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.     

微腔中nc-Si/SiN超晶格的光致发光

研究了一维光子晶体微腔结构对nc-Si/a-SiNz超晶格发射的调制.一维光子晶体微腔采用两种具有不同折射率的非化学组分非晶氮化硅的周期调制结构,腔中嵌入采用激光晶化方法制备的硅量子点阵列,从Raman谱和透射电子显微镜分析得到其尺寸约为3～4 nm.从光致发光谱上观察到明显的选模作用、明显变窄的发光峰以及约两个量级的发光强度的增强.微腔对硅量子点阵列发光的调制主要表现在两个方面:共振模式的增强和非共振模式的抑制.硅量子点中位于腔共振模式的辐射跃迁被增强,非共振模式的辐射跃迁被抑制,因此位于腔共振频率处的跃迁通道成为硅量子点中唯一的辐射跃迁通道,导致光致发光谱的窄化和强度的增强.因此,在提高硅材料发光效率方面,光子晶体微腔具有非常大的应用前景.     

微腔中nc-Si/SiN超晶格的光致发光

研究了一维光子晶体微腔结构对nc-Si/a-SiNz超晶格发射的调制.一维光子晶体微腔采用两种具有不同折射率的非化学组分非晶氮化硅的周期调制结构,腔中嵌入采用激光晶化方法制备的硅量子点阵列,从Raman谱和透射电子显微镜分析得到其尺寸约为3～4 nm.从光致发光谱上观察到明显的选模作用、明显变窄的发光峰以及约两个量级的发光强度的增强.微腔对硅量子点阵列发光的调制主要表现在两个方面:共振模式的增强和非共振模式的抑制.硅量子点中位于腔共振模式的辐射跃迁被增强,非共振模式的辐射跃迁被抑制,因此位于腔共振频率处的跃迁通道成为硅量子点中唯一的辐射跃迁通道,导致光致发光谱的窄化和强度的增强.因此,在提高硅材料发光效率方面,光子晶体微腔具有非常大的应用前景.     

微腔中nc-Si/SiN超晶格的光致发光

研究了一维光子晶体微腔结构对nc-Si/a-SiNz超晶格发射的调制. 一维光子晶体微腔采用两种具有不同折射率的非化学组分非晶氮化硅的周期调制结构，腔中嵌入采用激光晶化方法制备的硅量子点阵列，从Raman谱和透射电子显微镜分析得到其尺寸约为 3～4nm. 从光致发光谱上观察到明显的选模作用、明显变窄的发光峰以及约两个量级的发光强度的增强. 微腔对硅量子点阵列发光的调制主要表现在两个方面：共振模式的增强和非共振模式的抑制. 硅量子点中位于腔共振模式的辐射跃迁被增强，非共振模式的辐射跃迁被抑制，因此位于腔共振频率处的跃迁通道成为硅量子点中唯一的辐射跃迁通道，导致光致发光谱的窄化和强度的增强. 因此，在提高硅材料发光效率方面，光子晶体微腔具有非常大的应用前景.     

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.     

Growth of Space Ordered 1.3μm InAs Quantum Dots on GaAs(100) Vicinal Substrates by MOCVD

用MOCVD技术在偏(1100)GaAs衬底上生长了发光波长在1.3μm的线状空间规则排列InAs量子点.光致发光实验表明,相对于正(100)衬底,偏(100)GaAs衬底上生长的InAs量子点具有更好的材料质量,光谱有更大的强度和更窄的线宽.为了得到发光波长为1.3μm的量子点,对比研究了不同In含量的InGaAs应力缓冲层(SBL)和应力盖层(SCL)的应力缓冲作用.结果表明,增加SCL中In含量能有效延伸量子点发光波长到1. 3μm,但是随着SBL中In的增加,发光波长变化不明显,并且材料质量明显下降.     

用MOCVD在偏(100)GaAs基片上生长空间规则排列的1.3μm InAs量子点

用MOCVD技术在偏(1100)GaAs衬底上生长了发光波长在1.3μm的线状空间规则排列InAs量子点.光致发光实验表明,相对于正(100)衬底,偏(100)GaAs衬底上生长的InAs量子点具有更好的材料质量,光谱有更大的强度和更窄的线宽.为了得到发光波长为1.3μm的量子点,对比研究了不同In含量的InGaAs应力缓冲层(SBL)和应力盖层(SCL)的应力缓冲作用.结果表明,增加SCL中In含量能有效延伸量子点发光波长到1. 3μm,但是随着SBL中In的增加,发光波长变化不明显,并且材料质量明显下降.     

利用多层堆垛InAs/GaAs量子点结构实现1.3μm光致发光

在GaAs衬底上用分子束外延分别生长了单层和五层垂直堆垛的InAs/GaAs量子点结构.室温光致发光实验表明,五层堆垛结构较单层结构的发光峰位红移180nm,实现了1.3μm发光.结合透射电镜分析,多层堆垛量子点材料发光的显著红移是由于量子点层间应力耦合导致的上层量子点体积增大以及各量子点层间的能态耦合.     

利用多层堆垛InAs/GaAs量子点结构实现1.3μm光致发光

在GaAs衬底上用分子束外延分别生长了单层和五层垂直堆垛的InAs/GaAs量子点结构.室温光致发光实验表明,五层堆垛结构较单层结构的发光峰位红移180nm,实现了1.3μm发光.结合透射电镜分析,多层堆垛量子点材料发光的显著红移是由于量子点层间应力耦合导致的上层量子点体积增大以及各量子点层间的能态耦合.     

