大尺寸InAs／GaAs量子点的静压光谱

在低温15K和0～9GPa范围内对厚度为7．3nm、横向尺寸为78nm的自组织InAs／GaAs量子点进行了压力光谱研究．观测到大量子点的基态与第一激发态发光峰，其压力系数只有69和72meV／GPa，比小量子点的压力系数更小．基于非线性弹性理论的分析表明失配应变与弹性系数随压力的变化是大量子点压力系数小的主要原因之一．压力实验结果还表明大量子点的第一激发态发光峰来源于电子的第一激发态到空穴的第一激发态的跃迁．     

InGaAs/InAlAs盖帽层对InAs自组装量子点发光性质的影响

采用变温及时间分辨光致发光谱研究了MBE设备生长的具有不同盖帽层的InAs量子点样品.发现引入InGaAs盖帽层可以使InAs量子点发光的半高宽减小,且向长波长移动.InGaAs/InAlAs联合盖帽层可以进一步改善InAs量子点发光性能,使得室温发光波长超过1.3μm;在10～300K温度范围内,发光峰值能量及半高宽随温度的变化都较小.随温度升高,InAs量子点的发光寿命首先增大,当温度升高到临界温度TC后,发光寿命逐渐减小.但覆盖不同盖帽层的InAs量子点样品,其发光寿命具有不同的温度关系,联合盖帽层样品具有较大的TC及发光寿命.根据应力及载流子迁移模型对以上实验结果进行了分析.     

InAs/GaAs量子点光致发光光谱多峰结构发光本质

研究了InAs/GaAs量子点光致发光光谱中出现的多峰结构. 观察到随着激发功率的增加光谱中发光峰的数目逐渐增多并且部分发光峰的峰位随激发功率的增加向高能量方向移动. 解释了各发光峰的来源并结合量子点能级结构的特点,计算了量子点中电子和空穴各子带间的能级间距.     

InAs/GaAs量子点光致发光光谱多峰结构发光本质

研究了InAs/GaAs量子点光致发光光谱中出现的多峰结构.观察到随着激发功率的增加光谱中发光峰的数目逐渐增多并且部分发光峰的峰位随激发功率的增加向高能量方向移动.解释了各发光峰的来源并结合量子点能级结构的特点,计算了量子点中电子和空穴各子带间的能级间距.     

In0．2Ga0．8As-GaAs复合应力缓冲层上的1.3μm InAs／GaAs自组织量子点

用光荧光谱和原子力显微镜测试技术系统研究了在2 nm In0.2Ga0.8As和x ML GaAs的复合应力缓冲层上生长的InAs/GaAs自组织量子点的发光特性和表面形貌.采用In0.2Ga0.8As与薄层GaAs复合的应力缓冲层,由于减少了晶格失配度致使量子点密度从约1.7×109 cm-2显著增加到约3.8×109cm-2.同时,复合层也有利于提高量子点中In的组份,使量子点的高宽比增加,促进量子点发光峰红移.对于x=10 ML的样品室温下基态发光峰达到1350 nm.     

室温全电可操作的InAs/GaAs量子点存储器

报道基于高电子迁移率晶体管(HEMT)结构的InAs/GaAs量子点存储器,它既可以在室温下工作,又可以完全由栅极电压来控制其存储状态.在室温下通过对InAs/GaAs量子点存储器的延滞回线、偏压降温C-V等特性的实时测试,证明了其存储机理是由量子点层的深能级引起的,而并非是由量子点本征能级的充、放电所造成的.     

室温全电可操作的InAs/GaAs量子点存储器

报道基于高电子迁移率晶体管(HEMT)结构的InAs/GaAs量子点存储器,它既可以在室温下工作,又可以完全由栅极电压来控制其存储状态.在室温下通过对InAs/GaAs量子点存储器的延滞回线、偏压降温C-V等特性的实时测试,证明了其存储机理是由量子点层的深能级引起的,而并非是由量子点本征能级的充、放电所造成的.     

利用大周期光子晶体结构增强InAs/GaAs量子点的激发态发光

在该研究中,通过激光全息和湿法腐蚀的方法在InAs/GaAs量子点材料上制备光子晶体,研究了由激光二极管激发制备了光子晶体的InAs / GaAs量子点材料的光致发光光谱.发现具有光子晶体的量子点材料的光谱显示出多峰结构,光子晶体对短波长部分的发光增强和调制比对长波长部分的增强和调制更明显.InAs / GaAs量子点的光致发光光谱通过刻蚀形成的光子晶体结构得到了调控,并且量子点的激发态发光得到了明显增强.     

利用大周期光子晶体结构增强InAs/GaAs量子点的激发态发光（英文）

在该研究中,通过激光全息和湿法腐蚀的方法在InAs/GaAs量子点材料上制备光子晶体,研究了由激光二极管激发制备了光子晶体的InAs/GaAs量子点材料的光致发光光谱.发现具有光子晶体的量子点材料的光谱显示出多峰结构,光子晶体对短波长部分的发光增强和调制比对长波长部分的增强和调制更明显.InAs/GaAs量子点的光致发光光谱通过刻蚀形成的光子晶体结构得到了调控,并且量子点的激发态发光得到了明显增强.     

内嵌自组装InAs量子点调制掺杂场效应管的光电特性

研究了阱中生长自组装InAs量子点的光谱特性,获得了室温1.265μm近红外荧光发光,探讨了与量子点尺寸分布相关的发光峰随温度的超常红移现象.制备了内嵌InAs量子点的异质结调制掺杂场效应晶体管,获得了高耐压的场效应器件电学特性,并有望制成新型红外光电探测场效应管.     

