JP3620105B2 - Method for producing gallium nitride crystal - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は窒化ガリウム結晶の製造方法に係り、特にｐ型不純物を活性化するための熱処理方法を改善したものに関する。
【０００２】
【従来の技術】
低消費電力で長寿命な発光素子である発光ダイオードは、インジケータランプ、警告表示、公告表示などに広く用いられている。現在、実用化されている発光ダイオードの発光色は、赤色、橙色、黄色、緑色である。赤・緑・青の光の三原色のうち、青色だけが実用化されていない。青色発光ダイオードが実用化できればフルカラー表示が可能となり、情報表示を多彩に行なうことができる。
【０００３】
青色を発光させるためには、広い禁制帯幅をもつ半導体結晶が必要であり、そのため、窒化ガリウム（ＧａＮ）、ＳｉＣ、ＺｎＳｅ等の広い禁制帯幅の半導体結晶について開発が進められている。なかでも、ＧａＮは直接遷移型であるため、高い発光効率が期待されている。
【０００４】
発光ダイオード用ＧａＮエピタキシャルウェハの構造は、基板にサファイアを、その上に窒化アルミニウム（ＡｌＮ）やＧａＮのバッファ層を設け、さらにその上に、ｎ型ＧａＮ、ｐ型ＧａＮのエピタキシャル層を成長させた構造となっている。
【０００５】
これらのエピタキシャル層の成長には、水素ガスをキャリアガスとして、有機金属ガスであるトリメチルガリウム（ＴＭＧ）、トリメチルアルミニウム（ＴＭＡ）、及びアンモニア（ＮＨ３ ）ガスを用いて行なう。ドープ不純物には、ｎ型としてはシラン（ＳｉＨ４ ）をｐ型にはビスシクロペンタディエニルマグネシウム（Ｃｐ２ Ｍｇ）を用いる。成長過程、冷却過程とも水素雰囲気で行なわれる。
【０００６】
【発明が解決しようとする課題】
上述したＧａＮの成長方法において、ｐ型不純物を十分にドープしてＧａＮ結晶の成長を行なっても、成長後の結晶には、ｐ型キャリアは非常に少なく、結晶は高抵抗を示す。これはｐ型不純物の活性化が低いためである。
【０００７】
発光ダイオードが高輝度で発光するためには電子と正孔が必要であり、正孔はｐ型不純物が活性化してできる。ｐ型不純物の活性化が低いと輝度が低くなってしまう。
【０００８】
ｐ型不純物を活性化させるために、従来は、成長過程、冷却過程を経て結晶を成長した後、成長装置から結晶を取り出し、電子線照射や窒素雰囲気でのアニール処理工程が行なわれている。すなわち、成長プロセス以外にｐ型不純物を活性化させるためだけの別工程を必要としていた。なお、ここで、成長プロセスとは、成膜過程後の冷却過程までも含めた工程をいう。
【０００９】
本発明の目的は、前記した従来技術の欠点を解消し、成長プロセスだけでｐ型不純物の活性化を大幅に高めることができる新規なＧａＮ結晶の製造方法を提供することにある。
【００１０】
【課題を解決するための手段】
本発明のＧａＮ結晶の製造方法は、ＧａＮ結晶の原料となる有機金属及びアンモニアを用いた気相成長法によってｐｎ接合をもつＧａＮ結晶を製造する方法において、ｐ型ＧａＮ結晶の成膜を水素ガス雰囲気において行なった後の冷却過程の内、１０００℃以上の温度域における雰囲気として水素ガスとアンモニアガスを使用し、１０００℃以下にて前記水素ガスとアンモニアガスを窒素ガスのみに切り替えて冷却するようにしたものである。
【００１１】
この場合、窒素ガスのみとせずに、窒素ガスと水素ガスからなる混合ガスとしてもよく、そのとき窒素ガスの割合は７０％〜１００％未満である。
【００１２】
ＧａＮ結晶の成長プロセスは、前処理過程、成膜過程、冷却過程の３つの過程を備える。前処理過程は表面処理などを行ない、成膜過程はバッファ層やＧａＮ層をエピタキシャル成長させる。冷却過程は、ＧａＮ層の成膜に必要な高温の成長温度から降温するためにエピタキシャルウェハを冷却する。
【００１３】
