JP2006351956A - Method of growing compound semiconductor crystal, and semiconductor device and semiconductor substrate provided with compound semiconductor crystal layer grown using the method - Google Patents
Method of growing compound semiconductor crystal, and semiconductor device and semiconductor substrate provided with compound semiconductor crystal layer grown using the method Download PDFInfo
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- 239000004065 semiconductor Substances 0.000 title claims abstract description 75
- 238000000034 method Methods 0.000 title claims abstract description 68
- 239000013078 crystal Substances 0.000 title claims abstract description 61
- 150000001875 compounds Chemical class 0.000 title claims abstract description 47
- 239000000758 substrate Substances 0.000 title claims abstract description 24
- 239000002994 raw material Substances 0.000 claims abstract description 90
- 229910021478 group 5 element Inorganic materials 0.000 claims abstract description 42
- 238000002488 metal-organic chemical vapour deposition Methods 0.000 claims abstract 2
- 239000002096 quantum dot Substances 0.000 claims description 91
- 239000010410 layer Substances 0.000 claims description 64
- 229910001218 Gallium arsenide Inorganic materials 0.000 claims description 39
- RPQDHPTXJYYUPQ-UHFFFAOYSA-N indium arsenide Chemical compound [In]#[As] RPQDHPTXJYYUPQ-UHFFFAOYSA-N 0.000 claims description 19
- 229910000673 Indium arsenide Inorganic materials 0.000 claims description 12
- 238000002109 crystal growth method Methods 0.000 claims description 9
- 238000000151 deposition Methods 0.000 claims description 5
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- 239000002356 single layer Substances 0.000 claims description 3
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- QTQRGDBFHFYIBH-UHFFFAOYSA-N tert-butylarsenic Chemical compound CC(C)(C)[As] QTQRGDBFHFYIBH-UHFFFAOYSA-N 0.000 description 11
- 230000015572 biosynthetic process Effects 0.000 description 10
- 230000000694 effects Effects 0.000 description 7
- IBEFSUTVZWZJEL-UHFFFAOYSA-N trimethylindium Chemical compound C[In](C)C IBEFSUTVZWZJEL-UHFFFAOYSA-N 0.000 description 7
- 229910000980 Aluminium gallium arsenide Inorganic materials 0.000 description 6
- 230000003287 optical effect Effects 0.000 description 6
- 238000005253 cladding Methods 0.000 description 5
- 238000011160 research Methods 0.000 description 5
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
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- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- DIIIISSCIXVANO-UHFFFAOYSA-N 1,2-Dimethylhydrazine Chemical compound CNNC DIIIISSCIXVANO-UHFFFAOYSA-N 0.000 description 3
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- 238000005424 photoluminescence Methods 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- RGGPNXQUMRMPRA-UHFFFAOYSA-N triethylgallium Chemical compound CC[Ga](CC)CC RGGPNXQUMRMPRA-UHFFFAOYSA-N 0.000 description 3
- 229910052785 arsenic Inorganic materials 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
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Abstract
Description
本発明は、ＭＯＣＶＤ(Metal-Organic Chemical Vapor Deposition)法を用いて 化合物半導体結晶を成長させる化合物半導体結晶の成長方法、その成長方法を用いて成長した化合物半導体結晶の層を備えた半導体装置及び半導体基板に関する。 The present invention relates to a compound semiconductor crystal growth method for growing a compound semiconductor crystal using a MOCVD (Metal-Organic Chemical Vapor Deposition) method, a semiconductor device having a layer of the compound semiconductor crystal grown using the growth method, and a semiconductor Regarding the substrate.
量子ドット構造は電子を３次元的に閉じ込めることで、状態密度がδ関数的な離散準位を持つ。したがって量子ドットにキャリアを注入すると、キャリアは離散準位のエネルギーに集中する。その結果、量子ドットからの発光スペクトルはエネルギー広がりが非常に狭く、強度が大きいものになる。この量子ドット構造を例えば半導体レーザの活性層に適用すると、半導体レーザの閾値が低減する、温度特性が向上する、変調帯域が拡大することなどが期待される。 The quantum dot structure has a discrete level in which the density of states is a δ function by confining electrons three-dimensionally. Therefore, when carriers are injected into the quantum dots, the carriers are concentrated at discrete level energy. As a result, the emission spectrum from the quantum dots has a very narrow energy spread and a high intensity. When this quantum dot structure is applied to, for example, an active layer of a semiconductor laser, it is expected that the threshold of the semiconductor laser is reduced, temperature characteristics are improved, and the modulation band is expanded.
こうした優れた特性の量子ドットデバイスを実現するためには、サイズ均一性に優れ、かつ発光強度の強い量子ドット構造を、制御性良く作製する必要がある。 In order to realize a quantum dot device having such excellent characteristics, it is necessary to produce a quantum dot structure having excellent size uniformity and strong emission intensity with good controllability.
量子ドット構造を得るためには、従来はリソグラフィーとドライエッチングなどによる加工技術を用いていたが、この作製方法の場合、加工に伴う損傷が結晶中に導入されるため、発光効率などが低下するという問題点があった。 In order to obtain a quantum dot structure, processing techniques such as lithography and dry etching have been used in the past. However, in the case of this manufacturing method, damage caused by processing is introduced into the crystal, resulting in a decrease in luminous efficiency and the like. There was a problem.
これに対し、基板と量子ドット材料間の格子不整合からくる歪を利用した、ＳＫ(Stransky-Krastanov)モード成長と呼ばれる自己形成成長法によって量子ドットを成長する手法が提案され、現在ではこの自己形成方法が量子ドット研究の主流となっている。この方法を用いると、先に述べたような加工による結晶への損傷を回避でき、かつ高密度に量子ドットを形成できる。また、この自己形成方法において、原料供給方法に創意工夫を凝らし特性を向上する提案もなされている。例えば、特許文献１では、この量子ドットの自己形成法において量子ドット原料のうち一方の族の元素を含む原料と他方の族の元素を含む原料を交互に供給する成長方法を提案している。また、特許文献１によれば、この成長方法を用いることで量子ドットを高密度に成長することができる。 On the other hand, a method for growing quantum dots by a self-forming growth method called SK (Stransky-Krastanov) mode growth using strain resulting from lattice mismatch between the substrate and the quantum dot material has been proposed. The formation method has become the mainstream of quantum dot research. When this method is used, damage to the crystal due to the processing as described above can be avoided, and quantum dots can be formed at a high density. Also, in this self-forming method, proposals have been made to improve the characteristics by ingenuating the raw material supply method. For example, Patent Document 1 proposes a growth method in which, in this quantum dot self-forming method, a raw material containing an element of one group and a raw material containing an element of the other group are alternately supplied. Further, according to Patent Document 1, quantum dots can be grown at high density by using this growth method.
また、例えば特許文献２では、Ｖ族元素を含む原料を連続的に供給するとともにIII族元素を含む原料を断続的に供給する量子ドットの自己形成方法を提案している。そして、特許文献２によれば、この量子ドットの自己形成方法を用いると量子ドットの形成が促進され、半導体量子ドットレーザ素子の発振閾値電流密度が低閾値化する。 For example, Patent Document 2 proposes a self-forming method of quantum dots that continuously supplies a raw material containing a group V element and intermittently supplies a raw material containing a group III element. According to Patent Document 2, when this quantum dot self-forming method is used, the formation of quantum dots is promoted, and the oscillation threshold current density of the semiconductor quantum dot laser element is lowered.
