首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 93 毫秒
1.
We present a study on InAs/InGaAs QDs nanostructures grown by molecular beam epitaxy on InGaAs metamorphic buffers, that are designed so as to determine the strain of QD and, then, to shift the luminescence emission towards the 1.5 μm region (QD strain engineering). Moreover, we embed the QDs in InAIAs or GaAs barriers in addition to the InGaAs confining layers, in order to increase the activation energy for confined carrier thermal escape; thus, we reduce the thermal quenching of the photoluminescence, which prevents room temperature emission in the long wavelength range. We study the dependence of QD properties, such as emission energy and activation energy, on barrier thickness and height and we discuss how it is possible to compensate for the barrier-induced QD emission blue-shift taking advantage of QD strain engineering. Furthermore, the combination of enhanced barriers and QD strain engineering in such metamorphic QD nanostmctures allowed us to obtain room temperature emission up to 1.46μm, thus proving how this is a valuable approach in the auest for 1.55 um room temperature emission from ODs grown on GaAs substrates.  相似文献   

2.
Molecular beam epitaxy growth of a bilayer stacked InAs/GaAs quantum dot structure on a pure GaAs matrix has been systemically investigated.The influence of growth temperature and the InAs deposition of both layers on the optical properties and morphologies of the bilayer quantum dot(BQD) structures is discussed.By optimizing the growth parameters,InAs BQD emission at 1.436μm at room temperature with a narrower FWHM of 27 meV was demonstrated.The density of QDs in the second layer is around 9×109 to 1.4×1010 cm-2. The BQD structure provides a useful way to extend the emission wavelength of GaAs-based material for quantum functional devices.  相似文献   

3.
ZnO quantum dots (QDs)with the sizes of 3.0-5.6 nm are synthesized by solution-phase method at different temperatures. We find that temperature has great influence on the size of ZnO QDs. The growth process is the most sensitive to temperature, and the process is well explained by Lifshitz-Slyozov-Wagner (LSW) model. By photoluminescence (PL) spectra of the quantum dots at different temperatures and reactive time, we come to a conclusion that ultraviolet emission is mainly due to surface defects, and the or...  相似文献   

4.
A high temperature sensor based on the multi-parameter temperature dependent characteristic of photoluminescence (PL) of quantum dot (QD) thin film is demonstrated by depositing the CdSe/ZnS core/shell QDs on the SiO2 glass substrates. The variations of the intensity, the peak wavelength and the full width at half maximum (FWHM) of PL spectra with temperature are studied experimentally and theoretically. The results indicate that the peak wavelength of the PL spectra changes linearly with temperature, while the PL intensity and FWHM vary exponentially for the tem- perature range from 30 ℃ to 180 ℃. Using the obtained temperature dependent optical parameters, the resolution of the designed sensor can reach 0.1 nm/℃.  相似文献   

5.
Results of photoluminescence (PL) studies of self-organized nanoscale InP islands (quantum dots, QDs) in the In0.49Ga0.51P matrix, grown on a GaAs substrate by metalorganic vapor phase epitaxy (MOVPE), are presented. Dependences of the PL efficiency on temperature in the range 77–300 K and on excitation level at pumping power densities of 0.01–5 kW/cm2 have been obtained. The PL spectra are a superposition of emission peaks from QDs and the wetting layer. Their intensity ratio depends on the pumping power and temperature, and the emission wavelength varies in the range 0.65–0.73 μm. At 77 K and low excitation level, InP QDs exhibit high temperature stability of the emission wavelength and high quantum efficiency. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 2, 2001, pp. 242–244. Original Russian Text Copyright ? 2001 by Vinokurov, Kapitonov, Nikolaev, Sokolova, Tarasov.  相似文献   

6.
CdS nanocrystals have been successfully grown on porous silicon (PS) by sol-gel method. The plan-view field emission scanning electron microscopy (FESEM) shows that the pore size of PS is smaller than 5 μm in diameter and the agglomerates of CdS are broadly distributed on the surface of PS substrate. With the increase of annealing time, the CdS nanoparticles grow in both length and diameter along the preferred orientation. The cross-sectional FESEM images of ZnO/PS show that CdS nanocrystals are uniformly penetrated into all PS layers and adhere to them very well. photoluminescence (PL) spectra demonstrate that the intensity of PL peak located at about 425 nm has almost no change after the annealing time increases. The range of emission wavelength of CdS/PS is from 425 nm to 455 nm and the PL intensity is decreasing with the annealing temperature increasing from 100 °C to 200 °C.  相似文献   

7.
InAs/GaAs quantum dot(QD)lasers were grown on silicon substrates using a thin Ge buffer and three-step growth method in the molecular beam epitaxy(MBE)system.In addition,strained superlattices were used to prevent threading disloca-tions from propagating to the active region of the laser.The as-grown material quality was characterized by the transmission electron microscope,scanning electron microscope,X-ray diffraction,atomic force microscope,and photoluminescence spectro-scopy.The results show that a high-quality GaAs buffer with few dislocations was obtained by the growth scheme we de-veloped.A broad-area edge-emitting laser was also fabricated.The O-band laser exhibited a threshold current density of 540 A/cm2 at room temperature under continuous wave conditions.This work demonstrates the potential of large-scale and low-cost manufacturing of the O-band InAs/GaAs quantum dot lasers on silicon substrates.  相似文献   