ＧａＮ結晶の成長を行なうためにサファイア基板を用いる。また、本発明に用いる有機金属は、ＴＭＧ、ＴＭＡなどの有機金属ガスである。水素ガス雰囲気下でＮＨ３ とＴＭＡまたはＴＭＧによりサファイア基板上にＡｌＮまたはＧａＮのバッファ層を設け、その上にＮＨ３ とＴＭＧによりＧａＮの成長を行なう。
【００１４】
ｐｎ接合を形成するためのドープ不純物には、ｎ型としてはＳｉＨ４ を、ｐ型にはＣｐ２ Ｍｇを用いる。成膜過程は水素雰囲気で行なわれるが、冷却過程は窒素ガスのみか、または窒素と水素との混合ガス雰囲気とする。これにより、ｐ型不純物の活性化が大幅に高められる。
【００１５】
エピタキシャル成長は、有機金属気相成長法（ＭＯＶＰＥ法）で行なうことができる。その場合、縦型炉を使用することもできるが、横型炉を使用することが好ましい。
【００１６】
ＧａＮ結晶の成長を水素キャリアにおいて行なった後の冷却過程において、雰囲気として窒素ガスを使用するのは、結晶の温度が１０００℃以下の温度になってからとする。１０００℃以上の状態では、水素ガスとアンモニアガスを用いる。これは、１０００℃以上の状態では、雰囲気が窒素ガスだけでは、ＧａＮ結晶からの窒素解離が起きるからである。
【００１７】
成膜後の結晶冷却過程において、雰囲気ガスとして水素ガスではなく、窒素ガスまたは水素との混合ガス（窒素雰囲気等）を使用すると、従来、ｐ型不純物の活性化のために、成長プロセスとは別工程で行なっていた窒素雰囲気下でのアニールと同じ条件が形成される。すなわち、ＧａＮ結晶を窒素雰囲気等で冷却熱処理すると、解離されないまま結晶中に取り込まれてｐ型不純物と結びつき、ｐ型不純物の活性化を抑え込んでいた結晶原料原子の結びつきが解かれて、、結晶中にドープしたｐ型不純物原子の活性化あるいはｐ型不純物原子への分解が促進される。その結果、ｐ型不純物の活性化が向上する。
【００１８】
このように本発明によれば、ＧａＮ結晶の成長プロセス中にｐ型活性化のためのアニール処理を組み込んでしまうので、結晶製造工程の簡素化が図れる。
【００１９】
【発明の実施の形態】
以下、本発明のＧａＮ結晶の製造方法の実施例を説明するが、ここでは次の３つの特性比較に基づいて説明していく。
【００２０】
（１） ｐ型不純物をドープしたＧａＮのエピタキシャル成長を行ない、従来技術で処理した従来例の結晶と、本発明方法で処理した実施例の結晶との特性比較をウェハレベルで行なった。また、水素ガスに代えて窒素ガスをキャリアガスとして成長させた比較例の結晶についての特性も併せて評価した。
【００２１】
（２） ｐｎ接合を有するＧａＮ結晶のエピタキシャル成長を行ない、従来技術で処理した従来例の結晶と、本発明方法で処理した実施例の結晶とのそれぞれから発光ダイオードを作製し、ダイオードレベルの特性比較を行なった。
【００２２】
（３） 冷却過程の雰囲気ガスを、窒素のみとせずに、窒素と水素の混合ガスとし、その割合を変えて処理した結晶の特性比較をウェハレベルで行なった。
【００２３】
（ウェハレベルの特性比較）
エピタキシャル成長は、有機金属気相成長法（ＭＯＶＰＥ法）で行なった。横型炉を使用し、成長圧力は１．３×１０４ Ｐａで行なった。基板には表面を鏡面仕上げしたサファイア基板を用いた。
【００２４】
図１に示すように、冷却過程の前までは従来例、本実施例とも条件は同じである。成長は、まず、流量１０ｌ／ｍｉｎの水素雰囲気下で１１２５℃でサファイア基板を２０分間保持し、表面処理を行なった（前処理過程）。
【００２５】
次に、５５０℃に降温させた後、２５μｍｏｌ／ｍｉｎのＴＭＡ、５ｌ／ｍｉｎのＮＨ３ 、および５ｌ／ｍｉｎの水素を３分間流し、ＡｌＮのバッファ層を成長させた（バッファ層成膜過程）。
【００２６】
そして、次に、１０００℃に昇温し、８０μｍｏｌ／ｍｉｎのＴＭＧ、５ｌ／ｍｉｎのＮＨ３ 、２ｎｍｍｏｌ／ｍｉｎのＣｐ２ Ｍｇ、および５ｌ／ｍｉｎの水素を２０分間流し、ｐ型ＧａＮ層を成長させた。ＧａＮ層は約１μｍ成長した（ＧａＮ層成膜過程）。
【００２７】
ここで、成膜後の冷却過程では、水素雰囲気のままで冷却する従来技術による従来例の方法と、窒素雰囲気で冷却する本発明による実施例の方法とで、それぞれ別個に処理し、両者の特性比較を行なった。両者の成長プログラムは図１に示す。
