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综述了对自组装量子点形态和生长过程所做的探讨和研究。介绍了关于量子点成核和形态的热力学理论、量子点生长过程的计算机模拟及Ge/Si(001)和InAs/GaAs(001)量子点生长和形态的实验观察。鉴于InAs/GaAs(001)体系的复杂性,把对InAs量子点的观察和研究分为"微观"和"宏观"两种。微观研究对象包括量子点原子尺度上的结构、量子点表面小晶面的晶体学的精确取向等,这些性质可能受热运动的影响比较大,在一定程度上是随机的,它们代表了量子点生长行为的复杂性;宏观研究的对象是指量子点密度、纳米尺度形态等大量粒子统计意义上的集体行为,这些性质和行为可能更具有实际意义。因此作者认为,目前研究量子点生长和形态更为有效的方法应该是探寻以量子点宏观行为所表征的简单性。重点介绍中科院半导体所半导体材料重点实验室最近所做的对InAs/GaAs(001)量子点生长过程的实验观察。结果表明,在一般生长条件下(富As,500℃,0.1ML/s),InAs量子点成核和生长应该都是连续的,没有经历被普遍认为的不连续(一级)相变。按照作者的观察,把InAs量子点成核看作是连续(二级)相变更为贴切。 相似文献
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在分子束外延生长的InAs/In0.52Al0.48As/InP异质结体系中,形成InAs量子线.这些InAs量子线在生长和结构方面有一些独到的特性,并介绍了本实验室在研究InAs量子线的生长和结构方面所做的工作. 相似文献
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利用分子束外延技术在(100)和(113)B GaAs衬底上进行了有/无AlAs盖帽层量子点的生长,测量了其在4~100 K温度区间的PL光谱。通过对PL光谱的积分强度、峰值能量和半高宽进行分析进而研究载流子的热传输特性。无AlAs盖帽层的(113)B面量子点的PL光谱的热淬灭现象可以由载流子极易从量子点向浸润层逃逸来解释。然而,有AlAs盖帽层的(113)B量子点的PL热淬灭主要是由于载流子进入了量子点与势垒或者浸润层界面中的非辐射中心引起的。并且其PL的温度依存性与利用Varshni定律计算的体材料InAs的温度依存性吻合很好,表明载流子通过浸润层进行传输受到了抑制,由于AlAs引起的相分离机制(113)B量子点的浸润层已经消失或者减小了。(100)面有AlAs盖帽层的PL半高宽的温度依存性与无AlAs盖帽层的量子点大致相同,表明在相同外延条件下相分离机制在(100)面上不如(113)B面显著。 相似文献
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调Q光纤激光器在光纤传感、激光雷达、激光加工和光纤通信等众多方面有着广泛的应用。半导体量子点(QD)由于具有较高的损伤阈值和宽光谱特性,是一种优良的可饱和吸收体(SA),但是目前制备发光中心波长为1 550 nm的QD SA依然是一个巨大的挑战。通过在分子束外延(MBE)生长InAs QD过程中加入两次间断制备了1 550 nm InAs/GaAs量子点半导体可饱和吸收镜(QD-SESAM),并通过构建光纤直线腔,研制出发光中心波长约为1 550 nm的被动调Q光纤激光器。该激光器最大输出功率约为2.5 mW,实现了55 kHz的重复频率,同时达到了1.45μs的脉冲宽度和45.36 nJ的单脉冲能量,表现出了InAs/GaAs QD材料在1 550 nm调Q光纤激光器应用中的巨大潜力。 相似文献
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D. H. Tomich K. G. Eyink L. Grazulis G. L. Brown F. Szmulowicz K. Mahalingam M. L. Seaford C. H. Kuo W. Y. Hwang C. H. Lin 《Journal of Electronic Materials》2000,29(7):940-943
This paper contains the characterization results for indium arsenide/indium gallium antimonide (InAs/InGaSb) superlattices
(SL) that were grown by molecular beam epitaxy (MBE) on standard gallium arsenide (GaAs), standard GaSb, and compliant GaAs
substrates. The atomic force microscopy (AFM) images, peak to valley (P-V) measurement, and surface roughness (RMS) measurements
are reported for each sample. For the 5 μm×5 μm images, the P-V heights and RMS measurements were 37 ? and 17 ?, 12 ? and
2 ?, and 10 ? and 1.8 ? for the standard GaAs, standard GaSb, and compliant GaAs respectively. The high resolution x-ray diffraction
(HRXRD) analysis found different 0th order SL peak to GaSb peak spacings for the structures grown on the different substrates. These peak separations are consistent
with different residual strain states within the SL structures. Depending on the constants used to determine the relative
shift of the valance and conduction bands as a function of strain for the individual layers, the change in the InAs conduction
band to InGaSb valance band spacing could range from +7 meV to −47 meV for a lattice constant of 6.1532 ?. The cutoff wavelength
for the SL structure on the compliant GaAs, control GaSb, and control GaAs was 13.9 μm, 11 μm, and no significant response,
respectively. This difference in cutoff wavelength corresponds to approximately a −23 meV change in the optical gap of the
SL on the compliant GaAs substrate compared to the same SL on the control GaSb substrate. 相似文献
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R. Heitz I. Mukhametzhanov A. Madhukar A. Hoffmann D. Bimberg 《Journal of Electronic Materials》1999,28(5):520-527
