双单量子阱材料的调制光谱研究

本文采用光调制光谱方法测量了GaAs/Ga_(1-x)Al_xAs双单量子阱材料的光调制反射光谱(PR),同时观察到了二个单量子阱中的带间激子跃迁,采用电场调制线形可以拟合出激子跃迁的能量,与简单的有限方势阱模型的计算结果符合。并且由调制反射光谱中的Franz-Keldysh振荡,计算得到材料表面内建电场约为29.3kV/cm。     

半导体量子阱材料的调制光谱研究

我们采用光调制透射方法从In_xGa_(1-x)As/GaAs单量子阱样品测量了调制透射谱,得到了InGaAs量子阱中激子的清晰的调制结构.由电场调制原理对调制透射谱进行拟合,得到了激子的跃迁能量.结果与其他测量以及理论计算结果有较好的一致.     

量子阱光反射光谱的电调制机理

研究了量子阱材料光反射光谱的电调制机理,根据斯塔克效应,对量子阱中非激子的带间跃迁和激子跃迁两种情况,分析了电场引起的介电函数的改变和相应的光反射调制光谱线形,对GaAs/AlGaAs量子阱所得光反射光谱的实验结果与理论分析基本符合.     

808nm量子阱激光器电流调制特性的实验研究

本文首次对高功率GaAs/GaAIAs量子阱激光器（808nm)的低频（100Hz-20KHz)电流调制特性进行了实验研究。结果表明：激光发射的接通延迟时间、阈值电流、正脉冲的占空比、平均功率、峰值功率随调制频率和电流而变化。     

介质折射率对光子晶体量子阱滤波性能的调制

为设计高品质的光学滤波器件,利用传输矩阵法理论,通过数值计算模拟的方法,研究垒、阱层介质折射率对光量子阱滤波带宽的调制机制,结果表明,光量子阱滤波带宽对垒、阱层介质折射率的响应相当灵敏:垒层高折射率介质的折射率越大,光量子阱的滤波带宽越窄;垒、阱层介质的折射率和的比值越大,光量子阱的滤波带宽越窄。光量子阱滤波带宽对介质折射率的响应机制,为提高光子晶体光学滤波器件的品质、性能提供方法依据,同时对光量子阱的理论研究也具有积极的指导意义。     

磁场对ZnO抛物量子阱中施主态的影响

ZnO半导体是宽带隙半导体领域继GaAs和GaN之后的研究热点。ZnO对于蓝光、紫光、近紫外波段的光电子器件是一种极具潜力的宽带隙光电子半导体材料。因此,对于ZnO半导体材料构成的抛物量子阱材料物理特性的研究有深远的意义。本文利用变分法研究了在磁场作用下ZnO抛物量子阱中类氢杂质的基态结合能、2p()态能量及1s→2p()跃迁能。结果表明,基态结合能、2p( )态能量以及1s→2p( )跃迁能随磁场单调增加,而2p(-)态能量和1s→2p(-)跃迁能随磁场的变化出现了极小值,然后随磁场的增加线性增加。     

基于GHZ态局域测量的量子秘密共享

提出了一个基于GHZ态局域测量的新颖且高效的量子秘密共享方案.该方案充分利用了GHZ态3个粒子间的相关性,不需要进行任何酉操作或纠缠交换,只通过局域测量,就可在通信者之间建立共享联合密钥.除去用于窃听检测的粒子,其余粒子全部用于消息传输,每个GHZ态可以共享一个比特经典消息,效率达到100%.同时,对于可能存在的攻击方式,文中给出了详细的安全性证明.最后,建立了效率与安全的关系模型,并用MATLAB进行了比较深入的仿真分析.     

