JP2013149889A - GaN-BASED SEMICONDUCTOR LIGHT-EMITTING ELEMENT - Google Patents

GaN-BASED SEMICONDUCTOR LIGHT-EMITTING ELEMENT Download PDF

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JP2013149889A
JP2013149889A JP2012010809A JP2012010809A JP2013149889A JP 2013149889 A JP2013149889 A JP 2013149889A JP 2012010809 A JP2012010809 A JP 2012010809A JP 2012010809 A JP2012010809 A JP 2012010809A JP 2013149889 A JP2013149889 A JP 2013149889A
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Akira Iwayama
章 岩山
Masahiko Mogi
正彦 茂木
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Stanley Electric Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide a GaN-based semiconductor light-emitting element with a novel structure and improving luminance efficiency.SOLUTION: A GaN-based semiconductor light-emitting element comprises: an n-type semiconductor layer formed of a GaN-based semiconductor with n-type conductivity; an active layer having a multiquantum well structure formed on the n-type semiconductor layer, formed of the GaN-based semiconductor, and in which a plurality of barrier layers and a plurality of well layers are alternately stacked; and a p-type semiconductor layer formed on the active layer and formed of a GaN-based semiconductor with p-type conductivity. The active layer consists of a first barrier layer at a side closest to the n-type semiconductor layer formed of a GaN/AlGaN layer, the barrier layers at a side closer to the p-type semiconductor layer than the first barrier layer formed of InGaN/GaN layer; and the well layers formed of an InGaN layer having a band gap being narrower than that of an InGaN layer in the barrier layer of the InGaN/GaN layer.

Description

本発明は、ＧａＮ系半導体発光素子に関する。   The present invention relates to a GaN-based semiconductor light emitting device.

ＧａＮ系半導体を用いた発光ダイオード（ＬＥＤ）は、近年、照明用途等として、大電流で大出力のものが求められている。しかし、ＧａＮ系半導体を用いたＬＥＤは、電流密度を増加させると発光効率が低下するＤｒｏｏｐ現象が生じるなど、発光効率を向上させることが容易ではない。   In recent years, a light-emitting diode (LED) using a GaN-based semiconductor is required to have a large current and a large output for lighting applications. However, it is not easy to improve the luminous efficiency of LEDs using GaN-based semiconductors, for example, a drop phenomenon occurs in which the luminous efficiency decreases when the current density is increased.

Ａｐｐｌ. Ｐｈｙｓ. Ｌｅｔｔ. ９１, １８３５０７（２００７）Appl. Phys. Lett. 91, 183507 (2007). Ａｐｐｌ. Ｐｈｙｓ. Ｌｅｔｔ. ９４, ０１１１１３（２００９）Appl. Phys. Lett. 94, 011313 (2009). Ａｐｐｌ. Ｐｈｙｓ. Ｌｅｔｔ. ９５, ２４１１０９（２００９）Appl. Phys. Lett. 95, 241109 (2009). 特開２００４−８７９０８号公報JP 2004-87908 A

本発明の一目的は、発光効率向上が図られた新規な構造のＧａＮ系半導体発光素子を提供することである。   An object of the present invention is to provide a GaN-based semiconductor light-emitting device having a novel structure with improved light emission efficiency.

本発明の一観点によれば、ｎ型導電性を有するＧａＮ系半導体で形成されたｎ型半導体層と、前記ｎ型半導体層上に形成され、ＧａＮ系半導体で形成され、バリア層とウェル層とが交互に複数層積層された多重量子井戸構造を有する活性層と、前記活性層上に形成され、ｐ型導電性を有するＧａＮ系半導体で形成されたｐ型半導体層とを有し、前記活性層は、最もｎ型半導体層側の第１バリア層がＧａＮ／ＡｌＧａＮ層で形成され、前記第１バリア層よりもｐ型半導体層側のバリア層がＩｎＧａＮ／ＧａＮ層で形成され、ウェル層が、前記ＩｎＧａＮ／ＧａＮ層のバリア層のＩｎＧａＮ層よりもバンドギャップの狭いＩｎＧａＮ層で形成されているＧａＮ系半導体発光素子が提供される。   According to one aspect of the present invention, an n-type semiconductor layer formed of a GaN-based semiconductor having n-type conductivity, a barrier layer and a well layer formed on the n-type semiconductor layer and formed of a GaN-based semiconductor. And an active layer having a multiple quantum well structure in which a plurality of layers are alternately stacked, and a p-type semiconductor layer formed on the active layer and formed of a GaN-based semiconductor having p-type conductivity, The active layer has a first barrier layer closest to the n-type semiconductor layer formed of a GaN / AlGaN layer, a barrier layer closer to the p-type semiconductor layer than the first barrier layer formed of an InGaN / GaN layer, and a well layer However, there is provided a GaN-based semiconductor light-emitting element formed of an InGaN layer having a narrower band gap than the InGaN layer of the barrier layer of the InGaN / GaN layer.

