Growth conditions effects on optical properties of InAs quantum dots grown by molecular beam epitaxy on GaAs (1 1 3)A substrate

We have investigated the optical properties of InAs/GaAs (1 1 3)A quantum dots grown by molecular beam epitaxy (MBE) with different growth rates by photoluminescence spectroscopy (PL) as a function of the excitation density and the sample temperature (10–300 K). Reflection high-energy electron diffraction (RHEED) is used to investigate the formation process of InAs quantum dots (QDs). A redshift of the InAs QDs PL band emission was observed when the growth rate was increased. This result was explained by the increase of the InAs quantum dot size with increasing growth rate. A significant redshift was observed when the arsenic flux was decreased. The evolution of the PL peak energy with increasing temperature has showed an S-shaped form due to the localization effects and is attributed to the efficient relaxation process of carriers in different InAs quantum dots and to the exciton transfer localized at the wetting layer.     

Wetting layers effect on InAs/GaAs quantum dots

FEM combining with the K·P theory is adopted to systematically investigate the effect of wetting layers on the strain-stress profiles and electronic structures of self-organized InAs quantum dot. Four different kinds of quantum dots are introduced at the same height and aspect ratio. We found that 0.5 nm wetting layer is an appropriate thickness for InAs/GaAs quantum dots. Strain shift down about 3%∼4.5% for the cases with WL (0.5 nm) and without WL in four shapes of quantum dots. For band edge energy, wetting layers expand the potential energy gap width. When WL thickness is more than 0.8 nm, the band edge energy profiles cannot vary regularly. The electron energy is affected while for heavy hole this impact on the energy is limited. Wetting layers for the influence of the electronic structure is obviously than the heavy hole. Consequently, the electron probability density function spread from buffer to wetting layer while the center of hole's function moves from QDs internal to wetting layer when introduce WLs. When WLs thickness is larger than 0.8 nm, the electronic structures of quantum dots have changed obviously. This will affect the instrument's performance which relies on the quantum dots' optical properties.     

Growth of InAs/GaAs quantum dots on germanium-on-insulator-on-silicon substrate for silicon photonics

We report the growth of self-assembled InAs/GaAs quantum dots (QDs) on germanium-on-insulator-on-silicon (GeOI/Si) substrate by antimony-mediated metal organic chemical vapor deposition. The influence of various growth procedures for the GaAs buffer layer on the QD formation and optical quality was investigated. We obtained QDs with density above 10¹⁰ cm⁻², and ground state emission in the 1.3 μm band at room temperature. These results demonstrate the promising suitability of germanium-on-insulator for the monolithic integration of QD-based and other GaAs-based photonic devices on silicon.     

Studying the mechanism of ordered growth of InAs quantum dots on GaAs/InP

We study the mechanism of ordered growth of InAs quantum dots (islands) on a GaAs/InP substrate in theory and point out that the tensile strain can be used to control InAs/InP self-assembled quantum dots arrangement. Photoluminescence spectrum, and atomic force microscopy images have been investigated. In the experiment, ordered InAs islands have been obtained and the maximum density of quantum dots is 1.6×10¹⁰ cm⁻² at 4 monolayers InAs layer.     

Effect of B atoms on the properties of InAs quantum dots in the GaAs matrix

The effect of B dopants on the properties of InAs quantum dots is studied experimentally. It is shown that the incorporation of B atoms decreases the integral amount of InAs that is needed to form islands according to the Stransky-Krastanov mechanism and leads to an increase in the density of dots. At the same time, it is discovered that the sensitivity of InAs quantum dots to annealing increases, which leads to the degradation of the optical properties of these quantum dots during growth of covering layers.     

Fabrication and optical properties of type‐II InP/InAs nanowire/quantum‐dot heterostructures

The growth and optical properties of InAs quantum dots on a pure zinc blende InP nanowire are investigated. The quantum dots are formed in Stranski–Krastanov mode and exhibit pure zinc blende crystal structure. A substantial blueshift of the dots peak with a cube‐root dependence on the excitation power is observed, suggesting a type‐II band alignment. The peak position of dots initially red‐shifts and then blue‐shifts with increasing temperature, which is attributed to the carrier redistribution among the quantum dots. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Carrier hopping in InAs/AlyGa1−yAs quantum dot heterostructures: effects on optical and laser properties

The optical properties of InAs/Al_yGa_1−yAs self-assembled quantum dots are studied as a function of temperature from 10 K to room temperature. The temperature dependence of carrier hopping between dots is discussed in terms of the depth of the dot confinement potential and the dispersion in dot size and composition. We show that carrier hopping between dots influences both the electrical and optical properties of laser devices having dots as active medium.     

