度が大きい材料を用いることが有効である。特に、ｐ−ＡｌＸＧａ１−ＸＡｓ（Ｘ≦０．５）は比較的キャリア濃度が高く、移動度が大きい材料として好適である。
しかしながら、最表面エピタキシャル層としてＡｌＸＧａ１−ＸＡｓ（Ｘ≦０．５）を用いると、その上に低抵抗な金属酸化物膜を形成することが困難であった。
【０００５】
【課題を解決するための手段】
本発明は、上記の課題に鑑みてなされたものであり、ＡｌＸＧａ１−ＸＡｓ系半導体層（０≦Ｘ≦０．５）上に低抵抗な金属酸化物膜を形成するため、ＧａＡｓ半導体基板またはＡｌＸＧａ１−ＸＡｓ（但し、０≦Ｘ≦０．５）からなる最表面エピタキシャル層上に金属酸化物を成膜する方法において、酸素を含む雰囲気において４５０℃以上の温度で金属酸化物を成膜する工程を含む金属酸化物の成膜方法を提供するものである。
【０００６】
また、本発明は、ＧａＡｓ半導体基板またはＡｌＸＧａ１−ＸＡｓ（但し、０≦Ｘ≦０．５）からなる最表面エピタキシャル層上に金属酸化物を成膜する方法において、酸素を含む雰囲気において４５０℃以上の温度で基板または最表面エピタキシャル層を熱処理する工程と、該熱処理工程の後、基板または最表面エピタキシャル層上に金属酸化物を成膜する工程を含む金属酸化物の成膜方法を提供するものである。
【０００７】
また、本発明は、上記方法により形成される低抵抗な金属酸化物からなる薄膜を、ＧａＡｓ半導体基板またはＡｌＸＧａ１−ＸＡｓ（但し、０≦Ｘ≦０．５）からなる最表面エピタキシャル層上に有した半導体発光素子及び半導体発光素子用エピタキシャルウエハを提供するものである。
【０００８】
【発明の実施の形態】
本発明は、酸素を含む雰囲気において４５０℃以上の温度（基板温度）で上記基板または最表面エピタキシャル層を成膜するか、あるいは、成膜に先立って上記基板または最表面エピタキシャル層を熱処理することに特徴を有している。
本発明による金属酸化物の成膜温度または成膜前熱処理温度においては、ＡｌＸＧａ１−ＸＡｓ層の表面に酸化物が形成されていることが確認されており（ＳＩＭＳ分析に基づく）、該酸化物の存在により、該ＡｌＸＧａ１−ＸＡｓ層上に、良質（低抵抗）の金属酸化物膜が形成されると考えられる。従って、本発明の本質は、少なくとも、ＡｌＸＧａ１−ＸＡｓ層の表面に酸化物が形成されることにある。因みに、４５０℃以上の熱処理を行ったＡｌＸＧａ１−ＸＡｓ層上に、直ちに金属酸化物膜（ＩＴＯ）を形成した場合と、数十日放置してから金属酸化物膜を形成した場合を較べても、金属酸化物膜の比抵抗特性は変化しないことが確認されている。
【０００９】
本発明において、適用可能な金属酸化物は、ＳｎＯ２系、ＺｎＯ系、Ｉｎ２Ｏ３系である。特に、ＩＴＯが好ましい。
本発明において、金属酸化物の成膜方法として、スプレー法の他、蒸着法、スパッタ法、塗布法等を適用することができる。
【００１０】
一方、本発明により、ＧａＡｓ半導体基板またはＡｌＸＧａ１−ＸＡｓ（但し、０≦Ｘ≦０．５）からなる最表面エピタキシャル層上に金属酸化物からなる薄膜を有した半導体発光素子において、前記金属酸化物が、上記方法により形成され、３×１０−４Ω・ｃｍ以下の比抵抗を有する半導体発光素子を作製することができる。
また、本発明により、ＧａＡｓ半導体基板またはＡｌＸＧａ１−ＸＡｓ（但し、０≦Ｘ≦０．５）からなる最表面エピタキシャル層上に金属酸化物からなる薄膜を有した半導体発光素子用エピタキシャルウエハにおいて、前記金属酸化物が、上記方法により形成され、３×１０−４Ω・ｃｍ以下の比抵抗を有する半導体発光素子用エピタキシャルウエハを作製することができる。
【００１１】
【実施例】
以下、本発明に従う実施例１、２を図面を参照しつつ説明する。比較例１、２は、ＩＴＯ膜の成長温度およびＩＴＯ成膜前熱処理温度による比抵抗の低下傾向を、実施例１、２とそれぞれ比較するために行なわれた。
実施例１
ｎ型ＧａＡｓ基板上に、膜厚が３００ｎｍ、キャリア濃度が２×１０１８ｃｍ−３以上のｐ型ＧａＡｓ、ｐ型Ａｌ０．１Ｇａ０．９Ａｓ、ｐ型Ａｌ０．２Ｇａ０．８Ａｓ、ｐ型Ａｌ０．３Ｇａ０．７Ａｓ、ｐ型Ａｌ０．４Ｇａ０．６Ａｓ、ｐ型Ａｌ０．５Ｇａ０．５Ａｓ（ｐ型化は何れもＺｎドープによる）の各層をＭＯＶＰＥ法で成長させ、６種類のエピタキシャルウェハを作製した。