ＧａＮ系半導体発光素子の多重量子井戸構造の活性層において、最もｎ型半導体層側の第１バリア層をＧａＮ／ＡｌＧａＮ層で形成し、第１バリア層よりもｐ型半導体層側のバリア層をＩｎＧａＮ／ＧａＮ層で形成することにより、発光効率の向上を図ることができる。   In the active layer having a multiple quantum well structure of the GaN-based semiconductor light emitting device, the first barrier layer closest to the n-type semiconductor layer is formed of a GaN / AlGaN layer, and the barrier layer closer to the p-type semiconductor layer than the first barrier layer is formed. By forming the InGaN / GaN layer, the luminous efficiency can be improved.

図１は、第１シミュレーションで想定した発光素子の構造を示す概略断面図である。FIG. 1 is a schematic cross-sectional view showing the structure of the light emitting element assumed in the first simulation. 図２Ａ及び図２Ｂは、それぞれ、第１比較例及び第１実施例によるＧａＮ系半導体発光素子のコンダクションバンドの概略的なバンド図である。2A and 2B are schematic band diagrams of conduction bands of GaN-based semiconductor light emitting devices according to the first comparative example and the first example, respectively. 図３は、第１シミュレーションで得られた第１実施例及び第１比較例によるＧａＮ系半導体発光素子のＩＱＥの電流密度依存性を示すグラフである。FIG. 3 is a graph showing the current density dependence of IQE of the GaN-based semiconductor light emitting devices according to the first example and the first comparative example obtained in the first simulation. 図４は、活性層のファーストバリア層をＧａＮ／ＡｌＧａＮ層とした場合の影響を示した、コンダクションバンド及びバレンスバンドの概略的なバンド図である。FIG. 4 is a schematic band diagram of a conduction band and a valence band, showing the effect when the first barrier layer of the active layer is a GaN / AlGaN layer. 図５は、第１実施例の変形例によるＧａＮ系半導体発光素子のコンダクションバンドの概略的なバンド図である。FIG. 5 is a schematic band diagram of a conduction band of a GaN-based semiconductor light emitting device according to a modification of the first embodiment. 図６Ａ及び図６Ｂは、それぞれ、第２シミュレーションで得られた第２比較例及び第３比較例の活性層におけるコンダクションバンドのバンド図及びバレンスバンドのバンド図である。6A and 6B are a band diagram of a conduction band and a band diagram of a valence band in the active layers of the second comparative example and the third comparative example, respectively, obtained in the second simulation.

まず、本発明の第１実施例によるＧａＮ系半導体発光素子、及び、第１比較例によるＧａＮ系半導体発光素子に対し、内部量子効率（ＩＱＥ）の電流密度依存性を調べた第１シミュレーションについて説明する。   First, the first simulation for examining the current density dependence of the internal quantum efficiency (IQE) for the GaN-based semiconductor light-emitting device according to the first embodiment of the present invention and the GaN-based semiconductor light-emitting device according to the first comparative example will be described. To do.

なお、ＧａＮ系半導体は、少なくともＧａとＮとを含む。例えばＩｎをＧａＮに添加してＩｎＧａＮとすることにより、Ｉｎ組成に応じてバンドギャップを狭くすることができる。また、例えばＡｌをＧａＮに添加してＡｌＧａＮとすることにより、Ａｌ組成に応じてバンドギャップを広くすることができる。   Note that the GaN-based semiconductor contains at least Ga and N. For example, by adding In to GaN to form InGaN, the band gap can be narrowed according to the In composition. Further, for example, by adding Al to GaN to form AlGaN, the band gap can be widened according to the Al composition.

