共查询到18条相似文献,搜索用时 453 毫秒
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自组织量子点光致荧光的温度依赖性研究对实现高效的量子点光电器件有着非常重要的意义,而量子点中载流子的动力学过程会对量子点光致荧光产生直接影响。采用稳态速率方程模型,在考虑了自组织量子点中载流子热迁移的情况下,模拟获得了不同温度下自组织量子点的光致荧光光谱,并着重研究了三组具有不同基态能量的量子点的光致荧光强度随温度的变化。研究表明,随着温度升高,基态能量较高的量子点光致荧光强度减弱,而基态能量较低的量子点光致荧光强度则增强,当温度达到一定值时,所有量子点的光致荧光都将发生热猝灭。 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
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《光谱学与光谱分析》2020,(9)
InGaN半导体材料具有带隙宽度通过改变In组分可调的特点,被广泛应用在新一代光电子器件中,但绿光LED依然存在"绿隙(green gap)"问题有待解决。本文深入研究载流子复合机制,为解决"绿隙"提供新思路。利用光致荧光光谱(PL)和时间分辨光谱(TRPL)研究了不同温度下对应不同光子能量的InGaN量子点(QDs)发光二极管器件的载流子复合动力学过程,得到了InGaN QDs的瞬态光致发光特性和辐射/非辐射复合的瞬态寿命。稳态光致发光谱在15~300 K的温度范围内,峰值出现先蓝移再红移(S-shaped)的偏移现象,发射峰值蓝移约4.2 meV,在60 K时达到最大值,随后发射峰红移,形成随温度呈S形的变化。这种变化说明QDs结构中载流子局域化行为,激子复合是InGaN量子点绿光发射的主要原因。通过拟合不同温度下的归一化PL积分强度,获得激活能E_(act)约为204.07 meV,激活能较高,证明了InGaN量子点具有较强的载流子限制作用,可以更好抑制载流子向非辐射复合中心迁移,内量子效率(internal quantum efficiency)为35.1%。InGaN QDs中自由载流子复合的平均复合寿命τ_(rad)=73.85ns。能量边界值E_(me)=2.34 eV远高于局域深度E_0=62.55 meV,可见能级完全低于迁移率边缘,因此InGaN QDs寿命衰减归因于载流子局域态复合。通过使用改进的光谱数据分析手段对基于内嵌量子点新结构的荧光器件进行研究,得到了有意义的结论,为进一步了解InGaN量子点内部发光机理和研制新一代照明器件提供借鉴,说明引入InGaN量子点对光电器件的发展具有很好的推动作用。 相似文献
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采用固态源分子束外延技术在GaAs(100)衬底上,制备了InAs量子点,对样品进行原子力显微镜测试,统计结果表明量子点尺寸呈双模分布。光致发光谱研究表明,在室温和77 K下,小量子点的发光峰均占主导地位,原因可能是:(1)大量子点的态密度小于小量子点;(2)捕获载流子速率,大量子点小于小量子点;(3)大量子点与盖层存在较大的应变势垒和可能出现的位错和缺陷,导致温度变化引起载流子从小尺寸量子点转移到大尺寸的量子点中概率很小。 相似文献
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采用稳态速率方程模型,对双模自组织量子点光致发光的温度依赖性进行了研究,模拟获得了不同温度下双模自组织量子点的光致发光光谱,并进一步研究了两组量子点分布的光致发光强度比的温度依赖性。研究表明:在低温下(<75K),两组量子点分布的发光强度比基本保持不变;随着温度的升高(75K相似文献
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M. Bennour L. Bouza?ene F. Saidi L. Sfaxi H. Maaref 《Journal of nanoparticle research》2011,13(12):6527-6535
We have investigated the temperature dependence of photoluminescence (PL) peak position of InAs self-assembled quantum dots (QDs) grown on GaAs(11N)A (N = 3, 5) substrates. The interband transition energy is calculated by the resolution of the 3D Schrödinger equation for a parallelepipedic InAs QD, with a width of about 8 nm and a height around 3 nm. Experimentally, it was found that the PL spectra quenches at about 160 K. In addition, the full width at half maximum (FWHM) has an abnormal evolution with varying temperature. The latter effect maybe due to the carrier repopulation between QDs. The disorientation of the GaAs substrate and the low width of terraces which was presented in the high index surfaces have an important contribution in the PL spectra. Despite the non-realist chosen shape of QD and the simplest adopted model, theoretical and experimental results revealed a clear agreement. 相似文献
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M. H. Hadj Alouane B. Ilahi L. Sfaxi H. Maaref 《Journal of nanoparticle research》2011,13(11):5809-5813
In this article, comprehensive combination of photomodulated optical spectroscopy (PR) and temperature-dependent photoluminescence
(PL) is carried out to investigate the electronic energy levels and carrier dynamics in nanometers’ size InAs quantum dots
(QDs) in different surrounding material. Depending on the temperature range, the integrated PL intensity as a function of
temperature, correlated to a rate equation model reveals two thermal escape channels for the InAs QDs in a pure GaAs matrix
and three thermal escape channels for InAs/InGaAs dots-in-a-well structure. The extraction of the electronic energy levels
by room temperature PR allow analyzing the impact of the surrounding material composition on the thermal activation energies
and resulting PL quenching process. 相似文献