【００２８】
まず、従来例の方法で冷却した。この冷却過程では、１０００℃での成長終了後、直ちに雰囲気ガスを１０ｌ／ｍｉｎの水素だけにしてから冷却を開始し、１００℃まで冷却した。冷却速度は１０００℃から６００℃までは０．２５℃／秒で、６００℃から１００℃までは０．７５℃／秒で行なった。
【００２９】
次に、本実施例の方法で冷却した。この冷却過程では、１０００℃での成長終了後、直ちに雰囲気ガスを１０ｌ／ｍｉｎの窒素だけにしてから冷却を開始し、１００℃まで冷却した。冷却速度は、従来例と同じく、１０００℃から６００℃までは０．２５℃／秒で、６００℃から１００℃までは０．７５℃／秒で行なった。
【００３０】
この２つの結晶の比抵抗をｖａｎ ｄｅｒ Ｐａｕｗ法により測定した。その結果を図２に示す。従来例による結晶では１０６ Ω・ｃｍ以上の高比抵抗を示し、成長プロセスのみではｐ型不純物の活性化が非常に低いことがわかった。一方、本実施例による結晶では成長プロセスのみでも３０Ω・ｃｍの低比抵抗を示し、ｐ型不純物の活性化が高いことがわかった。
【００３１】
次に、成膜および冷却をすべて、窒素ガスをキャリアガスとして成長させた比較例により成長させたところ、結晶表面はくもり、結晶は異常成長していた。したがって、窒素ガスのみでの成長は適さないことがわかった。
【００３２】
（発光ダイオードレベルの特性比較）
次に、図３に示した青色発光ダイオードチップを製作し、発光出力を比較した。結晶成長は上記したＭＯＶＰＥ法を用いて同様に行なった。すなわち、サファイア基板１上に、ＡｌＮバッファ層２を成長した後、ｎ型不純物をドープして層厚２．５μｍ、キャリア濃度１×１０１８ｃｍ−３のｎ型ＧａＮ層３を成長させ、その上に前述したのと同条件のＣｐ２ Ｍｇをドープしたｐ型ＧａＮ層４を１μｍ成膜させた。
【００３３】
ｎ型ＧａＮ層３はドープ不純物としてＳｉＨ４ を用いた。１ｐｐｍ濃度で１０ｃｃ／ｍｉｎ流した。このときのＴＭＧ、ＮＨ３ 、水素の条件は、Ｃｐ２ Ｍｇをドープしたｐ型ＧａＮ層４の場合と同じである。
【００３４】
ここで、成膜後の冷却では、水素雰囲気のままで冷却する従来例の方法と、窒素雰囲気で冷却する本発明による実施例の方法とで、それぞれ別個に処理してＧａＮエピタキシャルウェハを得た。
【００３５】
両ウェハに所定のプロセス（エッチング等）を施し、電極５を取り付けて図３の発光ダイオードチップを製作した。
【００３６】
製作した各チップに電流を２０ｍＡ流し、発光出力を測定した。従来例の方法で冷却したウェハから製作した発光ダイオードチップの発光出力は２５μＷであったが、本実施例の方法で冷却したウェハから製作した発光ダイオードチップの発光出力は２００μＷと８倍高い値であった。本実施例で作製した結晶の方が高い発光出力が得られることが確かめられた。
【００３７】
（窒素と水素の割合を変えたときのウェハレベルの特性比較）
上記の実施例においては、冷却過程の雰囲気ガスが窒素のみの場合で、ｐ型不純物の活性化が高くなることが確かめられた。次に冷却過程の雰囲気ガスが窒素と水素の混合ガスの場合について調べてみよう。
【００３８】
ｐ型不純物をドープしたＧａＮ層のエピタキシャル成長を行ない、冷却過程を窒素と水素の混合ガスで行なった。そして、結晶の特性評価をした。成長方法は、ウェハレベルでの実施例と同様である。冷却過程の冷却速度も同様とした。冷却過程の窒素と水素の混合ガスの流量は全体で１０ｌ／ｍｉｎとした。そして、窒素と水素の割合を変えて冷却し、結晶の比抵抗を調べた。図４にその結果を示す。
【００３９】
窒素の割合が７０％から１００％の場合、比抵抗が３０Ω・ｃｍから６０Ω・ｃｍとなったが、窒素の割合が７０％より低い場合には１０６ Ω・ｃｍ以上の高抵抗を示した。これよりｐ型不純物を活性化させる上で、成長後の冷却過程で、雰囲気ガスとして窒素の割合が７０％から１００％の窒素と水素の混合ガスで効果があることがわかった。
【００４０】
【発明の効果】