应变层InGaAsP量子阱激光器结构的调制光谱研究

利用光调制反射谱(PR)对1.55μm应变层InCaAsP三量子阱激光器结构进行了研究,在样品的波导层观察到了Franz-Keldysh振荡。利用Bastard包络函数方法和Kane模型从理论上计算了该应变层InGaAsP四元合金三量子阱内电子和空穴的能级和跃迁能量,计算结果与实验数据符合得很好,得到了In_(0.758)Ga_(0.242)As_(0.83)P_(0.17)与In_(0.758)Ga_(0.242)As_(0.525)P_(0.475)四元合金应变界面的导带不连续性。     

量子阱态光电子谱研究的理论模型

近年来，光电子谱被广泛应用于薄膜中量子阱态的研究。为解释薄膜中分立的量子阱态和薄膜的光电子谱间的关系，发展了一些理论模型。介绍了近自由电子模型、相位积累模型和电子干涉模型等关于薄膜中量子阱态的理论模型，并用它们解释了量子阱态在光电子谱中峰位和线宽．线宽由准粒子寿命的倒数Γ以及电子在表面和界面反射系数的和R决定，电子波矢κ以及电子在表面和界面相位移之和Φ决定了峰的位置。     

Optical properties and defects in GaAsN and InGaAsN films and quantum well structures

Photoluminescence and microcathodoluminescence spectra of thick-film GaAsN and InGaAsN structures and GaAs/InGaAsN, AlGaAs/InGaAsN quantum wells (QWs) were studied for InGaAsN layers with low nitrogen concentration of 0.35–0.5%. It is shown that in thick-film structures the bandedge luminescence intensity is strongly decreased in the row homoepitaxial GaAs, GaAsN on GaAs buffer, GaAsN, GaAs on GaAsN buffer, InGaAsN which correlates with the increasing concentration of electron traps with activation energy 0.53–0.55 eV. The type of defect bands in the thick-film structures was found to strongly depend on composition of the layers. For the GaAs/InGaAsN QW structures the intensity of luminescence was found to be more than an order of magnitude higher than in InGaAsN single films.     

Large Stark effects for transitions from local states to globalstates in quantum well structures

The electric-field dependence of the optical absorption for the type of quantum well structure in which one or more small wells are embedded in a big well is discussed. In such structures, local energy states confined by the small well(s) and global states confined by the big well have different electric-field dependences while their wave functions remain overlapped. Thus, a large Stark effect (large energy shift and oscillator strength) can be achieved for the optical transition from a local state to a global state. This concept of using the local and global states can be applied to both interband and intersubband transitions. For intersubband transitions, a typical 10-20 meV shift is predicted, compared to a reported 1.1 meV blue shift at the field 30 kV/cm. For interband transitions, the Stark shift is larger than that in the single quantum wells     

Photoreflectance spectroscopy of electron-hole states in a graded-width GaAs/InGaAs/GaAs quantum well

The spectrum of electron-hole states in a GaAs/In_0.5Ga_0.5As quantum well with a width graded in the range from 1.1 to 3.6 nm is studied by photoreflectance spectroscopy. The energies of the size-quantization levels of electrons and holes are calculated taking into account the strain-induced changes in the band structures of the quantum well. It is shown that the best fit of the experimental data to the results of calculations is attained if the ratio between the offset of the conduction band and that of the valence band at the heterojunction is Q = ΔE _c /ΔE _v = 0.62/0.38. A photoreflectance signal is detected in the region of the shadow of modulating radiation beam at a spacing between the spots produced by probing and modulating radiation shorter than 6 mm.     

Novel strained quantum well laser grown by MOVPE

Strained-layer broad-area lasers have been grown by MOVPE. The structures contain 3.5 nm-wide Ga/sub 0.3/In/sub 0.7/As quantum wells. They emit close to 1.5 mu m and have been made to lase under current injection. These structures were compared with similar lasers containing unstrained 7.0 nm-wide Ga/sub 0.47/In/sub 0.53/As quantum wells also emitting at 1.5 mu m. No improvement has been found in J/sub th/ (933 A cm/sup -2/) or T/sub 0/ (47 K) in the case of the strained structure, despite the expected band structure modification.<>     

Light emission by semiconductor structure with quantum well and array of quantum dots

A new type of composite active region of a laser, which contains an In_0.2Ga_0.8As quantum well (QW) and an array of InAs quantum dots (QDs) embedded in GaAs is studied. The QW acts as accumulator of injected carriers, and the QD array is the emitting system located in tunneling proximity to the QW. A theory for the calculation of electron and hole energy levels in the QD is developed. Occupation of the QDs due to the resonance tunneling of electrons and holes from the QW to the QD is considered; the conclusions are compared with the results obtained in studying an experimental laser with a combined active region.     

