Control of biexciton localization and optical functionality in ZnMgCdS-based semiconductor quantum structures

ZnMgCdS 基半导体量子结构中双激子局域化和光学功能的控制

• 批准号: 12650315
• 负责人: YAMADA Yoichi
• 金额: $ 2.62万
• 依托单位: Yamaguchi University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650315/
• 关键词: wide-gap semiconductor; low-dimensional structure; biexciton; radiative recombination; locallization; optical gain; exciton engineering; ZnS

We have studied the effects of quantum confinement and localization on biexcitons in Cd_xZn_<1-x>S/(ZnS) quantum-well structures and Cd_xZn_<1-x>S/(ZnS)/(Mg_yZn_<1-y>S) separate-confinement heterostructures for application to highly efficient biexcitonic ultraviolet laser diodes. The samples used in the present study were grown by low-pressure metalorganic chemical vapor deposition. We first optimized growth conditions of Mg_yZn_<1-y>S ternary alloys and fabricated Cd_xZn_<1-x>S/(ZnS)/(Mg_yZn_<1-y>S) separate-confinement heterostructures. We confirmed that the insertion of Mg_yZn_<1-y>S ternary alloys as a cladding layer was effective for carrier confinement into Cd_xZn_<1-x>S quantum wells and resulted in the improvement of luminescence efficiency at RT. We also succeeded in the reduction of inhomogeneous broadening of both exciton and biexciton density of states due to alloy disorder by refining structural design and growth conditions of quantum wells. The binding energy of biexciton … More s was found to be larger than 40 meV in the quantum well with optimized quantum confinement.The degree of biexciton localization due to alloy disorder was evaluated quantitatively for the first time on the basis of experimental observations by photoluminescence excitation spectroscopy of biexcitons. The value was defined as a Stokes shift of biexcitons. We observed that the Stokes shift of biexcitons (S_<xx>) was smaller than that of excitons (S_x) and the value of S_<xx>/S_x was about 0.54. This resulted from the larger spatial extent of biexcitons compared with that of excitons. Finally, we studied stimulated emission properties of a variety of quantum-well samples with different structural parameters. We observed that the threshold excitation density for stimulated emission due to radiative recombination of biexcitons was concerned with the degree of biexciton localization as well as the binding energy of biexcitons. In particular, we clarified that the stability enhanced by the localization of biexcitons resulted in the suppression of temperature-induced increase in the threshold excitation density for stimulated emission. Less

我们研究了Cd_xZn_<1-x>S/(ZnS)量子阱结构和Cd_xZn_<1-x>S/(ZnS)/(Mg_yZn_<1-y>S)分离约束异质结构中量子限制和局域化对双激子的影响，并将其应用于高效双激子紫外激光二极管。本研究中使用的样品是通过低压金属有机化学气相沉积法生长的。我们首先优化了Mg_yZn_<1-y>S三元合金的生长条件并制备了Cd_xZn_<1-x>S/(ZnS)/(Mg_yZn_<1-y>S)分离约束异质结构。我们证实，插入 Mg_yZn_<1-y>S 三元合金作为包覆层可有效将载流子限制在 Cd_xZn_<1-x>S 量子阱中，并提高室温下的发光效率。我们还通过改进量子阱的结构设计和生长条件，成功地减少了由于合金无序导致的激子和双激子态密度的不均匀展宽。在优化量子限制的量子阱中，发现双激子的结合能大于40 meV。基于双激子光致发光激发光谱的实验观察，首次定量评估了合金无序导致的双激子局域化程度。该值被定义为双激子的斯托克斯位移。我们观察到双激子的斯托克斯位移（S_<xx>）小于激子（S_x）的斯托克斯位移，并且S_<xx>/S_x的值约为0.54。这是由于与激子相比，双激子的空间范围更大。最后，我们研究了具有不同结构参数的各种量子阱样品的受激发射特性。我们观察到，由于双激子辐射复合引起的受激发射的阈值激发密度与双激子定位程度以及双激子的结合能有关。特别是，我们阐明了双激子局域化增强的稳定性导致了受激发射阈值激发密度的温度诱导增加的抑制。较少的

项目成果

Y.Yamada: "Dense excitonic luminescence and optical gain in ZnS-based quantum wells"Journal of Luminescence. 87-89. 140-144 (2000)

Y.Yamada：“ZnS 基量子阱中的密集激子发光和光学增益”发光杂志。

Y.Kanemitsu: "Free excitons in cubic CdS films"Applied Physics Letters. 80. 267-269 (2002)

Y.Kanemitsu：“立方 CdS 薄膜中的自由激子”应用物理快报。

T. Nagai et al.: "Optical Properties of cubic CdS"Physica Status Solidi (b). Vol. 229, No.1. 611-614 (2002)

T. Nagai 等人：“立方 CdS 的光学性质”Physica Status Solidi (b)。

K.Yoshimura: "Optical and structural characterization of Mg_xZn_<1-x>S mixed films grown by low-pressure MOCVD"Journal of Crystal Growth. 214/215. 364-367 (2000)

K.Yoshimura：“低压MOCVD生长的Mg_xZn_<1-x>S混合薄膜的光学和结构表征”晶体生长杂志。

S.Nakamura: "Luminescence properties of lithium-doped ZnS epitaxial layers grown by low-pressure MOCVD"Journal of Crystal Growth. 237-239. 1570-1574 (2002)

S.Nakamura：“低压 MOCVD 生长的锂掺杂 ZnS 外延层的发光特性”晶体生长杂志。