（１） 請求項１に記載の発明によれば、冷却過程を窒素ガス雰囲気で行なうようにしたので、１回の成長プロセスでＧａＮ結晶にドープしたｐ型不純物の活性化を高めることができ、成長プロセスとは別に活性化の工程を設ける必要がない。その結果、工程の簡素化が図れてＧａＮ結晶を安価に製造することができる。
【００４１】
（２） 請求項２に記載の発明によれば、特定割合の窒素ガスと水素ガスの混合ガスによっても（１） と同様の効果を発揮できる。
【図面の簡単な説明】
【図１】本発明の実施例と従来例の冷却過程を含む成長プロセスの温度、ガス流量のプログラム図。
【図２】本実施例と従来例の方法から得た結晶の比抵抗を示す比較図。
【図３】本実施例と従来例の発光ダイオードの発光出力特性を比較するために製作した発光ダイオードチップの断面図。
【図４】本発明の他の実施例での冷却過程における混合ガスの窒素の割合と結晶の比抵抗の関係を示す図。
【符号の説明】
１ サファイア基板
２ ＡｌＮバッファ層
３ ｎ型ＧａＮ層
４ ｐ型ＧａＮ層
５ 電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a gallium nitride crystal, and more particularly to an improved heat treatment method for activating p-type impurities.
[0002]
[Prior art]
Light-emitting diodes, which are light-emitting elements with low power consumption and long life, are widely used for indicator lamps, warning displays, announcement displays, and the like. Currently, light emitting diodes in practical use are red, orange, yellow, and green. Of the three primary colors of red, green and blue light, only blue has not been put into practical use. If a blue light-emitting diode can be put into practical use, full-color display becomes possible, and information display can be performed in various ways.
[0003]
In order to emit blue light, a semiconductor crystal having a wide forbidden band width is required. Therefore, development of a semiconductor crystal having a wide forbidden band width such as gallium nitride (GaN), SiC, ZnSe or the like is underway. Especially, since GaN is a direct transition type, high luminous efficiency is expected.
[0004]
The structure of the GaN epitaxial wafer for light-emitting diodes was such that sapphire was provided on the substrate, an aluminum nitride (AlN) or GaN buffer layer was provided thereon, and an n-type GaN or p-type GaN epitaxial layer was further grown thereon. It has a structure.