図１は、第１シミュレーションで想定した発光素子の構造を示す概略断面図である。厚さ５μｍのｎ型ＧａＮ層１上に、多重量子井戸構造の活性層２が形成され、活性層２上に、ｐ型Ａｌ０．１５Ｇａ０．８５Ｎ層による厚さ２０ｎｍのｐ型クラッド層（電子ブロック層）３が形成され、ｐ型クラッド層３上に、厚さ８０ｎｍのｐ型ＧａＮ層４が形成されている。第１実施例及び第１比較例によるＧａＮ系半導体発光素子は、それぞれ、活性層２の構造が異なり、残りの構造は共通である。 FIG. 1 is a schematic cross-sectional view showing the structure of the light emitting element assumed in the first simulation. An active layer 2 having a multiple quantum well structure is formed on an n-type GaN layer 1 having a thickness of 5 μm, and a p-type cladding having a thickness of 20 nm by a p-type Al 0.15 Ga 0.85 N layer on the active layer 2. A layer (electron block layer) 3 is formed, and a p-type GaN layer 4 having a thickness of 80 nm is formed on the p-type cladding layer 3. In the GaN-based semiconductor light emitting devices according to the first example and the first comparative example, the structure of the active layer 2 is different, and the remaining structure is common.

図２Ａ及び図２Ｂは、それぞれ、第１比較例及び第１実施例によるＧａＮ系半導体発光素子のコンダクションバンドの概略的なバンド図であり、活性層２の積層構造を示す。   2A and 2B are schematic band diagrams of a conduction band of a GaN-based semiconductor light emitting device according to the first comparative example and the first example, respectively, and show a stacked structure of the active layer 2.

積層構造のバリア層、例えば、ＩｎＧａＮ層とＧａＮ層との積層構造のバリア層を、ＩｎＧａＮ／ＧａＮ層等と表記する。「／」の左方側に、ｎ型半導体層側に配置される層を記す。   A barrier layer having a stacked structure, for example, a barrier layer having a stacked structure of an InGaN layer and a GaN layer is referred to as an InGaN / GaN layer. A layer arranged on the n-type semiconductor layer side is described on the left side of “/”.

第１比較例及び第１実施例の活性層２において共通に、１０層のバリア層ｂ１〜ｂ１０と、９層のウェル層ｗ１〜ｗ９とが、交互に積層されている。最もｎ型半導体層側のバリア層ｂ１をファーストバリア層、最もｐ型半導体層側のバリア層ｂ１０をラストバリア層と呼び、中間のバリア層ｂ２〜ｂ９を、内部バリア層と呼ぶ。   In the active layer 2 of the first comparative example and the first example, 10 barrier layers b1 to b10 and 9 well layers w1 to w9 are alternately stacked. The barrier layer b1 closest to the n-type semiconductor layer is referred to as a first barrier layer, the barrier layer b10 closest to the p-type semiconductor layer is referred to as a last barrier layer, and the intermediate barrier layers b2 to b9 are referred to as internal barrier layers.

第１比較例による活性層２は、以下のようなものである。   The active layer 2 according to the first comparative example is as follows.

バリア層・・・ ファーストバリア：ＧａＮ（厚さ５ｎｍ）
内部バリア：Ｉｎ０．０３Ｇａ０．９７Ｎ／ＧａＮ（厚さ２ｎｍ／３ｎｍ）
ラストバリア：Ｉｎ０．０３Ｇａ０．９７Ｎ／ＧａＮ（厚さ２ｎｍ／３ｎｍ）
バリア数：１０
ウェル層・・・ Ｉｎ０．１７Ｇａ０．８３Ｎ（厚さ３．５ｎｍ）
ウェル数：９
第１実施例による活性層２は、以下のようなものである。 Barrier layer: First barrier: GaN (thickness 5 nm)
Internal barrier: In 0.03 Ga 0.97 N / GaN (thickness 2 nm / 3 nm)
Last barrier: In 0.03 Ga 0.97 N / GaN (thickness 2 nm / 3 nm)
Number of barriers: 10
Well layer: In 0.17 Ga 0.83 N (thickness 3.5 nm)
Number of wells: 9
The active layer 2 according to the first embodiment is as follows.