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The intermixing of Sb and As atoms induced by rapid thermal annealing (RTA) was investigated for type II GaSb/GaAs self-assembled quantum dots (QD) formed by molecular beam epitaxy growth. Just as in InAs/GaAs QD systems, the intermixing induces a remarkable blueshift of the photoluminescence (PL) peak of QDs and reduces the inhomogeneous broadening of PL peaks for both QD ensemble and wetting layer (WL) as consequences of the weakening of quantum confinement. Contrary to InAs/GaAs QDs systems, however, the intermixing has led to a pronounced exponential increase in PL intensity for GaSb QDs with annealing temperature up to 875 °C. By analyzing the temperature dependence of PL for QDs annealed at 700, 750 and 800 °C, activation energies of PL quenching from QDs at high temperatures are 176.4, 146 and 73.9 meV. The decrease of QD activation energy with annealing temperatures indicates the reduction of hole localization energy in type II QDs due to the Sb/As intermixing. The activation energy for the WL PL was found to drastically decrease when annealed at 800 °C where the QD PL intensity surpassed WL. 相似文献
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利用分子束外延方法制备了应用于四结光伏电池的1.05 eV InGaAsP薄膜, 并对其超快光学特性进行了研究. 温度和激发功率有关的发光特性表明: InGaAsP材料以自由激子发光为主. 室温下InGaAsP材料的载流子发光弛豫时间达到10.4 ns, 且随激发功率增大而增大. 发光弛豫时间随温度升高呈现S形变化, 在低于50 K时随温度升高而增大, 在50–150 K之间时减小, 而温度高于150 K时再次增大. 基于载流子弛豫动力学, 分析并解释了温度及非辐射复合中心浓度对样品材料载流子发光弛豫时间S形变化的影响. 相似文献
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Z.Y. Zhang C.L. YangY.Q. Wei X.L. YeP. Jin Ch.M. LiX.Q. Meng B. XuZ.G. Wang 《Solid State Communications》2003,126(7):391-394
In this report we have investigated the temperature dependence of photoluminescence (PL) from self-assembled InAs quantum dots (QDs) covered by an InAlAs/InGaAs combination layer. The ground state experiences an abnormal variation of PL linewidth from 15 K up to room temperature. Meanwhile, the PL integrated intensity ratio of the first excited state to the ground state for InAs QDs unexpectedly decreases with increasing temperature, which we attribute to the phonon bottleneck effect. We believe that these experimental results are closely related to the partially coupled quantum dots system and the large energy separation between the ground and the first excited states. 相似文献
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PHOTOLUMINESCENCE STUDY OF InAs/GaAs SELF-ORGANIZED QUANTUM DOTS WITH BIMODAL SIZE DISTRIBUTION
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We have investigated the temperature dependence of the photoluminescence (PL) spectrum of self-organized InAs/GaAs quantum dots. A distinctive double-peak feature of the PL spectra from quantum dots has been observed, and a bimodal distribution of dot sizes has also been confirmed by scanning tunneling microscopy image for uncapped sample. The power-dependent PL study demonstrates that the distinctive PL emission peaks are associated with the ground-state emission of islands in different size branches. The temperature-dependent PL study shows that the PL quenching temperature for different dot families is different. Due to lacking of the couple between quantum dots, an unusual temperature dependence of the linewidth and peak energy of the dot ensemble photoluminescence has not been observed. In addition, we have tuned the emission wavelength of InAs QDs to 1.3 μm at room temperature. 相似文献
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We investigate size-dependent carrier dynamics in self-assembled CdTe/ZnTe quantum dots (QDs) grown using molecular beam epitaxy and atomic layer epitaxy. Photoluminescence (PL) spectra show that the excitonic peak corresponding to transitions from the ground electronic subband to ground heavy-hole band in CdTe/ZnTe QDs shifts to a lower energy with increasing ZnTe buffer thicknesses. This shift of the PL peak can be attributed to size variation of the CdTe QDs. In particular, carrier dynamics in CdTe QDs grown on various ZnTe buffer layer thicknesses is studied using time-resolved PL measurements. As a result, the decay time of CdTe QDs is shown to increase with increasing ZnTe buffer layer thicknesses due to the reduction of the exciton oscillator strength in the larger QDs. 相似文献