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

研究了量子限制和局域化对Cd_xZn_<1-x>S/（ZnS）量子阱结构和Cd_xZn_<1-x>S/（ZnS）/（Mg_yZn_<1-y>S）分别限制异质结中双激子的影响。在本研究中使用的样品生长的低压金属有机化学气相沉积。我们首先优化了Mg_yZn_ S三元合金的生长条件<1-y>，制备了Cd_xZn_<1-x>S/（ZnS）/（Mg_yZn_<1-y>S）分别限制异质结。我们证实了Mg_yZn_<1-y>S三元合金作为包覆层的插入对Cd_xZn_ S量子威尔斯阱中载流子的限制是有效<1-x>的，并导致在室温下发光效率的提高。我们还成功地通过改进量子威尔斯阱的结构设计和生长条件来减少由于合金无序引起的激子和双激子态密度的不均匀展宽。双激子的结合能 关于我们 在优化量子限制条件下，双激子的光致发光激发光谱的实验观测结果表明，在量子阱中，双激子的光致发光强度大于40 meV，并首次定量评价了合金无序引起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>）比激子的斯托克斯位移（S_x）小，S_<xx>/S_x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，我们研究了不同结构参数的量子阱样品的受激发射特性。我们观察到双激子辐射复合受激发射的阈值激发密度与双激子的局域化程度以及双激子的结合能有关。特别是，我们澄清了由双激子的本地化增强的稳定性导致在抑制温度诱导的阈值激发密度的增加受激发射。少

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