等离子诱导QWI对InP/InGaAsP结构的影响

为了比较简单地在同一外延片上得到具有不同带隙结构的有源器件与无源器件的PIC(光子集成电路)和OEIC(光电子集成电路),采用等离子诱导QWI(量子阱混杂)与RTA(快速热退火)技术获得了InP/InGaAsP结构材料的带隙蓝移,其中通过在材料表面沉积不同占空比的SiO2灰度掩膜来灵活控制带隙偏移量。实验中这种方法在基片上获得了5种带隙波长,其中最大波长偏移为75nm,实验结果说明这种技术是实现PIC和OEIC的有效手段,特别是在多带隙结构中具有广阔的应用前景。     

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。     

低能氦离子注入引入的量子阱混杂带隙波长蓝移

提出了采用低能氦离子注入多量子阱(MQW)材料和合适的快速退火条件,实现了MQW带隙波长的蓝移.用这种材料制作了FP腔激光器,与未注入器件相比,实现了37nm的激射波长蓝移.     

低能氦离子注入引入的量子阱混杂带隙波长蓝移

提出了采用低能氦离子注入多量子阱(MQW)材料和合适的快速退火条件,实现了MQW带隙波长的蓝移.用这种材料制作了FP腔激光器,与未注入器件相比,实现了37nm的激射波长蓝移.     

Si3N4无杂质空位诱导InGaAs/InP 量子阱结构带隙的蓝移

用光荧光谱和二次离子质谱的方法,研究了由Si3N4电介质薄膜引起的无杂质空位诱导InGaAs/InP多量子阱结构的带隙蓝移。实验中选用Si3N4作为电介质层,用以产生空位,并经快速热退火处理。实验结果表明,带隙蓝移同退火时间和退火温度有关,合理选用退火条件可以控制带隙的蓝移量。二次离子质谱分析表明,电介质盖层Si3N4和快速热退火导致量子阱中阱和垒之间互扩,这种互扩是导致带隙蓝移的主要原因。     

ZnO量子点／SiO2复合器件的可调控电致发光研究

在不同浓度的SiO2乙醇溶液中制备了一系列ZnO量子点／SiO2复合材料,通过匀胶方法将其制备成复合薄膜器件。器件的电致发光（EL）随着SiO2浓度的增加逐渐蓝移。通过实验,探索了发生蓝移的机制。选取一种ZnO量子点／SiO2复合材料均匀混入不同质量的纯SiO2后,测试结果表明,该蓝移现象不是SiO2自身发光引起的。通...     

太赫兹波段光子晶体传输特性的研究

为了得到光子晶体太赫兹波段的传输特性,研究了晶体材料和晶体类型两个主要因素对传输特性的影响。利用MATLAB程序分别优化计算得到宽禁带和窄禁带光子晶体材料的最大完全带隙以及不同晶格结构和最大完全带隙之间的关系。对于相同晶格结构,带隙随介电常数比增大,对于不同晶格结构,三角晶格形成的最大带隙最大,最后根据太赫兹波的性质设计了太赫兹传输器件。研究结果为太赫兹波器件的开发提供了理论依据。     

可调谐光子带隙晶体的研究进展

近几年来,人们对可调谐光子晶体的兴趣日益增长,并且实际光子器件的应用推动着动态调谐方法的进一步发展。本文主要从光子带隙晶体的调谐机制、调谐途径、所用材料等方面,综述了可调谐光子晶体的研究进展。系统介绍了利用外部应力、电场、磁场、温度等激励,控制晶体结构参数的变化,实现光子带隙的改变;还介绍了通过控制介电材料来改变光子带隙,主要介绍了液晶材料、电光材料等几种常用的材料。比较了不同调谐方法的特点。最后分析了光子晶体带隙调谐的进一步研究方向。     

一种低电源电压带隙基准的设计

设计了一种可以工作在1V电源电压下的CMOS带隙基准。普通的带隙基准是通过VBE(双极型晶体管的基极-发射极电压)和kVT(VT=k·T/q)的和来实现输出基准电平,由于器件本身的特性而决定了其输出电平一般在1.25V左右。本文的带隙基准通过两个分别正比于VBE和kVT和的电流的叠加来实现低电平输出。使用SMIC0.35um模型仿真,得该电路的输出电平为506mV。     

太赫兹波段蜂巢晶格二维光子晶体传输特性的研究

运用平面波展开法优化了太赫兹波段蜂巢晶格二维光子晶体带隙结构,数值模拟得到了太赫兹波段蜂巢晶格光子晶体的最大TE模、TM模和完全带隙,通过光子晶体态密度分布进一步验证了所优化的带隙结构,并设计了对应带隙范围的太赫兹波器件。研究结果为太赫兹器件的开发提供了理论依据。     

Critical layer thickness of strained-layer InGaAs/GaAs multiple quantum wells determined by double-crystal x-ray diffraction