We report photoluminescence (PL), time-resolved PL, and PL excitation experiments on InAs/GaAs quantum dots (QDs) of different
size as a function of temperature. The results indicate that both the inhomogeneous properties of the ensemble and the intrinsic
properties of single QDs are important in understanding the temperature-dependence of the optical properties. With increasing
temperature, excitons are shown to assume a local equilibrium distribution between the localized QD states, whereas the formation
of a position-independent Fermi-level is prevented by carrier-loss to the barrier dominating thermally stimulated lateral
carrier transfer. The carrier capture rate is found to decrease with increasing temperature and, at room temperature, long
escape-limited ground state lifetimes of some 10 ps are estimated. PL spectra excited resonantly in the ground state transition
show matching ground state absorption and emission, indicating the intrinsic nature of exciton recombination in the QDs. Finally,
the PL excitation spectra are shown to reveal size-selectively the QD absorption, demonstrating the quantum-size effect of
the excited state splitting. 相似文献
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Z. M. Wang S. L. Feng Z. D. Lu Q. Zhao X. P. Yang Z. G. Chen Z. Y. Xu H. Z. Zheng 《Journal of Electronic Materials》1998,27(2):59-61
We investigate the annealing behavior of InAs layers with different thicknesses in a GaAs matrix. The diffusion enhancement
by strain, which is well established in strained quantum wells, occurs in InAs/GaAs quantum dots (QDs). A shift of the QD
luminescence peak toward higher energies results from this enhanced diffusion. In the case of structures where a significant
portion of the strain is relaxed by dislocations, the interdiffusion becomes negligible, and there is a propensity to generate
additional dislocations. This results in a decrease of the QD luminescence intensity, and the QD peak energy is weakly affected. 相似文献
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T. Lien Tran Fariba Hatami W. Ted Masselink Vas P. Kunets G.J. Salamo 《Journal of Electronic Materials》2008,37(12):1799-1805
We describe the epitaxial growth of InSb films on both Si (001) and GaAs (100) substrates using molecular-beam epitaxy and
discuss the structural and electrical properties of the resulting films. The complete 2 μm InSb films on GaAs (001) were grown
at temperatures between 340°C and 420°C and with an Sb/In flux ratio of approximately 5 and a growth rate of 0.2 nm/s. The
films were characterized in terms of background electron concentration, mobility, and x-ray rocking curve width. Our best
results were for a growth temperature of 350°C, resulting in room-temperature mobility of 41,000 cm2/V s. For the growth of InSb on Si, vicinal Si(001) substrates offcut by 4° toward (110) were used. We investigated growth
temperatures between 340°C and 430°C for growth on Si(001). In contrast to growth on GaAs, the best results were achieved
at the high end of the range of T
S = C, resulting in a mobility of 26,100 cm2/V s for a 2 μm film. We also studied the growth and properties of InSb:Mn films on GaAs with Mn content below 1%. Our results
showed the presence of ferromagnetic ordering in the samples, opening a new direction in the diluted magnetic semiconductors. 相似文献