[0005]
These epitaxial layers are grown using hydrogen gas as a carrier gas and using organometallic gases such as trimethyl gallium (TMG), trimethyl aluminum (TMA), and ammonia (NH 3 ) gas. For the doped impurities, silane (SiH 4 ) is used as the n-type, and biscyclopentadienyl magnesium (Cp 2 Mg) is used as the p-type. Both the growth process and the cooling process are performed in a hydrogen atmosphere.
[0006]
[Problems to be solved by the invention]
In the GaN growth method described above, even if p-type impurities are sufficiently doped to grow a GaN crystal, the grown crystal has very few p-type carriers and the crystal exhibits high resistance. This is because the activation of p-type impurities is low.
[0007]
In order for the light emitting diode to emit light with high brightness, electrons and holes are required, and holes are formed by activating p-type impurities. If the activation of the p-type impurity is low, the luminance is lowered.
[0008]
In order to activate the p-type impurity, conventionally, after a crystal is grown through a growth process and a cooling process, the crystal is taken out from the growth apparatus and subjected to an electron beam irradiation or an annealing process in a nitrogen atmosphere. That is, a separate process only for activating the p-type impurity is required in addition to the growth process. Here, the growth process refers to a process including a cooling process after the film formation process.
[0009]
An object of the present invention is to provide a novel method for producing a GaN crystal that can eliminate the above-mentioned drawbacks of the prior art and can significantly increase the activation of p-type impurities only by a growth process.
[0010]
[Means for Solving the Problems]
Method for producing a GaN crystal of the present invention, Oite to a method of manufacturing the GaN crystal having a pn junction by vapor deposition using an organometallic and ammonia as a raw material for the GaN crystal, the formation of the p-type GaN crystal In the cooling process after performing in a hydrogen gas atmosphere, hydrogen gas and ammonia gas are used as an atmosphere in a temperature range of 1000 ° C. or higher , and cooling is performed by switching the hydrogen gas and ammonia gas to nitrogen gas only at 1000 ° C. or lower. It is what you do.
[0011]
In this case, not only nitrogen gas but also a mixed gas composed of nitrogen gas and hydrogen gas may be used, and the ratio of nitrogen gas is 70% to less than 100%.
[0012]
The GaN crystal growth process includes three processes: a pretreatment process, a film formation process, and a cooling process. In the pretreatment process, surface treatment is performed, and in the film formation process, a buffer layer and a GaN layer are epitaxially grown. In the cooling process, the epitaxial wafer is cooled in order to lower the temperature from a high growth temperature necessary for forming the GaN layer.
[0013]
A sapphire substrate is used to perform GaN crystal growth. The organic metal used in the present invention is an organic metal gas such as TMG or TMA. A buffer layer of AlN or GaN is provided on the sapphire substrate by NH 3 and TMA or TMG in a hydrogen gas atmosphere, and GaN is grown thereon by NH 3 and TMG.
[0014]
SiH 4 is used for the n-type and Cp 2 Mg is used for the p-type as the doped impurity for forming the pn junction. The film forming process is performed in a hydrogen atmosphere, but the cooling process is performed using only nitrogen gas or a mixed gas atmosphere of nitrogen and hydrogen. Thereby, the activation of the p-type impurity is greatly enhanced.
[0015]
Epitaxial growth can be performed by metal organic vapor phase epitaxy (MOVPE method). In that case, although a vertical furnace can be used, it is preferable to use a horizontal furnace.
[0016]
In the cooling process after the growth of the GaN crystal in the hydrogen carrier, the nitrogen gas is used as the atmosphere after the temperature of the crystal reaches 1000 ° C. or less. In a state of 1000 ° C. or higher, hydrogen gas and ammonia gas are used. This is because in a state of 1000 ° C. or higher, nitrogen dissociation from the GaN crystal occurs when the atmosphere is only nitrogen gas.