次いで、上記６種類のエピタキシャルウェハおよび（別途作製した）ｐ型ＧａＡｓ基板上に、スプレー法によりＩＴＯ膜を３００ｎｍ成膜し、合計７種類のサンプルを作製した。ここで、ＩＴＯ膜の成膜温度は、各サンプルについて、４５０℃、５００℃、６００℃、８００℃（４点）とした。
表１に示されるように、上記７種類のサンプルのＩＴＯ膜の比抵抗を４探針法にて評価した所、（ＩＴＯ成膜温度４５０℃以上の）全サンプルで３×１０−４Ω・ｃｍ以下の値が得られた。
【表１】
比較例１
実施例１と同様の方法で、７種類のサンプルを作製した。ただし、ＩＴＯ膜の成膜温度は、各サンプルについて、３５０℃、４００℃（２点）とした。
表１に示されるように、上記７種類のサンプルのＩＴＯ膜の比抵抗を４探針法にて評価した所、（ＩＴＯ成膜温度４００℃以下の）全サンプルで４．５×１０−２Ω・ｃｍ以上の値が得られた。
従って、ＩＴＯ膜を成膜する場合、成膜温度を４５０℃以上とすれば（実施例１）、成膜温度４００℃以下の場合（比較例１）と較べて、約２桁以上低い比抵抗が得られる。つまり、図１に示されるように、ＩＴＯ膜の成膜温度による比抵抗の低下傾向は、成膜温度４５０℃以上で著しいことが判明した。
【００１３】
実施例２
ｎ型ＧａＡｓ基板上に、膜厚が３００ｎｍ、キャリア濃度が２×１０１８ｃｍ−３以上のｐ型ＧａＡｓ、ｐ型Ａｌ０．１Ｇａ０．９Ａｓ、ｐ型Ａｌ０．２Ｇａ０．８Ａｓ、ｐ型Ａｌ０．３Ｇａ０．７Ａｓ、ｐ型Ａｌ０．４Ｇａ０．６Ａｓ、ｐ型Ａｌ０．５Ｇａ０．５Ａｓ（ｐ型化は何れもＺｎドープによる）の各層をＭＯＶＰＥ法で成長させ、６種類のエピタキシャルウェハを作製した。
次いで、上記６種類のエピタキシャルウェハおよび（別途作製した）ｐ型ＧａＡｓ基板を、４５０℃、５００℃、６００℃、８００℃の各温度（４点）で熱処理を施した（ＩＴＯ成膜前熱処理）。その後、上記６種類のエピタキシャルウェハおよびｐ型ＧａＡｓ基板上に、スプレー法によりＩＴＯ膜を３００ｎｍ成膜し、合計７種類のサンプルを作製した。ここで、ＩＴＯ膜の成膜温度は、全サンプルについて、３５０℃とした。
表２に示されるように、上記７種類のサンプルのＩＴＯ膜の比抵抗を４探針法にて評価した所、（ＩＴＯ成膜前熱処理温度４５０℃以上の）全サンプルで３×１０−４Ω・ｃｍ以下の値が得られた。
【表２】
比較例２
実施例２と同様の方法で、７種類のサンプルを作製した。ただし、ＩＴＯ成膜前熱処理温度は、各サンプルについて、３５０℃、４００℃（２点）とした。
表２に示されるように、上記７種類のサンプルのＩＴＯ膜の比抵抗を４探針法にて評価した所、（ＩＴＯ成膜温度４００℃以下の）全サンプルで４．５×１０−２Ω・ｃｍ以上の値が得られた。
従って、ＩＴＯ成膜前に熱処理する場合、熱処理温度を４５０℃以上とすれば（実施例２）、熱処理温度４００℃以下の場合（比較例２）と較べて、約２桁以上低い比抵抗が得られる。つまり、図２に示されるように、ＩＴＯ成膜前熱処理温度による比抵抗の低下傾向は、熱処理温度４５０℃以上で著しいことが判明した。
【００１５】
上記実施例１、２ではスプレー法でＩＴＯ膜を形成したが、蒸着法、スパッタ法、塗布法等の方法でＩＴＯ膜を形成した場合でも、本発明のＩＴＯ成膜温度、ＩＴＯ成膜前熱処理温度においては、実施例１、２と同様に低抵抗なＩＴＯ膜を成膜することができる。何故なら、本発明によるＩＴＯ成膜温度またはＩＴＯ成膜前熱処理温度においては、（製法を問わず）ＡｌＸＧａ１−ＸＡｓ層の表面に酸化物が形成され、それにより、該ＡｌＸＧａ１−ＸＡｓ層上に良質のＩＴＯ膜が形成されるからである。
【００１６】
【発明の効果】
本発明の金属酸化物の成膜方法によれば、ＧａＡｓ半導体基板またはＡｌＸＧａ１−ＸＡｓ（但し、０≦Ｘ≦０．５）からなる最表面エピタキシャル層上に金属酸化物を成膜する方法において、酸素を含む雰囲気において４５０℃以上の温度で金属酸化物を成膜する工程を含むことにより、ＡｌＸＧａ１−ＸＡｓ系半導体層（０≦Ｘ≦０．５）上に低抵抗な金属酸化物膜を形成することができる。
【００１７】
また、本発明の金属酸化物の成膜方法によれば、ＧａＡｓ半導体基板またはＡｌＸＧａ１−ＸＡｓ（但し、０≦Ｘ≦０．５）からなる最表面エピタキシャル層上に金属酸化物を成膜する方法において、酸素を含む雰囲気において４５０℃以上の温度で基板または最表面エピタキシャル層を熱処理する工程と、該熱処理工程の後、基板または最表面エピタキシャル層上に金属酸化物を成膜する工程を含むことにより、ＡｌＸＧａ１−ＸＡｓ系半導体層（０≦Ｘ≦０．５）上に低抵抗な金属酸化物膜を形成することができる。
