JP2007266401A - Nitride semiconductor light-emitting device and manufacturing method therefor - Google Patents

Nitride semiconductor light-emitting device and manufacturing method therefor Download PDF

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JP2007266401A
JP2007266401A JP2006090858A JP2006090858A JP2007266401A JP 2007266401 A JP2007266401 A JP 2007266401A JP 2006090858 A JP2006090858 A JP 2006090858A JP 2006090858 A JP2006090858 A JP 2006090858A JP 2007266401 A JP2007266401 A JP 2007266401A
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Masanobu Ando
雅信 安藤
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Toyoda Gosei Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride semiconductor light-emitting device (LED or LD) that has an active layer comprised of a nitride semiconductor not containing indium and that achieved a shorter wavelength, a higher light emitting output, and a lower drive voltage (low threshold) by providing uneveness (Alloy-Disorder) in the active layer and/or an uneven shape on the surface of the active layer to activate the dispersion of electrons and holes in the active layer, and thereby to obtain Gain at a wavelength longer than that of an absorption edge of the active layer (= a low energy). <P>SOLUTION: The uneven shape having a period of 6 to 500 nm is formed on the surface of the active layer by forming the active layer that is comprised of Al<SB>x</SB>Ga<SB>1-x</SB>N not containing indium and has a film thickness between 3 nm and 500 nm at a low temperature below 950°C lower than conventional crystal growth temperature (1,040°C to 1,100°C). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、インジウムを含まない窒化物半導体よりなる活性層を備える窒化物半導体よりなる発光ダイオード（ＬＥＤ）、レーザダイオード（ＬＤ）等の発光素子に係り、特に発光出力、低駆動電圧（低しきい値）に関する。   The present invention relates to a light emitting diode (LED), a laser diode (LD), or the like made of a nitride semiconductor having an active layer made of a nitride semiconductor that does not contain indium. Threshold).

近年、近紫外〜赤色の領域に発光する発光素子の材料として、インジウムを含む窒化物半導体（ＩｎｘＡｌｙＧａ１−ｘ−ｙＮ（０＜ｘ≦１、０≦ｙ≦１、ｘ＋ｙ≦１）よりなる材料が用いられ、紫色ＬＥＤ、青色ＬＥＤ、青緑色ＬＥＤ、緑色ＬＥＤ及び青紫ＬＤが実用化されている。そして、更なる高出力化、短波長化の研究開発が精力的に進められている。 In recent years, as a material of a light-emitting element that emits light in the near ultraviolet to red region, a nitride semiconductor containing indium (In x Al y Ga 1-xy N (0 <x ≦ 1, 0 ≦ y ≦ 1, x + y ≦ 1) materials are used, and purple LEDs, blue LEDs, blue-green LEDs, green LEDs, and blue-violet LDs have been put into practical use, and research and development for further increasing the output and shortening the wavelength has been vigorously advanced. It has been.

本出願人は、結晶成長温度１０４０℃で、ＳｉドープしたＧａＡｌＮ層、ＧａＮ層、ＭｇドープしたＧａＡｌＮ層を順じ形成、積層した構造からなるレーザダイオードを作製した（例えば、特許文献１を参照）。また、他の文献において、インジウムを含む活性層を有するレーザ素子ではあるが、活性層とクラッド層との界面に凹凸を有することで、量子箱、量子ディスクに基くエキシトン効果による高出力を実現している（例えば、特許文献２を参照）
特開平４−２４２９８５号公報 特開平９−３３１１１６号公報 The present applicant manufactured a laser diode having a structure in which a Si-doped GaAlN layer, a GaN layer, and an Mg-doped GaAlN layer were sequentially formed and laminated at a crystal growth temperature of 1040 ° C. (see, for example, Patent Document 1) . In other literature, although it is a laser element having an active layer containing indium, by providing irregularities at the interface between the active layer and the cladding layer, high output is achieved by the exciton effect based on the quantum box and quantum disk. (For example, see Patent Document 2)
JP-A-4-242985 Japanese Patent Laid-Open No. 9-331116

ところで、特に高出力を必要とするＬＤに関しては、Ｇａｉｎ獲得について、ＬＤを構成する層での吸収による効率の低下とのバランスを考慮する必要がある。インジウムを含む素子においては、インジウム組成に基く発振波長の揺らぎの問題があり、また、短波長化に問題があった。更には面発光レーザとしてのＧａｉｎ獲得が、従来の５ペア程度の多重量子井戸（ＭＱＷ）構造では達成が難しく、活性層厚を大きくする場合、インジウムを多量に用いたＭＱＷ構造では、特に井戸ごとのインジウム組成のズレが大きくなるという問題を生じていた。   By the way, especially for an LD that requires a high output, it is necessary to consider a balance between gain acquisition and a decrease in efficiency due to absorption in the layers constituting the LD. In the element containing indium, there is a problem of fluctuation of the oscillation wavelength based on the indium composition, and there is a problem of shortening the wavelength. Furthermore, gain as a surface emitting laser is difficult to achieve with the conventional multi-quantum well (MQW) structure of about 5 pairs. There has been a problem that the deviation of the indium composition becomes large.

