共查询到19条相似文献,搜索用时 109 毫秒
1.
研究了GaSb/GaAs复合应力缓冲层上自组装生长的InAs量子点.在2ML GaSb/1ML GaAs复合应力缓冲层上获得了高密度的、沿[100]方向择优分布量子点.随着复合应力缓冲层中GaAs层厚度的不同,量子点的密度可以在1.2×1010cm-2和8×1010cm-2进行调控.适当增加GaAs层的厚度至5ML,量子点的发光波长红移了约25nm,室温下PL光谱波长接近1300nm.
关键词:
自组装量子点
分子束外延
Ⅲ-Ⅴ族化合物半导体 相似文献
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利用分子束外延技术,通过InAs/GaAs数字合金超晶格代替传统的直接生长InGaAs层的方式,在GaAs(100)衬底上生长了InAs量子点结构并成功制备了1.3μm InAs量子点激光器.通过原子力显微镜和光致荧光谱测试手段,对传统生长模式和数字合金超晶格生长模式的两种样品进行了表征,研究发现采用32周期InAs/GaAs数字合金超晶格样品的量子点密度非常高,发光性能良好.通过与常规生长方式所制备激光器的性能对比,发现采用InAs/GaAs数字合金超晶格生长InAs量子点的有源区也可以得到高质量的激光器.利用该方式生长的InAs量子点激光器的阈值电流为24 mA,相应的阈值电流密度仅为75 A/cm2,最高工作温度达到120℃.InAs/GaAs数字合金超晶格既可以保证生长过程中源炉的温度保持不变,还可以对InGaAs层的组分实现灵活调控.不需要改变生长速度,通过改变InAs/GaAs数字合金超晶格的周期数以及InAs层和GaAs层的厚度,便可以获得任意组分的InGaAs,从而得到不同发光波长的激光器.这种生长方式对量子点有源区的结构设计和外延生长提供了新思路. 相似文献
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InAs/GaAs量子点是重要的单光子源,位置可控量子点对实现可寻址易集成的高性能量子点光源具有重要意义.本文详细研究了氢原子条件下GaAs (001)图形衬底的低温脱氧过程,低温GaAs缓冲层生长中沟槽形貌的演化过程,以及沟槽形貌对量子点形核位置的影响.发现GaAs衬底上纳米沟槽侧壁的倾斜角较小时, InAs量子点会优先生长于沟槽底部;当沟槽的侧壁倾斜角较大时, InAs量子点则会优先生长于沟槽两侧的外边沿位置.此外,本文还研究了纳米孔洞侧壁的倾斜角对量子点成核位置的影响,实现了双量子点分子和四量子点分子的定位生长. 相似文献
5.
在InAs/GaAs(001)量子点生长过程中, 当InAs沉积量为0.9 ML时, 利用紫外纳秒脉冲激光辐照浸润层表面, 由于高温下In原子的不稳定性, 激光诱导的原子脱附效应被放大, 样品表面出现了原子层移除和纳米孔. 原子力显微镜测试表明纳米孔呈现以[110]方向为长轴(尺寸: 20-50 nm)、[110]方向为短轴(尺寸: 15-40 nm)的表面椭圆开口形状, 孔的深度为0.5-3 nm. 纳米孔的密度与脉冲激光的能量密度正相关. 脉冲激光的辐照对量子点生长产生了显著的影响: 一方面由于纳米孔的表面自由能低, 沉积的InAs优先迁移到孔内, 纳米孔成为量子点优先成核的位置; 另一方面, 孔外的区域因为In原子的脱附, 量子点的成核被抑制. 由于带有纳米孔的浸润层表面具有类似于传统微纳加工技术制备的图形衬底对量子点选择性生长的功能, 该研究为量子点的可控生长提供了一种新的思路. 相似文献
6.
利用固源分子束外延(MBE)的方法经SK模式自组装生长由多层InAs/GaAs量子点组成的柱形岛.具体分析了GaAs间隔层厚度,生长停顿时间以及InAs淀积量对发光峰波长的影响.原子力显微镜(AFM)结果显示柱形岛表面的形状和尺寸都比较均匀;室温下不同高度的柱形岛样品的发光波长分别达到1.32和1.4μm,而单层量子点的发光波长仅为1.1μm,充分说明了量子点高度对发光波长的决定性影响,这为调节量子点发光波长提供了一种直观且行之有效的方法.