【００１８】
さらに、本発明の半導体発光素子によれば、ＧａＡｓ半導体基板またはＡｌＸＧａ１−ＸＡｓ（但し、０≦Ｘ≦０．５）からなる最表面エピタキシャル層上に金属酸化物からなる薄膜を有した半導体発光素子において、前記金属酸化物が、上記方法により形成され、３×１０−４Ω・ｃｍ以下の比抵抗を有する半導体発光素子を作製することができる。
また、本発明の半導体発光素子用エピタキシャルウエハによれば、ＧａＡｓ半導体基板またはＡｌＸＧａ１−ＸＡｓ（但し、０≦Ｘ≦０．５）からなる最表面エピタキシャル層上に金属酸化物からなる薄膜を有した半導体発光素子用エピタキシャルウエハにおいて、前記金属酸化物が、上記方法により形成され、３×１０−４Ω・ｃｍ以下の比抵抗を有する半導体発光素子用エピタキシャルウエハを作製することができる。
【図面の簡単な説明】
【図１】本発明の金属酸化物の成膜方法の第一の実施例、及びその比較例において、スプレー法によるＩＴＯ膜の成膜温度とＩＴＯ膜の比抵抗との関係を示すグラフである。
【図２】本発明の金属酸化物の成膜方法の第二の実施例、及びその比較例において、ＩＴＯ成膜前の熱処理温度とＩＴＯ膜の比抵抗との関係を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for forming a low-resistance metal oxide on a semiconductor substrate or a semiconductor epitaxial layer, particularly on a GaAs-based substrate or an AlGaAs-based epitaxial layer. Further, the present invention provides a method of forming a thin film of a low-resistance metal oxide formed by the above method on a GaAs semiconductor substrate or an outermost surface epitaxial layer of Al X Ga 1-X As (0 ≦ X ≦ 0.5). The present invention relates to a semiconductor light emitting device provided on a layer and an epitaxial wafer for a semiconductor light emitting device.
[0002]
[Prior art]
Conventionally, metal oxides such as ITO (tin-added indium oxide) have been mostly used for glass substrates. However, recently, for example, ITO has a band gap of about 3 eV. Studies have been made on the use as a window layer or a current spreading layer of a light emitting diode or the like, which is a semiconductor light emitting element, because it can transmit light well and can form a film having a very low resistance. In particular, studies on the use of an ITO film in a high-luminance AlGaInP-based LED having a pn junction type double hetero structure in which a window layer or a current dispersion layer is formed thick by the MOVPE method have been actively conducted.