[0017]
In the crystal cooling process after film formation, when a nitrogen gas or a mixed gas with hydrogen (such as a nitrogen atmosphere) is used as an atmosphere gas instead of hydrogen gas, conventionally, a growth process is used to activate p-type impurities. The same conditions are formed as in the annealing in a nitrogen atmosphere that has been performed in a separate process. That is, when a GaN crystal is cooled and heat-treated in a nitrogen atmosphere or the like, it is taken into the crystal without being dissociated and is associated with the p-type impurity, and the crystal raw material atoms that have suppressed the activation of the p-type impurity are unbound, and the crystal Activation of p-type impurity atoms doped therein or decomposition into p-type impurity atoms is promoted. As a result, the activation of the p-type impurity is improved.
[0018]
As described above, according to the present invention, the annealing process for p-type activation is incorporated into the growth process of the GaN crystal, so that the crystal manufacturing process can be simplified.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, examples of the method for producing a GaN crystal of the present invention will be described. Here, description will be made based on the following three characteristic comparisons.
[0020]
(1) Epitaxial growth of GaN doped with a p-type impurity was performed, and the characteristics of the crystal of the conventional example processed by the conventional technique and the crystal of the example processed by the method of the present invention were compared at the wafer level. In addition, the characteristics of the comparative crystal grown using nitrogen gas instead of hydrogen gas as a carrier gas were also evaluated.
[0021]
(2) Epitaxial growth of a GaN crystal having a pn junction, a light emitting diode is fabricated from each of the conventional crystal processed by the conventional technique and the crystal of the exemplary embodiment processed by the method of the present invention, and the diode level characteristic comparison Was done.
[0022]
(3) The atmosphere gas in the cooling process was not limited to nitrogen, but a mixed gas of nitrogen and hydrogen, and the characteristics of the processed crystals were changed at the wafer level at a different ratio.
[0023]
(Wafer level characteristics comparison)
Epitaxial growth was performed by metal organic vapor phase epitaxy (MOVPE method). A horizontal furnace was used and the growth pressure was 1.3 × 10 4 Pa. A sapphire substrate having a mirror-finished surface was used as the substrate.
[0024]
As shown in FIG. 1, the conditions are the same for the conventional example and the present example until the cooling process. In the growth, first, a sapphire substrate was held at 1125 ° C. for 20 minutes in a hydrogen atmosphere at a flow rate of 10 l / min, and surface treatment was performed (pretreatment process).
[0025]
Next, after the temperature was lowered to 550 ° C., 25 μmol / min TMA, 5 l / min NH 3 , and 5 l / min hydrogen were allowed to flow for 3 minutes to grow an AlN buffer layer (buffer layer deposition process) .
[0026]
Next, the temperature is raised to 1000 ° C., and 80 μmol / min TMG, 5 l / min NH 3 , 2 nmol / min Cp 2 Mg, and 5 l / min hydrogen are allowed to flow for 20 minutes to grow a p-type GaN layer. I let you. The GaN layer grew about 1 μm (GaN layer formation process).
[0027]
Here, in the cooling process after the film formation, the conventional method according to the prior art that cools in a hydrogen atmosphere and the method according to the embodiment according to the present invention that cools in a nitrogen atmosphere are processed separately. A characteristic comparison was made. Both growth programs are shown in FIG.
[0028]
First, it was cooled by the conventional method. In this cooling process, after the growth at 1000 ° C. was completed, the atmosphere gas was immediately changed to only 10 l / min of hydrogen, and then cooling was started to cool to 100 ° C. The cooling rate was 0.25 ° C./second from 1000 ° C. to 600 ° C., and 0.75 ° C./second from 600 ° C. to 100 ° C.
[0029]
Next, it was cooled by the method of this example. In this cooling process, immediately after the growth at 1000 ° C., the atmosphere gas was changed to nitrogen at 10 l / min immediately, and then cooling was started to cool to 100 ° C. The cooling rate was 0.25 ° C./second from 1000 ° C. to 600 ° C. and 0.75 ° C./second from 600 ° C. to 100 ° C. as in the conventional example.
[0030]
The specific resistance of these two crystals was measured by the van der Pauw method. The result is shown in FIG. The crystal according to the conventional example showed a high specific resistance of 10 6 Ω · cm or more, and it was found that the activation of the p-type impurity was very low only by the growth process. On the other hand, it was found that the crystal according to this example showed a low specific resistance of 30 Ω · cm only by the growth process, and the activation of the p-type impurity was high.