上記の課題を解決するために、請求項１に記載の手段によれば、インジウムを含まない窒化物半導体よりなる活性層を備える窒化物半導体発光素子であって、該活性層は層内に組成不均一（Ａｌｌｏｙ−Ｄｉｓｏｒｄｅｒ）及び／又は表面に凹凸を有することを特徴とする。 In order to solve the above-mentioned problem, according to the means of claim 1, a nitride semiconductor light emitting device comprising an active layer made of a nitride semiconductor not containing indium, the active layer having a composition in the layer. It is characterized by having unevenness on the surface and / or irregularities on the surface.

このような構成を有する請求項１に記載の発明においては、活性層内に形成される組成不均一（Ａｌｌｏｙ−Ｄｉｓｏｒｄｅｒ）により活性層内に微小エネルギー領域を作り出し、励起子を束縛することができ、また、表面に凹凸を形成させることで、マクロ的に励起子の移動を妨げる及び励起子の存在位置を固定することができる。その結果、電子と正孔を積極的に散乱させることができ、活性層の吸収端波長よりも長波長（＝低エネルギー）でＧａｉｎを獲得し、効率のよい発光素子を得ることができる。   In the invention described in claim 1 having such a configuration, a micro-energy region can be created in the active layer by the compositional non-uniformity (Alloy-Disorder) formed in the active layer, and excitons can be bound. Further, by forming irregularities on the surface, it is possible to prevent the exciton from moving macroscopically and to fix the position of the exciton. As a result, electrons and holes can be actively scattered, gain can be obtained at a wavelength (= low energy) longer than the absorption edge wavelength of the active layer, and an efficient light-emitting element can be obtained.

上記の課題を解決するために、請求項２に記載の手段によれば、前記活性層は、ＡｌｘＧａ１−ｘＮ（０≦ｘ≦１）からなることを特徴とする。 In order to solve the above-mentioned problem, according to the means described in claim 2, the active layer is made of Al x Ga 1-x N (0 ≦ x ≦ 1).

このような構成を有する請求項２に記載の発明においては、活性層をＡｌｘＧａ１−ｘＮ（０≦ｘ≦１）とすることにより、更なる短波長で発振若しくは発光する効率のよい発光素子を得ることができる。 In the invention according to claim 2 having such a configuration, by making the active layer Al x Ga 1-x N (0 ≦ x ≦ 1), it is possible to efficiently oscillate or emit light at a further shorter wavelength. A light emitting element can be obtained.

上記の課題を解決するために、請求項３に記載の手段によれば、前記活性層の表面の凹凸は、周期が６ｎｍ以上５００ｎｍ以下であることを特徴とする。   In order to solve the above-mentioned problem, according to the means described in claim 3, the irregularities on the surface of the active layer have a period of 6 nm or more and 500 nm or less.

このような構成を有する請求項３に記載の発明においては、凹凸の周期を６ｎｍ以上５００ｎｍ以下とすることにより、活性層内に生じる組成不均一（Ａｌｌｏｙ−Ｄｉｓｏｒｄｅｒ）や表面の凹凸での電子と正孔の散乱を積極的に行うことができ、活性層の吸収端波長よりも長波長（＝低エネルギー）でＧａｉｎを獲得することができる。   In the invention according to claim 3 having such a configuration, by setting the period of irregularities to be 6 nm or more and 500 nm or less, the composition unevenness (Alloy-Disorder) generated in the active layer and the electrons in the irregularities on the surface Hole scattering can be performed positively, and Gain can be obtained at a wavelength (= low energy) longer than the absorption edge wavelength of the active layer.

上記の課題を解決するために、請求項４に記載の手段によれば、前記活性層の厚さは、３ｎｍ以上５００ｎｍ以下であることを特徴とする。   In order to solve the above-mentioned problem, according to the means described in claim 4, the thickness of the active layer is 3 nm or more and 500 nm or less.

このような構成を有する請求項４に記載の発明においては、活性層の厚さを３ｎｍ以上５００ｎｍ以下とすることで、低しきい値と高出力の双方を満足する発光素子を得ることができる。   In the invention according to claim 4 having such a configuration, a light emitting element satisfying both a low threshold and a high output can be obtained by setting the thickness of the active layer to 3 nm or more and 500 nm or less. .