しかしながら、こうした自己形成方法を用いての量子ドット成長は結晶成長技術として難しく、現在のところマージン幅の非常に狭い成長条件下でしか、品質の良い量子ドットは得られていない。しかも、量子ドットに本来期待されている、状態密度の離散性を示すために必要なドットのサイズ均一性や、レーザ素子に応用した場合などに要求される高い発光特性などの性能は未だ不十分である。
自己形成方法による量子ドット成長方法の現状の課題として、量子ドットのサイズ均一性と発光効率が不十分であることが挙げられる。現状では量子ドットのサイズ均一性を向上するための手法としては、成長速度の最適化、Ｖ族元素を含む原料とIII族元素を含む原料との供給比の最適化、量子ドットの積層化、量子ドット形成後の結晶成長中アニールなどの手法が研究されているが、いずれの手法も結晶成長条件のマージン幅が狭い、量子ドットのサイズ均一性が不十分であるなどの問題点がある。 A current problem with the self-forming quantum dot growth method is that the quantum dot size uniformity and light emission efficiency are insufficient. At present, methods for improving the size uniformity of quantum dots include optimization of growth rate, optimization of the supply ratio of raw materials containing group V elements and group III elements, stacking of quantum dots, Methods such as annealing during crystal growth after the formation of quantum dots have been studied. However, each method has problems such as a narrow margin width for crystal growth conditions and insufficient quantum dot size uniformity.
また、発光効率を向上する目的では、結晶成長条件の詳細な検討、結晶成長終了後の熱アニールなどの研究が行われているが、やはり結晶成長条件のマージン幅が狭い、発光強度は増大するものの発光波長が短波長化してしまうなどの問題点がある。 In addition, for the purpose of improving luminous efficiency, detailed studies of crystal growth conditions and research on thermal annealing after the completion of crystal growth have been conducted. However, the margin width of crystal growth conditions is also narrow and the emission intensity increases. However, there is a problem that the light emission wavelength is shortened.
本発明は、上記事情を考慮してなされたものであって、量子ドットのサイズ均一性と発光効率を向上させることのできる化合物半導体結晶の成長方法、その成長方法を用いて成長した化合物半導体結晶の層を備えた半導体装置及び半導体基板を提供することを目的とする。 The present invention has been made in view of the above circumstances, and a compound semiconductor crystal growth method capable of improving quantum dot size uniformity and light emission efficiency, and a compound semiconductor crystal grown using the growth method An object of the present invention is to provide a semiconductor device and a semiconductor substrate including the above layers.
本発明の第１の態様による化合物半導体結晶の成長方法は、ＭＯＣＶＤ法を用いて、化合物半導体基板上に、III族元素およびＶ族元素を含む化合物半導体結晶を成長させる化合物半導体結晶の成長方法であって、
前記III族元素を含む原料を連続的に供給し、前記Ｖ族元素を含む原料の供給と停止とを繰り返して行う工程を備えたことを特徴とする。
The compound semiconductor crystal growth method according to the first aspect of the present invention is a compound semiconductor crystal growth method in which a compound semiconductor crystal containing a group III element and a group V element is grown on a compound semiconductor substrate using MOCVD. There,
The method includes a step of continuously supplying a raw material containing the group III element and repeatedly supplying and stopping the raw material containing the group V element.
なお、前記III族元素およびＶ族元素を含む化合物半導体の堆積量が１モノレイヤー以下である間に前記Ｖ族元素を含む原料の供給と停止とを繰り返してもよい。 The supply and stop of the raw material containing the group V element may be repeated while the deposition amount of the compound semiconductor containing the group III element and the group V element is one monolayer or less.
なお、記化合物半導体基板としてＧａＡｓを用い、前記化合物半導体結晶はＧａ１−ｘＩｎｘＡｓ１−ｙＮｙ（０．３≦ｘ≦１、０≦１−ｘ≦０．７、０≦ｙ≦０．３、０．７≦１−ｙ≦１）であってもよい。 Incidentally, a GaAs as serial compound semiconductor substrate, said compound semiconductor crystal Ga 1-x In x As 1 -y N y (0.3 ≦ x ≦ 1,0 ≦ 1-x ≦ 0.7,0 ≦ y ≦ 0.3, 0.7 ≦ 1-y ≦ 1).
なお、前記化合物半導体基板としてＧａＡｓまたはＩｎＡｓを用い、前記化合物半導体結晶はＧａ１−ｘＩｎｘＡｓ１−ｙＮｙ（０．７≦ｘ≦１、０≦１−ｘ≦０．３、０≦ｙ≦１、０≦１−ｙ≦１）であってもよい。 Note that GaAs or InAs is used as the compound semiconductor substrate, and the compound semiconductor crystal is Ga 1-x In x As 1-y N y (0.7 ≦ x ≦ 1, 0 ≦ 1-x ≦ 0.3, 0 ≦ y ≦ 1, 0 ≦ 1−y ≦ 1).
なお、前記化合物半導体結晶を成長する際に、Ｖ族元素であるＡｓの原料が供給されているときにＮの原料の供給を停止し、Ｖ族元素であるＡｓの原料の供給が停止されているときにＮの原料を供給してもよい。 When growing the compound semiconductor crystal, the supply of the N raw material is stopped when the source of the As group V element is supplied, and the supply of the As raw material of the group V element is stopped. N raw material may be supplied when
また、本発明の第２の態様による半導体装置は、上記いずれかの成長方法を用いて成長した化合物半導体結晶の層を備えたことを特徴とする。 According to a second aspect of the present invention, there is provided a semiconductor device comprising a compound semiconductor crystal layer grown using any one of the above growth methods.
なお、前記化合物半導体結晶の層が量子ドット層であってもよい。 The compound semiconductor crystal layer may be a quantum dot layer.
なお、前記量子ドット層は、半導体レーザの活性層であってもよい。 The quantum dot layer may be an active layer of a semiconductor laser.
また、本発明の第３の態様による半導体基板は、上記いずれかの成長方法を用いて成長した化合物半導体結晶の層を備えたことを特徴とする。 According to a third aspect of the present invention, there is provided a semiconductor substrate comprising a compound semiconductor crystal layer grown using any one of the above growth methods.
なお、前記化合物半導体結晶の層が量子ドット層であってもよい。 The compound semiconductor crystal layer may be a quantum dot layer.
本発明によれば、量子ドットのサイズ均一性と発光効率を向上させることができる。 According to the present invention, the quantum dot size uniformity and light emission efficiency can be improved.
以下に本発明の実施形態を、図を参照して説明する。 Embodiments of the present invention will be described below with reference to the drawings.
（第１実施形態）
本発明の第１実施形態による化合物半導体結晶の成長方法を図１乃至図２を参照して説明する。
(First embodiment)
A method of growing a compound semiconductor crystal according to the first embodiment of the present invention will be described with reference to FIGS.