8.
王军  张红燕 《光电子快报》2017,13(3):214-216
In this work, indium nitride (InN) films were successfully grown on porous silicon (PS) using metal oxide chemical vapor deposition (MOCVD) method. Room temperature photoluminescence (PL) and field emission scanning electron microscopy (FESEM) analyses are performed to investigate the optical, structural and morphological properties of the InN/PS nanocomposites. FESEM images show that the pore size of InN/PS nanocomposites is usually less than 4 μm in diameter, and the overall thickness is approximately 40 μm. The InN nanoparticles penetrate uniformly into PS layer and adhere to them very well. Nitrogen (N) and indium (In) can be detected by energy dispersive spectrometer (EDS). An important gradual decrease of the PL intensity for PS occurs with the increase of oxidation time, and the PL intensity of PS is quenched after 24 h oxidization. However, there is a strong PL intensity of InN/PS nanocomposites at 430 nm (2.88 eV), which means that PS substrate can influence the structural and optical properties of the InN, and the grown InN on PS substrate has good optical quality.  相似文献   

9.
Photoluminescence origin of nanocrystalline SiC films   总被引:1,自引:0,他引:1  
The nanocrystalline SiC films were prepared on Si then annealed at 800℃ and 1 000℃ for 30 minutes (111) substrates by rf magnetron sputtering and in a vacuum annealing system. The crystal structure and crystallization of as-annealed SiC films were determined by the Fourier transform infrared (FIR) absorption spectra and the X-ray diffraction (XRD) analysis. Measurement of photoluminescence (PL) of the nanocrystalline SiC (nc-SiC) films shows that the blue light with 473 nm and 477 nm wavelengths emitted at room temperature and that the PL peak shifts to shorter wavelength side and the PL intensity becomes stronger as the annealing temperature decreases. The time-resolved spectrum of the PL at 477 nm exhibits a bi-exponential decay process with lifetimes of 600 ps and 5 ns and a characteristic of the direct band gap. The strong blue light emission with short PL lifetimes suggests that the quantum confinement effect of the SiC nanocrystals resulted in the radiative recombination of the direct optical transitions.  相似文献   

10.
Zinc oxide (ZnO) thin films were grown on n-GaN/sapphire substrates by radio-frequency (RF) magnetron sputtering. The films were grown at substrate temperatures ranging from 400 to 700 ℃ for 1 h at a RF power of 80 W in pure Ar gas ambient. The effect of the substrate temperature on the structural and optical properties of these films was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and photoluminescence (PL) spectra. XRD results indicated that ZnO films exhibited wurtzite symmetry and c-axis orientation when grown epitaxially on n-GaN/sapphire. The best crystalline quality of the ZnO film is obtained at a growth temperature of 600 ℃. AFM results indicate that the growth mode and degree of epitaxy strongly depend on the substrate temperature. In PL measurement, the intensity of ultraviolet emission increased initially with the rise of the substrate temperature, and then decreased with the temperature. The highest UV intensity is obtained for the film grown at 600 ℃ with best crystallization. oindent  相似文献   

11.
为了获得波长长、均匀性好和发光效率高的量子点,采用分子束外延(MBE)技术和S-K应变自组装模式,在GaAs(100)衬底上研究生长了三种InAs量子点。采用MBE配备的RHEED确定了工艺参数:As压维持在1.33×10-5Pa;InAs量子点和In0.2Ga0.8As的生长温度为500℃;565℃生长50nmGaAs覆盖层。生长了垂直耦合量子点(InAs1.8ML/GaAs5nm/InAs1.8ML)、阱内量子点(In0.2Ga0.8As5nm/InAs2.4ML/In0.2Ga0.8As5nm)和柱状岛量子点(InAs分别生长1.9、1.7、1.5ML,停顿20s后,生长间隔层GaAs2nm)。测得对应的室温光致发光(PL)谱峰值波长分别为1.038、1.201、1.087μm,半峰宽为119.6、128.0、72.2nm、相对发光强度为0.034、0.153、0.29。根据PL谱的峰位、半峰宽和相对发光强与量子点波长、均匀性和发光效率的对应关系,可知量子点波长有不同程度的增加、均匀性越来越好、发光效率显著增强。  相似文献   

12.
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   

13.
This article reviews the recent progress in the growth and device applications of InAs/InP quantum dots (QDs) for telecom applications. Wavelength tuning of the metalorganic vapor-phase epitaxy grown single layer and stacked InAs QDs embedded in InGaAsP/InP (1 0 0) over the 1.55-μm region at room temperature (RT) is achieved using ultra-thin GaAs interlayers underneath the QDs. The GaAs interlayers, together with reduced growth temperature and V/III ratio, and extended growth interruption suppress As/P exchange to reduce the QD height in a controlled way. Device quality of the QDs is demonstrated by temperature-dependent photoluminescence (PL) measurements, revealing zero-dimensional carrier confinement and defect-free InAs QDs, and is highlighted by continuous-wave ground-state lasing at RT of narrow ridge-waveguide QD lasers, exhibiting a broad gain spectrum. Unpolarized PL from the cleaved side, important for realization of polarization insensitive semiconductor optical amplifiers, is obtained from closely stacked QDs due to vertical electronic coupling.  相似文献   