Effect of a low-temperature-grown GaAs layer on InAs quantum-dot photoluminescence

The photoluminescence of InAs semiconductor quantum dots overgrown by GaAs in the low-temperature mode (LT-GaAs) using various spacer layers or without them is studied. Spacer layers are thin GaAs or AlAs layers grown at temperatures normal for molecular-beam epitaxy (MBE). Direct overgrowth leads to photoluminescence disappearance. When using a thin GaAs spacer layer, the photoluminescence from InAs quantum dots is partially recovered; however, its intensity appears lower by two orders of magnitude than in the reference sample in which the quantum-dot array is overgrown at normal temperature. The use of wider-gap AlAs as a spacer-layer material leads to the enhancement of photoluminescence from InAs quantum dots, but it is still more than ten times lower than that of reference-sample emission. A model taking into account carrier generation by light, diffusion and tunneling from quantum dots to the LT-GaAs layer is constructed.     

Optical studies of a two-dimensional photonic crystal with the InAs/InGaAs quantum-dot structure as an active region

A two-dimensional semiconductor photonic crystal with a hexagonal lattice of submicrometer holes is produced by etching the GaAs/AlGaAs planar structure containing the InAs/InGaAs quantum dots in the waveguide layer. By analyzing the reflectance spectra at variable angles of incidence and polarizations of light, the photonic band structure is determined. The Fano resonance peaks revealed in the reflectance spectra at the TM (TE) polarization along the Γ-K (Γ-M) symmetry direction are due to the resonance interaction of optically active photonic bands with the incident light. The band structure of the radiation leakage modes is investigated by studying the angular dependence of the photoluminescence intensity. A threefold increase in the photoluminescence intensity revealed at the resonance frequency of the photonic crystal is attributed to the Purcell effect.     

Room-temperature 1.5–1.6 µm photoluminescence from InGaAs/GaAs heterostructures grown at low substrate temperature

Heterostructures with In(Ga)As/GaAs quantum dots and quantum wells grown at low substrate temperature were studied by reflection high-energy electron diffraction, transmission electron microscopy, and photoluminescence methods. It is shown that InAs deposited onto (100) GaAs surface at low substrate temperature forms 2D clusters composed of separate quantum dots. Optical spectra of structures containing such clusters demonstrate emission in the 1.5–1.6 μm range. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 37, No. 12, 2003, pp. 1456–1460. Original Russian Text Copyright ? 2003 by Tonkikh, Tsyrlin, Talalaev, Novikov, Egorov, Polyakov, Samsonenko, Ustinov, Zakharov, Werner.     

Low threshold current operation of self-assembled InAs/GaAs quantum dot lasers by metal organic chemical vapour deposition

Low threshold current operation of self-assembled InAs/GaAs quantum dot lasers grown by metal organic chemical vapour deposition is reported. Continuous-wave lasing at room temperature with low threshold current (6.7 mA) was achieved at the wavelength of 1.18 /spl mu/m. The threshold current of 6.7 mA is the lowest value so far achieved in quantum dot lasers grown by metal organic chemical vapour deposition. Comparison with photoluminescence spectra indicates that the observed lasing originates from the ground state of InAs quantum dots.     

Heterostructures with InAs/AlAs Quantum Wells and Quantum Dots Grown on GaAs/Si Hybrid Substrates

Semiconductors - Heterostructures with InAs/AlAs quantum dots are grown on GaAs/Si hybrid substrates. The experimentally observed low-temperature (5–80 K) photoluminescence spectra of...     

Optical detection of asymmetric quantum-dot molecules in double-layer InAs/GaAs structures

Self-assembled quantum dots (QDs) in double-layer InAs/GaAs structures are studied by resonant photoluminescence and photoluminescence excitation spectroscopy. A weakly correlated (50%) double-layer system with an array of vertically coupled QDs (asymmetric quantum-dot molecules) was formed in a structure consisting of the 1.8-monolayer-thick first and the 2.4-monolayer-thick second InAs layers separated by 50 monolayers of GaAs. The nature of discrete quantum states in this system was studied and resonances corresponding to vertically coupled QDs were clearly observed for the first time.     

Photoluminescence of InAs quantum dots coupled to a two-dimensional electron gas

Self-assembled InAs quantum dots have been extensively studied by a variety of experimental techniques. Works have been done on the transport properties of the InAs dots located near a two-dimensional electron gas (2DEG). However, there have been few reports on the optical properties of the InAs dots located closely to 2DEG. In this work, InAs dots samples with 2DEG and without 2DEG growth by solid source molecular beam epitaxy were studied using photoluminescence measurements. Different photoluminescence behaviors between the InAs dots and the InAs dots near the 2DEG were observed. It was found that the emission efficiency of the InAs dots was significantly enhanced by the existence of the nearby 2DEG and the thermal activation energy of the InAs dots was decreased by the 2DEG. It was speculated that the 2DEG at the AlGaAs/GaAs interface worked as an electron reservoir to the InAs dots. As a result, the conduction band between the dots and 2DEG is lowered, and thus the thermal activation energy of PL is lowered. It was concluded that in this way the optical properties of the InAs quantum dots could be tailored for optical applications.     

Baric properties of InAs quantum dots

In the context of the deformation potential model, baric dependences of the energy structure of InAs quantum dots in a GaAs matrix are calculated. Under the assumption of the absence of interaction between the spherical quantum dots of identical sizes, the energy dependence of the baric coefficient of energy of the radiative transition in the quantum dot is determined. A similar dependence is also found experimentally in the photoluminescence spectra under uniform compression of the InAs/GaAs structures. Qualitative agreement between the theory and experiment as well as possible causes for their quantitative difference are discussed. It is concluded that such factors as the size dispersion, Coulomb interaction of charge carriers, and tunnel interaction of quantum dots contribute to this difference.