本実施形態の方法は、ＭＯＣＶＤ法(Metal-Organic Chemical Vapor Deposition)を用いて、図２に示すような、ＧａＡｓ基板１上に膜厚５００ｎｍのＧａＡｓからなるバッファー層２、膜厚２．７ＭＬ（モノレイヤー（単原子層））のＩｎＡｓからなる量子ドット３を順次成長した構造を持つ化合物半導体結晶を成長するものである。III族であるＧａの原料としてＴＥＧ（トリエチルガリウム）、Ｉｎの原料としてＴＭＩ（トリメチルインジウム）、Ｖ族であるＡｓの原料としてｔＢＡ（ターシャルブチルアルシン）を使用する。 The method of this embodiment uses MOCVD (Metal-Organic Chemical Vapor Deposition), as shown in FIG. 2, on a GaAs substrate 1 with a buffer layer 2 made of GaAs having a thickness of 500 nm, a thickness of 2.7 ML ( A compound semiconductor crystal having a structure in which quantum dots 3 made of InAs of monolayer (monoatomic layer) are sequentially grown is grown. TEG (triethylgallium) is used as the raw material for Ga which is a group III, TMI (trimethylindium) is used as the raw material for In, and tBA (tertiarybutylarsine) is used as the raw material for As which is a group V.
本実施形態においては、ＧａＡｓからなるバッファー層２の形成は、III族であるＧａの原料ＴＥＧと、Ｖ族であるＡｓの原料ｔＢＡを６５０℃の反応室に連続的に供給して形成する。これに対して、ＩｎＡｓ量子ドット３の形成は、図１に示すように、III族であるＩｎの原料ＴＭＩを所定温度の反応室に連続的に供給するが、Ｖ族であるＡｓの原料ｔＢＡを断続的に供給する。すなわち、Ａｓの原料ｔＢＡを時間ｔ１だけ供給した後、時間ｔ２の間Ａｓの原料ｔＢＡの供給を停止し、これを所定回数繰り返す。 In this embodiment, the buffer layer 2 made of GaAs is formed by continuously supplying a Group III Ga source TEG and a Group V As source tBA to a reaction chamber at 650 ° C. On the other hand, as shown in FIG. 1, the InAs quantum dots 3 are formed by continuously supplying a group III In raw material TMI to a reaction chamber at a predetermined temperature. Supply intermittently. That is, after supplying the source tBA of As by a time t 1, to stop the supply of the raw material tBA of As during the time t 2, repeat this predetermined number of times.
ＩｎＡｓ量子ドット３は約４００℃〜６００℃の成長温度で成長可能である。成長温度が４００℃未満では原料分解効率が低下し量子ドットが形成されない。また６００℃を超えると結晶成長表面からの原子の脱離が激しく、やはり量子ドットが形成されない。品質の良い量子ドットを成長するためには、成長温度は特に４５０℃〜５２０℃が好ましく、本実施形態においては４９０℃を選択している。 The InAs quantum dots 3 can be grown at a growth temperature of about 400 ° C. to 600 ° C. If the growth temperature is less than 400 ° C., the raw material decomposition efficiency is lowered and quantum dots are not formed. On the other hand, when the temperature exceeds 600 ° C., the detachment of atoms from the crystal growth surface is severe, and no quantum dots are formed. In order to grow high quality quantum dots, the growth temperature is particularly preferably 450 ° C. to 520 ° C., and 490 ° C. is selected in this embodiment.
また、ＩｎＡｓ量子ドット３は成長速度０．００１ＭＬ／ｓ〜０．２ＭＬ／ｓで成長可能であるが、品質の良い量子ドットを成長するためには、特に０．００５ＭＬ／ｓ〜０．０２ＭＬ／ｓが好ましく、本実施形態においては０．０１３ＭＬ／ｓを選択している。品質の良い量子ドットの成長には、後述するが、熱平衡状態に近い状態を保つ時間が必要である。このため０．２ＭＬ／ｓを超える成長速度では量子ドットが形成されない。また、成長速度が０．００１ＭＬ／ｓ未満であると結晶成長表面からの原子の脱離が激しく、やはり量子ドットが形成されない。 InAs quantum dots 3 can be grown at a growth rate of 0.001 ML / s to 0.2 ML / s. In order to grow high-quality quantum dots, 0.005 ML / s to 0.02 ML / s s is preferable, and 0.013 ML / s is selected in the present embodiment. As will be described later, the growth of high-quality quantum dots requires time to maintain a state close to a thermal equilibrium state. For this reason, quantum dots are not formed at a growth rate exceeding 0.2 ML / s. Further, when the growth rate is less than 0.001 ML / s, the detachment of atoms from the crystal growth surface is severe, and the quantum dots are not formed.
ＩｎＡｓ量子ドット３の成長速度を０．０１３ＭＬ／ｓとすると、２．７ＭＬの量子ドット層の成長には約２１０秒が必要である。この際、従来の成長方法では、III族元素を含む原料、Ｖ族元素を含む原料ともに２１０秒間連続で供給し続け、Ｖ族元素を含む原料とIII族元素を含む原料との比の制御などは供給する各原料の流量で制御する。 If the growth rate of the InAs quantum dots 3 is 0.013 ML / s, about 210 seconds are required for the growth of the 2.7 ML quantum dot layer. At this time, in the conventional growth method, the raw material containing the group III element and the raw material containing the group V element are continuously supplied for 210 seconds, and the ratio of the raw material containing the group V element and the raw material containing the group III element is controlled. Is controlled by the flow rate of each raw material to be supplied.
これに対し、本実施形態では、Ｖ族元素を含む原料の供給を時分割的に行う。すなわち、図１に示すように、III族であるＩｎの原料ＴＭＩは連続で２１０秒間供給し続けるが、Ｖ族であるＡｓの原料ｔＢＡは、３秒（＝ｔ１）供給と、７秒（＝ｔ２）供給停止というサイクルを２１回繰り返すなどの形で、時分割的に供給する。 On the other hand, in this embodiment, the raw material containing a group V element is supplied in a time-sharing manner. That is, as shown in FIG. 1, the group III In raw material TMI is continuously supplied for 210 seconds, while the group V As raw material tBA is supplied for 3 seconds (= t 1 ) and 7 seconds ( = T 2 ) Supply in a time-sharing manner, for example, by repeating a cycle of supply stop 21 times.
このようにして本実施形態の成長方法を用いて量子ドット３を成長した場合、Ｖ族元素を含む原料の供給を停止している間は、結晶の成長最表面でのＶ族元素を含む原料の濃度が低下するためにIII族原子の表面拡散距離が増し、従来の成長方法と比較してより熱平衡に近い条件で量子ドット形成が促進されるようになる。 Thus, when the quantum dot 3 is grown using the growth method of the present embodiment, the raw material containing the group V element on the crystal growth outermost surface is stopped while the supply of the raw material containing the group V element is stopped. As a result, the surface diffusion distance of group III atoms increases, and the formation of quantum dots is promoted under conditions closer to thermal equilibrium as compared with conventional growth methods.