バリア層・・・ ファーストバリア：ＧａＮ／Ａｌ０．０３Ｇａ０．９７Ｎ（厚さ３ｎｍ／２ｎｍ）
内部バリア：Ｉｎ０．０３Ｇａ０．９７Ｎ／ＧａＮ（厚さ２ｎｍ／３ｎｍ）
ラストバリア：Ｉｎ０．０３Ｇａ０．９７Ｎ／ＧａＮ（厚さ２ｎｍ／３ｎｍ）
バリア数：１０
ウェル層・・・ Ｉｎ０．１７Ｇａ０．８３Ｎ（厚さ３．５ｎｍ）
ウェル数：９
つまり、第１比較例はファーストバリア層ｂ１がＧａＮ層であり、第１実施例はファーストバリア層ｂ１がＧａＮ／ＡｌＧａＮ層である。 Barrier layer: First barrier: GaN / Al 0.03 Ga 0.97 N (thickness 3 nm / 2 nm)
Internal barrier: In 0.03 Ga 0.97 N / GaN (thickness 2 nm / 3 nm)
Last barrier: In 0.03 Ga 0.97 N / GaN (thickness 2 nm / 3 nm)
Number of barriers: 10
Well layer: In 0.17 Ga 0.83 N (thickness 3.5 nm)
Number of wells: 9
That is, in the first comparative example, the first barrier layer b1 is a GaN layer, and in the first example, the first barrier layer b1 is a GaN / AlGaN layer.

なお、ウェル層に用いられるＩｎｘＧａ１−ｘＮ層のＩｎ組成ｘは、バリア層に用いられるＩｎｙＧａ１−ｙＮ層のＩｎ組成ｙに対し、バンドギャップが狭くなるように選ばれており、例えば０．１０≦ｘ≦０．２５であり、０．０１≦ｙ≦０．０５である。本シミュレーションでは一例として、ｘ＝０．１７、ｙ＝０．０３としている。 The In composition x of the In x Ga 1-x N layer used for the well layer is selected so that the band gap is narrower than the In composition y of the In y Ga 1-y N layer used for the barrier layer. For example, 0.10 ≦ x ≦ 0.25 and 0.01 ≦ y ≦ 0.05. In this simulation, as an example, x = 0.17 and y = 0.03.

シミュレーションには、ＳＴＲ社のバンドギャップモデリングシミュレーションソフトウェアであるＳｉＬＥＮＳｅを用い、歪み、分極、転位欠陥、オージェ効果等を考慮した計算を行った。電子移動度を２００ｃｍ２／Ｖ．ｓとし、ホール移動度を５ｃｍ２／Ｖ．ｓとした。 In the simulation, SiLENSe, which is a band gap modeling simulation software manufactured by STR, was used, and calculations were performed in consideration of strain, polarization, dislocation defects, Auger effect, and the like. The electron mobility is 200 cm 2 / V. s, and the hole mobility is 5 cm 2 / V. s.

図３は、第１シミュレーションで得られた第１実施例及び第１比較例によるＧａＮ系半導体発光素子のＩＱＥの電流密度依存性を示すグラフである。第１実施例の結果を四角のプロットで示し、第１比較例の結果を菱形のプロットで示す。   FIG. 3 is a graph showing the current density dependence of IQE of the GaN-based semiconductor light emitting devices according to the first example and the first comparative example obtained in the first simulation. The results of the first example are shown by square plots, and the results of the first comparative example are shown by rhombus plots.

どちらのサンプルについても、ＩＱＥは、電流密度が０から増えると急激に大きくなり、最大値を取った後、電流密度増加に伴い緩やかに減少する傾向を示している。ファーストバリア層をＧａＮとした第１比較例に比べ、ファーストバリア層をＧａＮ／ＡｌＧａＮとした第１実施例は、調べた電流密度のほぼ全域に亘ってＩＱＥがやや高くなる傾向が見られる。   In both samples, IQE increases rapidly when the current density increases from 0, and after taking the maximum value, shows a tendency to gradually decrease as the current density increases. Compared to the first comparative example in which the first barrier layer is GaN, in the first example in which the first barrier layer is GaN / AlGaN, IQE tends to be slightly higher over almost the entire current density examined.