[0003]
For example, Patent Literature 1 below discloses an AlGaInP-based LED in which a window layer made of ITO is formed on a p-type ohmic contact layer.
[Patent Document 1] US Patent No. 5,481,122 Also, Patent Document 2 below discloses an AlGaInP-based LED in which a current distribution layer made of ITO is formed on a p-type ohmic contact layer.
[Patent Document 2] Japanese Patent Application Laid-Open No. 11-4020
[Problems to be solved by the invention]
Generally, the outermost epitaxial layer (window layer, contact layer, current distribution layer) of an AlGaInP-based LED is composed of p-GaP, p-AlGaInP, p-Al X Ga 1-X As (X ≦ 0.7). The ITO film formed on the outermost surface epitaxial layer is n-type. Therefore, it is effective to use a material having a high carrier concentration and a high mobility as the outermost surface epitaxial layer in order to allow a current to flow through these layers. In particular, p-Al X Ga 1-X As (X ≦ 0.5) is suitable as a material having a relatively high carrier concentration and a high mobility.
However, when Al X Ga 1-X As (X ≦ 0.5) is used as the outermost epitaxial layer, it has been difficult to form a low-resistance metal oxide film thereon.
[0005]
[Means for Solving the Problems]
The present invention has been made in view of the above problems, and has been made in order to form a low-resistance metal oxide film on an Al X Ga 1-X As-based semiconductor layer (0 ≦ X ≦ 0.5). In a method of forming a metal oxide on a semiconductor substrate or an outermost surface epitaxial layer composed of Al X Ga 1-X As (where 0 ≦ X ≦ 0.5), the method is performed at a temperature of 450 ° C. or more in an atmosphere containing oxygen. An object of the present invention is to provide a metal oxide film forming method including a step of forming a metal oxide film.