关键词:
柱形岛
生长停顿
间隔层厚度
PL谱 相似文献
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采用有效质量模型和非线性弹性理论计算了不同尺寸InAs/GaAs量子点的静压光谱发光峰的 压力系数(PC).量子点峰位随压力的变化主要来自禁带宽度和电子束缚能随压力变化两方面 的贡献.由于InAs/GaAs量子点是一个应变体系,体系的晶格常数,失配应变和弹性系数均随 外加压力变化,使得加压后量子点的禁带宽度相对于非应变体系略有减小,同时势垒高度增 加,电子束缚程度增加.两者共同作用引起的InAs应变层的禁带宽度压力系数减小是导致量 子点的压力系数小于InAs体材料的主要原因.同时计算结果表明,电子束缚能随压力变化对 不同尺寸量子点的压力系数的影响不同,量子点尺寸越小,受其影响越大,压力系数也越大 .
关键词:
量子点
压力系数
应变 相似文献
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S.I. Jung J.J. Yoon H.J. Park Y.M. Park M.H. Jeon J.Y. Leem C.M. Lee E.T. Cho J.I. Lee J.S. Kim J.S. Son J.S. Kim D.Y. Lee I.K. Han 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):100
We investigate the effects of a thin AlAs layer with different position and thickness on the optical properties of InAs quantum dots (QDs) by using transmission electron microscopy and photoluminescence (PL). The energy level shift of InAs QD samples is observed by introducing the thin AlAs layer without any significant loss of the QD qualities. The emission peak from InAs QDs directly grown on the 4 monolayer (ML) AlAs layer is blueshifted from that of reference sample by 219 meV with a little increase in FWHM from 42–47 meV for ground state. In contrast, InAs QDs grown under the 4 ML AlAs layer have PL peak a little redshifted to lower energy by 17 meV. This result is related to the interdiffusion of Al atom at the InAs QDs caused by the annealing effect during growing of InAs QDs on AlAs layer. 相似文献
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S. Kiravittaya H. Heidemeyer O. G. Schmidt 《Physica E: Low-dimensional Systems and Nanostructures》2004,23(3-4):253
The growth of a three-dimensional (3D) InAs quantum dot (QD) crystal on a patterned GaAs (0 0 1) substrate is demonstrated. The morphology of QDs grown on a surface patterned with shallow holes is studied as a function of the amount of deposited InAs. We observe that the QDs form in the patterned holes close to each other forming lateral QD bimolecules for InAs coverages below the commonly observed critical thickness of 1.6 monolayers. When the coverage increases, the QD bimolecules coalesce to form larger single QDs. The QDs in the holes are then capped with a Ga(Al)As spacer. The buried QD array serves as a strain template for controlling the formation site of the QDs in the second layer. By tuning the growth conditions for the second and subsequent layers, we achieve a 3D InAs QD crystal with a high degree of perfection. A detail investigation of the growth on hole patterns with different periodicities is presented. 相似文献
13.
《Superlattices and Microstructures》1999,25(1-2):97-104
We report on studies of excitation transfer processes in vertically self-organized pairs of unequal-sized quantum dots (QDs), created in InAs/GaAs bilayers having differing InAs deposition amounts in the first (seed) and subsequent layer. The former and latter enable independent control, respectively, of the density and the size distribution of the second layer QDs. This approach allows us to enhance the average volume and improve the uniformity of InAs QDs, resulting in low-temperature photoluminescence at 1.028 eV with a linewidth of 25 meV for 1.74 ML (seed)/3.00 ML InAs stacking. The optical properties of the formed pairs of unequal-sized QDs with clearly discernible ground-state transition energy depend on the spacer thickness and composition. Photoluminescence results provide evidence for nonresonant energy transfer from the smaller QDs in the seed layer to the larger QDs in the second layer in such asymmetric QD pairs. Transfer times down to 20 ps (36 ML GaAs spacer) are estimated, depending exponentially on the GaAs spacer thickness. 相似文献
14.
D.M. Schaadt S. Krauss R. Koch K.H. Ploog 《Applied Physics A: Materials Science & Processing》2006,83(2):267-269
We investigated the stress evolution during molecular-beam epitaxy of bilayer InAs/GaAs(001) quantum dot (QD) structures in
real time and with sub-monolayer precision using an in-situ cantilever beam setup. During growth of the InAs at 470 °C a stress
of 5.1 GPa develops in the wetting layer, in good agreement with the theoretical misfit stress. At a critical thickness of
1.5 monolayers the strain is relieved by the QD formation. In the case of InAs/GaAs bilayer structures, the second InAs layer
grows identical to the first for GaAs spacer thicknesses exceeding ∼13 nm. For thinner spacers the critical thickness for
the 2D/3D transition in the second layer decreases. The stress of the second InAs layer does not reach the value of the first,
indicating that InAs QDs grow on partially strained areas due to the strain field of the previous InAs layer.
