Research on Five-Layer Asymmetric Coupled Quantum Wells and Their Application to Ultra-Fast and Ultra-Low Voltage Optical Modulators and Switches

五层非对称耦合量子阱研究及其在超快超低压光调制器和开关中的应用

• 批准号: 11450028
• 负责人: TADA Kunio
• 金额: $ 9.34万
• 依托单位: Yokohama National University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B).
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11450028/
• 关键词: Potential-tailored quantum well; Five-layer asymmetric coupled quantum well (FACQW); Optical modulator; Optical switch; Electrorefractive index change; Molecular beam epitaxy (MBE); Migration enhanced epitaxy (MEE); Layer thickness fluctuation; 光変

The five-layer asymmetric coupled quantum well (FACQW) structure, in contrast to the conventional rectangular quantum well (RQW), can produce very large electrorefractive index change Δn in the transparency wavelength region far from the absorption edge. We theoretically and experimentally studied fabrication of high-quality GaAs/AlGaAs FACQWs and their application to optical modulators and switches.1. Fabrication and Characterization of the FACQW structuresThe FACQWs were grown by molecular beam epitaxy (MBE) with precise shutter control.Photoluminescence and photocurrent measurements of the samples revealed that the structures were fabricated as designed and their Δn characteristucs were consistent with calculation results.2. Influence of layer thickness fluctuation on electrorefractive index change of the FACQWThe influence of 1 ML thickness deviations and fluctuations from the designed FACQW structure on Δn was studied theoretically.i) The thickness variation of the thicker GaAs we … More ll layers in the FACQW has a considerable influence on Δn. The influence of the two thin Al(Ga)As barrier layers is small compared with that of other GaAs well layers.ii) The ratio of the thicknesses of the two thicker GaAs layers significantly affects the Δn, characteristics of the FACQW.The value Δn does not change as long as the ratio of the thicknesses of the layers is kept constant.iii) The physical origin of the sharp dip in the Δn-electric field characteristic was studied theoretically. The dip can be removed by changing the position or Al content of the thin AlGaAs barrier layer for potential modification.iv) The influence of the statistical fluctuation of the layer thickness by 1 ML on the Δn characteristics was discussed. Even when An decreases with the increase of the occurrence probability of a layer being thicker or thinner by 1 ML (the ratio of well area with deviated thicknesses to total area of the layer), the FACQW still maintains a much larger Δn than the conventional rectangular quantum wells (RQWs).3. Growth of high-quality quantum well structures with migration enhanced epitaxy methodThe migration enhanced epitaxy (MEE) method is a promising growth technique that can obtain flatter and steeper heterointerfaces at lower growth temperature than conventional MBE.We introduced the MEE method to growth of high-quality quantum well structures.i) A computer-controlled system of K-cell shutters was installed for complicated gowthsequence of MEE.ii) K-cell shutter sequence for AlGaAs growth was investigated. We found the sequence that after Al and Ga atoms are supplied simultaneously, Ga and As atoms are supplied alternatively can realize flatter heterointerface without Al content fluctuation. Utilizing this sequence, high-quality RQWs were successfully grown at 500℃.4. Electrorefrative effect in a modified FACQWA modified FACQW has a slightly different structure from the normal FACQW, and it is expected to obtain very large negative Δn. We theoretically studied in detail electrorefrative effect in the modified FACQW.We discussed the detailed mechanism of large Δn in the modified FACQW.In addition, we found that the modified FACQW has more tolerance of layer thickness fluctuation than the normal FACQW. Less