第１実施例で第１比較例に比べＩＱＥが向上した理由について考察する。なお、以下の考察は、上述のシミュレーション結果を解釈するための１つの考え方を示すものである。   The reason why IQE is improved in the first embodiment compared to the first comparative example will be considered. In addition, the following consideration shows one way of thinking for interpreting the above-described simulation result.

図４は、活性層のファーストバリア層をＧａＮ／ＡｌＧａＮ層とした場合の影響を示した、コンダクションバンド及びバレンスバンドの概略的なバンド図である。ファーストバリア層ＢＲをＧａＮ単層とした場合、及びファーストバリア層ＢＲをＧａＮ／ＡｌＧａＮ層とした場合のバンド図を、それぞれ、実線及び破線で示す。   FIG. 4 is a schematic band diagram of a conduction band and a valence band, showing the effect when the first barrier layer of the active layer is a GaN / AlGaN layer. Band diagrams when the first barrier layer BR is a GaN single layer and when the first barrier layer BR is a GaN / AlGaN layer are shown by a solid line and a broken line, respectively.

ファーストバリア層ＢＲにＡｌＧａＮ層を形成したことにより、バンドギャップが広がり、ファーストバリア層のコンダクションバンドにおける電子に対するポテンシャル、及び、バレンスバンドのホールに対するポテンシャルが増加する。   By forming the AlGaN layer in the first barrier layer BR, the band gap is widened, and the potential for electrons in the conduction band of the first barrier layer and the potential for holes in the valence band are increased.

これにより、ファーストバリア層の電子に対するバリア性が向上し、ｎ型半導体層側から活性層に流入する電子が減少すると考えられる。ＧａＮ系半導体素子では、電子に対しホールの移動度が遅く、電子がｐ型半導体層側にリークしやすい。ｎ型半導体層側から活性層に流入する電子の減少により、電子のｐ型半導体層側へのリークが抑制されて、発光効率が向上するのではないかと推測される。   Thereby, it is considered that the barrier property against electrons of the first barrier layer is improved, and electrons flowing into the active layer from the n-type semiconductor layer side are reduced. In a GaN-based semiconductor element, the mobility of holes is slow with respect to electrons, and electrons are likely to leak to the p-type semiconductor layer side. It is presumed that the reduction of electrons flowing from the n-type semiconductor layer side into the active layer suppresses the leakage of electrons to the p-type semiconductor layer side, thereby improving the light emission efficiency.

また、ファーストバリア層のホールに対するバリア性が向上し、活性層からｎ型半導体層側にリークして非発光再結合するホールが減少して、発光効率が向上するのではないかと推測される。   In addition, it is estimated that the barrier property against holes in the first barrier layer is improved, and the number of holes that leak from the active layer to the n-type semiconductor layer and non-light-emitting recombination decreases, thereby improving the light emission efficiency.

なお、第１実施例の構造において、ラストバリア層側では、バリア層がＩｎＧａＮ／ＧａＮ層のままであり、ホールに対するポテンシャル増加が（ホールに対するバリア性の増加が）抑制されている。これにより、ｐ型半導体層側から活性層に入るホールの流れの低減は抑制されている。   In the structure of the first embodiment, on the last barrier layer side, the barrier layer remains an InGaN / GaN layer, and an increase in potential with respect to holes (increase in barrier properties against holes) is suppressed. Thereby, the reduction of the flow of holes entering the active layer from the p-type semiconductor layer side is suppressed.

図５は、第１実施例の変形例によるＧａＮ系半導体発光素子のコンダクションバンドの概略的なバンド図である。第１実施例との差は、活性層２の構造であり、本変形例は、ラストバリア層ｂ１０をＩｎＧａＮ層（例えば厚さ５ｎｍのＩｎ０．０３Ｇａ０．９７Ｎ層）としている。 FIG. 5 is a schematic band diagram of a conduction band of a GaN-based semiconductor light emitting device according to a modification of the first embodiment. The difference from the first embodiment is the structure of the active layer 2. In this modification, the last barrier layer b10 is an InGaN layer (for example, an In 0.03 Ga 0.97 N layer having a thickness of 5 nm).