[0006]
The present invention also provides a method for forming a metal oxide on a GaAs semiconductor substrate or a top surface epitaxial layer made of Al X Ga 1-X As (where 0 ≦ X ≦ 0.5), wherein an oxygen-containing atmosphere is used. Heat-treating the substrate or the outermost surface epitaxial layer at a temperature of 450 ° C. or more, and, after the heat-treating step, forming a metal oxide on the substrate or the uppermost surface epitaxial layer. Is provided.
[0007]
Further, the present invention provides a method of forming a thin film of a low-resistance metal oxide formed by the above method on a GaAs semiconductor substrate or an outermost surface epitaxial layer of Al X Ga 1-X As (0 ≦ X ≦ 0.5). An object of the present invention is to provide a semiconductor light emitting device and an epitaxial wafer for a semiconductor light emitting device provided on a layer.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
According to the present invention, the substrate or the outermost surface epitaxial layer is formed at a temperature of 450 ° C. or more (substrate temperature) in an atmosphere containing oxygen, or the substrate or the uppermost surface epitaxial layer is subjected to a heat treatment prior to the film formation. It has features.
It has been confirmed that an oxide is formed on the surface of the Al X Ga 1-X As layer at the film forming temperature or the heat treatment temperature before film forming of the metal oxide according to the present invention (based on SIMS analysis), the presence of the oxide, in the Al X Ga 1-X as layer, considered metal oxide film of high quality (low resistance) are formed. Thus, the essence of the present invention, at least, in the oxide on the surface of the Al X Ga 1-X As layer is formed. Incidentally, a case where a metal oxide film (ITO) is immediately formed on an Al X Ga 1-X As layer which has been subjected to a heat treatment at 450 ° C. or more, and a case where a metal oxide film is formed after leaving it for several tens of days. By comparison, it was confirmed that the specific resistance characteristics of the metal oxide film did not change.
[0009]
In the present invention, applicable metal oxides are SnO 2 -based, ZnO-based, and In 2 O 3 -based. In particular, ITO is preferable.
In the present invention, a vapor deposition method, a sputtering method, a coating method, or the like can be applied as a metal oxide film formation method in addition to a spray method.
[0010]
On the other hand, according to the present invention, in a semiconductor light emitting device having a thin film made of a metal oxide on a GaAs semiconductor substrate or an outermost surface epitaxial layer made of Al X Ga 1-X As (where 0 ≦ X ≦ 0.5), The metal oxide is formed by the above method, and a semiconductor light emitting device having a specific resistance of 3 × 10 −4 Ω · cm or less can be manufactured.
Further, according to the present invention, an epitaxial layer for a semiconductor light emitting device having a thin film made of a metal oxide on a GaAs semiconductor substrate or an outermost surface epitaxial layer made of Al X Ga 1-X As (where 0 ≦ X ≦ 0.5) In the wafer, the metal oxide is formed by the above method, and an epitaxial wafer for a semiconductor light emitting device having a specific resistance of 3 × 10 −4 Ω · cm or less can be manufactured.
[0011]
【Example】
Hereinafter, embodiments 1 and 2 according to the present invention will be described with reference to the drawings. Comparative Examples 1 and 2 were performed to compare the tendency of the specific resistance to decrease with the growth temperature of the ITO film and the heat treatment temperature before the ITO film formation, with Examples 1 and 2, respectively.
Example 1
On an n-type GaAs substrate, p-type GaAs having a thickness of 300 nm and a carrier concentration of 2 × 10 18 cm −3 or more, p-type Al 0.1 Ga 0.9 As, and p-type Al 0.2 Ga 0.8 Each layer of As, p-type Al 0.3 Ga 0.7 As, p-type Al 0.4 Ga 0.6 As, p-type Al 0.5 Ga 0.5 As (p-type is formed by Zn doping) Was grown by MOVPE to produce six types of epitaxial wafers.
Next, an ITO film was formed to a thickness of 300 nm on the above-mentioned six types of epitaxial wafers and a p-type GaAs substrate (prepared separately) by a spray method, thereby preparing a total of seven types of samples. Here, the deposition temperature of the ITO film was 450 ° C., 500 ° C., 600 ° C., and 800 ° C. (4 points) for each sample.