本実施形態の成長方法によって形成された量子ドット３は自己サイズ制御効果が強く働き、従来の場合と比較してサイズ均一性が大幅に向上する。またその結果、発光に寄与するサイズの量子ドット密度が大幅に上昇することから、発光強度も増大する。すなわち、本実施形態の成長方法を用いることで、量子ドットのサイズ制御性・発光効率を向上することができる。本実施形態の成長方法において、非常に重要なことは、特許文献１（特開２０００−２２１３０号公報）や特許文献２（特開２００４−３４２８５１号公報）に記載された従来の成長方法と異なり、III族元素を含む原料の供給を停止してはいけないことである。III族元素を含む原料の供給を停止する時間を設けると、III族原子の空孔型欠陥が導入され、量子ドット３の発光強度が低下するからである。 The quantum dots 3 formed by the growth method of the present embodiment have a strong self-size control effect, and the size uniformity is greatly improved as compared with the conventional case. As a result, the density of quantum dots having a size contributing to light emission greatly increases, and the light emission intensity also increases. That is, by using the growth method of the present embodiment, the size controllability and light emission efficiency of the quantum dots can be improved. In the growth method of this embodiment, what is very important is different from the conventional growth methods described in Patent Document 1 (Japanese Patent Laid-Open No. 2000-22130) and Patent Document 2 (Japanese Patent Laid-Open No. 2004-342851). The supply of raw materials containing group III elements should not be stopped. This is because if a time for stopping the supply of the raw material containing the group III element is provided, the vacancy type defect of the group III atom is introduced and the emission intensity of the quantum dot 3 is lowered.
また、本実施形態においては、Ｖ族であるＡｓの原料ｔＢＡを、３秒供給→７秒供給停止というサイクルで時分割供給しているが、必ずしもこの値である必要は無い。サイズ制御性向上の効果を得るには、量子ドットが所望以上の大きさ（発光に寄与しなくなる大きさ）に成長してしまう前に、上記したような熱平衡に近い状態にし、自己サイズ制御効果が働くことでサイズ均一性が向上する時分割値であることが好ましい。 In this embodiment, the As raw material tBA of Group V is supplied in a time-sharing manner in a cycle of 3 second supply → 7 second supply stop, but this value is not necessarily required. In order to obtain the effect of improving the size controllability, before the quantum dot grows to a size larger than desired (a size that does not contribute to light emission), it is brought into a state close to the thermal equilibrium as described above, and the self size control effect is achieved. It is preferable that the time division value improves the size uniformity by working.
そうした高いサイズ均一性が得られる最適時分割値は、成長速度等の他の成長条件にも依存するため一概に決定することはできない。しかしながら、大きい量子ドットの成長を効果的に抑制するためには、量子ドットの原料（本実施形態ではＩｎＡｓ）の堆積量が１ＭＬ以下である間にＶ族原料の供給を停止するような時分割値を取り、量子ドットを短い間隔で繰り返し熱平衡に近い状態にしてやることが効果的である。堆積量が１ＭＬ以上となるまで量子ドットの原料を時分割せずに、連続的に供給してしまうと、サイズ均一性が悪いまま量子ドットの成長が進み、その後熱平衡状態に置いても自己サイズ制御効果が得られない。 The optimum time division value for obtaining such a high size uniformity depends on other growth conditions such as the growth rate, and cannot be determined unconditionally. However, in order to effectively suppress the growth of large quantum dots, the time division is such that the supply of group V materials is stopped while the amount of deposited quantum dot materials (InAs in this embodiment) is 1 ML or less. It is effective to take a value and make the quantum dot close to thermal equilibrium at short intervals. If the raw material of the quantum dots is continuously supplied without time division until the deposition amount reaches 1 ML or more, the growth of the quantum dots proceeds with poor size uniformity, and then self-size even when placed in a thermal equilibrium state. The control effect cannot be obtained.
また、時間の制御も重要である。本発明者の鋭意研究の結果によると、時分割供給においてＶ族元素を含む原料の供給の停止を３０秒以上にすると、Ｖ族元素の空孔欠陥が導入され発光強度が大幅に低下したり、結晶成長表面でのＶ族元素を含む原料の量が足りなくなり量子ドットが成長されないことがわかっている。また、Ｖ族元素を含む原料の供給する時間を連続で３０秒間以上にすると、上述した熱平衡に近い状態を保持する時間が少なく、形成される量子ドットのサイズ制御性は、従来の場合の量子ドットと大差が無い。III族元素を含む原料の供給量が１ＭＬ未満であるうちに、量子ドットを上記したような熱平衡に近い状態にすることが重要であるためだと考えられる。 Time control is also important. According to the result of earnest research by the present inventor, when the supply of the raw material containing the group V element is stopped for 30 seconds or more in the time division supply, the vacancy defect of the group V element is introduced and the emission intensity is greatly reduced. It has been found that quantum dots are not grown because the amount of the raw material containing the group V element is insufficient on the crystal growth surface. Further, when the supply time of the raw material containing the group V element is continuously set to 30 seconds or more, the time for maintaining the above-described state close to thermal equilibrium is small, and the size controllability of the formed quantum dots is the same as that of the conventional case. There is no big difference with dots. It is considered that it is important to bring the quantum dots into a state close to thermal equilibrium as described above while the supply amount of the raw material containing the group III element is less than 1 ML.
また、一般にＭＯＣＶＤ装置の原料流量制御装置の特性上、時分割の時間値を０．１秒以下にしようとしても、制御不可能である。このため、時分割法に適用できる供給する時間と、供給を停止する時間は０．１秒〜３０秒が限度である。ＧａＡｓバッファー層２上のＩｎＡｓ量子ドット３の成長においては、成長速度０．０１３ＭＬ／ｓの時にＶ族元素を含む原料（この場合Ａｓを含む原料）を１秒〜３秒供給し、その後７秒〜９秒の供給の停止を行うサイクルを繰り返す時分割比が、上記したような効果が最も得られ、量子ドットのサイズ均一性・発光効率が最も高くなり好ましい。 In general, due to the characteristics of the raw material flow rate control device of the MOCVD apparatus, control is impossible even if the time division time value is set to 0.1 seconds or less. For this reason, the supply time applicable to the time division method and the time for stopping the supply are limited to 0.1 to 30 seconds. In the growth of InAs quantum dots 3 on the GaAs buffer layer 2, a raw material containing a group V element (in this case, a raw material containing As) is supplied for 1 to 3 seconds at a growth rate of 0.013 ML / s, and then 7 seconds. A time division ratio of repeating a cycle of stopping supply for ˜9 seconds is preferable because the above-described effects can be most obtained, and the quantum dot size uniformity and luminous efficiency are the highest.
なお、成長速度が上記例（０．０１３ＭＬ／ｓ）よりも速い場合には、供給する時間と供給を停止する時間をともに短くし、１サイクルにかかる時間を短くしてやると良い。これに対して、成長速度が遅い場合には供給する時間と供給を停止する時間をともに長くし、１サイクルにかかる時間を長くしてやると良い。 When the growth rate is faster than the above example (0.013 ML / s), it is preferable to shorten both the supply time and the supply stop time and the time required for one cycle. On the other hand, when the growth rate is slow, it is preferable to increase both the supply time and the supply stop time, and increase the time required for one cycle.