上記課題を解決するために、請求項５に記載の手段によれば、インジウムを含まない窒化物半導体よりなる活性層を備える窒化物半導体発光素子の製造方法であって、該活性層の結晶成長温度が９５０℃以下であることを特徴とする。   In order to solve the above problem, according to the means of claim 5, there is provided a method for manufacturing a nitride semiconductor light emitting device comprising an active layer made of a nitride semiconductor not containing indium, wherein the crystal growth of the active layer The temperature is 950 ° C. or lower.

このような構成を有する請求項５に記載の発明においては、インジウムを含まない窒化物半導体よりなる活性層を９５０℃以下で成長することで、活性層内に組成不均一（Ａｌｌｏｙ−Ｄｉｓｏｒｄｅｒ）や表面に凹凸を形成することができる。   In the invention according to claim 5 having such a configuration, an active layer made of a nitride semiconductor not containing indium is grown at 950 ° C. or less, so that compositional inhomogeneity (Alloy-Disorder) or Unevenness can be formed on the surface.

上記課題を解決するために、請求項６に記載の手段によれば、前記活性層は、ＡｌｘＧａ１−ｘＮ（０≦ｘ≦１）からなることを特徴とする。 In order to solve the above problem, according to the means described in claim 6, the active layer is made of Al x Ga 1-x N (0 ≦ x ≦ 1).

このような構成を有する請求項６に記載の発明においては、表面に凹凸が形成された活性層をＡｌｘＧａ１−ｘＮ（０≦ｘ≦１）とすることにより、更なる短波長で発振若しくは発光する効率のよい発光素子を得ることができる。 In the invention according to claim 6 having such a configuration, the active layer having irregularities formed on the surface is made to be Al x Ga 1-x N (0 ≦ x ≦ 1), thereby further shortening the wavelength. An efficient light-emitting element that oscillates or emits light can be obtained.

上記課題を解決するために、請求項７に記載の手段によれば、前記活性層の厚さは、３ｎｍ以上５００ｎｍ以下であることを特徴とする。   In order to solve the above problem, according to the means described in claim 7, the thickness of the active layer is 3 nm or more and 500 nm or less.

このような構成を有する請求項７に記載の発明においては、活性層の厚さを３ｎｍ以上５００ｎｍ以下とすることで、低しきい値と高出力の双方を満足する発光素子を得ることができる。   In the invention according to claim 7 having such a configuration, a light emitting element satisfying both a low threshold and a high output can be obtained by setting the thickness of the active layer to 3 nm or more and 500 nm or less. .

請求項１乃至請求項７の発明は、ＡｌｘＧａ１−ｘＮを活性層に用い、その結晶成長温度を９５０℃以下とすることで、活性層内に組成不均一（Ａｌｌｏｙ−Ｄｉｓｏｒｄｅｒ）を形成し、また、活性層表面に凹凸を形成させ、更に、凹凸の周期や活性層の膜厚を調整することで、短波長化と同時にＧａｉｎを獲得し、効率のよい発光素子が実現する。したがって、その利用価値は高い。 According to the first to seventh aspects of the present invention, Al x Ga 1-x N is used for the active layer, and the crystal growth temperature is set to 950 ° C. or lower, so that compositional non-uniformity (Alloy-Disorder) is generated in the active layer. In addition, by forming irregularities on the surface of the active layer and adjusting the period of the irregularities and the film thickness of the active layer, gain can be obtained simultaneously with shortening the wavelength, and an efficient light-emitting element can be realized. Therefore, its utility value is high.

（第１の実施の形態）
図１は、本発明に係る窒化物半導体発光素子１の断面図であり、具体的にはレーザ（ＬＤ）素子の構造を示している。このレーザ素子は、サファイアからなる基板１１の上に、ＡｌＮからなるバッファ層１２と、Ｓｉをドープしたｎ型ＧａＮからなるコンタクト層１３と、Ｓｉをドープしたｎ型Ａｌ０．３Ｇａ０．７Ｎからなるクラッド層１４と、Ｓｉをドープしたｎ型ＧａＮからなる光ガイド層１５と、表面に凹凸形状を有するＧａＮからなる活性層１６と、Ｍｇをドープしたｐ型ＧａＮからなる光ガイド層１７と、Ｍｇをドープしたｎ型Ａｌ０．３Ｇａ０．７Ｎからなるクラッド層１８と、Ｍｇをドープしたｐ型ＧａＮからなるコンタクト層１９が順に積層された構造を有しており、ｐ型コンタクト層１９にはストライプ状の正電極２０が、ｎ型コンタクト層１３には、正電極と平行な負電極２１が設けられている。図２は、図１における活性層１６表面の凹凸形状の模式図である。 (First embodiment)
FIG. 1 is a cross-sectional view of a nitride semiconductor light emitting device 1 according to the present invention, and specifically shows the structure of a laser (LD) device. This laser device has a substrate 11 made of sapphire, a buffer layer 12 made of AlN, a contact layer 13 made of n-type GaN doped with Si, and an n-type Al 0.3 Ga 0.7 doped with Si. A cladding layer 14 made of N, a light guide layer 15 made of n-type GaN doped with Si, an active layer 16 made of GaN having a concavo-convex shape on the surface, and a light guide layer 17 made of p-type GaN doped with Mg A clad layer 18 made of Mg-doped n-type Al 0.3 Ga 0.7 N and a contact layer 19 made of Mg-doped p-type GaN are sequentially stacked, and p-type The contact layer 19 is provided with a striped positive electrode 20, and the n-type contact layer 13 is provided with a negative electrode 21 parallel to the positive electrode. FIG. 2 is a schematic view of the uneven shape on the surface of the active layer 16 in FIG.