As shown in Table 1, when the specific resistances of the ITO films of the above seven types of samples were evaluated by a four-point probe method, all the samples (with an ITO film formation temperature of 450 ° C. or higher) had 3 × 10 −4 Ω · cm or less.
[Table 1]
Comparative Example 1
Seven types of samples were produced in the same manner as in Example 1. However, the film formation temperature of the ITO film was 350 ° C. and 400 ° C. (two points) for each sample.
As shown in Table 1, when the specific resistances of the ITO films of the above seven types of samples were evaluated by a four-probe method, it was 4.5 × 10 −2 for all the samples (with an ITO film formation temperature of 400 ° C. or lower). A value of Ω · cm or more was obtained.
Therefore, when the ITO film is formed at a temperature of 450 ° C. or higher (Example 1), the specific resistance is about two orders of magnitude lower than that at a temperature of 400 ° C. or lower (Comparative Example 1). Is obtained. That is, as shown in FIG. 1, it was found that the tendency of the specific resistance to decrease with the film formation temperature of the ITO film was remarkable at the film formation temperature of 450 ° C. or higher.
[0013]
Example 2
On an n-type GaAs substrate, p-type GaAs having a thickness of 300 nm and a carrier concentration of 2 × 10 18 cm −3 or more, p-type Al 0.1 Ga 0.9 As, and p-type Al 0.2 Ga 0.8 Each layer of As, p-type Al 0.3 Ga 0.7 As, p-type Al 0.4 Ga 0.6 As, p-type Al 0.5 Ga 0.5 As (p-type is formed by Zn doping) Was grown by MOVPE to produce six types of epitaxial wafers.
Next, the six types of epitaxial wafers and the p-type GaAs substrate (prepared separately) were subjected to heat treatment at 450 ° C., 500 ° C., 600 ° C., and 800 ° C. (four points) (heat treatment before ITO film formation). . Thereafter, an ITO film having a thickness of 300 nm was formed on the above-described six types of epitaxial wafers and p-type GaAs substrates by a spray method, thereby preparing a total of seven types of samples. Here, the deposition temperature of the ITO film was set to 350 ° C. for all the samples.
As shown in Table 2, when the specific resistances of the ITO films of the above seven types of samples were evaluated by a four-probe method, 3 × 10 −4 was obtained for all the samples (the heat treatment temperature before the ITO film formation was 450 ° C. or higher). A value of Ω · cm or less was obtained.
[Table 2]
Comparative Example 2
Seven types of samples were produced in the same manner as in Example 2. However, the heat treatment temperature before the ITO film formation was 350 ° C. and 400 ° C. (two points) for each sample.
As shown in Table 2, when the specific resistances of the ITO films of the above seven types of samples were evaluated by a four-point probe method, all the samples (with an ITO film formation temperature of 400 ° C. or lower) were 4.5 × 10 −2. A value of Ω · cm or more was obtained.
Therefore, when the heat treatment is performed before the ITO film formation, if the heat treatment temperature is set to 450 ° C. or higher (Example 2), the specific resistance is lower by about two orders of magnitude as compared with the case where the heat treatment temperature is set to 400 ° C. or lower (Comparative Example 2). can get. That is, as shown in FIG. 2, it was found that the tendency of the specific resistance to decrease due to the heat treatment temperature before the ITO film formation was significant at a heat treatment temperature of 450 ° C. or higher.
[0015]
In the first and second embodiments, the ITO film is formed by the spray method. However, even when the ITO film is formed by a vapor deposition method, a sputtering method, a coating method, or the like, the ITO film forming temperature of the present invention and the heat treatment before the ITO film formation are performed. At a temperature, a low-resistance ITO film can be formed as in the first and second embodiments. Because, in the ITO film-forming temperature or ITO deposition before the heat treatment temperature according to the present invention, oxide is formed (whether process) Al X Ga 1-X As layer surface, whereby the Al X Ga This is because a high-quality ITO film is formed on the 1-X As layer.