また、本実施形態の成長方法を用いると、Ｖ族元素を含む原料の供給を停止する時間を変えることで平均的なＶ族元素を含む原料とIII族元素を含む原料との比を厳密に制御することが可能になるため、量子ドットの自己形成成長法において重要な成長条件の一つであるＶ族元素を含む原料とIII族元素を含む原料との比の制御性を格段に高めることが可能である。 Further, when the growth method of the present embodiment is used, the ratio of the average raw material containing the group V element and the raw material containing the group III element is strictly determined by changing the time for stopping the supply of the raw material containing the group V element. Because it becomes possible to control, the controllability of the ratio of the raw material containing the group V element and the raw material containing the group III element, which is one of the important growth conditions in the self-forming growth method of quantum dots, is remarkably improved. Is possible.
また通常、量子ドットの自己形成法による成長では、量子井戸やバルクの成長と比較して１桁〜２桁ほども低い０．１前後のＶ族元素を含む原料とIII族元素を含む原料との比が適応され、しかもそのマージン幅は非常に狭い。そして、一つの流量制御器でバルク層部分と量子ドット層部分の両方のＶ族元素を含む原料とIII族元素を含む原料との比に対応できるような広域に渡る制御性を得ることは難しく、従来は、ＭＯＣＶＤ装置のＶ族元素を含む原料供給ラインをバルク用と量子ドット用の２つ以上にする方法が一般的である。 In general, in the growth of quantum dots by a self-forming method, a raw material containing a group V element of about 0.1 and a raw material containing a group III element, which is about 1 to 2 orders of magnitude lower than a quantum well or bulk growth, And the margin width is very narrow. And it is difficult to obtain controllability over a wide area so that a single flow rate controller can cope with the ratio of the raw material containing the group V element and the raw material containing the group III element in both the bulk layer portion and the quantum dot layer portion. Conventionally, a method of using two or more raw material supply lines containing a group V element in an MOCVD apparatus for bulk and for quantum dots is generally used.
これに対し、本実施形態の成長方法を用いれば、Ｖ族元素を含む原料の供給を停止する時間を変えることで、Ｖ族元素を含む原料とIII族元素を含む原料との供給比が高い流量制御器を用いてＶ族元素を含む原料とIII族元素を含む原料との低い供給比が厳密に制御することが可能になるため、量子ドット専用のＶ族元素を含む原料供給ラインの必要が無い。このことはＭＯＣＶＤ装置設計の自由度を高め、ＭＯＣＶＤ装置の値段の低減にもつながる。 On the other hand, if the growth method of this embodiment is used, the supply ratio of the raw material containing a V group element and the raw material containing a III group element is high by changing the time which stops supply of the raw material containing a V group element. Since it is possible to strictly control the low supply ratio of the raw material containing the group V element and the raw material containing the group III element by using the flow rate controller, it is necessary to provide a raw material supply line containing the group V element dedicated to the quantum dot. There is no. This increases the degree of freedom in designing the MOCVD apparatus and leads to a reduction in the price of the MOCVD apparatus.
本実施形態では、ＧａＡｓ基板上のＩｎＡｓ量子ドットを例にとって説明したが、成長する化合物半導体のIII族材料としてはＩｎの他にＧａやＡｌでも良い。 In the present embodiment, the InAs quantum dots on the GaAs substrate have been described as an example, but the group III material of the compound semiconductor to be grown may be Ga or Al in addition to In.
またＶ族材料としてはＡｓの他にＮやＰ、Ｓｂなどでも良い。 In addition to As, the group V material may be N, P, Sb, or the like.
また、量子ドットのサイズ制御性・発光特性が向上する技術であるので、ＧａＮやＩｎＧａＮなどの材料を用いた量子ドットでも良い。その際は格子整合の問題から基板としては、サファイアやＳｉＣなどでも良い。 In addition, since the quantum dot size controllability and light emission characteristics are improved, quantum dots using materials such as GaN and InGaN may be used. In this case, sapphire, SiC, or the like may be used as the substrate due to lattice matching problems.
なお、量子ドットの原料としては特にＧａ１−ｘＩｎｘＡｓ１−ｙＮｙ（０．３≦ｘ≦１、０≦１−ｘ≦０．７、０≦ｙ≦０．３、０．７≦１−ｙ≦１）である場合にはより効果的である。 Incidentally, in particular Ga 1-x In x As 1 -y N y (0.3 ≦ x ≦ 1,0 ≦ 1-x ≦ 0.7,0 ≦ y ≦ 0.3,0 as a raw material of the quantum dots. It is more effective when 7 ≦ 1-y ≦ 1).
（実施例１）
次に、本発明の実施例１の成長方法を説明する。この実施例は、ＧａＡｓ基板上に形成されたＧａＡｓバッファー層上に、ＩｎＡｓ量子ドットを結晶成長させるものである。これに対して、比較例として、Ｖ族元素を含む原料の供給を時分割せずに連続して供給する以外は、平均的な、Ｖ族元素を含む原料とIII族元素を含む原料との供給比を初めとする諸成長条件を本実施例と全て等しくして成長した量子ドットサンプルも作成した。
Example 1
Next, the growth method of Example 1 of the present invention will be described. In this embodiment, InAs quantum dots are grown on a GaAs buffer layer formed on a GaAs substrate. On the other hand, as a comparative example, an average raw material containing a group V element and a raw material containing a group III element, except that the supply of the raw material containing a group V element is continuously supplied without time division. Quantum dot samples grown with all the growth conditions including the supply ratio equal to those in this example were also prepared.
サンプルの構造は図２に示した構造とほぼ同等であり、ＧａＡｓ基板１上にＧａＡｓバッファー層２、ＩｎＡｓ量子ドット３を順次成長している。量子ドット３の成長温度は４９０℃、成長速度は０．０１３ＭＬ／ｓ、堆積量は２．７ＭＬ、成長時間２１０秒、ドット成長中の平均的な、Ｖ族元素を含む原料とIII族元素を含む原料との供給比は約０．４である。Ｉｎの原料ＴＭＩの供給流量はバブリング水素量にして３．４ｃｃ／ｍｉｎ、Ａｓの原料ｔＢＡの供給流量は同じくバブリング水素量にして、比較例では０．３ｃｃ／ｍｉｎ、本実施例では３ｃｃ／ｍｉｎである。量子ドットを形成する際に、比較例ではＩｎ、Ａｓ共に連続で供給しているが、本実施例ではＡｓの原料ｔＢＡを、１秒供給と９秒供給停止とを含むサイクルを２１回繰り返す形で時分割供給している。この時分割比で供給することで、比較例によるサンプルと時間平均のＶ族元素を含む原料とIII族元素を含む原料との供給比を等しくしている。Ｖ族元素を含む原料とIII族元素を含む原料との供給比は量子ドットの特性に大きく影響する成長条件であるため、時分割成長法の効果のみを観察するためには、このように厳密に等しくする必要がある。 The structure of the sample is almost the same as that shown in FIG. 2, and a GaAs buffer layer 2 and InAs quantum dots 3 are sequentially grown on a GaAs substrate 1. The growth temperature of the quantum dots 3 is 490 ° C., the growth rate is 0.013 ML / s, the deposition amount is 2.7 ML, the growth time is 210 seconds, and the average raw material containing group V elements and group III elements are grown during dot growth. The supply ratio with the raw material contained is about 0.4. The supply flow rate of the In raw material TMI is 3.4 cc / min in terms of the bubbling hydrogen amount, the supply flow rate of the As raw material tBA is also the same as the bubbling hydrogen amount, 0.3 cc / min in the comparative example, and 3 cc / min in the present embodiment. It is. In forming the quantum dots, both In and As are continuously supplied in the comparative example, but in this embodiment, the As raw material tBA is repeated 21 times in a cycle including supplying for 1 second and stopping supplying for 9 seconds. In time-sharing supply. By supplying at this time division ratio, the supply ratio of the sample according to the comparative example, the time-averaged raw material containing the Group V element, and the raw material containing the Group III element is made equal. Since the supply ratio of the raw material containing the group V element and the raw material containing the group III element is a growth condition that greatly affects the characteristics of the quantum dot, in order to observe only the effect of the time division growth method, Must be equal to
図３（ａ）、（ｂ）に、比較例による量子ドットと、本実施例による量子ドットのＡＦＭ(Atomic Force Microscope)による表面観察像を示す。図３（ａ）が比較例によるサンプル、図３（ｂ）が本実施例によるサンプルである。なお、図に示される表面観察像は１μｍ×１μｍの大きさである。比較例と比べて、本実施例によるサンプルは、発光に寄与すると考えられる直径１５〜２５ｎｍの量子ドットの割合が、全ドット数に対し約６５％から９０％へと向上しており、サイズ均一性の大幅な向上が確認できる。 FIGS. 3A and 3B show surface observation images of the quantum dots according to the comparative example and the quantum dots according to the present embodiment using an AFM (Atomic Force Microscope). FIG. 3A shows a sample according to the comparative example, and FIG. 3B shows a sample according to this example. The surface observation image shown in the figure is 1 μm × 1 μm in size. Compared with the comparative example, in the sample according to this example, the proportion of quantum dots having a diameter of 15 to 25 nm, which is considered to contribute to light emission, is improved from about 65% to 90% with respect to the total number of dots, and the size is uniform. A significant improvement in performance can be confirmed.