实现高效光滤波与放大功能的掺激活杂质光量子阱

通过传输矩阵法理论,研究激活杂质对双重势垒光量子阱滤波器特性的影响,结果表明:介质未掺激活杂质时,双重势垒光量子阱滤波器品质随垒层周期数的增大而提高,同时滤波通道的频率发生位移;内、外垒层或阱层介质分别掺激活杂质时,各共振隧穿模出现高倍光放大现象,且各共振隧穿模的频率位置恒定;随激活介质介电虚部大小的增大光量子阱滤波器品质迅速提高,特别是阱层介质掺杂时品质提高尤为明显,高达8.010104倍;利用双重势垒光量子阱的阱层或内、外垒层掺杂激活特性,可实现高品质光滤波、光信号放大功能,且为光量子阱的实际设计与应用提供积极指导。     

Cu溅射诱导增强量子阱混杂实验研究

在InP基异质结InGaAsP多量子阱(MQW)结构上溅射Cu/SiO2复合层,开展了量子阱混杂(QWI)材料的实验研究。经快速退火(RTA),实现了比常规无杂质空位扩散(IFVD)方法更大的带隙波长蓝移量。在750℃、200s的退火条件下,获得最大172nm的波长蓝移;通过改变退火条件,可实现不同程度的蓝移,满足光子集成技术中不同器件对带隙波长的需求。为了验证其用于光子集成领域的可行性,利用混杂技术分别制备了宽条激光器和单片集成电吸收调制激光器(EML)。在675℃退火温度,80s、120s和200s的退火时间下分别实现了61、81和98nm的波长蓝移;并且,相应的宽条激光器的电激射光(EL)谱偏调量与其材料的光致荧光(PL)谱偏调量基本一致。在675℃、120s退火条件下,制备的EML集成器件中,电吸收调制器(EAM)和分布反馈(DFB)激光器区的蓝移量分别83nm和23.7nm,相对带隙差为59.3nm。EML集成器件在激光器注入电流为100mA、调制器零偏压时出光功率达到9.6mW;EAM施加-5V反向偏压时静态消光比达16.4dB。     

Determination of carrier-transfer length from side-wall quantum well to quantum wire by micro-photoluminescence scanning

Micro-photoluminescence (μ-PL) line scanning across a single V-groove, GaAs/AlGaAs quantum wire (QWR) has been performed at room temperature, revealing a clear spatial-dependence of the PL. After fitting each PL spectrum by multi-Gaussian line shapes, intensity profiles of each PL component from confined structures have been obtained as functions of the scanning position. The PL quenching of a side-wall quantum well (SQWL) has been recognized in a certain area in the vicinity of the QWR and is interpreted by carrier transfer into the QWR within effective transfer length. By simulating the carrier-transfer process from SQWL to QWR as a convolution of a step function for carrier distribution and a Gaussian function for exciting laser irradiance, the effective transfer length of about 1.8±0.3 μm has, therefore, been concluded.     

Low-threshold patterned quantum well lasers grown by molecular beamepitaxy

GaAs/AlGaAs patterned quantum well lasers were grown by molecular beam epitaxy on grooved substrates. The carrier confinement and the real-index waveguiding in these lasers rely on lateral thickness variations in the quantum well active layer. Very low threshold currents, as low as 1.8 mA for uncoated devices at room temperature, with 63% differential efficiency have been obtained