Nonequilibrium room-temperature carrier distribution in InAs quantum dots overgrown with thin AlAs/InAlAs layers

The optical properties of quantum dots (QDs) formed in GaAs or Al_0.3Ga_0.7As matrices by overgrowth of initial InAs islands formed in the Stranski-Krastanov mode with thin AlAs/InAlAs layers have been studied. It is shown that no transport of carriers between the QDs occurs in the temperature range 10–300 K, so the carrier distribution is of a nonequilibrium nature. The thermal excitation of carriers from the QDs is suppressed by an increase in the energy spacing between the ground and excited states, absence of the level related to the wetting layer, and higher carrier localization energy in the QDs with respect to the continuum states when the Al_0.3Ga_0.7As matrix is used.     

InAs quantum-dot lasers operating near 1.3 μm with highcharacteristic temperature for continuous-wave operation

A high characteristic temperature with T₀ of 126 K under continuous-wave operation is obtained for an InAs/GaAs quantum dot laser. A triple-stacked active region with an energy separation of 95 meV between the ground and first excited radiative transitions is used to achieve a ground state saturation gain at 300 K of 13 cm^-1, and high internal quantum efficiency of 74%     

Temperature dependent optical properties of self-organized InAs/GaAs quantum dots

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.     

Coupling of electron states in the InAs/GaAs quantum dot molecule

Deep level transient spectroscopy (DLTS) is used to study electron emission from the states in the system of vertically correlated InAs quantum dots in the p-n InAs/GaAs heterostructures, in relation to the thickness of the GaAs spacer between the two layers of InAs quantum dots and to the reverse-bias voltage. It is established that, with the 100 Å GaAs spacer, the InAs/GaAs heterostructure manifests itself as a system of uncoupled quantum dots. The DLTS spectra of such structures exhibit two peaks that are defined by the ground state and the excited state of an individual quantum dot, with energy levels slightly shifted (by 1–2 eV), due to the Stark effect. For the InAs/GaAs heterostructure with two layers of InAs quantum dots separated by the 40 Å GaAs spacer, it is found that the quantum dots are in the molecule-type phase. Hybridization of the electron states of two closely located quantum dots results in the splitting of the levels into bonding and antibonding levels corresponding to the electron ground states and excited states of the 1s ⁺, 1s ^?, 2p ⁺, 2p ^?, and 3d ⁺ types. These states manifest themselves as five peaks in the DLTS spectra. For these quantum states, a large Stark shift of energy levels (10–40 meV) and crossing of the dependences of the energy on the electric field are observed. The structures with vertically correlated quantum dots are grown by molecular beam epitaxy, with self-assembling effects.     

Transistor performance and electron transport properties of highperformance InAs quantum-well FET's

A novel field-effect transistor based on a pseudomorphic InAs quantum well in a doped InGaAs/InAlAs double heterostructure is reported. Low-field mobility, electron peak velocity, and transistor performance are studied as functions of InAs quantum well thickness, where the InAs layer is in the center of a 300-Å uniformly doped InGaAs/InAlAs quantum well lattice matched to InP. Electron transport-both at low and high fields-along with transistor transconductance are optimal for structures with a 30-Å InAs quantum well. Transistors based on the InAs quantum well structures with 0.5-μm gate lengths yielded room temperature extrinsic transconductances of 708 mS/mm, more than a 100% increase over those with no InAs     

Optical and structural properties of InAs quantum dot arrays grown in an InxGa1−x As matrix on a GaAs substrate

Structural and optical properties of InAs quantum dots (QDs) deposited on the surface of a thick InGaAs metamorphic layer grown on a GaAs substrate have been studied. The density and lateral size of QDs are shown to increase in comparison with the case of QDs grown directly on a GaAs substrate. The rise of In content in the InGaAs layer results in the red shift of the photoluminescence (PL) line, so that with 30 at % indium in the metamorphic layer the PL peak lies at 1.55 μm. The PL excitation spectroscopy of the electronic spectrum of QDs has shown that the energy separation between the sublevels of carriers in QDs decreases as the In content in the InGaAs matrix increases. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 7, 2004, pp. 867–871. Original Russian Text Copyright ? 2004 by Kryzhanovskaya, Gladyschev, Blokhin, Musikhin, Zhukov, Maksimov, Zakharov, Tsatsul’nikov, Ledentsov, Werner, Guffart, Bimberg.     

Lasing at a wavelength close to 1.3 µm in InAs quantum-dot structures

The feasibility of lasing at a wavelength close to 1.3 μm is demonstrated in InAs quantum-dot structures placed in an external InGaAs/GaAs quantum well. It is shown that the required wavelength can be attained with the proper choice of thickness of the InAs layer deposited to form an array of three-dimensional islands and with a proper choice of mole fraction of InAs in the InGaAs quantum well. Since the gain attained in the ground state is insufficient, lasing is implemented through excited states in the temperature interval from 85 K to 300 K in a structure based on a single layer of quantum dots. The maximum attainable gain in the laser structure can be raised by using three rows of quantum dots, and this configuration, in turn, leads to low-threshold (70 A/cm²) lasing through the ground state at a wavelength of 1.26 μm at room temperature. Fiz. Tekh. Poluprovodn. 33, 1020–1023 (August 1999)     

Recombination emission from InAs quantum dots grown on vicinal GaAs surfaces

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.