次に、本発明に係る窒化物半導体発光素子１の製造方法を詳説する。洗浄したサファイアＡ面よりなる基板１１を結晶成長装置のサセプタ部（図示せず）にセットし、基板の温度を１１００℃まで上昇させ、基板表面を水素でクリーニングする。基板にはサファイアＡ面の他に、サファイアにおけるＣ面、Ｒ面等の別方位基板、また、スピネル（ＭｇＡｌ２Ｏ４）、ＳｉＣ、ＭｇＯ、Ｓｉ、ＺｎＯ、ＧａＮ等の単結晶よりなる、公知の基板も適用可能である。 Next, a method for manufacturing the nitride semiconductor light emitting device 1 according to the present invention will be described in detail. The substrate 11 made of the cleaned sapphire A surface is set on a susceptor portion (not shown) of the crystal growth apparatus, the temperature of the substrate is raised to 1100 ° C., and the substrate surface is cleaned with hydrogen. In addition to the sapphire A plane, the substrate is made of a different orientation substrate such as a C plane or R plane in sapphire, or a single crystal such as spinel (MgAl 2 O 4 ), SiC, MgO, Si, ZnO, GaN, etc. These substrates are also applicable.

次に、基板温度を４００℃まで下げ、キャリアガスに水素、原料ガスにアンモニアとＴＭＡ（トリメチルアルミニウム）を用いて、４００℃で基板１０１上にＡｌＮからなるバッファ層１２を４００オングストローム成長させる。バッファ層１２は基板と次に成長する窒化物半導体との格子定数差を緩和するために設けられるものである。バッファ層には、ＡｌＮの他にＧａＮ、ＡｌＧａＮが通常用いられる。なお、バッファ層は基板との格子定数差の緩和するもの故、その機能を有していれば１０００℃程度の高温で形成しても良い。また、窒化物半導体と格子定数の整合した基板を用いる場合は、省略することもできる。   Next, the substrate temperature is lowered to 400 ° C., and the buffer layer 12 made of AlN is grown on the substrate 101 at 400 ° C. at 400 ° C. using hydrogen as the carrier gas and ammonia and TMA (trimethylaluminum) as the source gas. The buffer layer 12 is provided to alleviate the lattice constant difference between the substrate and the next grown nitride semiconductor. In addition to AlN, GaN and AlGaN are usually used for the buffer layer. Note that since the buffer layer relaxes the difference in lattice constant with the substrate, the buffer layer may be formed at a high temperature of about 1000 ° C. as long as it has the function. Further, in the case of using a substrate having a lattice constant matched with the nitride semiconductor, it can be omitted.

次に、バッファ層１２成長後、基板温度を１１００℃まで上昇させ、原料ガスにＴＭＧ（トリメチルガリウム）とアンモニアガス、不純物ガスにＳｉＨ４（シラン）ガスを用いて、ＳｉをドープしたＧａＮからなるｎ型コンタクト層１３を４μｍの膜厚で成長させる。ｎ型コントクト層１３は、負電極２１と良好なオーミック接合が形成できれば、他の窒化物半導体（ＡｌＧａＩｎＮ）でもよい。
次に、基板温度を１１００℃に維持したまま、原料ガスにＴＭＧとＴＭＡとアンモニアガス、不純物ガスにＳｉＨ４（シラン）ガスを用いて、ＳｉをドープしたＡｌ０．３Ｇａ０．７Ｎからなるｎ型クラッド層１４を６００ｎｍの膜厚で成長させる。なお、ＳｉをドープしたＡｌｘＧａ1-ｘＮを用いる場合は、ｎ型コンタクト層とｎ型クラッド層を兼ねることができる。この場合には、負電極とのオーミック特性とクラッド層としての光閉じ込め機能を確保する観点より、基板側のＡｌ組成比が小さく、次に成長させる活性層側の組成比が大きい、即ち組成傾斜構造とすることが望ましい。 Next, after the growth of the buffer layer 12, the substrate temperature is increased to 1100 ° C., and TMG (trimethylgallium) and ammonia gas are used as the source gas, and SiH 4 (silane) gas is used as the impurity gas. The n-type contact layer 13 is grown to a thickness of 4 μm. The n-type contract layer 13 may be another nitride semiconductor (AlGaInN) as long as a good ohmic junction with the negative electrode 21 can be formed.
Then, while maintaining the substrate temperature at 1100 ° C., TMG and TMA and ammonia gas as a source gas, the impurity gas with SiH 4 (silane) gas, a Si doped at Al 0.3 Ga 0.7 N An n-type cladding layer 14 is grown to a thickness of 600 nm. In the case of using the Al x Ga 1-x N doped with Si, it can also serve as a n-type contact layer and the n-type cladding layer. In this case, from the viewpoint of ensuring ohmic characteristics with the negative electrode and the light confinement function as the cladding layer, the Al composition ratio on the substrate side is small, and the composition ratio on the active layer side to be grown next is large, that is, the composition gradient A structure is desirable.