Electronic and optical properties of InAs/InP self-assembled quantum dots on patterned substrates

We present atomistic theory of electronic and optical properties of a single InAs quantum dot grown on a pyramidal InP nanotemplate. The shape and size of the dot is assumed to follow the nanotemplate shape and size. The electron and valence hole single particle states are calculated using atomistic effective–bond–orbital model with second nearest-neighbor interactions. The electronic calculations are coupled to separately calculated strain distribution via Bir–Pikus Hamiltonian. The optical properties of InAs dots embedded in InP pyramids are calculated by solving the many-exciton Hamiltonian for interacting electron and hole complexes using the configuration–interaction method. The effect of quantum-dot geometry on the optical spectra is investigated by a comparison between dots of different shapes.     

The refractive nonlinearities of InAs/GaAs quantum dots above-bandgap energy

The third-order optical nonlinear refractive properties of InAs/GaAs quantum dots grown by molecular beam epitaxy have been measured using the reflection Z-scan technique at above-bandgap energy. The nonlinear refractive index and nonlinear absorption index of the InAs/GaAs quantum dots were determined for wavelengths from 740 to 777 nm. The measured results are compared with the nonlinear refractive response of several typical III-V group semiconductor materials. The corresponding mechanisms responsible for the large nonlinear response are discussed.     

Formation of InAs quantum dots in silicon by sequential ion implantation and flash lamp annealing

InAs quantum dots (QDs) were successfully formed in single-crystalline Si by sequential ion implantation and subsequent milliseconds range flash lamp annealing (FLA). Samples were characterized by μ-Raman spectroscopy, Rutherford Backscattering Spectrometry (RBS) high-resolution transmission electron microscopy (HRTEM) and low temperature photoluminescence (PL). The Raman spectrum shows two peaks at 215 and 235 cm^?1 corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs phonon modes, respectively. The PL band at around 1.3 μm originates from the InAs QDs with an average diameter 7.5±0.5 nm and corresponds to the increased band gap energy due to the strong quantum confinement size effect. The FLA of 20 ms is sufficient for InAs QDs formation. It also prevents the out-diffusion of implanted elements. Moreover, the silicon layer amorphized during ion implantation is recrystallized by solid-phase epitaxial regrowth during FLA.     

半导体红外量子点发展现状与前景

半导体量子点具有独特的光学与电学性质,特别是红外量子点良好的光稳定性和生物相容性等优点使其在光电器件、生物医学等领域受到广泛关注。综述了吸收或发射光谱位于红外波段的量子点在激光、能源、光电探测以及生物医学等方面的应用现状与前景,归纳了适用于红外量子点材料的制备方法,并对比了不同方法在应用中的优势。半导体红外量子点材料选择丰富、应用形式多样:InAs量子点被动锁模激光器在1.3 μm波长处产生7.3 GHz的近衍射极限脉冲输出;InAs/GaAs量子点双波长激光器可泵浦产生0.6 nW的THz波;PbS量子点掺杂光纤放大器可在1.53 μm中心波长处实现10.5 dB光增益,带宽160 nm;CdSeTe量子点敏化太阳能电池、异质结Si基量子点太阳能电池的总转换效率可达8%和14.8%;胶质HgTe量子点制成的量子点红外探测器(QDIP)可实现3 μm~5 μm中波红外探测,Ge/Si量子点可实现3 μm~7 μm红外探测;CdTe/ZnSe核壳量子点可用于检测DNA序列的损伤与突变。半导体红外量子点上述应用形式的发展,将进一步促进红外光电系统向高效、快速、大规模集成的方向演进,也将极大地促进临床医学中活体成像检测的应用推广。     

The emission wavelength tuning of InAs/InP quantum dots with thin GaAs, InGaAs, InP capping layers by MOCVD

InAs quantum dots (QDs) were grown on InP substrates by metalorganic chemical vapor deposition. The width and height of the dots were 50 and 5.8 nm, respectively on the average and an areal density of 3.0×10¹⁰ cm⁻² was observed by atomic force microscopy before the capping process. The influences of GaAs, In_0.53Ga_0.47As, and InP capping layers (5–10 ML thickness) on the InAs/InP QDs were studied. Insertion of a thin GaAs capping layer on the QDs led to a blue shift of up to 146 meV of the photoluminescence (PL) peak and an InGaAs capping layer on the QDs led to a red shift of 64 meV relative to the case when a conventional InP capping layer was used. We were able to tune the emission wavelength of the InAs QDs from 1.43 to 1.89 μm by using the GaAs and InGaAs capping layers. In addition, the full-width at half-maximum of the PL peak decreased from 79 to 26 meV by inserting a 7.5 ML GaAs layer. It is believed that this technique is useful in tailoring the optical properties of the InAs QDs at mid-infrared regime.     

应变补偿层对量子点生长影响的理论研究

量子点的光学特性与量子点的大小均匀性、密度、内部应变以及隔离层的厚度等有密切关系.文中从理论角度定量研究了GaNXAs1-X应变补偿层对InAs/GaAs量子点生长质量的改善作用,分析了应变补偿层对隔离层厚度减小的作用.讨论了应变补偿层的补偿位置和补偿层N组分X对量子点生长时局部应变和体系应变的补偿作用.分析了应变补偿层对体系应变的减少作用,并计算了相邻层量子点的垂直对准概率.研究结果对实验中应变补偿的优化和高质量量子点阵列的生长实现提供了理论依据.     