与传统的矩形量子阱（RQW）相比，五层不对称耦合量子阱（FACQW）结构可以在远离吸收边缘的透明波长区域产生非常大的电折射率变化Δn。我们从理论上和实验上研究了高质量GaAs/AlGaAs facqw的制备及其在光调制器和开关中的应用。FACQW结构的制备和表征FACQW是通过分子束外延（MBE）在精确的快门控制下生长的。样品的光致发光和光电流测量结果表明，所制备的结构符合设计要求，其Δn特性与计算结果一致。层厚波动对FACQW电折射率变化的影响从理论上研究了设计的FACQW结构的1 ML厚度偏差和波动对Δn的影响。i) FACQW中更厚的GaAs层的厚度变化对Δn有相当大的影响。两个薄Al(Ga)As势垒层的影响与其他GaAs势垒层相比较小。ii)两层较厚的GaAs层厚度的比例显著影响FACQW的Δn，特性。只要各层厚度的比例保持不变，Δn值就不会改变。iii)从理论上研究了Δn-electric场特征陡倾的物理成因。可以通过改变薄AlGaAs势垒层的位置或Al含量来去除浸出。iv)讨论了层厚1 ML的统计波动对Δn特性的影响。即使An随层变厚或变薄的概率增加1 ML（厚度偏差的井面积与层总面积之比）而减小，FACQW仍保持比常规矩形量子阱（rqw）大得多的Δn。迁移增强外延法（MEE）是一种很有前途的生长技术，可以在较低的生长温度下获得比传统MBE更平坦、更陡峭的异质界面。我们将MEE方法引入到高质量量子阱结构的生长中。i)安装了计算机控制的k细胞百叶窗系统，用于复杂的MEE生长序列。ii)研究了AlGaAs生长的k细胞关闭序列。我们发现，同时提供Al和Ga原子后，Ga和As原子交替提供的顺序可以实现更平坦的异质界面，且Al含量没有波动。利用该序列，在500℃条件下成功培养出了高质量的rqw。修饰FACQWA的电折射效应与普通FACQW结构略有不同，预计可获得非常大的负Δn。从理论上详细研究了改进后的FACQW的电折射效应。在改进的FACQW中详细讨论了大Δn的机理。此外，我们发现改进的FACQW比普通的FACQW对层厚波动有更大的容忍度。少

项目成果

T.Arakawa,K.Tada,N.Kurosawa,J.-H.Noh: "Anomalous Sharp Dip of Large Field-Induced Refractive Index Change in GaAs/AlGaAs Five-Layer Asymmetric Coupled Quantum Well"Japanese Journal of Applied Physics. Vol.39,No.11. 6329-6333 (2000)

T.Arakawa，K.Tada，N.Kurosawa，J.-H.Noh：“GaAs/AlGaAs 五层不对称耦合量子阱中大场诱导折射率变化的异常急剧下降”日本应用物理学杂志。

数馬研介,多田邦雄,荒川太郎,盧柱亨: "5層非対称結合量子井戸の層厚ゆらぎを考慮した電界誘起屈折率変化特性の解析"第61回応用物理学会学術講演会・予稿集(4aZE-3). (2000)

Kensuke Kazuma、Kunio Tada、Taro Arakawa、Toru Rokuju：“考虑五层非对称耦合量子阱中层厚度波动的电场引起的折射率变化特性分析”日本应用物理学会第 61 届年会论文集（4aZE-3））（2000）。

多田邦雄,荒川太郎,黒澤直樹: "5層非対称結合量子井戸(FACQW)の電界誘起屈折率変化の特異なディップ"第60回応用物理学会学術講演会・予稿集(3a-ZB-9). (1999)

Kunio Tada、Taro Arakawa、Naoki Kurosawa：“五层不对称耦合量子阱 (FACQW) 电场引起的折射率变化中的特殊下降”日本应用物理学会第 60 届年会论文集 (3a -ZB-9）（1999）。

多田邦雄: "ポテンシャル制御量子井戸と高性能光変調デバイス"応用物理. Vol.69,No.11. 1292-1298 (2000)

Kunio Tada：“势控量子阱和高性能光调制器件”应用物理学第 69 卷，第 1292-1298 期（2000 年）。

岡宮由樹,盧柱亨,荒川太郎,鈴木達也,酒井信昭,長谷川怜雄,多田邦雄: "MEE法の5層非対称結合量子井戸光変調器作製への応用(II)"第48回応用物理学関係連合講演会・予稿集(28a-YF-5). (2001)

Yuki Okamiya、Toru Roshi、Taro Arakawa、Tatsuya Suzuki、Nobuaki Sakai、Reio Hasekawa、Kunio Tada：“MEE 方法在五层非对称耦合量子阱光调制器制造中的应用（II）”第 48 届应用物理协会讲座/论文集（ 28a-YF-5）（2001）。