次に、基板温度を１１００℃に維持したまま、原料ガスにＴＭＧとアンモニアガス、不純物ガスにＳｉＨ４（シラン）ガスを用いて、ＳｉをドープしたＧａＮからなるｎ型光ガイド層１５を５０ｎｍの膜厚で成長させる。
次に、基板温度を８５０℃に下げ、原料ガスにＴＭＧ、アンモニアガスを用いて、ノンドープのＧａＮからなる活性層１６を５００ｎｍの膜厚で成長させる。基板温度が８５０℃においては、活性層１６の表面に約１３０ｎｍ〜２００ｎｍの周期２２を有する凹凸が形成される。
活性層１５成長後、基板温度を１１００℃まで上昇させ、原料ガスにＴＭＧとアンモニアガス、不純物ガスにＣｐ２Ｍｇ（シクロペンタジエニルマグネシウム）を用いて、ＭｇをドープしたＧａＮからなるｐ型光ガイド層１７を５０ｎｍの膜厚で成長させる。
次に、基板温度を１１００℃に維持したまま、原料ガスにＴＭＧとＴＭＡとアンモニアガス、不純物ガスにＣｐ２Ｍｇ（シクロペンタジエニルマグネシウム）を用いて、ＭｇをドープしたＡｌ０．３Ｇａ０．７Ｎからなるｐ型クラッド層１８を５００ｎｍの膜厚で成長させる。
次に、基板温度を１１００℃に維持したまま、原料ガスにＴＭＧとアンモニアガス、不純物ガスにＣｐ２Ｍｇ（シクロペンタジエニルマグネシウム）を用いて、ＭｇをドープしたＧａＮからなるｐ型コンタクト層１９を２００ｎｍの膜厚で成長させる。
以上のようにして窒化物半導体を積層したウエハを結晶成長装置から取出し、図１に示すように、最上層のｐ型コンタクト層１９から選択エッチングを行い、負電極を形成すべきｎ型コンタクト層１３の表面を露出させる。さらに、ｐ型コンタクト層側からエッチングし、ストライプ状のリッジ形状を形成した後、リッジに平行な位置に正電極２０と負電極２１とをストライプ状に形成してレーザ素子１を作製した。
（第２の実施の形態）
第２の実施の形態は、第1の実施の形態におけるノンドープのＧａＮからなる活性層１６を量子井戸構造で形成したもので、ノンドープのＧａＮからなる６ｎｍの井戸層１６１とノンドープのＡｌ０．１Ｇａ０．９Ｎからなる５ｎｍの障壁層１６２の積層構造で形成される。ちなみに、ノンドープのＧａＮからなる６ｎｍの井戸層１６１のみの場合は、第1の実施の形態と同じ構造となるが、量子効果を生じる点で、第1の実施の形態と異なる。井戸層１６１のみの場合を単一量子井戸構造と呼び、井戸層１６１と障壁層１６２の積層構造の場合を多重量子井戸構造と呼ぶ。いずれの場合も、井戸層１６１を形成する時の基板温度は、８５０℃であり、障壁層１６２を形成する時の基板温度は１１００℃である。井戸層／障壁層／・・・／井戸層／障壁層で形成され、活性層１６の最上層は障壁層１６２である。図３は、第２の実施の形態における活性層１６近辺の領域を拡大して部分的に示す模式断面図である。
第1の実施の形態、第２の実施の形態を通じて、活性層１６のＧａＮ層を通常の結晶成長温度より低温で形成することで、活性層１６内に自然的に発生するＡｌｌｏｙ−Ｄｉｓｏｒｄｅｒ及び表面に凹凸形状のモフォロジーとなる。特に６００℃以上９５０℃以下の温度で形成することで、その凹凸形状の周期２２が６ｎｍ〜５００ｎｍとなり、かつ、内部にＡｌｌｏｙ−Ｄｉｓｏｒｄｅｒを十分に含むようになる。この結果、活性層１６での電子―正孔対の散乱確率が増大し、活性層の吸収端波長よりも長波長（＝低エネルギー）でＧａｉｎを獲得することができる。なお、凹凸形状の周期２２については、散乱対象の励起子の半径がほぼ３ｎｍであることから、６ｎｍ以上であれば、本発明の効果を生ずることができるが、更に制御するという観点からは、転移間距離相当程度の１００ｎｍ以上（５００ｎｍ以下）が望ましい。
第1の実施の形態、第２の実施の形態を通じて、活性層１６の膜厚は３ｎｍ〜５００ｎｍが好ましく、更には６ｎｍ〜２００ｎｍが好ましい。３ｎｍより薄い場合は、電子−正孔対が安定して入り込むことができず、量子効果を生ぜず、活性層としての機能を有しない。また、５００ｎｍより厚くなると、低温成長に起因するＧａＮ層の歪み分布が大きくなり、発振波長のズレが発生する。出力との関係については、しきい値を下げる観点からは、薄い方がよく、出力を向上させる観点からは、厚い方がよい。６ｎｍ〜２００ｎｍが更に好ましいのは、トレードオフにある低しきい値と高出力の双方を満足するからである。
第２の実施の形態における障壁層を形成するＡｌｘＧａ１−ｘＮのＡｌの組成ｘは、０．０５〜０．３が望ましい。０．０５を未満では電子と正孔の閉じ込めが困難となり、０．３より大きい場合は、結晶品質が低下し、レーザ素子としての特性が悪化するからである。
第1の実施の形態、第２の実施の形態を通じて、ＧａＮからなるｎ型コンタクト層１３とｐ型コンタクト層１９の電子濃度と正孔濃度を均一にすることが望ましい。窒化物半導体においては、一般的にアクセプタ（本発明での実施例ではＭｇ）の活性化率がドナー（本発明の実施例ではＳｉ）より低いため、素子としては、ｎ型コンタクト層１３の電子濃度＞ｐ型コンタクト層１９の正孔濃度の関係となっている。したがって、本発明においては、ｎ型コンタクト層１３の電子濃度を下げるようなドーピングの調整を行うことが望ましい。例えば、一般的な窒化物半導体のｐ型ＧａＮ層にＭｇをドープした場合の正孔濃度は、５×１０１７／ｃｍ３程度と言われているので、ＧａＮからなるｎ型コンタクト層１３のＳｉドープ量を５×１０１７／ｃｍ３程度に調整することが望ましい。 Next, while maintaining the substrate temperature at 1100 ° C., using TMG and ammonia gas as source gases and SiH 4 (silane) gas as impurity gas, an n-type light guide layer 15 made of Si-doped GaN is formed to a thickness of 50 nm. Grow with film thickness.
Next, the substrate temperature is lowered to 850 ° C., and the active layer 16 made of non-doped GaN is grown to a thickness of 500 nm using TMG and ammonia gas as source gases. When the substrate temperature is 850 ° C., irregularities having a period 22 of about 130 nm to 200 nm are formed on the surface of the active layer 16.