Double-crystal x-ray diffraction (DCXD) is shown to reveal the onset of relaxation in strained-layer InGaAs/GaAs multiple quantum well (MQW) structures. The MQW structures contain 10 nm thick In_0.16Ga_0.84As quantum wells and 55 nm thick GaAs barrier layers. As the number of periods in the structure was increased from to 3 to 15, the x-ray rocking curves were characterized by increasing distortion of superlattice interference fringes, broadening of superlattice peaks, and reduction in peak intensity. The x-ray diffraction data are correlated with an asymmetric crosshatched surface pattern as observed under Nomarski contrast microscopy. By using DCXD and Nomarski microscopy, the onset of strain relaxation in InGaAs/GaAs MQW structures was established for samples with various GaAs barrier layer thicknesses. For MQW structures in which the thickness of the barrier layers is the same or greater than that of the strained quantum wells, the critical layer thickness can be calculated according to the Matthews and Blakeslee force-balance model with dislocation formation by the single-kink mechanism.     

Impact of silicon quantum dot super lattice and quantum well structure as intermediate layer on p‐i‐n silicon solar cells

The photovoltaic effect of the silicon (Si)/silicon carbide (SiC) quantum dot super lattice (QDSL) and multi‐quantum well (QW) strucutres is presented based on numerical simulation and experimental studies. The QDSL and QW structures act as an intermediate layer in a p‐i‐n Si solar cell. The QDSL consists of a stack of four 4‐nm Si nano disks and 2‐nm SiC barrier layers embedded in a SiC matrix fabricated with a top‐down etching process. The Si nano disks were observed with bright field‐scanning transmission electron microscopy. The simulation results based on the 3D finite element method confirmed that the quantum effect on the band structure for the QDSL and QW structures was different and had different effects on solar cell operation. The effect of vertical wave‐function coupling to form a miniband in the QDSL was observed based on the solar‐cell performance, showing a dramatic photovoltaic response in generating a high photocurrent density J_sc of 29.24 mA/cm², open circuit voltage V_oc of 0.51 V, fill factor FF of 0.74, and efficiency η of 11.07% with respect to a i‐QW solar cell with J_sc of 25.27 mA/cm², V_oc of 0.49 V, FF of 0.69, and η of 8.61% and an i‐Si solar cell with J_sc of 27.63 mA/cm², V_oc of 0.55 V, FF of 0.61, and η of 10.00%. A wide range of photo‐carrier transports by the QD arrays in the QDSL solar cell is possible in the internal quantum efficiency spectra with respect to the internal quantum efficiency of the i‐QW solar cell. Copyright © 2015 John Wiley & Sons, Ltd.     

Development of a permittivity extraction method for ultra low k dielectrics integrated in advanced interconnects

An extraction method to determine the permittivity of ultra low k (ULK) dielectrics on real integrated structures is presented. It is a two-step method based on a comparison between measured and simulated capacitance. A best-estimate value of the k_ULK value is first extracted with optimization software coupled to capacitance extraction software. Secondly, uncertainties on material and process parameters are considered to determine an error margin on the best-estimate extracted k value. The uncertainty on the best-estimate value is approximated by a function of the uncertainties on material and process variables. This function is calculated using a multi-linear approximation model and a numerical design of experiments. The same method is applied for the extraction of a ULK material k value (k_ULK) value and an effective k value (k_eff) but with two different simulation structures. In the simulation structure used for k_eff extraction, an equivalent dielectric layer including the ULK layer, the etch-stop and capping layers is used. This method was applied to metal 1 single damascene structures. First results of extraction are presented for two different ULK dielectrics. With the estimated uncertainty used for the parameters in this work, the uncertainties obtained for the best-estimate value of k_ULK and k_effective are significant. Due to the linearity of the model, the method is still applicable with different values for parameters uncertainty. An analysis work will be realized to improve the parameters uncertainty estimation. Future work will also include extraction of ULK permittivity for more complex structures like double damascene structures.     

Effect of p-d exchange with an itinerant carrier in a GaMnAs quantum dot

Hydrogenic acceptor binding energy as a function of dot radius in a GaMnAs/Ga_0.6Al_0.4As quantum dot is calculated including the exchange interaction of Mn alloy content with an itinerant carrier.Calculations are performed by varying its dot radius,for various Mn alloy contents in GaMnAs quantum dot within a single band effective mass approximation using variational method.The spin polaronic energy of the acceptor impurity for different Mn²⁺ is evaluated for different dot radii using a mean field theory in the presence of magnetic field strength.The magnetization is computed in the influence of magnetic field and the Mn ions.The effective g-factor of the valence band electron with the inclusion of effects of Mn ion impurities is found in the influence of the magnetic field.The exchange coupling constant is calculated for various magnetic field strengths.The results show that the p-d exchange interaction in the GaMnAs/Ga_0.6Al_0.4As quantum dot has a strong dependence on spatial confinement,effect of magnetic field strength and the Mn alloy content.Our results are in good agreement with the other investigators.     