[0016]
【The invention's effect】
According to the method for forming a metal oxide of the present invention, a metal oxide is formed on a GaAs semiconductor substrate or an outermost surface epitaxial layer made of Al x Ga 1-x As (where 0 ≦ X ≦ 0.5). The method includes a step of forming a metal oxide film at a temperature of 450 ° C. or more in an atmosphere containing oxygen, so that the metal oxide film is formed on the Al X Ga 1-X As-based semiconductor layer (0 ≦ X ≦ 0.5). A resistive metal oxide film can be formed.
[0017]
Further, according to the metal oxide film forming method of the present invention, the metal oxide is deposited on the GaAs semiconductor substrate or the outermost surface epitaxial layer composed of Al x Ga 1-x As (where 0 ≦ X ≦ 0.5). In the method for forming a film, a step of heat-treating the substrate or the uppermost surface epitaxial layer at a temperature of 450 ° C. or more in an atmosphere containing oxygen, and forming a metal oxide on the substrate or the uppermost surface epitaxial layer after the heat treatment step By including the step, a low-resistance metal oxide film can be formed over the Al X Ga 1-X As-based semiconductor layer (0 ≦ X ≦ 0.5).
[0018]
Further, according to the semiconductor light emitting device of the present invention, a thin film made of a metal oxide is provided on a GaAs semiconductor substrate or an outermost surface epitaxial layer made of Al x Ga 1-x As (where 0 ≦ X ≦ 0.5). In the semiconductor light emitting device, the metal oxide is formed by the above method, and a semiconductor light emitting device having a specific resistance of 3 × 10 −4 Ω · cm or less can be manufactured.
Further, according to the epitaxial wafer for a semiconductor light emitting device of the present invention, a metal oxide is formed on the GaAs semiconductor substrate or the outermost surface epitaxial layer made of Al x Ga 1-x As (where 0 ≦ X ≦ 0.5). In a semiconductor light emitting device epitaxial wafer having a thin film, the metal oxide is formed by the above method, and a semiconductor light emitting device epitaxial wafer having a specific resistance of 3 × 10 −4 Ω · cm or less can be manufactured. .
[Brief description of the drawings]
FIG. 1 is a graph showing a relationship between a film forming temperature of an ITO film by a spray method and a specific resistance of the ITO film in a first embodiment of a metal oxide film forming method of the present invention and a comparative example thereof. .
FIG. 2 is a graph showing the relationship between the heat treatment temperature before ITO film formation and the specific resistance of the ITO film in the second example of the metal oxide film forming method of the present invention and the comparative example.
Claims (11)
酸素を含む雰囲気において４５０℃以上の温度で前記金属酸化物を成膜する工程を含む金属酸化物の成膜方法。In a method of forming a metal oxide on a GaAs semiconductor substrate or an outermost surface epitaxial layer made of Al X Ga 1-X As (where 0 ≦ X ≦ 0.5),
A method for forming a metal oxide, comprising the step of forming the metal oxide at a temperature of 450 ° C. or higher in an atmosphere containing oxygen.
酸素を含む雰囲気において４５０℃以上の温度で前記基板または最表面エピタキシャル層を熱処理する工程と、
該熱処理工程の後、前記基板または最表面エピタキシャル層上に前記金属酸化物を成膜する工程を含む金属酸化物の成膜方法。In a method of forming a metal oxide on a GaAs semiconductor substrate or an outermost surface epitaxial layer made of Al X Ga 1-X As (where 0 ≦ X ≦ 0.5),
Heat-treating the substrate or the topmost epitaxial layer at a temperature of 450 ° C. or more in an atmosphere containing oxygen;
A method for forming a metal oxide, comprising the step of forming the metal oxide on the substrate or the outermost surface epitaxial layer after the heat treatment step.
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