After growing the active layer 15, the substrate temperature is raised to 1100 ° C., TMG and ammonia gas are used as source gas, Cp 2 Mg (cyclopentadienylmagnesium) is used as impurity gas, and p-type light composed of GaN doped with Mg The guide layer 17 is grown to a thickness of 50 nm.
Next, while maintaining the substrate temperature at 1100 ° C., Al 0.3 Ga 0 doped with Mg using TMG, TMA and ammonia gas as source gases and Cp 2 Mg (cyclopentadienylmagnesium) as impurity gas. .7 N-type p-type cladding layer 18 is grown to a thickness of 500 nm.
Next, while maintaining the substrate temperature at 1100 ° C., the p-type contact layer 19 made of GaN doped with Mg using TMG and ammonia gas as the source gas and Cp 2 Mg (cyclopentadienylmagnesium) as the impurity gas. Is grown to a thickness of 200 nm.
As described above, the nitride semiconductor wafer is taken out of the crystal growth apparatus, and as shown in FIG. 1, the uppermost p-type contact layer 19 is selectively etched to form an n-type contact layer for forming a negative electrode. 13 surfaces are exposed. Further, after etching from the p-type contact layer side to form a striped ridge shape, the positive electrode 20 and the negative electrode 21 were formed in a stripe shape at a position parallel to the ridge, and the laser device 1 was fabricated.
(Second Embodiment)
In the second embodiment, the active layer 16 made of non-doped GaN in the first embodiment is formed in a quantum well structure, and a 6 nm well layer 161 made of non-doped GaN and non-doped Al 0.1. It is formed by a laminated structure of a 5 nm barrier layer 162 made of Ga 0.9 N. Incidentally, only the 6 nm well layer 161 made of non-doped GaN has the same structure as the first embodiment, but differs from the first embodiment in that a quantum effect is generated. The case of only the well layer 161 is called a single quantum well structure, and the case of a stacked structure of the well layer 161 and the barrier layer 162 is called a multiple quantum well structure. In any case, the substrate temperature when the well layer 161 is formed is 850 ° C., and the substrate temperature when the barrier layer 162 is formed is 1100 ° C. Well layer / barrier layer /.. ./Well layer / barrier layer. The uppermost layer of the active layer 16 is a barrier layer 162. FIG. 3 is a schematic cross-sectional view partially showing an enlarged region in the vicinity of the active layer 16 in the second embodiment.