ラストバリア層ｂ１０をＩｎＧａＮ／ＧａＮ層からＩｎＧａＮ層に変えることにより、ラストバリア層ｂ１０のバンドギャップが狭くなり、ホールに対するバリア性が減少する。これにより、ｐ型半導体層側から活性層２に入るホールの流れの増加が図られ、さらなる発光効率向上が期待される。   By changing the last barrier layer b10 from the InGaN / GaN layer to the InGaN layer, the band gap of the last barrier layer b10 is narrowed, and the barrier property against holes is reduced. Thereby, the flow of holes entering the active layer 2 from the p-type semiconductor layer side is increased, and further improvement in luminous efficiency is expected.

なお、上述の実施例では、バリア層として、ｎ型半導体層側にＩｎＧａＮ層を形成したＩｎＧａＮ／ＧａＮ層を用いた。以下、ＧａＮ系半導体発光素子の多重量子井戸構造の活性層における、ＧａＮバリア層とＩｎＧａＮ／ＧａＮバリア層との違いについて調べた第２シミュレーションについて説明する。   In the above-described embodiment, an InGaN / GaN layer in which an InGaN layer is formed on the n-type semiconductor layer side is used as the barrier layer. Hereinafter, a second simulation in which the difference between the GaN barrier layer and the InGaN / GaN barrier layer in the active layer having the multiple quantum well structure of the GaN-based semiconductor light-emitting device will be described.

第２シミュレーションでは、活性層のバリア層をＧａＮ層とした第２比較例のＧａＮ系半導体発光素子と、活性層のバリア層をＩｎ０．０３Ｇａ０．９７Ｎ／ＧａＮ層とした第３比較例のＧａＮ系半導体発光素子とについて、シミュレーションを行った。第２比較例及び第３比較例とも、ウェル層はＩｎ０．１７Ｇａ０．８３Ｎ層とした。バリア層やウェル層の厚さや、層数等の条件は、第２比較例及び第３比較例で共通である。 In the second simulation, the GaN-based semiconductor light-emitting device of the second comparative example in which the barrier layer of the active layer is a GaN layer and the third comparison in which the barrier layer of the active layer is an In 0.03 Ga 0.97 N / GaN layer. A simulation was performed for the example GaN-based semiconductor light emitting device. In both the second comparative example and the third comparative example, the well layer was an In 0.17 Ga 0.83 N layer. Conditions such as the thickness of the barrier layer and the well layer and the number of layers are common to the second comparative example and the third comparative example.

シミュレーションには、ＳＴＲ社のバンドギャップモデリングシミュレーションソフトウェアであるＳｉＬＥＮＳｅを用い、歪み、分極、転位欠陥、オージェ効果等を考慮した計算を行った。   In the simulation, SiLENSe, which is a band gap modeling simulation software manufactured by STR, was used, and calculations were performed in consideration of strain, polarization, dislocation defects, Auger effect, and the like.

図６Ａ及び図６Ｂは、それぞれ、第２シミュレーションで得られた第２比較例及び第３比較例の活性層におけるコンダクションバンドのバンド図及びバレンスバンドのバンド図である。バレンスバンドにおいて、バリア層をＧａＮ層とした第２比較例に比べ、バリア層をＩｎＧａＮ／ＧａＮ層とした第３比較例の方が、バリア層のホールに対するポテンシャルのピークがやや低くなっていることわかる。これにより、ＩｎＧａＮ／ＧａＮバリア層の方が、ＧａＮバリア層に比べて、例えば、ホールを活性層へ注入しやすくなる効果等があるものと期待される。   6A and 6B are a band diagram of a conduction band and a band diagram of a valence band in the active layers of the second comparative example and the third comparative example, respectively, obtained in the second simulation. In the valence band, the potential peak for the hole in the barrier layer is slightly lower in the third comparative example in which the barrier layer is an InGaN / GaN layer than in the second comparative example in which the barrier layer is a GaN layer. Recognize. Thereby, it is expected that the InGaN / GaN barrier layer has an effect of facilitating injection of holes into the active layer, for example, as compared with the GaN barrier layer.