不同形状量子阱的量子限制效应

采用差分法求解有效质量方程，考虑轻重空穴的混合效应及应变效应，对三种不同形状的量子阱的能带结构、价带态密度、跃迁矩阵元进行了比较。在阱宽相同的条件下，方阱有最大的限制能力，但抛物阱和三角阱有更平坦的态密度曲线，使得以抛物阱和三角阱为有源区的激光器和半导体激光放大器可以有较低的透明电流密度。同时价带子带的耦合强烈改变了跃迁矩阵元，这对量子阱的增益特性会产生影响。     

渐变In组分InGaN/GaN多量子阱结构中的相分凝及其对提高量子效率的作用研究

利用光荧光、阴极荧光以及时间分辨荧光光谱技术研究了具有不同In组分的渐变InGaN/GaN多量子阱结构中的相分凝现象。在10 K的荧光光谱中,所有的三个样品中除了主发光峰位外,在其高能及低能位置处还出现了另外两个发光峰,表现出了明显的相分凝现象。三个样品阴极荧光结果中呈现出了明显的强度对比,证明了相分凝现象随着量子阱中In组分的增加而加剧。在15 K的时间分辨荧光光谱中,随着In组分的增加,谱线的上升时间得到了延迟,这表明了载流子在由于相分凝而造成的低、高In组分结构中的输运。     

Effects of Rapid Thermal Annealing on the Device Characteristics of Quantum Well Infrared Photodetectors

The effect of rapid thermal annealing (RTA) on important detector characteristics such as dark current, absolute response, noise, and detectivity is investigated for quantum-well infrared photodetectors (QWIP) operating in the 8–12 μm wavelength regime. A comprehensive set of experiments is conducted on QWIPs fabricated from both as-grown and annealed multiple-quantum-well structures. RTA is done at an anneal temperature of 850°C for 30 s using an SiO₂ encapsulant. In general, a decrease in performance is observed for RTA QWIPs when compared to the as-grown detectors. The peak absolute response of the annealed QWIPs is lower by almost a factor of four, which results in a factor of four decrease in quantum efficiency. In addition, a degraded noise performance results in a detectivity which is five times lower than that of QWIPs using asgrown structures. Theoretical calculations of the absorption coefficient spectrum are in excellent agreement with the experimental data.     

非对称应变纤锌矿AlxGa1-xN/GaN/AlyGa1-yN量子阱中浅杂质态的结合能

本文采用变分法数值计算应变纤锌矿AlxGa1−xN/GaN/AlyGa1−yN量子阱中类氢杂质的基态结合能. 计及由自发极化和压电极化引起的内建电场, 讨论阱宽、杂质位置以及左右垒中Al组分对结合能的影响. 结果表明, 尤其在非对称量子阱即势垒宽度或（和）高度不一样的情形下, 杂质位置和垒高对结合能随阱宽变化关系的影响比垒宽更为明显. 对称或非对称结构中, 结合能随杂质位置的变化形如电子基态波函数的空间分布. 此外, 左垒中Al组分对结合能的影响较右垒更甚.     

Absorption Properties of Hybrid SnO<Subscript>2</Subscript> Nanocrystal-Carbon Nanotube Structures

Tin oxide (SnO₂) nanocrystals of a few nanometers are of great interest for electronic applications. Here we present a mini-arc plasma method to produce aerosol tin oxide nanocrystals at atmospheric pressure. The product SnO₂ nanocrystals are then assembled onto the external surface of carbon nanotubes (CNTs) to form hybrid SnO₂–CNT structures. The absorption properties of both the SnO₂ nanocrystals and the SnO₂–CNT hybrid structures have been characterized. Quantum size effects have been observed for as-produced SnO₂ nanocrystals. The intrinsic nanoparticle size selection during the assembly process results in a blue shift of the absorption spectrum for hybrid nanostructures.     

Wavelength tuning in strained layer InGaAs-GaAs-AlGaAs quantum well lasers by selective-area MOCVD

Selective-area growth and regrowth using conventional atmospheric pressure metalorganic chemical vapor deposition is investigated for wavelength tuning in strained layer In_xGa_1-xAsGaAs-Al_y Ga_1-yAs quantum well lasers. Growth inhibition from a silicon dioxide mask is the mechanism used for the selective-area growth rate enhancement. By varying the width of the oxide stripe opening, differences in the growth rate yield different quantum well thicknesses, and hence different lasing wavelengths for devices on the same wafer. Both two-and three-step growth processes are utilized for selective-area epitaxy of strained layer In_xGa_1-xAs-GaAs quantum well active regions, with lasers successfully fabricated from the three-step growth. Scanning electron microscopy and transmission electron microscopy indicate that the absence of an oxide mask during Al_yGa_1-yAs growth is essential for successful device operation. A wide wavelength tuning range of over 630Å is achieved for lasers grown on the same substrate.