Through the first embodiment and the second embodiment, the GaN layer of the active layer 16 is formed at a temperature lower than the normal crystal growth temperature, so that the alloy-disorder naturally generated in the active layer 16 and the surface It has a concavo-convex morphology. In particular, by forming at a temperature of 600 ° C. or more and 950 ° C. or less, the period 22 of the concavo-convex shape is 6 nm to 500 nm, and the alloy-disorder is sufficiently contained therein. As a result, the scattering probability of electron-hole pairs in the active layer 16 increases, and Gain can be obtained at a wavelength longer than the absorption edge wavelength of the active layer (= low energy). In addition, about the period 22 of uneven | corrugated shape, since the radius of the exciton of scattering object is about 3 nm, if it is 6 nm or more, the effect of this invention can be produced, but from a viewpoint of controlling further, 100 nm or more (500 nm or less) corresponding to the distance between transitions is desirable.
Throughout the first embodiment and the second embodiment, the thickness of the active layer 16 is preferably 3 nm to 500 nm, and more preferably 6 nm to 200 nm. When the thickness is less than 3 nm, electron-hole pairs cannot stably enter, do not produce a quantum effect, and do not have a function as an active layer. On the other hand, when the thickness is greater than 500 nm, the strain distribution of the GaN layer due to the low temperature growth becomes large, and the oscillation wavelength shifts. Regarding the relationship with the output, the thinner is better from the viewpoint of lowering the threshold, and the thicker is better from the viewpoint of improving the output. The reason why 6 nm to 200 nm is more preferable is that both the low threshold and the high output which are in a trade-off are satisfied.
The Al composition x of Al x Ga 1-x N forming the barrier layer in the second embodiment is preferably 0.05 to 0.3. If it is less than 0.05, it becomes difficult to confine electrons and holes, and if it is more than 0.3, the crystal quality deteriorates and the characteristics as a laser element deteriorate.
Through the first embodiment and the second embodiment, it is desirable to make the electron concentration and the hole concentration of the n-type contact layer 13 and the p-type contact layer 19 made of GaN uniform. In nitride semiconductors, the activation rate of the acceptor (Mg in the embodiment of the present invention) is generally lower than that of the donor (Si in the embodiment of the present invention). The relationship of the concentration> the hole concentration of the p-type contact layer 19 is established. Therefore, in the present invention, it is desirable to adjust the doping so as to reduce the electron concentration of the n-type contact layer 13. For example, the hole concentration when doped with Mg into the p-type GaN layer of a general nitride semiconductor, because it is said that 5 × 10 17 / cm 3 approximately, Si of the n-type contact layer 13 made of GaN It is desirable to adjust the doping amount to about 5 × 10 17 / cm 3 .