Effect of thermal annealing in the microstructural and the optical properties of uncapped InAs quantum dots grown on GaAs buffer layers

The effect of thermal annealing on self-assembled uncapped InAs/GaAs quantum dots (QDs) has been investigated using transmission electron microscopy (TEM) and photoluminescence (PL) measurements. The TEM images showed that the lateral sizes and densities of the InAs QDs were not changed significantly up to 650 °C. When the InAs/GaAs QDs were annealed at 700 °C, while the lateral size of the InAs QDs increased, their density decreased. The InAs QDs disappeared at 800 °C. PL spectra showed that the peaks corresponding to the interband transitions of the InAs QDs shifted slightly toward the high-energy side, and the PL intensity decreased with increasing annealing temperature. These results indicate that the microstructural and the optical properties of self-assembled uncapped InAs/GaAs can be modified due to postgrowth thermal annealing.     

Single InAs/InP quantum dot spectroscopy in 1.3–1.55 μm telecommunication band

We present an optical spectroscopy and photon correlation measurement at telecommunication wavelengths performed on single InAs/InP quantum dots. Two main approaches brought high optical quality: an application of a ‘double-cap’ growth method to metalorganic chemical vapor deposition, and fabrication of a small mesa structure using low-damage wet chemical etching. Sharp and discrete exciton transition lines have been observed on the single quantum dots, which widely cover the spectral range of 1.3–1.55 μm. Using a pulsed excitation source and gated single-photon detection modules, we observed a photon antibunching behavior for an isolated exciton emission line, indicating nonclassical light emission near the wavelength of 1.3 μm.     

Optical transitions of InAs/In0.36Ga0.64As/GaAs(311B) surface quantum dots clearly identified by the piezoreflectance technique

The bilayer InAs/In_0.36Ga_0.64As/GaAs(311B) quantum dots (QDs), including one InAs buried quantum dot (BQD) layer and the other InAs surface quantum dot (SQD) layer, have been grown by molecular beam epitaxy (MBE). The optical properties of these three samples have been studied by the piezoreflectance (PzR) spectroscopy. The PzR spectra do not exhibit only the optical transitions originated from the InAs BQDs, but the features originated from the InAs SQDs. After the InAs SQDs have been removed chemically, those optical transitions from InAs SQDs have been demonstrated clearly by investigating the PzR spectra of the residual InAs BQDs in these samples. The great redshift of these interband transitions of InAs SQDs has been well discussed. Due to the suitable InAs SQD sizes and the thickness of In_0.36Ga_0.64As layer, the interband transition of InAs SQDs has been shifted to ∼1.55 μm at 77 K.     

Infrared photodetection with semiconductor self-assembled quantum dots

Semiconductor self-assembled quantum dots are potential candidates to develop a new class of midinfrared quantum photodetectors and focal plane arrays. In this article, we present the specific midinfrared properties of InAs/GaAs quantum dots associated with the intersublevel transitions. The electronic structure, which accounts for the strain field in the islands, is obtained within the framework of a three-dimensional 8 band k.p formalism. The midinfrared intersublevel absorption in n-doped quantum dots is described. We show that the carrier dynamics can be understood in terms of polarons which result from the strong coupling regime for the electron–phonon interaction in the dots. The principle of operation of vertical and lateral quantum dot infrared photodetectors is described and discussed by comparison with quantum well infrared photodetectors. We review the performances of different type of detectors developed to date and finally give some orientation to realize high performance quantum dot infrared photodetectors. To cite this article: P. Boucaud, S. Sauvage, C. R. Physique 4 (2003).     

Dependence of bimodal size distribution on temperature and optical properties of InAs quantum dots grown on vicinal GaAs （100） substrates by using MOCVD

Self-assembled InAs quantum dots (QDs) are grown on vicinal GaAs (100) substrates by using metal-organic chemical vapour deposition (MOCVD). An abnormal temperature dependence of bimodal size distribution of InAs quantum dots is found. As the temperature increases, the density of the small dots grows larger while the density of the large dots turns smaller, which is contrary to the evolution of QDs on exact GaAs (100) substrates. This trend is explained by taking into account the presence of multiatomic steps on the substrates. The optical properties of InAs QDs on vicinal GaAs(100) substrates are also studied by photoluminescence (PL) . It is found that dots on a vicinal substrate have a longer emission wavelength, a narrower PL line width and a much larger PL intensity.     

InSb/InAsSb nanostructures for Mid-IR optoelectronics

The technique of preparation of nanostructures with InSb quantum dots in an InAs(Sb) matrix, emitting in the mid-IR range upon optical and injection pumping, by molecular beam epitaxy is considered and the structural and optical properties of these nanostructures are investigated. The characteristics of the first injection lasers based on III–V/II–VI hybrid heterostructures with InSb/InAs(Sb) quantum dots in the active region are reported.