PACS 68.35.-p; 68.35.Gy; 68.65.Hb; 81.07.Ta; 81.10.Aj 相似文献
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Formation of a multimodal quantum dot (QD) ensemble by strained layer epitaxy of InAs on GaAs near the critical value for the onset of the 2D-3D transition is studied. Reflection anisotropy spectroscopy is employed to confirm that a smooth surface is maintained during strained layer growth prior to QD formation. Instantaneous capping after deposition leads to InAs quantum wells with some thickness flucuations. Multimodal QD InAs ensembles form after an at least short growth interruption prior to cap layer deposition. The QDs consist of pure InAs with heights varying in steps of complete InAs monolayers. Related exciton energies indicate a simultaneous increase of both height and lateral extension, i.e. a shell-like increase of sizes. The formation of the multimodal QD ensemble is described by a kinetic approach. A growth scenario is presented where QDs having initially shorter base length stop vertical growth at a smaller height, accounting for the experimentally observed shell-like sub-ensemble structure. 相似文献
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Coherent InAs islands separated by GaAs spacer (d) layers are shown to exhibit self-organized growth along the vertical direction. A vertically stacked layer structure is useful for controlling the size distribution of quantum dots. The thickness of the GaAs spacer has been varied to study its influence on the structural and optical properties. The structural and optical properties of multilayer InAs/GaAs quantum dots (QDs) have been investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM), and photoluminescence (PL) measurements. The PL full width at half maximum (FWHM), reflecting the size distribution of the QDs, was found to reach a minimum for an inter-dots GaAs spacer layer thickness of 30 monolayers (ML). For the optimized structure, the TEM image shows that multilayer QDs align vertically in stacks with no observation of apparent structural defects. Furthermore, AFM images showed an improvement of the size uniformity of the QDs in the last layer of QDs with respect to the first one. The effect of growth interruption on the optical properties of the optimized sample (E30) was investigated by PL. The observed red shift is attributed to the evolution of the InAs islands during the growth interruption. We show the possibility of increasing the size of the QDs approaching the strategically important 1.3 m wavelength range (at room temperature) with growth interruption after InAs QD deposition. 相似文献
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采用光致荧光发射谱(PL)和时间分辨荧光发射谱(TRPL)研究了GaAs间隔层厚度对自组装生长的双层InAs/GaAs量子点分子光学性质的影响.首先,测量低温下改变激发强度的PL谱,底层量子点和顶层量子点的PL强度比值随激发强度发生变化,表明两层量子点之间的耦合作用和层间载流子的转移随着间隔层厚度变大而变弱.接着测量改变温度的PL谱,量子点荧光光谱峰值位置(Emax)、半峰全宽及积分强度随温度发生变化,表明GaAs间隔层厚度直接影响到量子点内载流子的动力学过程和量子点发光的热淬灭过程.最后,TRPL测量发现60mL比40mL间隔层厚度样品的载流子隧穿时间有明显延长. 相似文献
18.
S. K. Park J. Tatebayashi Y. Arakawa 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):279
We have obtained high-density (>1011/cm2) InAs quantum dot (QD) structures by using an Al(Ga)As matrix layer. With increase of the AlAs matrix layer thickness, the density of QDs increases a little and the luminescence intensity emitted from InAs QDs decreases. We have used a thin GaAs insertion layer (IL) for the reason of keeping InAs QDs from an aluminum intermixing towards QDs. As the thickness of GaAs IL increases, the density of QDs decreases slightly due to the reduction of the roughness of an AlAs matrix layer. However, the luminescence intensity increases with increase in the thickness of GaAs IL resulting from the efficient blocking of an aluminum intermixing towards QDs. 相似文献
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Lu Wang Meicheng Li Wenxin Wang Haitao Tian Zhigang Xing Min Xiong Liancheng Zhao 《Applied Physics A: Materials Science & Processing》2011,104(2):567-572
The effect of strain accumulation in the InAs/In
x
Ga1−x
As quantum dots (QDs) system was studied in this work. It was found that strain in the In
x
Ga1−x
As layer accumulation in the QD layer. This effect resulted in a dramatic reduction of growth mode transition thickness of
the QD layer. For InAs/In0.25Ga0.75As QDs, critical thickness is measured to be as low as 1.08 ML. The experimental results in this work highlight the importance
of strain accumulation in the design and fabrication of QD-based devices with metamorphic buffer layer involved. 相似文献