[0031]
Next, when film formation and cooling were all performed by a comparative example in which nitrogen gas was used as a carrier gas, the crystal surface was cloudy and the crystal was abnormally grown. Therefore, it was found that growth using only nitrogen gas is not suitable.
[0032]
(Characteristic comparison of light emitting diode level)
Next, the blue light emitting diode chip shown in FIG. 3 was manufactured and the light output was compared. Crystal growth was performed in the same manner using the MOVPE method described above. That is, after growing an
[0033]
The n-type GaN layer 3 uses SiH 4 as a doping impurity. 10 cc / min was flowed at a concentration of 1 ppm. The conditions of TMG, NH 3 and hydrogen at this time are the same as in the case of the p-type GaN layer 4 doped with Cp 2 Mg.
[0034]
Here, in the cooling after the film formation, a GaN epitaxial wafer was obtained by separately treating the conventional method of cooling in a hydrogen atmosphere and the method of the embodiment according to the present invention of cooling in a nitrogen atmosphere. .
[0035]
Both wafers were subjected to a predetermined process (etching or the like), and the electrode 5 was attached to produce the light emitting diode chip of FIG.
[0036]
A current of 20 mA was passed through each manufactured chip, and the light emission output was measured. The light emission output of the light emitting diode chip manufactured from the wafer cooled by the method of the conventional example was 25 μW, but the light emission output of the light emitting diode chip manufactured from the wafer cooled by the method of the present embodiment was 200 μW, which is eight times higher. there were. It was confirmed that the crystal produced in this example can obtain higher light output.
[0037]
(Comparison of wafer level characteristics when the ratio of nitrogen and hydrogen is changed)
In the above embodiment, it was confirmed that the activation of the p-type impurity is high when the atmospheric gas in the cooling process is only nitrogen. Next, let's examine the case where the atmosphere gas in the cooling process is a mixed gas of nitrogen and hydrogen.
[0038]
A GaN layer doped with a p-type impurity was epitaxially grown, and the cooling process was performed with a mixed gas of nitrogen and hydrogen. And the characteristic of the crystal was evaluated. The growth method is the same as that of the embodiment at the wafer level. The cooling rate in the cooling process was also the same. The total flow rate of the mixed gas of nitrogen and hydrogen during the cooling process was 10 l / min. And it cooled by changing the ratio of nitrogen and hydrogen, and examined the specific resistance of the crystal. FIG. 4 shows the result.
[0039]
When the ratio of nitrogen was 70% to 100%, the specific resistance was changed from 30 Ω · cm to 60 Ω · cm, but when the ratio of nitrogen was lower than 70%, a high resistance of 10 6 Ω · cm or more was exhibited. . From this, it was found that, in activating the p-type impurity, a mixed gas of nitrogen and hydrogen having a nitrogen ratio of 70% to 100% as an atmospheric gas is effective in the cooling process after growth.
[0040]
【The invention's effect】
(1) According to the invention described in claim 1, since the cooling process is performed in a nitrogen gas atmosphere, the activation of the p-type impurity doped in the GaN crystal in one growth process can be enhanced. There is no need to provide an activation step separately from the growth process. As a result, the process can be simplified and the GaN crystal can be manufactured at a low cost.
[0041]
(2) According to the invention described in
[Brief description of the drawings]
FIG. 1 is a program diagram of temperature and gas flow rate of a growth process including a cooling process according to an embodiment of the present invention and a conventional example.
FIG. 2 is a comparative diagram showing the specific resistance of crystals obtained by the methods of this example and the conventional example.
FIG. 3 is a cross-sectional view of a light-emitting diode chip manufactured for comparing the light-emitting output characteristics of the light-emitting diodes of this example and the conventional example.
FIG. 4 is a graph showing the relationship between the ratio of nitrogen in a mixed gas and the specific resistance of crystals in the cooling process in another embodiment of the present invention.