また図４に、同様に同条件で成長した量子ドットのＰＬ(Photo Luminescence)強度を、比較例によるサンプル（グラフｇ１参照）と本実施例によるサンプル（グラフｇ２参照）で比較して示す。図４から本実施例による成長法のサンプルでは、約３倍に発光強度が増大していることが確認できる。発光に寄与するサイズの量子ドットが大幅に増加しているために、発光効率が向上しているためであると考えられる。 Also in Figure 4 shows a comparison of the PL (Photo Luminescence) intensity of the quantum dots grown Similarly same conditions, in the sample according to this embodiment and samples according to comparative example (see the graph g 1) (see graph g 2) . It can be confirmed from FIG. 4 that in the growth method sample according to this example, the emission intensity is increased about three times. This is probably because the emission efficiency is improved because the number of quantum dots having a size contributing to light emission is greatly increased.
従来、発光強度の増大を目的として、結晶成長終了後に熱アニール処理を行う研究が行われてきたが、この場合熱処理によってドットのサイズが縮小し、発光波長の大幅な短波長化が起きるという問題点があった。 Conventionally, research has been conducted to perform thermal annealing after crystal growth for the purpose of increasing the emission intensity, but in this case, the problem is that the dot size is reduced by the heat treatment and the emission wavelength is significantly shortened. There was a point.
しかし、本実施例では量子ドットのサイズ制御性を向上することによる発光効率の増大が得られているため、そのような発光波長の著しい短波長化は見られない。このことは量子ドットの１．２μｍ〜１．６μｍ帯の長波長通信用光源デバイスへの応用を考える際には、非常に有利な点である。 However, in this example, since the emission efficiency is increased by improving the size controllability of the quantum dots, such a remarkable shortening of the emission wavelength is not observed. This is a very advantageous point when considering application of a quantum dot to a light source device for long wavelength communication in the 1.2 μm to 1.6 μm band.
（実施例２）
次に、本発明の実施例２による半導体レーザを説明する。本実施例の半導体レーザは、本発明の第１実施形態による化合物半導体結晶の成長方法を用いて成長させた量子ドットを活性層として有するものであり、その断面を図５に示す。
(Example 2)
Next, a semiconductor laser according to Example 2 of the present invention will be described. The semiconductor laser of this example has, as an active layer, quantum dots grown using the compound semiconductor crystal growth method according to the first embodiment of the present invention, and a cross section thereof is shown in FIG.
ＭＯＣＶＤ法を用いてｎ型ＧａＡｓ基板４上に、Ｓｉがドープされた膜厚０．５μｍのｎ型ＧａＡｓバッファー層５、Ｓｉがドープされた膜厚１．５μｍのｎ型ＡｌＧａＡｓクラッド層６、膜厚０．１２μｍのＧａＡｓ光閉じ込め層７、膜厚１０ｎｍのＧａＡｓ層８，膜厚２．７ＭＬのＩｎＡｓ量子ドット活性層９、膜厚１０ｎｍのＧａＡｓ埋め込み層１０、膜厚０．１２μｍのＧａＡｓ光閉じ込め層１１、膜厚１．５μｍのｐ型ＡｌＧａＡｓクラッド層１２、膜厚０．５μｍのｐ型ＧａＡｓコンタクト層１３、膜厚０．１μｍのＧａＡｓキャップ層１４を順次成長する。 An n-type GaAs buffer layer 5 having a thickness of 0.5 μm doped with Si, an n-type AlGaAs cladding layer 6 having a thickness of 1.5 μm doped with Si, and a film on the n-type GaAs substrate 4 using MOCVD. 0.12 μm thick GaAs optical confinement layer 7, 10 nm thick GaAs layer 8, 2.7 ML InAs quantum dot active layer 9, 10 nm thick GaAs buried layer 10, 0.12 μm thick GaAs optical confinement A layer 11, a p-type AlGaAs cladding layer 12 having a thickness of 1.5 μm, a p-type GaAs contact layer 13 having a thickness of 0.5 μm, and a GaAs cap layer 14 having a thickness of 0.1 μm are sequentially grown.
ｎ型ＧａＡｓバッファー層５、ｎ型ＡｌＧａＡｓクラッド層６、ＧａＡｓ光閉じ込め層７、光閉じ込め層１１、およびｐ型ＡｌＧａＡｓクラッド層１２は、成膜温度が６５０℃で、成膜時間がそれぞれ２０分、６８分、５分、５分、６７．７分である。ＧａＡｓ層８およびＧａＡｓ埋め込み層１０は、成膜温度が４９０℃で、成膜時間が１７５秒である。ｐ型ＧａＡｓコンタクト層１３およびＧａＡｓキャップ層１４は、成膜膜温度が５５０℃で成膜時間がそれぞれ２２．３分および７３秒である。 The n-type GaAs buffer layer 5, the n-type AlGaAs cladding layer 6, the GaAs optical confinement layer 7, the optical confinement layer 11, and the p-type AlGaAs cladding layer 12 have a film formation temperature of 650 ° C. and a film formation time of 20 minutes, 68 minutes, 5 minutes, 5 minutes and 67.7 minutes. The GaAs layer 8 and the GaAs buried layer 10 have a film formation temperature of 490 ° C. and a film formation time of 175 seconds. The p-type GaAs contact layer 13 and the GaAs cap layer 14 have a film formation temperature of 550 ° C. and a film formation time of 22.3 minutes and 73 seconds, respectively.