なお、概略的なバンド図（例えば前述の図２Ａ参照）を考える限りは、ＧａＮ層のバリア層のポテンシャルのピークと、ＩｎＧａＮ／ＧａＮ層のバリア層のポテンシャルのピークとは、どちらもＧａＮ層の部分でピークを取って一致するように思われる。しかし、第２シミュレーションを実施したところ、バレンスバンドにおいて、ＧａＮバリア層よりも、ＩｎＧａＮ／ＧａＮバリア層の方が、ホールに対するポテンシャルのピークがやや低くなることがわかった。   As long as a schematic band diagram (for example, see FIG. 2A described above) is considered, the potential peak of the barrier layer of the GaN layer and the potential peak of the barrier layer of the InGaN / GaN layer are both in the GaN layer. It seems to match by taking a peak in the part. However, when the second simulation was performed, it was found that in the valence band, the InGaN / GaN barrier layer had a slightly lower potential peak for holes than the GaN barrier layer.

以上説明したように、ＧａＮ系半導体発光素子の多重量子井戸構造の活性層において、最もｎ型半導体層側のファーストバリア層をＧａＮ／ＡｌＧａＮ層で形成し、ファーストバリア層よりもｐ型半導体層側のバリア層をＩｎＧａＮ／ＧａＮ層で形成することにより、発光効率の向上を図ることができる。また、最もｐ型半導体層側のラストバリア層をＩｎＧａＮ層とすることにより、さらなる発光効率向上が期待される。   As described above, in the active layer having the multiple quantum well structure of the GaN-based semiconductor light emitting device, the first barrier layer closest to the n-type semiconductor layer is formed of a GaN / AlGaN layer, and the p-type semiconductor layer side of the first barrier layer. The light emission efficiency can be improved by forming the barrier layer of InGaN / GaN layers. Further, when the last barrier layer closest to the p-type semiconductor layer is an InGaN layer, further improvement in luminous efficiency is expected.

以上実施例に沿って本発明を説明したが、本発明はこれらに制限されるものではない。例えば、種々の変更、改良、組み合わせ等が可能なことは当業者に自明であろう。   Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

１ ｎ型ＧａＮ層
２ 活性層
３ ｐ型ＡｌＧａＮクラッド層
４ ｐ型ＧａＮ層
ｂ１〜ｂ１０ バリア層
ｗ２〜ｗ９ ウェル層 1 n-type GaN layer 2 active layer 3 p-type AlGaN cladding layer 4 p-type GaN layers b1 to b10 barrier layers w2 to w9 well layers

Claims (2)

ｎ型導電性を有するＧａＮ系半導体で形成されたｎ型半導体層と、
前記ｎ型半導体層上に形成され、ＧａＮ系半導体で形成され、バリア層とウェル層とが交互に複数層積層された多重量子井戸構造を有する活性層と、
前記活性層上に形成され、ｐ型導電性を有するＧａＮ系半導体で形成されたｐ型半導体層と
を有し、
前記活性層は、最もｎ型半導体層側の第１バリア層がＧａＮ／ＡｌＧａＮ層で形成され、前記第１バリア層よりもｐ型半導体層側のバリア層がＩｎＧａＮ／ＧａＮ層で形成され、ウェル層が、前記ＩｎＧａＮ／ＧａＮ層のバリア層のＩｎＧａＮ層よりもバンドギャップの狭いＩｎＧａＮ層で形成されているＧａＮ系半導体発光素子。 an n-type semiconductor layer formed of a GaN-based semiconductor having n-type conductivity;
An active layer formed on the n-type semiconductor layer, formed of a GaN-based semiconductor, and having a multiple quantum well structure in which a plurality of barrier layers and well layers are alternately stacked;
A p-type semiconductor layer formed on the active layer and formed of a GaN-based semiconductor having p-type conductivity;
The active layer has a first barrier layer closest to the n-type semiconductor layer formed of a GaN / AlGaN layer, a barrier layer closer to the p-type semiconductor layer than the first barrier layer formed of an InGaN / GaN layer, A GaN-based semiconductor light emitting device, wherein the layer is formed of an InGaN layer having a narrower band gap than the InGaN layer of the barrier layer of the InGaN / GaN layer. 前記活性層は、前記第１バリア層よりも前記ｐ型半導体層側のバリア層のうち、最もｐ型半導体層側のバリア層がＩｎＧａＮ層で形成されている請求項１に記載のＧａＮ系半導体発光素子。   2. The GaN-based semiconductor according to claim 1, wherein, in the active layer, a barrier layer closest to the p-type semiconductor layer among the barrier layers closer to the p-type semiconductor layer than the first barrier layer is formed of an InGaN layer. Light emitting element.
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