[Explanation of symbols]
1
Claims (2)
Priority Applications (1)
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| JP19149295A JP3620105B2 (en) | 1995-07-27 | 1995-07-27 | Method for producing gallium nitride crystal |
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| Application Number | Priority Date | Filing Date | Title |
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| JP19149295A JP3620105B2 (en) | 1995-07-27 | 1995-07-27 | Method for producing gallium nitride crystal |
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| JPH0940490A JPH0940490A (en) | 1997-02-10 |
| JP3620105B2 true JP3620105B2 (en) | 2005-02-16 |
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| JP19149295A Expired - Fee Related JP3620105B2 (en) | 1995-07-27 | 1995-07-27 | Method for producing gallium nitride crystal |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH10294490A (en) * | 1997-04-17 | 1998-11-04 | Toshiba Electron Eng Corp | P-type gallium nitride compound semiconductor, manufacture thereof, and blue light-emitting element |
| WO1999023693A1 (en) * | 1997-10-30 | 1999-05-14 | Sumitomo Electric Industries, Ltd. | GaN SINGLE CRYSTALLINE SUBSTRATE AND METHOD OF PRODUCING THE SAME |
| US6147363A (en) | 1997-12-25 | 2000-11-14 | Showa Denko K.K. | Nitride semiconductor light-emitting device and manufacturing method of the same |
| US7056755B1 (en) | 1999-10-15 | 2006-06-06 | Matsushita Electric Industrial Co., Ltd. | P-type nitride semiconductor and method of manufacturing the same |
| JP3569807B2 (en) | 2002-01-21 | 2004-09-29 | 松下電器産業株式会社 | Method for manufacturing nitride semiconductor device |
| TWI295483B (en) | 2002-01-31 | 2008-04-01 | Sumitomo Chemical Co | 3-5 group compound semiconductor, process for producing the same, and compound semiconductor element using the same |
| JP4720519B2 (en) * | 2006-01-23 | 2011-07-13 | パナソニック株式会社 | Method for manufacturing p-type nitride semiconductor |
| KR100757801B1 (en) * | 2006-06-30 | 2007-09-11 | 서울옵토디바이스주식회사 | Method of forming p-type compound semiconductor layer |
| DE112007000059T5 (en) * | 2006-06-30 | 2008-08-21 | Seoul Opto Device Co. Ltd., Ansan | A method of forming a compound semiconductor layer of P-type |
| JP2009177219A (en) * | 2009-05-15 | 2009-08-06 | Mitsubishi Chemicals Corp | METHOD FOR MANUFACTURING GaN-BASED SEMICONDUCTOR DEVICE |
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| JPS5645899A (en) * | 1979-09-18 | 1981-04-25 | Sanyo Electric Co Ltd | Vapor phase growing method for gallium nitride |
| JPS6065798A (en) * | 1983-09-19 | 1985-04-15 | Toyota Central Res & Dev Lab Inc | Growing of gallium nitride single crystal |
| JP2540791B2 (en) * | 1991-11-08 | 1996-10-09 | 日亜化学工業株式会社 | A method for manufacturing a p-type gallium nitride-based compound semiconductor. |
| JP2827794B2 (en) * | 1993-02-05 | 1998-11-25 | 日亜化学工業株式会社 | Method for growing p-type gallium nitride |
| JP3254931B2 (en) * | 1994-10-17 | 2002-02-12 | 松下電器産業株式会社 | Method for producing p-type gallium nitride-based compound semiconductor |
| JPH08125222A (en) * | 1994-10-25 | 1996-05-17 | Toyoda Gosei Co Ltd | Method for manufacture of group iii nitride semiconductor |
| JP3353527B2 (en) * | 1995-03-24 | 2002-12-03 | 松下電器産業株式会社 | Manufacturing method of gallium nitride based semiconductor |
| JP3198912B2 (en) * | 1995-03-30 | 2001-08-13 | 住友化学工業株式会社 | Method for producing group 3-5 compound semiconductor |
| JPH08213656A (en) * | 1995-11-29 | 1996-08-20 | Nichia Chem Ind Ltd | Gallium nitride based compound semiconductor light emitting element |
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