14.
用PL谱测试研究了GaAs和不同In组份InxGa1-xAs(x=0.1,0.2,0.3)覆盖层对分子外延生长的InAs/GaAs自组织量子点发光特性的影响,用InxGa1-xAs外延层覆盖InAs/GaAs量子点,比用GaAs做 其发光峰能量向低有端移动,发光峰半高度变窄,量子点发光峰能量随温度的红移幅度较小,理论计算证实这是由于覆盖层InxGa1-xAs减小了InAs表面应力导致发光峰红移,而In元素有效抑制了InAs/GaAs界面组份的混杂,量子点的均匀性得到改善,PL谱半高宽变窄,用InGaAs覆盖的In0.5Ga0.5As/GaAs自组织量子点实现了1.3μm发光,室温下PL谱半高宽为19.2meV,是目前最好的实验结果。  相似文献   

15.
GaAs/InAs quantum dot (QD) heterostructures prepared by metalloorganic chemical vapor deposition (MOCVD) are investigated. It is established that the introduction of isovalent bismuth doping during the growth of InAs QD layer results in the suppression of the nanocluster coalescence and favors the formation of more uniform QDs. Bismuth itself is virtually not incorporated into the dots, its role being mainly in limiting the migration mobility of atoms at the surface of the growing layer. A method for investigating the morphology of buried layers of InAs QDs in GaAs matrix by atomic-force microscopy is developed; it relies on the removal of the cap layer by selective chemical etching. The photoluminescence (PL) and photoelectric sensitivity spectra of the fabricated heterostructures and their relation to the morphology of the QD layer are studied. In doped structures, PL and selective photosensitivity owing to the QDs are observed at a wavelength of 1.41 µm with the linewidth of 43 meV at room temperature. Some of the morphological features and photoelectronic properties of the MOCVD-grown heterostructures are related to the formation of a transitional layer at the GaAs/InAs QD interface due to the diffusion-induced mixing of the components.  相似文献   

16.
In this paper, we present the growth and photoluminescence (PL) results of InAs quantum dots (QDs) on a p-type porous GaAs (001) substrate. It has been shown that critical layer thickness of InAs overgrowth on porous GaAs has been enhanced compared to that deposited on nominal GaAs. Using porous GaAs substrate, growth interruption and depositing 10 atomic monolayer (ML) In0.4Ga0.6As on InAs QDs, photoluminescence measured at 10 K exhibits an emission at 0.739 eV (∼1.67 μm) with an ultranarrow full width at half maximum (FWHM) of 16 meV. This emission represents the longer wavelength obtained up to date to our knowledge and has been attributed to the radiative transition in the InAs QDs.  相似文献   

17.
Photoluminescence (PL) spectra of InAs/GaAs heteroepitaxial structures with quantum dots (QDs) have been studied. The structures were grown by submonolayer migration-enhanced epitaxy on vicinal substrates with the amount of deposited InAs close to the critical value of 1.8 monolayer (ML). The origin and evolution of the structure of PL spectra were studied in relation to the direction and angle of misorientation, temperature, and power density and spectrum of the exciting radiation. A blue shift and narrowing of the PL band with increasing misorientation angle was established experimentally. The fact that QDs become smaller and more uniform in size is explained in terms of a lateral confinement of QDs on terraces with account taken of the step bunching effect. The temperature dependences of the positions and full widths at half-maximum (FWHM) of PL bands are fundamentally different for isolated and associated QDs. The exciton ground states contribute to all low-temperature spectral components. The excited exciton state contributes to the recombination emission from QDs, as evidenced by the temperature dependence of the integrated intensity of the PL bands. A quantitative estimate is given of the electronic structure of different families of InAs QDs grown on GaAs substrates misoriented by 7° in the [001] direction.  相似文献   

18.
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   

19.
用低温光荧光(PL)和透射电子显微镜(TEM)研究了表面氮化自组织InAs/GaAs量子点的光学性能和微观结构。结果表明氮化后形成薄层的InAsN薄膜作为应变缓和层覆盖在量子点的表面,使得随着氮化时间的增加,InAs量子点的位错密度提高、尺寸变大、纵横比提高、发光波长变长、强度变低。  相似文献   

20.
系统研究了InAlAs/InGaAs复合限制层对InAs量子点光学性质的影响;发现InAs量子点的基态发光峰位、半高宽以及基态与第一激发态的能级间距都强烈地依赖于InAlAs薄层的厚度和In的组分;得到了室温发光波长在1.35μm,基态与第一激发态的能级间距高达103 meV的InAs量子点的发光特性。这一结果对实现高T_0的长波长InAs量子点激光器的室温激射具有重要意义。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号