第1の実施の形態における窒化物半導体発光素子１の断面図Sectional drawing of the nitride semiconductor light-emitting device 1 in 1st Embodiment 第1の実施の形態における活性層１６表面の凹凸形状の模式図である。It is a schematic diagram of the uneven | corrugated shape on the surface of the active layer 16 in 1st Embodiment. 第２の実施の形態における活性層１６近辺の領域を拡大して部分的に示す模式断面図である。It is a schematic cross section which expands and shows partially the area | region of the active layer 16 vicinity in 2nd Embodiment.

符号の説明Explanation of symbols

１ 窒化物半導体発光素子
１１ サファイアからなる基板１１
１２ ＡｌＮからなるバッファ層
１３ Ｓｉをドープしたｎ型ＧａＮからなるコンタクト層
１４ Ｓｉをドープしたｎ型Ａｌ０．３Ｇａ０．７Ｎからなるクラッド層
１５ Ｓｉをドープしたｎ型ＧａＮからなる光ガイド層
１６ ＧａＮからなる活性層
１７ Ｍｇをドープしたｐ型ＧａＮからなる光ガイド層
１８ Ｍｇをドープしたｎ型Ａｌ０．３Ｇａ０．７Ｎからなるクラッド層
１９ Ｍｇをドープしたｐ型ＧａＮからなるコンタクト層
２０ 正電極
２１ 負電極
２２ 凹凸形状の周期
１６１ ＧａＮからなる井戸層
１６２ Ａｌ０．１Ｇａ０．９Ｎからなる障壁層 DESCRIPTION OF SYMBOLS 1 Nitride semiconductor light-emitting device 11 The board | substrate 11 which consists of sapphire
12 Buffer layer made of AlN 13 Contact layer made of n-type GaN doped with Si 14 Cladding layer made of n-type Al 0.3 Ga 0.7 N doped with Si 15 Light guide made of n-type GaN doped with Si Layer 16 Active layer 17 made of GaN Optical guide layer 18 made of p-type GaN doped with Mg Clad layer 19 made of n-type Al 0.3 Ga 0.7 N doped with Mg 19 Made of p-type GaN doped with Mg Contact layer 20 Positive electrode 21 Negative electrode 22 Concave and convex period 161 Well layer 162 made of GaN Barrier layer made of Al 0.1 Ga 0.9 N

Claims (7)

インジウムを含まない窒化物半導体よりなる活性層を備える窒化物半導体発光素子であって、該活性層は層内に組成不均一（Ａｌｌｏｙ−Ｄｉｓｏｒｄｅｒ）及び／又は表面に凹凸を有することを特徴とする窒化物半導体発光素子。 A nitride semiconductor light emitting device comprising an active layer made of a nitride semiconductor containing no indium, wherein the active layer has a compositional non-uniformity (Alloy-Disorder) in the layer and / or an uneven surface. Nitride semiconductor light emitting device. 前記活性層は、ＡｌｘＧａ１−ｘＮ（０≦ｘ≦１）からなることを特徴とする請求項１に記載の窒化物半導体発光素子。 The nitride semiconductor light emitting device according to claim 1, wherein the active layer is made of Al x Ga 1-x N (0 ≦ x ≦ 1). 前記活性層の表面の凹凸は、周期が６ｎｍ以上５００ｎｍ以下であることを特徴とする請求項１及び請求項２に記載の窒化物半導体発光素子。 3. The nitride semiconductor light emitting device according to claim 1, wherein the irregularities on the surface of the active layer have a period of 6 nm or more and 500 nm or less. 前記活性層の厚さは、３ｎｍ以上５００ｎｍ以下であることを特徴とする請求項１乃至請求項３に記載の窒化物半導体発光素子。 4. The nitride semiconductor light emitting device according to claim 1, wherein a thickness of the active layer is 3 nm or more and 500 nm or less. インジウムを含まない窒化物半導体よりなる活性層を備える窒化物半導体発光素子の製造方法であって、該活性層の結晶成長温度が９５０℃以下であることを特徴とする窒化物半導体発光素子の製造方法。 A method for manufacturing a nitride semiconductor light emitting device comprising an active layer made of a nitride semiconductor containing no indium, wherein the crystal growth temperature of the active layer is 950 ° C. or lower. Method. 前記活性層は、ＡｌｘＧａ１−ｘＮ（０≦ｘ≦１）からなることを特徴とする請求項５に記載の窒化物半導体発光素子の製造方法。 The method for manufacturing a nitride semiconductor light emitting device according to claim 5, wherein the active layer is made of Al x Ga 1-x N (0 ≦ x ≦ 1). 前記活性層の厚さは、３ｎｍ以上５００ｎｍ以下であることを特徴とする請求項５及び請求項６に記載の窒化物半導体発光素子の製造方法。
The method for manufacturing a nitride semiconductor light emitting device according to claim 5 or 6, wherein the thickness of the active layer is 3 nm or more and 500 nm or less.
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Publication number Priority date Publication date Assignee Title
JP2010021513A (en) * 2008-07-08 2010-01-28 Samsung Electro Mech Co Ltd Nitride semiconductor light-emitting element including pattern forming substrate, and its manufacturing method
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JP2011233810A (en) * 2010-04-30 2011-11-17 Toyota Motor Corp Photoelectric conversion element and manufacturing method thereof
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WO2021033459A1 (en) * 2019-08-22 2021-02-25 豊田合成株式会社 Light-emitting element and production method for same
JP2021034521A (en) * 2019-08-22 2021-03-01 豊田合成株式会社 Light-emitting device and manufacturing method thereof
JP7200068B2 (en) 2019-08-22 2023-01-06 豊田合成株式会社 Light emitting device and manufacturing method thereof

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