量子ドット活性層９の成長温度は４９０℃、成長速度は０．０１３ＭＬ／ｓ、堆積量は２．７ＭＬ、成長時間は２１０秒、ドット成長中の平均的なＶ族元素を含む原料とIII族元素を含む原料との供給比は約０．４とする。III族であるＩｎの原料ＴＭＩの供給流量はバブリング水素量にして３．４ｃｃ／ｍｉｎ、Ｖ族であるＡｓの原料ｔＢＡ供給流量は同じくバブリング水素量にして３ｃｃ／ｍｉｎとする。本実施例の半導体レーザの量子ドット活性層９の部分は成長時間２１０秒であるが、その間にIII族元素を含む原料であるＴＭＩの供給を連続的に行い、Ｖ族元素を含む原料であるｔＢＡの供給を、１秒供給と９秒供給停止とからなるサイクルを２１回繰り返すという時分割して行う。 The growth temperature of the quantum dot active layer 9 is 490 ° C., the growth rate is 0.013 ML / s, the deposition amount is 2.7 ML, the growth time is 210 seconds, the raw material containing the average group V element and the group III during the dot growth The supply ratio with the raw material containing the element is about 0.4. The supply flow rate of the In raw material TMI of Group III is 3.4 cc / min in terms of bubbling hydrogen amount, and the supply flow rate of the As raw material tBA of Group V is also 3 cc / min in terms of bubbling hydrogen amount. The portion of the quantum dot active layer 9 of the semiconductor laser of this example has a growth time of 210 seconds, during which TMI, which is a raw material containing a group III element, is continuously supplied and is a raw material containing a group V element. The tBA is supplied in a time-sharing manner in which a cycle consisting of 1-second supply and 9-second supply stop is repeated 21 times.
このようにして形成された本実施例によれば、サイズ均一性および発光効率が良い量子ドット活性層を有する半導体レーザが得ることができる。比較例として、III族元素を含む原料およびＶ族元素を含む原料を連続的に供給する成長方法を用いて成長させた量子ドット層を活性層とする量子ドットレーザを作成した。本実施例の半導体レーザは比較例に比べて、発振しきい値の低減や出力の向上といった特性の改善が得られた。 According to this embodiment formed in this way, a semiconductor laser having a quantum dot active layer with good size uniformity and good light emission efficiency can be obtained. As a comparative example, a quantum dot laser having an active layer of a quantum dot layer grown using a growth method that continuously supplies a raw material containing a group III element and a raw material containing a group V element was prepared. The semiconductor laser of this example has improved characteristics such as a reduction in oscillation threshold and an improvement in output as compared with the comparative example.
（第２実施形態）
次に、本発明の第２実施形態による化合物半導体結晶の成長方法を、図６および図７を参照して説明する。
(Second Embodiment)
Next, a compound semiconductor crystal growth method according to a second embodiment of the present invention will be described with reference to FIGS.
ＩｎＡｓ基板上にＧａＡｓ〜ＧａＩｎＡｓ〜ＩｎＡｓ間の３元系混晶を、成長温度４２０℃、４４０℃、４６０℃、４９０℃、５００℃、５５０℃で成長させる際に、ＤＭＨｙ(Dimethylhydrazine)を原料としてＮ添加を行った場合のＮ添加効率を調べた実験データを図６に示す。横軸は、グラフの横軸は結晶中のＩｎ組成であり、縦軸は固相対気相中のＮ：Ａｓ濃度、すなわち原料ガスから結晶へのＮとＡｓの取り込まれ効率を意味している。成長温度５５０℃において、ＧａＡｓに対してＮは容易に添加が可能であるが、Ｉｎ組成が３割ほどのＧａＩｎＡｓに対してはＮの添加効率は約２桁低下する。Ｉｎ組成が３割を超える結晶に対しては添加効率はさらに低下し、従来の手法では数％オーダーのＮ濃度を有するＧａＩｎＡｓＮ結晶の成長は実現困難である。 When a ternary mixed crystal between GaAs, GaInAs and InAs is grown on an InAs substrate at growth temperatures of 420 ° C., 440 ° C., 460 ° C., 490 ° C., 500 ° C. and 550 ° C., DMHy (Dimethylhydrazine) is used as a raw material. The experimental data which investigated N addition efficiency at the time of adding N is shown in FIG. The horizontal axis represents the In composition in the crystal, and the vertical axis represents the N: As concentration in the solid phase versus the gas phase, that is, the efficiency of incorporation of N and As from the source gas into the crystal. . At a growth temperature of 550 ° C., N can be easily added to GaAs, but the efficiency of N addition is reduced by about two orders of magnitude for GaInAs having an In composition of about 30%. For crystals whose In composition exceeds 30%, the addition efficiency further decreases, and it is difficult to achieve growth of GaInAsN crystals having an N concentration on the order of several percent by conventional methods.
成長温度を５００℃から４４０℃の低温にしていくことで、Ｎ添加効率は約２桁向上する。これは、一般にＧａＩｎＮＡｓ系結晶の成長技術においてＮ添加効率を向上するためには低温成長が重要であると認識されていることに対する直接的なデータである。しかしながら成長温度を下げることは、原料の分解効率を低下させ、結晶中のＣ（炭素）などの不純物濃度を高める、結晶品質の低下を招くなどといった弊害も起こすことになる。 By increasing the growth temperature from 500 ° C. to 440 ° C., the N addition efficiency is improved by about two orders of magnitude. This is direct data for the fact that low temperature growth is generally recognized as important for improving the N addition efficiency in the GaInNAs crystal growth technology. However, lowering the growth temperature also causes adverse effects such as lowering the decomposition efficiency of raw materials, increasing the concentration of impurities such as C (carbon) in the crystal, and lowering the crystal quality.
そこで、本実施形態の成長方法は、図７に示すように、Ａｓの原料とＮの原料であるＤＭＨｙを時分割法によって、５秒Ａｓ供給かつＮ停止と、５秒Ａｓ停止かつＮ供給とからなるサイクルを繰り返すことで、ＩｎＡｓＮ結晶を成長させるものである。なお、III族であるＩｎの原料は図７に示すように、第１実施形態と同様に、連続的に供給される。 Therefore, in the growth method of the present embodiment, as shown in FIG. 7, the As raw material and N raw material DMHy are time-divisionally divided into 5 seconds As supply and N stop, and 5 seconds As stop and N supply. The InAsN crystal is grown by repeating the cycle consisting of: Note that, as shown in FIG. 7, the group III In raw material is continuously supplied as in the first embodiment.
本実施形態の成長方法を用いて成長したＩｎＡｓＮ結晶では、成長温度４９０℃においても図６に示したように成長温度約４４０℃での結晶成長とほぼ同等のＮ添加効率が得られている。これは、Ｖ族元素を含む原料の供給を時分割法によって交互に行うことで、成長する結晶最表面でのＡｓ濃度が少ない時にＮが供給され、Ｖ族サイトに高濃度にＮが入るためだと考えられる。 In the InAsN crystal grown by using the growth method of the present embodiment, the N addition efficiency substantially equal to the crystal growth at the growth temperature of about 440 ° C. is obtained even at the growth temperature of 490 ° C. as shown in FIG. This is because the supply of the raw material containing the group V element is alternately performed by the time-sharing method, so that N is supplied when the As concentration on the outermost surface of the growing crystal is small, and N enters the group V site at a high concentration. It is thought that.
このように、本実施形態の結晶成長方法を用いると、従来実現が困難であった混晶材料系、特にＧａ１−ｘＩｎｘＡｓ１−ｙＮｙ（０．７≦ｘ≦１、０≦１−ｘ≦０．３、０≦ｙ≦１、０≦１−ｙ≦１）といった材料において半導体結晶の成長が可能になる。このことは結晶成長の分野の大きな発展に結びつくことは言うまでも無い。 Thus, when the crystal growth method of the present embodiment is used, a mixed crystal material system that has been difficult to realize in the past, particularly Ga 1-x In x As 1-y N y (0.7 ≦ x ≦ 1, 0 Semiconductor crystals can be grown in materials such as ≦ 1-x ≦ 0.3, 0 ≦ y ≦ 1, and 0 ≦ 1-y ≦ 1). Needless to say, this leads to a great development in the field of crystal growth.
また、上記したＮ添加効率の問題で、従来の成長方法では高Ｉｎ組成のＩｎＡｓ〜ＩｎＧａＡｓ量子ドットにも、数％オーダーのＮを添加することは非常に難しい。そのため、１．５５μｍ帯の通信用光源材料として期待されている、ＩｎＡｓＮやＧａＩｎＮＡｓ系材料を用いた量子ドットレーザの実現は困難であり、いまだ基礎研究段階である。 In addition, due to the above-mentioned problem of N addition efficiency, it is very difficult to add N of the order of several percent to InAs to InGaAs quantum dots having a high In composition by the conventional growth method. Therefore, it is difficult to realize a quantum dot laser using an InAsN or GaInNAs-based material, which is expected as a light source material for communication in the 1.55 μm band, and is still in a basic research stage.
これに対し、本実施形態の成長方法を用いれば、ＩｎＡｓやＧａＩｎＡｓにも高い成長温度でＮを添加することが可能であるため、こうした材料の特性を大幅に向上することが可能である。 On the other hand, if the growth method of this embodiment is used, N can be added to InAs and GaInAs at a high growth temperature, so that the characteristics of such a material can be greatly improved.
なお、本実施形態も第１実施形態と同様に、量子ドットのサイズ均一性と発光効率を向上させることができる。 In addition, this embodiment can also improve the quantum dot size uniformity and the light emission efficiency, as in the first embodiment.
１ ＧａＡｓ基板
２ ＧａＡｓバッファー層
３ ＩｎＡｓ量子ドット
４ ｎ型ＧａＡｓ基板
５ ｎ型ＧａＡｓ：Ｓｉバッファー層
６ ｎ型ＡｌＧａＡｓ：Ｓｉクラッド層
７ ＧａＡｓ光閉じ込め層
８ ＧａＡｓ層
９ ＩｎＡｓ量子ドット層
１０ ＧａＡｓ埋め込み層
１１ ＧａＡｓ光閉じ込め層
１２ ｐ型ＡｌＧａＡｓクラッド層
１３ ＧａＡｓ：Ａｌコンタクト層
１４ ＧａＡｓキャップ層
DESCRIPTION OF SYMBOLS 1 GaAs substrate 2 GaAs buffer layer 3 InAs quantum dot 4 n-type GaAs substrate 5 n-type GaAs: Si buffer layer 6 n-type AlGaAs: Si clad layer 7 GaAs optical confinement layer 8 GaAs layer 9 InAs quantum dot layer 10 GaAs buried layer 11 GaAs optical confinement layer 12 p-type AlGaAs cladding layer 13 GaAs: Al contact layer 14 GaAs cap layer
Claims (10)
前記III族元素を含む原料を連続的に供給し、前記Ｖ族元素を含む原料の供給と停止とを繰り返して行う工程を備えたことを特徴とする化合物半導体結晶の成長方法。 A compound semiconductor crystal growth method for growing a compound semiconductor crystal containing a group III element and a group V element on a compound semiconductor substrate using MOCVD,
A method for growing a compound semiconductor crystal, comprising the steps of continuously supplying a raw material containing the group III element and repeatedly supplying and stopping the raw material containing the group V element.
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5991535A (en) * | 1982-11-16 | 1984-05-26 | Matsushita Electric Ind Co Ltd | Setting switch of digital code |
| JP2009231601A (en) * | 2008-03-24 | 2009-10-08 | Pioneer Electronic Corp | Forming method of quantum dot |
| JP2010199414A (en) * | 2009-02-26 | 2010-09-09 | National Institute Of Information & Communication Technology | Semiconductor quantum dot and method of forming the same |
| WO2011010389A1 (en) * | 2009-07-24 | 2011-01-27 | パイオニア株式会社 | Method for manufacturing semiconductor device and semiconductor device |
| JP2014209609A (en) * | 2013-03-26 | 2014-11-06 | 京セラ株式会社 | Semiconductor laser |
| JP2017028318A (en) * | 2007-09-18 | 2017-02-02 | サントル ナシオナル ドゥ ラ ルシェルシェサイアンティフィク（セエヌエールエス） | Epitaxial solid semiconductor hetero structure and method for manufacturing the same |
| CN113113287A (en) * | 2021-03-29 | 2021-07-13 | 清华大学 | Indium gallium nitrogen quantum dot and preparation method and application thereof |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07201761A (en) * | 1993-11-26 | 1995-08-04 | Furukawa Electric Co Ltd:The | Growth of compound semiconductor |
| JPH10326749A (en) * | 1997-03-28 | 1998-12-08 | Sharp Corp | Manufacture of compound semiconductor |
-
2005
- 2005-06-17 JP JP2005178232A patent/JP4707475B2/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07201761A (en) * | 1993-11-26 | 1995-08-04 | Furukawa Electric Co Ltd:The | Growth of compound semiconductor |
| JPH10326749A (en) * | 1997-03-28 | 1998-12-08 | Sharp Corp | Manufacture of compound semiconductor |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5991535A (en) * | 1982-11-16 | 1984-05-26 | Matsushita Electric Ind Co Ltd | Setting switch of digital code |
| JP2017028318A (en) * | 2007-09-18 | 2017-02-02 | サントル ナシオナル ドゥ ラ ルシェルシェサイアンティフィク（セエヌエールエス） | Epitaxial solid semiconductor hetero structure and method for manufacturing the same |
| JP2009231601A (en) * | 2008-03-24 | 2009-10-08 | Pioneer Electronic Corp | Forming method of quantum dot |
| JP2010199414A (en) * | 2009-02-26 | 2010-09-09 | National Institute Of Information & Communication Technology | Semiconductor quantum dot and method of forming the same |
| WO2011010389A1 (en) * | 2009-07-24 | 2011-01-27 | パイオニア株式会社 | Method for manufacturing semiconductor device and semiconductor device |
| JP2014209609A (en) * | 2013-03-26 | 2014-11-06 | 京セラ株式会社 | Semiconductor laser |
| CN113113287A (en) * | 2021-03-29 | 2021-07-13 | 清华大学 | Indium gallium nitrogen quantum dot and preparation method and application thereof |
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| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
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| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |